//- Copyright (C) 2014  James Riely, DePaul University
//- Copyright (C) 2004  John Hamer, University of Auckland [Graphviz code]
//-
//-   This program is free software; you can redistribute it and/or
//-   modify it under the terms of the GNU General Public License
//-   as published by the Free Software Foundation; either version 2
//-   of the License, or (at your option) any later version.
//-
//-   This program is distributed in the hope that it will be useful,
//-   but WITHOUT ANY WARRANTY; without even the implied warranty of
//-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//-   GNU General Public License for more details.
//-
//-   You should have received a copy of the GNU General Public License along
//-   with this program; if not, write to the Free Software Foundation, Inc.,
//-   59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.package algs;

//- Event monitoring code based on
//-    http://fivedots.coe.psu.ac.th/~ad/jg/javaArt5/
//-    By Andrew Davison, ad@fivedots.coe.psu.ac.th, March 2009
//-
//- Graphviz code based on LJV
//-    https://www.cs.auckland.ac.nz/~j-hamer/
//-    By John Hamer, <J.Hamer@cs.auckland.ac.nz>, 2003
//-    Copyright (C) 2004  John Hamer, University of Auckland

package stdlib;

import java.io.*;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.TreeMap;
import java.util.function.Consumer;
import com.sun.jdi.*;
import com.sun.jdi.connect.*;
import com.sun.jdi.connect.Connector.Argument;
import com.sun.jdi.event.*;
import com.sun.jdi.request.*;

/**
 * <p>
 * Traces the execution of a target program.
 * </p><p>
 * See <a href="http://fpl.cs.depaul.edu/jriely/visualization/">http://fpl.cs.depaul.edu/jriely/visualization/</a>
 * </p><p>
 * Command-line usage: java Trace [OptionalJvmArguments] fullyQualifiedClassName
 * </p><p>
 * Starts a new JVM (java virtual machine) running the main program in
 * fullyQualifiedClassName, then traces it's behavior. The OptionalJvmArguments
 * are passed to this underlying JVM.
 * </p><p>
 * Example usages:
 * </p><pre>
 *   java Trace MyClass
 *   java Trace mypackage.MyClass
 *   java Trace -cp ".:/pathTo/Library.jar" mypackage.MyClass  // mac/linux
 *   java Trace -cp ".;/pathTo/Library.jar" mypackage.MyClass  // windows
 * </pre><p>
 * Two types of display are support: console and graphviz In order to use
 * graphziv, you must install http://www.graphviz.org/ and perhaps call
 * graphvizAddPossibleDotLocation to include the location of the "dot"
 * executable.
 * </p><p>
 * You can either draw the state at each step --- {@code drawSteps()} --- or
 * you can draw states selectively by calling {@code Trace.draw()} from the program
 * you are tracing. See the example in {@code ZTraceExample.java}.
 * </p><p>
 * Classnames that end in "Node" are drawn using rounded rectangles by default.  
 * This does not work until the class is loaded; thus, null references may show up 
 * as inline fields for a while, until the class is loaded.
 * </p>
 * @author James Riely, jriely@cs.depaul.edu, 2014-2015
 */
/* !!!!!!!!!!!!!!!!!!!!!!!! COMPILATION !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 *
 * This class requires Java 8. It also requires the file tools.jar, which comes
 * with the JDK (not the JRE)
 *
 * On windows, you can find it in
 *
 * <pre>
 *   C:\Program Files\Java\jdk...\lib\tools.jar
 * </pre>
 *
 * On mac, look in
 *
 * <pre>
 *   /Library/Java/JavaVirtualMachines/jdk.../Contents/Home/lib/tools.jar
 * </pre>
 *
 * To put this in your eclipse build path, select your project in the package
 * explorer, then:
 *
 * <pre>
 *  Project > Properties > Java Build Path > Libraries > Add External Library
 * </pre>
 *
 */
public class Trace {
        private Trace () {} // noninstantiable class
        protected static final String CALLBACK_CLASS_NAME = Trace.class.getCanonicalName ();
        protected static final String GRAPHVIZ_CLASS_NAME = Graphviz.class.getCanonicalName ();

        /**
         * Draw the given object.
         *
         * This is a stub method, which is trapped by the debugger. It only has an
         * effect if a variant of Trace.run() has been called to start the debugger
         * and Trace.drawSteps() is false.
         */     
        public static void drawObject (Object object) { } // See Printer. methodEntryEvent      
        protected static final String CALLBACK_DRAW_OBJECT = "drawObject";
        protected static final HashSet<String> CALLBACKS = new HashSet<> ();
        static { CALLBACKS.add (CALLBACK_DRAW_OBJECT); }
        /**
         * Draw the given object, labeling it with the given name.
         *
         * This is a stub method, which is trapped by the debugger. It only has an
         * effect if a variant of Trace.run() has been called to start the debugger
         * and Trace.drawSteps() is false.
         */
        public static void drawObjectWithName (String name, Object object) { } // See Printer. methodEntryEvent
        protected static final String CALLBACK_DRAW_OBJECT_NAMED = "drawObjectWithName";
        static { CALLBACKS.add (CALLBACK_DRAW_OBJECT_NAMED); }
        /**
         * Draw the given objects.
         *
         * This is a stub method, which is trapped by the debugger. It only has an
         * effect if a variant of Trace.run() has been called to start the debugger
         * and Trace.drawSteps() is false.
         */
        public static void drawObjects (Object... objects) { } // See Printer. methodEntryEvent
        protected static final String CALLBACK_DRAW_OBJECTS = "drawObjects";
        static { CALLBACKS.add (CALLBACK_DRAW_OBJECTS); }
        /**
         * Draw the given objects, labeling them with the given names. The array of
         * namesAndObjects must alternate between names and objects, as in
         * Trace.drawObjects("x", x, "y" y).
         *
         * This is a stub method, which is trapped by the debugger. It only has an
         * effect if a variant of Trace.run() has been called to start the debugger
         * and Trace.drawSteps() is false.
         */
        public static void drawObjectsWithNames (Object... namesAndObjects) { }  // See Printer. methodEntryEvent
        protected static final String CALLBACK_DRAW_OBJECTS_NAMED = "drawObjectsWithNames";
        static { CALLBACKS.add (CALLBACK_DRAW_OBJECTS_NAMED); }

        /**
         * Draw the current frame, as well as all reachable objects.
         *
         * This is a stub method, which is trapped by the debugger. It only has an
         * effect if a variant of Trace.run() has been called to start the debugger
         * and Trace.drawSteps() is false.
         */
        public static void drawThisFrame () { }  // See Printer. methodEntryEvent
        protected static final String CALLBACK_DRAW_THIS_FRAME = "drawThisFrame";
        static { CALLBACKS.add (CALLBACK_DRAW_THIS_FRAME); }

        /**
         * Stop drawing steps.
         *
         * This is a stub method, which is trapped by the debugger. It only has an
         * effect if a variant of Trace.run() has been called to start the debugger.
         */
        public static void drawStepsEnd () { }  // See Printer. methodEntryEvent
        protected static final String CALLBACK_DRAW_STEPS_END = "drawStepsEnd";
        static { CALLBACKS.add (CALLBACK_DRAW_STEPS_END); }

        /**
         * Start drawing steps.
         *
         * This is a stub method, which is trapped by the debugger. It only has an
         * effect if a variant of Trace.run() has been called to start the debugger.
         */
        public static void drawSteps () { }  // See Printer. methodEntryEvent
        protected static final String CALLBACK_DRAW_STEPS_BEGIN = "drawSteps";
        static { CALLBACKS.add (CALLBACK_DRAW_STEPS_BEGIN); }

        /**
         * Draw all stack frames and static variables, as well as all reachable
         * objects.
         *
         * This is a stub method, which is trapped by the debugger. It only has an
         * effect if a variant of Trace.run() has been called to start the debugger
         * and Trace.drawSteps() is false.
         */
        public static void draw () { }  // See Printer. methodEntryEvent
        protected static final String CALLBACK_DRAW_ALL_FRAMES = "draw";
        static { CALLBACKS.add (CALLBACK_DRAW_ALL_FRAMES); }

        /**
         * Draw all stack frames and static variables, as well as all reachable
         * objects, overriding showStaticClasses() if it is false.
         *
         * This is a stub method, which is trapped by the debugger. It only has an
         * effect if a variant of Trace.run() has been called to start the debugger
         * and Trace.drawSteps() is false.
         */
        public static void drawAll () { }  // See Printer. methodEntryEvent
        protected static final String CALLBACK_DRAW_ALL_FRAMES_AND_STATICS = "drawAll";
        static { CALLBACKS.add (CALLBACK_DRAW_ALL_FRAMES_AND_STATICS); }

        // Basic graphviz options
        /**
         * Run graphviz "dot" program to produce an output file (default==true). If
         * false, a graphviz source file is created, but no graphic file is
         * generated.
         */
        public static void graphvizRunGraphviz (boolean value) {
                GRAPHVIZ_RUN_GRAPHVIZ = value;
        }
        protected static boolean GRAPHVIZ_RUN_GRAPHVIZ = true;

        /**
         * The graphviz format -- see http://www.graphviz.org/doc/info/output.html .
         * (default=="png").
         */
        public static void graphvizOutputFormat (String value) {
                GRAPHVIZ_OUTPUT_FORMAT = value;
        }
        protected static String GRAPHVIZ_OUTPUT_FORMAT = "png";

        /**
         * Sets the graphviz output directory.
         * Creates the directory if necessary.
         * Relative pathnames are interpreted with respect to the user's "Desktop" directory.
         * Default is "GraphvizOutput".
         */
        public static void setGraphizOutputDir (String dirName) {
                GRAPHVIZ_DIR = dirName;
        }
        private static String GRAPHVIZ_DIR = "GraphvizOutput";

        /**
         * Sets the console output to the given filename. Console output will be
         * written to:
         *
         * <pre>
         * (user home directory)/(filename)
         * </pre>
         */
        public static void setConsoleFilenameRelativeToUserDesktop (String filename) {
                setConsoleFilename (Graphviz.getDesktop() + File.separator + filename);
        }
        /**
         * Sets the console output to the given filename.
         */
        public static void setConsoleFilename (String filename) {
                Printer.setFilename (filename);
        }
        /**
         * Sets the console output to the default (the terminal).
         */
        public static void setConsoleFilename () {
                Printer.setFilename ();
        }

        /**
         * Run graphviz "dot" program to produce an output file (default==true). If
         * false, a graphviz source file is created, but no graphic file is
         * generated.
         */
        public static void showOnlyTopFrame (boolean value) {
                GRAPHVIZ_SHOW_ONLY_TOP_FRAME = value;
        }
        protected static boolean GRAPHVIZ_SHOW_ONLY_TOP_FRAME = false;

        // Basic options --
        protected static boolean GRAPHVIZ_SHOW_STEPS = false;
        //      protected static void drawStepsOf (String className, String methodName) {
        //              GRAPHVIZ_SHOW_STEPS = true;
        //              if (GRAPHVIZ_SHOW_STEPS_OF == null)
        //                      GRAPHVIZ_SHOW_STEPS_OF = new HashSet<>();
        //              GRAPHVIZ_SHOW_STEPS_OF.add (new OptionalClassNameWithRequiredMethodName (className, methodName));
        //              REPRESS_RETURN_ON_GRAPHVIZ_SHOW_STEPS_OF = (GRAPHVIZ_SHOW_STEPS_OF.size () <= 1);
        //      }
        /**
         * Create a new graphviz drawing for every step of the named method.
         * The methodName does not include parameters.
         * In order to show a constructor, use the method name {@code <init>}.
         */
        public static void drawStepsOfMethod (String methodName) { }  // See Printer. methodEntryEvent
        /**
         * Create a new graphviz drawing for every step of the named methods.
         * The methodName does not include parameters.
         * In order to show a constructor, use the method name {@code <init>}.
         */
        public static void drawStepsOfMethods (String... methodName) { }  // See Printer. methodEntryEvent
        protected static final String CALLBACK_DRAW_STEPS_OF_METHOD = "drawStepsOfMethod";
        static { CALLBACKS.add (CALLBACK_DRAW_STEPS_OF_METHOD); }
        protected static final String CALLBACK_DRAW_STEPS_OF_METHODS = "drawStepsOfMethods";
        static { CALLBACKS.add (CALLBACK_DRAW_STEPS_OF_METHODS); }
        protected static void drawStepsOfMethodBegin (String methodName) {
                GRAPHVIZ_SHOW_STEPS = true;
                if (GRAPHVIZ_SHOW_STEPS_OF == null)
                        GRAPHVIZ_SHOW_STEPS_OF = new HashSet<>();
                GRAPHVIZ_SHOW_STEPS_OF.add (new OptionalClassNameWithRequiredMethodName (null, methodName));
                REPRESS_RETURN_ON_GRAPHVIZ_SHOW_STEPS_OF = (GRAPHVIZ_SHOW_STEPS_OF.size () <= 1);
        }
        protected static void drawStepsOfMethodEnd () {
                GRAPHVIZ_SHOW_STEPS = true;
                GRAPHVIZ_SHOW_STEPS_OF = new HashSet<>();
                REPRESS_RETURN_ON_GRAPHVIZ_SHOW_STEPS_OF = false;
        }

        protected static boolean drawStepsOfInternal (ThreadReference thr) {
                if (GRAPHVIZ_SHOW_STEPS_OF == null) return true;
                List<StackFrame> frames = null;
                try { frames = thr.frames (); } catch (IncompatibleThreadStateException e) { }
                return Trace.drawStepsOfInternal (frames, null);
        }
        protected static boolean drawStepsOfInternal (List<StackFrame> frames, Value returnVal) {
                if (GRAPHVIZ_SHOW_STEPS_OF == null) return true;
                if (frames == null) return true;
                if (REPRESS_RETURN_ON_GRAPHVIZ_SHOW_STEPS_OF && returnVal != null && !(returnVal instanceof VoidValue)) return false;
                StackFrame currentFrame = frames.get (0);
                String className = currentFrame.location ().declaringType ().name ();
                String methodName = currentFrame.location ().method ().name ();
                return Trace.drawStepsOfInternal (className, methodName);
        }
        protected static boolean drawStepsOfInternal (String className, String methodName) {
                if (GRAPHVIZ_SHOW_STEPS_OF == null) return true;
                //System.err.println (className + "." + methodName + " " + new OptionalClassNameWithRequiredMethodName(className, methodName).hashCode() + " "+ GRAPHVIZ_SHOW_STEPS_OF);
                return GRAPHVIZ_SHOW_STEPS_OF.contains (new OptionalClassNameWithRequiredMethodName(className, methodName));
        }
        protected static Set<OptionalClassNameWithRequiredMethodName> GRAPHVIZ_SHOW_STEPS_OF = null;
        private static boolean REPRESS_RETURN_ON_GRAPHVIZ_SHOW_STEPS_OF = false;
        protected static class OptionalClassNameWithRequiredMethodName {
                String className;
                String methodName;
                public OptionalClassNameWithRequiredMethodName (String className, String methodName) {
                        this.className = className;
                        this.methodName = methodName;
                }
                public String toString () {
                        return className + "." + methodName;
                }
                public boolean equals (Object other) {
                        //System.err.println (this + "==" + other);
                        if (other == this) return true;
                        if (other == null) return false;
                        if (other.getClass () != this.getClass ()) return false;
                        OptionalClassNameWithRequiredMethodName that = (OptionalClassNameWithRequiredMethodName) other;
                        if (this.className != null && that.className != null) {
                                if (! this.className.equals (that.className)) return false;
                        }
                        if (! this.methodName.equals (that.methodName)) return false;
                        return true;
                }
                public int hashCode() { return methodName.hashCode (); }
        }
        /**
         * Show events on the console (default==false).
         */
        public static void consoleShow (boolean value) {
                CONSOLE_SHOW_THREADS = value;
                CONSOLE_SHOW_CLASSES = value;
                CONSOLE_SHOW_CALLS = value;
                CONSOLE_SHOW_STEPS = value;
                CONSOLE_SHOW_VARIABLES = value;
                CONSOLE_SHOW_STEPS_VERBOSE = false;
        }
        /**
         * Show events on the console, including code (default==false).
         */
        public static void consoleShowVerbose (boolean value) {
                CONSOLE_SHOW_THREADS = value;
                CONSOLE_SHOW_CLASSES = value;
                CONSOLE_SHOW_CALLS = value;
                CONSOLE_SHOW_STEPS = value;
                CONSOLE_SHOW_VARIABLES = value;
                CONSOLE_SHOW_STEPS_VERBOSE = true;
        }

        /**
         * Directory for source code. This needs to be fixed before the class loading
         * begins. So currently no way to change dynamically.
         */
        protected static String SOURCE_DIRECTORY = "src";
        protected static boolean CONSOLE_SHOW_THREADS = false;
        protected static boolean CONSOLE_SHOW_CLASSES = false;
        protected static boolean CONSOLE_SHOW_CALLS = false;
        protected static boolean CONSOLE_SHOW_STEPS = false;
        protected static boolean CONSOLE_SHOW_STEPS_VERBOSE = false;
        protected static boolean CONSOLE_SHOW_VARIABLES = false;
        /**
         * Show String, Integer, Double, etc as simplified objects (default==false).
         */
        public static void showBuiltInObjects (boolean value) {
                if (value) showNodesAsRegularObjects ();
                SHOW_STRINGS_AS_PRIMITIVE = !value;
                SHOW_BOXED_PRIMITIVES_AS_PRIMITIVE = !value;
                GRAPHVIZ_SHOW_BOXED_PRIMITIVES_SIMPLY = true;
        }
        /**
         * Show String, Integer, Double, etc as regular objects (default==false).
         */
        public static void showBuiltInObjectsVerbose (boolean value) {
                if (value) showNodesAsRegularObjects ();
                SHOW_STRINGS_AS_PRIMITIVE = !value;
                SHOW_BOXED_PRIMITIVES_AS_PRIMITIVE = !value;
                GRAPHVIZ_SHOW_BOXED_PRIMITIVES_SIMPLY = false;
        }
        protected static boolean SHOW_STRINGS_AS_PRIMITIVE = true;
        protected static boolean SHOW_BOXED_PRIMITIVES_AS_PRIMITIVE = true;
        protected static boolean GRAPHVIZ_SHOW_BOXED_PRIMITIVES_SIMPLY = true;

        /**
         * Run the debugger on the current class. Execution of the current program
         * ends and a new JVM is started under the debugger.
         *
         * The debugger will execute the main method of the class that calls run.
         *
         * The main method is run with no arguments.
         */
        public static void run () {
                Trace.run (new String[] {});
        }
        /**
         * Run the debugger on the current class. Execution of the current program
         * ends and a new JVM is started under the debugger.
         *
         * The debugger will execute the main method of the class that calls run.
         *
         * The main method is run with the given arguments.
         */
        public static void run (String[] args) {
                StackTraceElement[] stackTrace = Thread.currentThread ().getStackTrace ();
                String mainClassName = stackTrace[stackTrace.length - 1].getClassName ();
                Trace.internalPrepAndRun (mainClassName, args, true);
        }
        /**
         * Run the debugger on the given class. The current program will continue to
         * execute after this call to run has completed.
         *
         * The main method of the given class is called with no arguments.
         */
        public static void run (String mainClassName) {
                Trace.internalPrepAndRun (mainClassName, new String[] {}, false);
        }
        /**
         * Run the debugger on the given class. The current program will continue to
         * execute after this call to run has completed.
         *
         * The main method of the given class is called with no arguments.
         */
        public static void run (Class<?> mainClass) {
                Trace.run (mainClass, new String[] {});
        }
        /**
         * Run the debugger on the given class. The current program will continue to
         * execute after this call to run has completed.
         *
         * The main method of the given class is called with the given arguments.
         */
        public static void run (String mainClassName, String[] args) {
                internalPrepAndRun (mainClassName, args, false);
        }
        /**
         * Run the debugger on the given class. The current program will continue to
         * execute after this call to run has completed.
         *
         * The main method of the given class is called with the given arguments.
         */
        public static void run (Class<?> mainClass, String[] args) {
                Trace.internalPrepAndRun (mainClass.getCanonicalName (), args, false);
        }
        /**
         * Run the debugger on the given class. The current program will continue to
         * execute after this call to run has completed.
         *
         * The main method of the given class is called with the given arguments.
         */
        public static void runWithArgs (Class<?> mainClass, String... args) {
                Trace.run (mainClass, args);
        }
        /**
         * Run the debugger on the given class. The current program will continue to
         * execute after this call to run has completed.
         *
         * The main method of the given class is called with the given arguments.
         */
        public static void runWithArgs (String mainClassName, String... args) {
                Trace.internalPrepAndRun (mainClassName, args, false);
        }
        /**
         * The debugger can be invoked from the command line using this method. The
         * first argument must be the fully qualified name of the class to be
         * debugged. Addition arguments are passed to the main method of the class
         * to be debugged.
         */
        public static void main (String[] args) {
                if (args.length == 0) {
                        System.err.println ("Usage: java " + Trace.class.getCanonicalName () + " [OptionalJvmArguments] fullyQualifiedClassName");
                        System.exit (-1);
                }
                ArrayList<String> prefixArgs = getPrefixArgsForVm();
                int length = prefixArgs.size ();
                String[] allArgs = new String[length + args.length];
                for (int i = 0; i < length; i++)
                        allArgs[i] = prefixArgs.get (i);
                System.arraycopy (args, 0, allArgs, length, args.length);
                internalRun ("Trace", allArgs, false);
        }

        //------------------------------------------------------------------------
        //          _______.___________.  ______   .______      __     __
        //         /       |           | /  __  \  |   _  \    |  |   |  |
        //        |   (----`---|  |----`|  |  |  | |  |_)  |   |  |   |  |
        //         \   \       |  |     |  |  |  | |   ___/    |  |   |  |
        //     .----)   |      |  |     |  `--'  | |  |        |__|   |__|
        //     |_______/       |__|      \______/  | _|        (__)   (__)
        //
        //          _______.  ______     ___      .______     ____    ____
        //         /       | /      |   /   \     |   _  \    \   \  /   /
        //        |   (----`|  ,----'  /  ^  \    |  |_)  |    \   \/   /
        //         \   \    |  |      /  /_\  \   |      /      \_    _/
        //     .----)   |   |  `----./  _____  \  |  |\  \----.   |  |
        //     |_______/     \______/__/     \__\ | _| `._____|   |__|
        //
        //     .___________. __    __   __  .__   __.   _______      _______.
        //     |           ||  |  |  | |  | |  \ |  |  /  _____|    /       |
        //     `---|  |----`|  |__|  | |  | |   \|  | |  |  __     |   (----`
        //         |  |     |   __   | |  | |  . `  | |  | |_ |     \   \
        //         |  |     |  |  |  | |  | |  |\   | |  |__| | .----)   |
        //         |__|     |__|  |__| |__| |__| \__|  \______| |_______/
        //
        //     .______    _______  __        ______   ____    __    ____    __
        //     |   _  \  |   ____||  |      /  __  \  \   \  /  \  /   /   |  |
        //     |  |_)  | |  |__   |  |     |  |  |  |  \   \/    \/   /    |  |
        //     |   _  <  |   __|  |  |     |  |  |  |   \            /     |  |
        //     |  |_)  | |  |____ |  `----.|  `--'  |    \    /\    /      |__|
        //     |______/  |_______||_______| \______/      \__/  \__/       (__)
        //
        //------------------------------------------------------------------------
        // This program uses all sorts of crazy java foo.
        // You should not have to read anything else in this file.

        /**
         * This code is based on the Trace.java example included in the
         * demo/jpda/examples.jar file in the JDK.
         *
         * For more information on JPDA and JDI, see:
         *
         * <pre>
         * http://docs.oracle.com/javase/8/docs/technotes/guides/jpda/trace.html
         * http://docs.oracle.com/javase/8/docs/jdk/api/jpda/jdi/index.html
         * http://forums.sun.com/forum.jspa?forumID=543
         * </pre>
         *
         * Changes made by Riely:
         *
         * - works with packages other than default
         *
         * - prints values of variables Objects values are printed as "@uniqueId"
         * Arrays include the values in the array, up to
         *
         * - handles exceptions
         *
         * - works for arrays, when referenced by local variables, static fields, or
         * fields of "this"
         *
         * - options for more or less detail
         *
         * - indenting to show position in call stack
         *
         * - added methods to draw the state of the system using graphviz
         *
         * Known bugs/limitations:
         *
         * - There appears to be a bug in the JDI: steps from static initializers
         * are not always reported. I don't see a real pattern here. Some static
         * initializers work and some don't. When the step event is not generated by
         * the JDI, this code cannot report on it, of course, since we rely on the
         * JDI to generate the steps.
         *
         * - Works for local arrays, including updates to fields of "this", but will
         * not print changes through other object references, such as
         * yourObject.publicArray[0] = 22 As long as array fields are private (as
         * they should be), it should be okay.
         *
         * - Updates to arrays that are held both in static fields and also in local
         * variables or object fields will be shown more than once in the console
         * view.
         *
         * - Space leak: copies of array references are kept forever. See
         * "registerArray".
         *
         * - Not debugged for multithreaded code. Monitor events are currently
         * ignored.
         *
         * - Slow. Only good for short programs.
         *
         * - This is a hodgepodge of code from various sources, not well debugged,
         * not super clean.
         *
         */
        /**
         * Macintosh OS-X sometimes sets the hostname to an unroutable name and this
         * may cause the socket connection to fail. To see your hostname, open a
         * Terminal window and type the "hostname" command. On my machine, the
         * terminal prompt is "$", and so the result looks like this:
         *
         * <pre>
         *   $ hostname
         *   escarole.local
         *   $
         * </pre>
         *
         * To see that this machine is routable, I can "ping" it:
         *
         * <pre>
         *   $ ping escarole.local
         *   PING escarole.local (192.168.1.109): 56 data bytes
         *   64 bytes from 192.168.1.109: icmp_seq=0 ttl=64 time=0.046 ms
         *   64 bytes from 192.168.1.109: icmp_seq=1 ttl=64 time=0.104 ms
         *   ^C
         *   --- escarole.local ping statistics ---
         *   2 packets transmitted, 2 packets received, 0.0% packet loss
         *   round-trip min/avg/max/stddev = 0.046/0.075/0.104/0.029 ms
         * </pre>
         *
         * When I am connected to some networks, the result is like this:
         *
         * <pre>
         *   $ hostname
         *   loop-depaulsecure-182-129.depaulsecure-employee.depaul.edu
         *   $ ping loop-depaulsecure-182-129.depaulsecure-employee.depaul.edu
         *   ping: cannot resolve loop-depaulsecure-182-129.depaulsecure-employee.depaul.edu: Unknown host
         * </pre>
         *
         * Or this:
         *
         * <pre>
         *   $ hostname
         *   asteelembook.cstcis.cti.depaul.edu
         *   $ ping asteelembook.cstcis.cti.depaul.edu
         *   PING asteelembook.cstcis.cti.depaul.edu (140.192.38.100): 56 data bytes
         *   Request timeout for icmp_seq 0
         *   Request timeout for icmp_seq 1
         *   ^C
         *   --- asteelembook.cstcis.cti.depaul.edu ping statistics ---
         *   3 packets transmitted, 0 packets received, 100.0% packet loss
         * </pre>
         *
         * To stop OS-X from taking bogus hostname like this, you can fix the
         * hostname, as follows:
         *
         * <pre>
         *   $ scutil --set HostName escarole.local
         *   $
         * </pre>
         *
         * Where "escarole" is your computer name (no spaces or punctuation). You
         * will be prompted for your password in order to modify the configuration.
         *
         * To reset OS-X to it's default behavior, do this:
         *
         * <pre>
         *   $ scutil --set HostName ""
         *   $
         * </pre>
         *
         * On OSX 10.10 (Yosemite), apple seems to have turned of DNS lookup for
         * .local addresses.
         *
         * https://discussions.apple.com/thread/6611817?start=13
         *
         * To fix this, you need to
         *
         * <pre>
         * sudo vi /etc/hosts
         * </pre>
         *
         * and change the line
         *
         * <pre>
         *   127.0.0.1       localhost
         * </pre>
         *
         * to
         *
         * <pre>
         *   127.0.0.1       localhost escarole.local
         * </pre>
         *
         * More robustly, the following "patch" fixes the JDI so that it uses the ip
         * address, rather than the hostname. The code is called from
         *
         * <pre>
         * com.sun.tools.jdi.SunCommandLineLauncher.launch ()
         * </pre>
         *
         * which calls
         *
         * <pre>
         * com.sun.tools.jdi.SocketTransportService.SocketListenKey.address ()
         * </pre>
         *
         * Here is the patch. Just compile this and put in your classpath before
         * tools.jar.
         *
         * <pre>
         * package com.sun.tools.jdi;
         *
         * import java.net.*;
         *
         * class SocketTransportService$SocketListenKey extends com.sun.jdi.connect.spi.TransportService.ListenKey {
         *     ServerSocket ss;
         *     SocketTransportService$SocketListenKey (ServerSocket ss) {
         *         this.ss = ss;
         *     }
         *     ServerSocket socket () {
         *         return ss;
         *     }
         *     public String toString () {
         *         return address ();
         *     }
         *
         *     // Returns the string representation of the address that this listen key represents.
         *     public String address () {
         *         InetAddress address = ss.getInetAddress ();
         *
         *         // If bound to the wildcard address then use current local hostname. In
         *         // the event that we don't know our own hostname then assume that host
         *         // supports IPv4 and return something to represent the loopback address.
         *         if (address.isAnyLocalAddress ()) {
         *             // JWR: Only change is to comment out the lines below
         *             // try {
         *             //     address = InetAddress.getLocalHost ();
         *             // } catch (UnknownHostException uhe) {
         *             byte[] loopback = { 0x7f, 0x00, 0x00, 0x01 };
         *             try {
         *                 address = InetAddress.getByAddress (&quot;127.0.0.1&quot;, loopback);
         *             } catch (UnknownHostException x) {
         *                 throw new InternalError (&quot;unable to get local hostname&quot;);
         *             }
         *             //  }
         *         }
         *
         *         // Now decide if we return a hostname or IP address. Where possible
         *         // return a hostname but in the case that we are bound to an address
         *         // that isn't registered in the name service then we return an address.
         *         String result;
         *         String hostname = address.getHostName ();
         *         String hostaddr = address.getHostAddress ();
         *         if (hostname.equals (hostaddr)) {
         *             if (address instanceof Inet6Address) {
         *                 result = &quot;[&quot; + hostaddr + &quot;]&quot;;
         *             } else {
         *                 result = hostaddr;
         *             }
         *         } else {
         *             result = hostname;
         *         }
         *
         *         // Finally return &quot;hostname:port&quot;, &quot;ipv4-address:port&quot; or &quot;[ipv6-address]:port&quot;.
         *         return result + &quot;:&quot; + ss.getLocalPort ();
         *     }
         * }
         * </pre>
         */
        private static String IN_DEBUGGER = "TraceDebuggingVMHasLaunched";
        private static boolean insideTestVM () {
                return System.getProperty (IN_DEBUGGER) != null;
        }
        /**
         * Prepares the args and then calls internalRun.
         */
        private static void internalPrepAndRun (String mainClassName, String[] args, boolean terminateAfter) {
                ArrayList<String> prefixArgs = getPrefixArgsForVm();
                int length = prefixArgs.size ();
                String[] allArgs = new String[length + args.length];
                for (int i = 0; i < length; i++)
                        allArgs[i] = prefixArgs.get (i);
                System.arraycopy (args, 0, allArgs, length, args.length);
                internalRun (mainClassName, allArgs, terminateAfter);
        }
        /**
         * This is the function that starts the JVM. If terminateAfter is true, then
         * the current thread is killed after the debug JVM terminates.
         */
        private static void internalRun (String mainClassName, String[] allArgs, boolean terminateAfter) {
                if (insideTestVM ()) return;
                Graphviz.setOutputDirectory (GRAPHVIZ_DIR, mainClassName);
                VirtualMachine vm = launchConnect (mainClassName, allArgs);
                monitorJVM (vm);
                if (terminateAfter) Thread.currentThread ().stop ();
        }

        /**
         * Possible location of java source files.  
         * By default this includes "src" (for eclipse) and
         * "src/main/java" (for maven).
         */
        public static void addPossibleSrcLocation (String value) {
                POSSIBLE_SRC_LOCATIONS.add (value);
        }
        protected static ArrayList<String> POSSIBLE_SRC_LOCATIONS;
        static {
                POSSIBLE_SRC_LOCATIONS = new ArrayList<>();
                POSSIBLE_SRC_LOCATIONS.add("src");
                POSSIBLE_SRC_LOCATIONS.add("src" + File.separator + "main" + File.separator + "java");
        }
        
        /**
         * Possible location of binary class files.  
         * By default this includes the system classpath, 
         * "./bin" (for eclipse), "./target/classes" (for maven), and ".".
         */
        public static void addPossibleBinLocation (String value) {
                POSSIBLE_BIN_LOCATIONS.add (value);
        }
        protected static ArrayList<String> POSSIBLE_BIN_LOCATIONS;
        static {
                POSSIBLE_BIN_LOCATIONS = new ArrayList<>();
                POSSIBLE_BIN_LOCATIONS.add(System.getProperty("java.class.path"));
                POSSIBLE_BIN_LOCATIONS.add(System.getProperty("user.dir") + File.separator + "bin");
                POSSIBLE_BIN_LOCATIONS.add(System.getProperty("user.dir") + File.separator + "target" + File.separator + "classes");
        }
        protected static ArrayList<String> getPrefixArgsForVm() {
                var cp = new StringBuilder();
                for (var s : POSSIBLE_BIN_LOCATIONS) {
                        cp.append(s);
                        cp.append(File.pathSeparator);
                }
                cp.append(".");

                var result = new ArrayList<String>();
                result.add("-cp");
                result.add(cp.toString());

                for (var s : PREFIX_ARGS_FOR_VM) {
                        result.add(s);
                }
                return result;
        }
        /**
         * Prefix options for the debugger VM. By default, the classpath is set to
         * the current classpath. Other options can be provided here.
         */
        public static void addPrefixOptionsForVm (String value) {
                PREFIX_ARGS_FOR_VM.add (value);
        }
        protected static ArrayList<String> PREFIX_ARGS_FOR_VM;
        static {
                PREFIX_ARGS_FOR_VM = new ArrayList<>();
                PREFIX_ARGS_FOR_VM.add ("-D" + IN_DEBUGGER + "=true");
                //for (Object key : System.getProperties().keySet()) {
                //      System.out.printf("%s=%s\n", key, System.getProperty((String)key));
                //}
                //System.out.printf("java.home=%s\n", System.getProperty("java.home"));
                //System.out.printf("java.class.path=%s\n", System.getProperty("java.class.path"));
        }
        /**
         * Turn on debugging information (default==false). Intended for developers.
         */
        public static void debug (boolean value) {
                DEBUG = value;
        }
        protected static boolean DEBUG = false;

        /**
         * Add an exclude pattern. Classes whose fully qualified name matches an
         * exclude pattern are ignored by the debugger. Regular expressions are
         * limited to exact matches and patterns that begin with '*' or end with
         * '*'; for example, "*.Foo" or "java.*". This limitation is inherited from
         * {@code com.sun.jdi.request.WatchpointRequest}. The default exclude
         * patterns include:
         *
         * <pre>
         *  "*$$Lambda$*" "java.*" "jdk.*" "sun.*"  "com.*"  "org.*"  "javax.*"  "apple.*"  "Jama.*"  "qs.*"
         *  "stdlib.A*" "stdlib.B*" "stdlib.C*" "stdlib.D*" "stdlib.E*" "stdlib.F*" "stdlib.G*" "stdlib.H*" 
         *  "stdlib.I*" "stdlib.J*" "stdlib.K*" "stdlib.L*" "stdlib.M*" "stdlib.N*" "stdlib.O*" "stdlib.P*" 
         *  "stdlib.Q*" "stdlib.R*" "stdlib.S*" 
         *  "stdlib.U*" "stdlib.V*" "stdlib.W*" "stdlib.X*" "stdlib.Y*" 
         * </pre>
         * 
         * The JDI excludes classes, but does not allow exceptions. This is
         * the reason for the unusual number of excludes for {@code
         * stdlib}. It is important that {@code stdlib.Trace} not be excluded
         * --- if it were, then callBacks to {@code Trace.draw} would
         * not function.  As a result, all classes in {@code stdlib}
         * that start with a letter other than {@code T} are excluded.
         * Be careful when adding classes to {@code stdlib}.
         *
         * Exclude patterns must include
         * 
         * <pre>
         *  "*$$Lambda$*" "java.*" "jdk.*" "sun.*"
         * </pre>
         * 
         * otherwise the Trace code itself will fail to run.
         */
        public static void addExcludePattern (String value) {
                EXCLUDE_GLOBS.add (value);
        }
        /**
         * Remove an exclude pattern.
         *
         * @see addExcludePattern
         */
        public static void removeExcludePattern (String value) {
                EXCLUDE_GLOBS.remove (value);
        }
        protected static HashSet<String> EXCLUDE_GLOBS;
        static {
                EXCLUDE_GLOBS = new HashSet<> ();
                EXCLUDE_GLOBS.add ("*$$Lambda$*");
                EXCLUDE_GLOBS.add ("java.*");
                EXCLUDE_GLOBS.add ("jdk.*");
                EXCLUDE_GLOBS.add ("sun.*");
                EXCLUDE_GLOBS.add ("com.*");
                EXCLUDE_GLOBS.add ("org.*");
                EXCLUDE_GLOBS.add ("javax.*");
                EXCLUDE_GLOBS.add ("apple.*");
                EXCLUDE_GLOBS.add ("Jama.*");
                EXCLUDE_GLOBS.add ("qs.*");
                EXCLUDE_GLOBS.add ("stdlib.A*");
                EXCLUDE_GLOBS.add ("stdlib.B*");
                EXCLUDE_GLOBS.add ("stdlib.C*");
                EXCLUDE_GLOBS.add ("stdlib.D*");
                EXCLUDE_GLOBS.add ("stdlib.E*");
                EXCLUDE_GLOBS.add ("stdlib.F*");
                EXCLUDE_GLOBS.add ("stdlib.G*");
                EXCLUDE_GLOBS.add ("stdlib.H*");
                EXCLUDE_GLOBS.add ("stdlib.I*");
                EXCLUDE_GLOBS.add ("stdlib.J*");
                EXCLUDE_GLOBS.add ("stdlib.K*");
                EXCLUDE_GLOBS.add ("stdlib.L*");
                EXCLUDE_GLOBS.add ("stdlib.M*");
                EXCLUDE_GLOBS.add ("stdlib.N*");
                EXCLUDE_GLOBS.add ("stdlib.O*");
                EXCLUDE_GLOBS.add ("stdlib.P*");
                EXCLUDE_GLOBS.add ("stdlib.Q*");
                EXCLUDE_GLOBS.add ("stdlib.R*");
                EXCLUDE_GLOBS.add ("stdlib.S*");
                EXCLUDE_GLOBS.add ("stdlib.U*");
                EXCLUDE_GLOBS.add ("stdlib.V*");
                EXCLUDE_GLOBS.add ("stdlib.W*");
                EXCLUDE_GLOBS.add ("stdlib.X*");
                EXCLUDE_GLOBS.add ("stdlib.Y*");
                //EXCLUDE_GLOBS.add ("stdlib.Z*");      
        }
        /**
         * Add an include pattern for drawing.  These are classes that should be shown in drawing and console logs, which would otherwise be excluded.
         * The default is:
         *
         * <pre>
         *  "java.util.*"
         * </pre>
         */
        public static void addDrawingIncludePattern (String value) {
                DRAWING_INCLUDE_GLOBS.add (value);
        }
        /**
         * Remove an include pattern.
         *
         * @see addDrawingIncludePattern
         */
        public static void removeDrawingIncludePattern (String value) {
                DRAWING_INCLUDE_GLOBS.remove (value);
        }
        protected static HashSet<String> DRAWING_INCLUDE_GLOBS;
        static {
                DRAWING_INCLUDE_GLOBS = new HashSet<> ();
                DRAWING_INCLUDE_GLOBS.add ("java.util.*");
        }
        
        /**
         * Clear the call tree, removing all previous entries.
         *
         * This is a stub method, which is trapped by the debugger. It only has an
         * effect if a variant of Trace.run() has been called to start the debugger.
         */
        private static void clearCallTree () { }  // See Printer. methodEntryEvent
        protected static final String CALLBACK_CLEAR_CALL_TREE = "clearCallTree";
        
        /**
         * When the debugged program ends, create a graphviz file showing the call tree (default==false).
         * NOT WORKING
         */
        private static void drawCallTree (boolean value) { SHOW_CALL_TREE = value; }
        protected static boolean SHOW_CALL_TREE = false;
        /**
         * Graphviz style for a call tree node.
         */
        private static void graphvizCallTreeBoxAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_ARRAY_BOX_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_CALL_TREE_BOX_ATTRIBUTES = ",shape=record";
        /**
         * Graphviz style for a call tree arrow.
         */
        private static void graphvizCallTreeArrowAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_ARRAY_ARROW_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_CALL_TREE_ARROW_ATTRIBUTES = ",fontsize=12";
        /**
         * Graphviz style for an array.
         */
        public static void graphvizArrayBoxAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_ARRAY_BOX_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_ARRAY_BOX_ATTRIBUTES = ",shape=record,color=blue";
        /**
         * Graphviz style for an arrow from an array to an Object.
         */
        public static void graphvizArrayArrowAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_ARRAY_ARROW_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_ARRAY_ARROW_ATTRIBUTES = ",fontsize=12,color=blue,arrowtail=dot,dir=both,tailclip=false";
        /**
         * Graphviz style for a frame.
         */
        public static void graphvizFrameBoxAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_FRAME_BOX_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_FRAME_BOX_ATTRIBUTES = ",shape=record,color=red";
        /**
         * Graphviz style for an arrow from a frame to an Object.
         */
        public static void graphvizFrameObjectArrowAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_FRAME_OBJECT_ARROW_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_FRAME_OBJECT_ARROW_ATTRIBUTES = ",fontsize=12,color=red";
        /**
         * Graphviz style for an arrow from a return value to a frame.
         */
        public static void graphvizFrameReturnAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_FRAME_RETURN_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_FRAME_RETURN_ATTRIBUTES = ",color=red";
        /**
         * Graphviz style for an arrow from an exception to a frame.
         */
        public static void graphvizFrameExceptionAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_FRAME_EXCEPTION_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_FRAME_EXCEPTION_ATTRIBUTES = ",color=red";
        /**
         * Graphviz style for an arrow from a frame to another frame.
         */
        public static void graphvizFrameFrameArrowAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_FRAME_FRAME_ARROW_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_FRAME_FRAME_ARROW_ATTRIBUTES = ",color=red,style=dashed";
        /**
         * Graphviz style for an object (non-array).
         */
        public static void graphvizObjectBoxAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_OBJECT_BOX_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_OBJECT_BOX_ATTRIBUTES = ",shape=record,color=purple";
        /**
         * Graphviz style for a wrapper object (in simple form).
         */
        public static void graphvizWrapperBoxAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_WRAPPER_BOX_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_WRAPPER_BOX_ATTRIBUTES = ",shape=ellipse,color=purple";
        /**
         * Graphviz style for a wrapper object (in simple form).
         */
        public static void graphvizNodeBoxAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_NODE_BOX_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_NODE_BOX_ATTRIBUTES = ",shape=box,style=\"rounded\",color=purple";
        /**
         * Graphviz style for an arrow from an object to an object.
         */
        public static void graphvizObjectArrowAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_OBJECT_ARROW_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_OBJECT_ARROW_ATTRIBUTES = ",fontsize=12,color=purple";
        /**
         * Extra Graphviz style for an arrow from an non-node to a node object.
         */
        public static void graphvizNodeArrowAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_NODE_ARROW_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_NODE_ARROW_ATTRIBUTES = ""; 
        // Intention was to set this to ",constraint=false", but this creates errors in running DOT on the resulting gv file.   
        /**
         * Graphviz style for a static class.
         */
        public static void graphvizStaticClassBoxAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_STATIC_CLASS_BOX_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_STATIC_CLASS_BOX_ATTRIBUTES = ",shape=record,color=orange";
        /**
         * Graphviz style for an arrow from a static class to an object.
         */
        public static void graphvizStaticClassArrowAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_STATIC_CLASS_ARROW_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_STATIC_CLASS_ARROW_ATTRIBUTES = ",fontsize=12,color=orange";
        /**
         * Graphviz style for box labels.
         */
        public static void graphvizLabelBoxAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_LABEL_BOX_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_LABEL_BOX_ATTRIBUTES = ",shape=none,color=black";
        /**
         * Graphviz style for arrow labels.
         */
        public static void graphvizLabelArrowAttributes (String value) {
                String v = (value == null || "".equals (value)) ? "" : "," + value;
                GRAPHVIZ_LABEL_ARROW_ATTRIBUTES = v;
        }
        protected static String GRAPHVIZ_LABEL_ARROW_ATTRIBUTES = ",color=black";

        // Graphiz execution
        /**
         * Add a filesystem location to search for the dot executable that comes
         * with graphviz. The default is system dependent.
         */
        public static void graphvizAddPossibleDotLocation (String value) {
                GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add (value);
        }
        protected static ArrayList<String> GRAPHVIZ_POSSIBLE_DOT_LOCATIONS;
        static {
                GRAPHVIZ_POSSIBLE_DOT_LOCATIONS = new ArrayList<> ();
                String os = System.getProperty ("os.name").toLowerCase ();
                if (os.startsWith ("win")) {
                        GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add ("c:/Program Files (x86)/Graphviz2.38/bin/dot.exe");         // installer 32 bit
                        GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add ("c:/Program Files/Graphviz/bin/dot.exe");                   // installer 64 bit
                        GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add ("c:/ProgramData/chocolatey/bin/dot.exe");                   // choco
                        GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add (System.getProperty ("user.home") + "/scoop/shims/dot.exe"); // scoop
                        GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add (System.getProperty ("user.dir") + "/lib/graphviz-windows/bin/dot.exe");
                } else if (os.startsWith ("mac")) {
                        GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add ("/opt/homebrew/bin/dot"); // homebrew
                        GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add ("/opt/local/bin/dot");    // macports 
                        GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add ("/usr/local/bin/dot");    // homebrew
                        GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add ("/usr/bin/dot");          // native
                        GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add (System.getProperty ("user.dir") + "/lib/graphviz-mac/bin/dot");
                } else {
                        GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add ("/usr/local/bin/dot");
                        GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add ("/usr/bin/dot");
                }
                // Annoyingly, the PATH is usually not what you want when running inside an IDE like eclipse, thus the nonsense above.
                String[] paths = System.getenv ("PATH").split(File.pathSeparator);
                for (String p : paths) 
                        GRAPHVIZ_POSSIBLE_DOT_LOCATIONS.add (p + File.separator + "dot");
        }
        /**
         * Remove graphviz files for which graphic files have been successfully
         * generated.
         */
        public static void graphvizRemoveGvFiles (boolean value) {
                GRAPHVIZ_REMOVE_GV_FILES = value;
        }
        protected static boolean GRAPHVIZ_REMOVE_GV_FILES = true;

        /**
         * Add classname to be drawn as a simple oval, with null as a dot.
         * Any classname with value as a suffix will be treated as a Node.
         * Default value includes "Node".
         */
        public static void graphvizAddNodeClass (String value) {
                GRAPHVIZ_NODE_CLASS.add (value);
        }
        /**
         * Remove a node class.
         *
         * @see graphvizAddNodeClass
         */
        public static void graphvizRemoveNodeClass (String value) {
                GRAPHVIZ_NODE_CLASS.remove (value);
        }
        /**
         * Remove all node classes.
         *
         * @see graphvizAddNodeClass
         */
        public static void showNodesAsRegularObjects () {
                GRAPHVIZ_NODE_CLASS = new ArrayList<> ();
        }
        protected static ArrayList<String> GRAPHVIZ_NODE_CLASS;
        static {
                GRAPHVIZ_NODE_CLASS = new ArrayList<> ();       
                GRAPHVIZ_NODE_CLASS.add ("Node");
        }
        /**
         * Show fully qualified class names (default==false). If
         * showPackageInClassName is true, then showOuterClassInClassName is ignored
         * (taken to be true).
         */
        public static void showPackageInClassName (boolean value) {
                SHOW_PACKAGE_IN_CLASS_NAME = value;
        }
        protected static boolean SHOW_PACKAGE_IN_CLASS_NAME = false;
        /**
         * Show static classes (default==true). 
         */
        public static void showStaticClasses (boolean value) {
                GRAPHVIZ_SHOW_STATIC_CLASSES = value;
        }
        protected static boolean GRAPHVIZ_SHOW_STATIC_CLASSES = true;
        /**
         * Include fully qualified class names (default==false).
         */
        public static void showOuterClassInClassName (boolean value) {
                SHOW_OUTER_CLASS_IN_CLASS_NAME = value;
        }
        protected static boolean SHOW_OUTER_CLASS_IN_CLASS_NAME = false;
        /**
         * Show the object type in addition to its id (default==false).
         */
        public static void consoleShowTypeInObjectName (boolean value) {
                CONSOLE_SHOW_TYPE_IN_OBJECT_NAME = value;
        }
        protected static boolean CONSOLE_SHOW_TYPE_IN_OBJECT_NAME = false;
        /**
         * The maximum number of displayed fields when printing an object on the
         * console (default==8).
         */
        public static void consoleMaxFields (int value) {
                CONSOLE_MAX_FIELDS = value;
        }
        protected static int CONSOLE_MAX_FIELDS = 8;
        /**
         * The maximum number of displayed elements when printing a primitive array
         * on the console (default==15).
         */
        public static void consoleMaxArrayElementsPrimitive (int value) {
                CONSOLE_MAX_ARRAY_ELEMENTS_PRIMITIVE = value;
        }
        protected static int CONSOLE_MAX_ARRAY_ELEMENTS_PRIMITIVE = 15;
        /**
         * The maximum number of displayed elements when printing an object array on
         * the console (default==8).
         */
        public static void consoleMaxArrayElementsObject (int value) {
                CONSOLE_MAX_ARRAY_ELEMENTS_OBJECT = value;
        }
        protected static int CONSOLE_MAX_ARRAY_ELEMENTS_OBJECT = 8;
        /**
         * Show object ids inside multidimensional arrays (default==false).
         */
        public static void consoleShowNestedArrayIds (boolean value) {
                CONSOLE_SHOW_NESTED_ARRAY_IDS = value;
        }
        protected static boolean CONSOLE_SHOW_NESTED_ARRAY_IDS = false;
        /**
         * Show fields introduced by the compiler (default==true);
         */
        public static void showSyntheticFields (boolean value) {
                SHOW_SYNTHETIC_FIELDS = value;
        }
        protected static boolean SHOW_SYNTHETIC_FIELDS = true;
        /**
         * Show methods introduced by the compiler (default==true);
         */
        public static void showSyntheticMethods (boolean value) {
                SHOW_SYNTHETIC_METHODS = value;
        }
        protected static boolean SHOW_SYNTHETIC_METHODS = true;
        /**
         * Show file names on the console (default==false).
         */
        public static void showFilenamesOnConsole (boolean value) {
                GRAPHVIZ_SHOW_FILENAMES_ON_CONSOLE = value;
        }
        protected static boolean GRAPHVIZ_SHOW_FILENAMES_ON_CONSOLE = false;
        /**
         * In graphviz, show field name in the label of an object (default==true).
         */
        public static void showFieldNamesInLabels (boolean value) {
                GRAPHVIZ_SHOW_FIELD_NAMES_IN_LABELS = value;
        }
        protected static boolean GRAPHVIZ_SHOW_FIELD_NAMES_IN_LABELS = true;
        /**
         * In graphviz, show field name in the label of a node object (default==false).
         */
        public static void showFieldNamesInNodeLabels (boolean value) {
                GRAPHVIZ_SHOW_FIELD_NAMES_IN_NODE_LABELS = value;
        }
        protected static boolean GRAPHVIZ_SHOW_FIELD_NAMES_IN_NODE_LABELS = false;
        /**
         * In graphviz, show field name on the arrow of a node object (default==true).
         */
        public static void showFieldNamesInNodeArrows (boolean value) {
                GRAPHVIZ_SHOW_FIELD_NAMES_IN_NODE_ARROWS = value;
        }
        protected static boolean GRAPHVIZ_SHOW_FIELD_NAMES_IN_NODE_ARROWS = true;
        /**
         * In graphviz, show object ids (default==false).
         */
        public static void showObjectIds (boolean value) {
                GRAPHVIZ_SHOW_OBJECT_IDS = value;
        }
        protected static boolean GRAPHVIZ_SHOW_OBJECT_IDS = false;
        /**
         * In graphviz, show object ids and redundant variables for arrows (default==false).
         * This also sets showBuiltInObjects to value.
         */
        public static void showObjectIdsRedundantly (boolean value) {
                Trace.showBuiltInObjects(value);
                GRAPHVIZ_SHOW_OBJECT_IDS = value;
                GRAPHVIZ_SHOW_OBJECT_IDS_REDUNDANTLY = value;
        }
        protected static boolean GRAPHVIZ_SHOW_OBJECT_IDS_REDUNDANTLY = false;
        /**
         * In graphviz, show stack frame numbers (default==true).
         */
        public static void showFrameNumbers (boolean value) {
                GRAPHVIZ_SHOW_FRAME_NUMBERS = value;
        }
        protected static boolean GRAPHVIZ_SHOW_FRAME_NUMBERS = true;
        /**
         * In graphviz, show null fields (default==true).
         */
        public static void showNullFields (boolean value) {
                GRAPHVIZ_SHOW_NULL_FIELDS = value;
        }
        protected static boolean GRAPHVIZ_SHOW_NULL_FIELDS = true;
        /**
         * In graphviz, show null variables (default==true).
         */
        public static void showNullVariables (boolean value) {
                GRAPHVIZ_SHOW_NULL_VARIABLES = value;
        }
        protected static boolean GRAPHVIZ_SHOW_NULL_VARIABLES = true;
        /**
         * Include line number in graphviz filename (default==true).
         */
        public static void graphvizPutLineNumberInFilename (boolean value) {
                GRAPHVIZ_PUT_LINE_NUMBER_IN_FILENAME = value;
        }
        protected static boolean GRAPHVIZ_PUT_LINE_NUMBER_IN_FILENAME = true;
        /**
         * Do not display any fields with this name (default includes only
         * "$assertionsDisabled").
         */
        public static void addGraphvizIgnoredFields (String value) {
                GRAPHVIZ_IGNORED_FIELDS.add (value);
        }
        protected static ArrayList<String> GRAPHVIZ_IGNORED_FIELDS;
        static {
                GRAPHVIZ_IGNORED_FIELDS = new ArrayList<> ();
                GRAPHVIZ_IGNORED_FIELDS.add ("$assertionsDisabled");
        }
        /**
         * Set the graphviz attributes for objects of the given class.
         */
        public static void graphvizSetObjectAttribute (Class<?> cz, String attrib) {
                Graphviz.objectAttributeMap.put (cz.getName (), attrib);
        }
        /**
         * Set the graphviz attributes for objects of the given class.
         */
        public static void graphvizSetStaticClassAttribute (Class<?> cz, String attrib) {
                Graphviz.staticClassAttributeMap.put (cz.getName (), attrib);
        }
        /**
         * Set the graphviz attributes for frames of the given class.
         */
        public static void graphvizSetFrameAttribute (Class<?> cz, String attrib) {
                Graphviz.frameAttributeMap.put (cz.getName (), attrib);
        }
        /**
         * Set the graphviz attributes for all fields with the given name.
         */
        public static void graphvizSetFieldAttribute (String field, String attrib) {
                Graphviz.fieldAttributeMap.put (field, attrib);
        }
        protected static String BAD_ERROR_MESSAGE = "\n!!!! This shouldn't happen! \n!!!! Please contact your instructor or the author of " + Trace.class.getCanonicalName ();

        // ---------------------- Launch the JVM  ----------------------------------

        // Set up a launching connection to the JVM
        private static VirtualMachine launchConnect (String mainClassName, String[] args) {
                // concatenate all the tracer's input arguments into a single string
                StringBuffer sb = new StringBuffer ();
                for (int i = 0; i < args.length; i++) {
                        sb.append ("\"" + args[i]+ "\" ");
                }
                String argsString = sb.toString ();

                LaunchingConnector conn = null;
                Map<String, ? extends Argument> connArgs = null;

                if (Graphviz.isWindows()) {
                        conn = Bootstrap.virtualMachineManager ().defaultConnector(); //"com.sun.jdi.CommandLineLaunch"
                        try {
                                connArgs = conn.defaultArguments ();
                                connArgs.get ("main").setValue (mainClassName);
                                connArgs.get ("options").setValue (argsString);
                                System.out.println(connArgs);
                                //TODO print default arguments (it's a map) and find the classpath
                        } catch (NullPointerException e) {
                                throw new Error ("\n!!!! Bad launching connector");
                        }

                } else {
                        // The default launcher works fine for windows, which uses shared memory
                        // for communication between the processes.
                        // The default launcher fails on unix-like systems, which uses sockets
                        // for communication between the processes.
                        // In particular, the communication is set up using hostname; this causes 
                        // communication to fail when the hostname is not routable in DNS or /etc/hosts
                        // The problem is in the file com/sun/tools/jdiSocketTransportService$SocketListenKey.java
                        // To fix, you just need to comment out the try block with "address = InetAddress.getLocalHost ();"
                        // As of Java 9, this fix is not available to outsiders, due to the module system
                        //                      
                        // The use of the raw launcher here is reverse engineered from 
                        //  com.sun.tools.jdi.SunCommandLineLauncher
                        //  com.sun.tools.jdi.RawCommandLineLauncher
                        //
                        // The raw connector has these attributes:
                        //   command = "" : Raw command to start the debugged application VM
                        //   address = "" : Address from which to listen for a connection after the raw command is run
                        //   quote = "\"" : Character used to combine space-delimited text into a single command line argument
                        //
                        // The default connector has these attributes:
                        //   home = System.getProperty("java.home") : Home directory of the SDK or runtime environment used to launch the application
                        //   options = ""    : Launched VM options
                        //   main = ""       : Main class and arguments, or if -jar is an option, the main jar file and arguments
                        //   suspend = true  : All threads will be suspended before execution of main
                        //   quote = "\""    : Character used to combine space-delimited text into a single command line argument
                        //   vmexec = "java" : Name of the Java VM launcher
                        String fs = System.getProperty ("file.separator");
                        String command = 
                                        "\"" + System.getProperty ("java.home") + fs + "bin" + fs + "java" + "\" " +
                                                        "-Xdebug " +
                                                        "-Xrunjdwp:transport=dt_socket,address=127.0.0.1:8900,suspend=y " + 
                                                        argsString +
                                                        " " +
                                                        mainClassName +
                                                        "";
                        //System.out.println (command);
                        for (LaunchingConnector lc : Bootstrap.virtualMachineManager ().launchingConnectors ()) {
                                if (lc.name ().equals ("com.sun.jdi.RawCommandLineLaunch")) conn = lc;
                        }
                        try {
                                connArgs = conn.defaultArguments ();
                                connArgs.get ("command").setValue (command);
                                connArgs.get ("address").setValue ("127.0.0.1:8900");
                        } catch (NullPointerException e) {
                                throw new Error ("\n!!!! Bad launching connector");
                        }
                }

                VirtualMachine vm = null;
                try {
                        vm = conn.launch (connArgs); // launch the JVM and connect to it
                } catch (IOException e) {
                        throw new Error ("\n!!!! Unable to launch JVM: " + e);
                } catch (IllegalConnectorArgumentsException e) {
                        throw new Error ("\n!!!! Internal error: " + e);
                } catch (VMStartException e) {
                        throw new Error ("\n!!!! JVM failed to start: " + e.getMessage ());
                }

                return vm;
        }

        // monitor the JVM running the application
        private static void monitorJVM (VirtualMachine vm) {
                // start JDI event handler which displays trace info
                JDIEventMonitor watcher = new JDIEventMonitor (vm);
                watcher.start ();

                // redirect VM's output and error streams to the system output and error streams
                Process process = vm.process ();
                Thread errRedirect = new StreamRedirecter ("error reader", process.getErrorStream (), System.err);
                Thread outRedirect = new StreamRedirecter ("output reader", process.getInputStream (), System.out);
                errRedirect.start ();
                outRedirect.start ();

                vm.resume (); // start the application

                try {
                        watcher.join (); // Wait. Shutdown begins when the JDI watcher terminates
                        errRedirect.join (); // make sure all the stream outputs have been forwarded before we exit
                        outRedirect.join ();
                } catch (InterruptedException e) {}
        }
}

/**
 * StreamRedirecter is a thread which copies it's input to it's output and
 * terminates when it completes.
 *
 * @author Robert Field, September 2005
 * @author Andrew Davison, March 2009, ad@fivedots.coe.psu.ac.th
 */
/* private static */class StreamRedirecter extends Thread {
        private static final int BUFFER_SIZE = 2048;
        private final Reader in;
        private final Writer out;

        public StreamRedirecter (String name, InputStream in, OutputStream out) {
                super (name);
                this.in = new InputStreamReader (in); // stream to copy from
                this.out = new OutputStreamWriter (out); // stream to copy to
                setPriority (Thread.MAX_PRIORITY - 1);
        }

        // copy BUFFER_SIZE chars at a time
        public void run () {
                try {
                        char[] cbuf = new char[BUFFER_SIZE];
                        int count;
                        while ((count = in.read (cbuf, 0, BUFFER_SIZE)) >= 0)
                                out.write (cbuf, 0, count);
                        out.flush ();
                } catch (IOException e) {
                        System.err.println ("StreamRedirecter: " + e);
                }
        }

}

/**
 * Monitor incoming JDI events for a program running in the JVM and print out
 * trace/debugging information.
 *
 * This is a simplified version of EventThread.java from the Trace.java example
 * in the demo/jpda/examples.jar file in the JDK.
 *
 * Andrew Davison: The main addition is the use of the ShowCodes and ShowLines
 * classes to list the line being currently executed.
 *
 * James Riely: See comments in class Trace.
 *
 * @author Robert Field and Minoru Terada, September 2005
 * @author Iman_S, June 2008
 * @author Andrew Davison, ad@fivedots.coe.psu.ac.th, March 2009
 * @author James Riely, jriely@cs.depaul.edu, August 2014
 */
/* private static */class JDIEventMonitor extends Thread {
        // exclude events generated for these classes
        private final VirtualMachine vm; // the JVM
        private boolean connected = true; // connected to VM?
        private boolean vmDied; // has VM death occurred?
        private final JDIEventHandler printer = new Printer ();

        public JDIEventMonitor (VirtualMachine jvm) {
                super ("JDIEventMonitor");
                vm = jvm;
                setEventRequests ();
        }

        // Create and enable the event requests for the events we want to monitor in
        // the running program.
        //
        // Created here:
        //
        //    createThreadStartRequest()
        //    createThreadDeathRequest()
        //    createClassPrepareRequest()
        //    createClassUnloadRequest()
        //    createMethodEntryRequest()
        //    createMethodExitRequest()
        //    createExceptionRequest(ReferenceType refType, boolean notifyCaught, boolean notifyUncaught)
        //    createMonitorContendedEnterRequest()
        //    createMonitorContendedEnteredRequest()
        //    createMonitorWaitRequest()
        //    createMonitorWaitedRequest()
        //
        // Created when class is loaded:
        //
        //    createModificationWatchpointRequest(Field field)
        //
        // Created when thread is started:
        //
        //    createStepRequest(ThreadReference thread, int size, int depth)
        //
        // Unused:
        //
        //    createAccessWatchpointRequest(Field field)
        //    createBreakpointRequest(Location location)
        //
        // Unnecessary:
        //
        //    createVMDeathRequest() // these happen even without being requested
        //
        private void setEventRequests () {
                EventRequestManager mgr = vm.eventRequestManager ();
                {
                        ThreadStartRequest x = mgr.createThreadStartRequest (); // report thread starts
                        x.enable ();
                }
                {
                        ThreadDeathRequest x = mgr.createThreadDeathRequest (); // report thread deaths
                        x.enable ();
                }
                {
                        ClassPrepareRequest x = mgr.createClassPrepareRequest (); // report class loads
                        for (String s : Trace.EXCLUDE_GLOBS)
                                x.addClassExclusionFilter (s);
                        // x.setSuspendPolicy(EventRequest.SUSPEND_ALL);
                        x.enable ();
                }
                {
                        ClassUnloadRequest x = mgr.createClassUnloadRequest (); // report class unloads
                        for (String s : Trace.EXCLUDE_GLOBS)
                                x.addClassExclusionFilter (s);
                        // x.setSuspendPolicy(EventRequest.SUSPEND_ALL);
                        x.enable ();
                }
                {
                        MethodEntryRequest x = mgr.createMethodEntryRequest (); // report method entries
                        for (String s : Trace.EXCLUDE_GLOBS)
                                x.addClassExclusionFilter (s);
                        x.setSuspendPolicy (EventRequest.SUSPEND_EVENT_THREAD);
                        x.enable ();
                }
                {
                        MethodExitRequest x = mgr.createMethodExitRequest (); // report method exits
                        for (String s : Trace.EXCLUDE_GLOBS)
                                x.addClassExclusionFilter (s);
                        x.setSuspendPolicy (EventRequest.SUSPEND_EVENT_THREAD);
                        x.enable ();
                }
                {
                        ExceptionRequest x = mgr.createExceptionRequest (null, true, true); // report all exceptions, caught and uncaught
                        for (String s : Trace.EXCLUDE_GLOBS)
                                x.addClassExclusionFilter (s);
                        x.setSuspendPolicy (EventRequest.SUSPEND_EVENT_THREAD);
                        x.enable ();
                }
                {
                        MonitorContendedEnterRequest x = mgr.createMonitorContendedEnterRequest ();
                        for (String s : Trace.EXCLUDE_GLOBS)
                                x.addClassExclusionFilter (s);
                        x.setSuspendPolicy (EventRequest.SUSPEND_EVENT_THREAD);
                        x.enable ();
                }
                {
                        MonitorContendedEnteredRequest x = mgr.createMonitorContendedEnteredRequest ();
                        for (String s : Trace.EXCLUDE_GLOBS)
                                x.addClassExclusionFilter (s);
                        x.setSuspendPolicy (EventRequest.SUSPEND_EVENT_THREAD);
                        x.enable ();
                }
                {
                        MonitorWaitRequest x = mgr.createMonitorWaitRequest ();
                        for (String s : Trace.EXCLUDE_GLOBS)
                                x.addClassExclusionFilter (s);
                        x.setSuspendPolicy (EventRequest.SUSPEND_EVENT_THREAD);
                        x.enable ();
                }
                {
                        MonitorWaitedRequest x = mgr.createMonitorWaitedRequest ();
                        for (String s : Trace.EXCLUDE_GLOBS)
                                x.addClassExclusionFilter (s);
                        x.setSuspendPolicy (EventRequest.SUSPEND_EVENT_THREAD);
                        x.enable ();
                }
        }

        // process JDI events as they arrive on the event queue
        public void run () {
                EventQueue queue = vm.eventQueue ();
                while (connected) {
                        try {
                                EventSet eventSet = queue.remove ();
                                for (Event event : eventSet)
                                        handleEvent (event);
                                eventSet.resume ();
                        } catch (InterruptedException e) {
                                // Ignore
                        } catch (VMDisconnectedException discExc) {
                                handleDisconnectedException ();
                                break;
                        }
                }
                printer.printCallTree ();
        }

        // process a JDI event
        private void handleEvent (Event event) {
                if (Trace.DEBUG) System.err.print (event.getClass ().getSimpleName ().replace ("EventImpl", ""));

                // step event -- a line of code is about to be executed
                if (event instanceof StepEvent) {
                        stepEvent ((StepEvent) event);
                        return;
                }

                // modified field event  -- a field is about to be changed
                if (event instanceof ModificationWatchpointEvent) {
                        modificationWatchpointEvent ((ModificationWatchpointEvent) event);
                        return;
                }

                // method events
                if (event instanceof MethodEntryEvent) {
                        methodEntryEvent ((MethodEntryEvent) event);
                        return;
                }
                if (event instanceof MethodExitEvent) {
                        methodExitEvent ((MethodExitEvent) event);
                        return;
                }
                if (event instanceof ExceptionEvent) {
                        exceptionEvent ((ExceptionEvent) event);
                        return;
                }

                // monitor events
                if (event instanceof MonitorContendedEnterEvent) {
                        monitorContendedEnterEvent ((MonitorContendedEnterEvent) event);
                        return;
                }
                if (event instanceof MonitorContendedEnteredEvent) {
                        monitorContendedEnteredEvent ((MonitorContendedEnteredEvent) event);
                        return;
                }
                if (event instanceof MonitorWaitEvent) {
                        monitorWaitEvent ((MonitorWaitEvent) event);
                        return;
                }
                if (event instanceof MonitorWaitedEvent) {
                        monitorWaitedEvent ((MonitorWaitedEvent) event);
                        return;
                }

                // class events
                if (event instanceof ClassPrepareEvent) {
                        classPrepareEvent ((ClassPrepareEvent) event);
                        return;
                }
                if (event instanceof ClassUnloadEvent) {
                        classUnloadEvent ((ClassUnloadEvent) event);
                        return;
                }

                // thread events
                if (event instanceof ThreadStartEvent) {
                        threadStartEvent ((ThreadStartEvent) event);
                        return;
                }
                if (event instanceof ThreadDeathEvent) {
                        threadDeathEvent ((ThreadDeathEvent) event);
                        return;
                }

                // VM events
                if (event instanceof VMStartEvent) {
                        vmStartEvent ((VMStartEvent) event);
                        return;
                }
                if (event instanceof VMDeathEvent) {
                        vmDeathEvent ((VMDeathEvent) event);
                        return;
                }
                if (event instanceof VMDisconnectEvent) {
                        vmDisconnectEvent ((VMDisconnectEvent) event);
                        return;
                }

                throw new Error ("\n!!!! Unexpected event type: " + event.getClass ().getCanonicalName ());
        }

        // A VMDisconnectedException has occurred while dealing with another event.
        // Flush the event queue, dealing only with exit events (VMDeath,
        // VMDisconnect) so that things terminate correctly.
        private synchronized void handleDisconnectedException () {
                EventQueue queue = vm.eventQueue ();
                while (connected) {
                        try {
                                EventSet eventSet = queue.remove ();
                                for (Event event : eventSet) {
                                        if (event instanceof VMDeathEvent) vmDeathEvent ((VMDeathEvent) event);
                                        else if (event instanceof VMDisconnectEvent) vmDisconnectEvent ((VMDisconnectEvent) event);
                                }
                                eventSet.resume (); // resume the VM
                        } catch (InterruptedException e) {
                                // ignore
                        } catch (VMDisconnectedException e) {
                                // ignore
                        }
                }
        }

        // ---------------------- VM event handling ----------------------------------

        // Notification of initialization of a target VM. This event is received
        // before the main thread is started and before any application code has
        // been executed.
        private void vmStartEvent (VMStartEvent event) {
                vmDied = false;
                printer.vmStartEvent (event);
        }

        // Notification of VM termination
        private void vmDeathEvent (VMDeathEvent event) {
                vmDied = true;
                printer.vmDeathEvent (event);
        }

        // Notification of disconnection from the VM, either through normal
        // termination or because of an exception/error.
        private void vmDisconnectEvent (VMDisconnectEvent event) {
                connected = false;
                if (!vmDied) printer.vmDisconnectEvent (event);
        }

        // -------------------- class event handling  ---------------

        // a new class has been loaded
        private void classPrepareEvent (ClassPrepareEvent event) {
                ReferenceType type = event.referenceType ();
                String typeName = type.name ();
                if (Trace.CALLBACK_CLASS_NAME.equals (typeName) || Trace.GRAPHVIZ_CLASS_NAME.equals (typeName)) return;
                List<Field> fields = type.fields ();

                // register field modification events
                EventRequestManager mgr = vm.eventRequestManager ();
                for (Field field : fields) {
                        ModificationWatchpointRequest req = mgr.createModificationWatchpointRequest (field);
                        for (String s : Trace.EXCLUDE_GLOBS)
                                req.addClassExclusionFilter (s);
                        req.setSuspendPolicy (EventRequest.SUSPEND_NONE);
                        req.enable ();
                }
                printer.classPrepareEvent (event);

        }
        // a class has been unloaded
        private void classUnloadEvent (ClassUnloadEvent event) {
                if (!vmDied) printer.classUnloadEvent (event);
        }

        // -------------------- thread event handling  ---------------

        // a new thread has started running -- switch on single stepping
        private void threadStartEvent (ThreadStartEvent event) {
                ThreadReference thr = event.thread ();
                if (Format.ignoreThread (thr)) return;
                EventRequestManager mgr = vm.eventRequestManager ();

                StepRequest sr = mgr.createStepRequest (thr, StepRequest.STEP_LINE, StepRequest.STEP_INTO);
                sr.setSuspendPolicy (EventRequest.SUSPEND_EVENT_THREAD);

                for (String s : Trace.EXCLUDE_GLOBS)
                        sr.addClassExclusionFilter (s);
                sr.enable ();
                printer.threadStartEvent (event);
        }

        // the thread is about to terminate
        private void threadDeathEvent (ThreadDeathEvent event) {
                ThreadReference thr = event.thread ();
                if (Format.ignoreThread (thr)) return;
                printer.threadDeathEvent (event);
        }

        // -------------------- delegated --------------------------------

        private void methodEntryEvent (MethodEntryEvent event) {
                printer.methodEntryEvent (event);
        }
        private void methodExitEvent (MethodExitEvent event) {
                printer.methodExitEvent (event);
        }
        private void exceptionEvent (ExceptionEvent event) {
                printer.exceptionEvent (event);
        }
        private void stepEvent (StepEvent event) {
                printer.stepEvent (event);
        }
        private void modificationWatchpointEvent (ModificationWatchpointEvent event) {
                printer.modificationWatchpointEvent (event);
        }
        private void monitorContendedEnterEvent (MonitorContendedEnterEvent event) {
                printer.monitorContendedEnterEvent (event);
        }
        private void monitorContendedEnteredEvent (MonitorContendedEnteredEvent event) {
                printer.monitorContendedEnteredEvent (event);
        }
        private void monitorWaitEvent (MonitorWaitEvent event) {
                printer.monitorWaitEvent (event);
        }
        private void monitorWaitedEvent (MonitorWaitedEvent event) {
                printer.monitorWaitedEvent (event);
        }
}

/**
 * Printer for events. Prints and updates the ValueMap. Handles Graphviz drawing
 * requests.
 *
 * @author James Riely, jriely@cs.depaul.edu, August 2014
 */
/* private static */interface IndentPrinter {
        public void println (ThreadReference thr, String string);
}

/* private static */interface JDIEventHandler {
        public void printCallTree ();
        /** Notification of target VM termination. */
        public void vmDeathEvent (VMDeathEvent event);
        /** Notification of disconnection from target VM. */
        public void vmDisconnectEvent (VMDisconnectEvent event);
        /** Notification of initialization of a target VM. */
        public void vmStartEvent (VMStartEvent event);
        /** Notification of a new running thread in the target VM. */
        public void threadStartEvent (ThreadStartEvent event);
        /** Notification of a completed thread in the target VM. */
        public void threadDeathEvent (ThreadDeathEvent event);
        /** Notification of a class prepare in the target VM. */
        public void classPrepareEvent (ClassPrepareEvent event);
        /** Notification of a class unload in the target VM. */
        public void classUnloadEvent (ClassUnloadEvent event);
        /** Notification of a field access in the target VM. */
        //public void accessWatchpointEvent (AccessWatchpointEvent event);
        /** Notification of a field modification in the target VM. */
        public void modificationWatchpointEvent (ModificationWatchpointEvent event);
        /** Notification of a method invocation in the target VM. */
        public void methodEntryEvent (MethodEntryEvent event);
        /** Notification of a method return in the target VM. */
        public void methodExitEvent (MethodExitEvent event);
        /** Notification of an exception in the target VM. */
        public void exceptionEvent (ExceptionEvent event);
        /** Notification of step completion in the target VM. */
        public void stepEvent (StepEvent event);
        /** Notification of a breakpoint in the target VM. */
        //public void breakpointEvent (BreakpointEvent event);
        /**
         * Notification that a thread in the target VM is attempting to enter a
         * monitor that is already acquired by another thread.
         */
        public void monitorContendedEnterEvent (MonitorContendedEnterEvent event);
        /**
         * Notification that a thread in the target VM is entering a monitor after
         * waiting for it to be released by another thread.
         */
        public void monitorContendedEnteredEvent (MonitorContendedEnteredEvent event);
        /**
         * Notification that a thread in the target VM is about to wait on a monitor
         * object.
         */
        public void monitorWaitEvent (MonitorWaitEvent event);
        /**
         * Notification that a thread in the target VM has finished waiting on an
         * monitor object.
         */
        public void monitorWaitedEvent (MonitorWaitedEvent event);
}

/* private static */class Printer implements IndentPrinter, JDIEventHandler {
        private final Set<ReferenceType> staticClasses = new HashSet<> ();
        private final Map<ThreadReference, Value> returnValues = new HashMap<> ();
        private final Map<ThreadReference, Value> exceptionsMap = new HashMap<> ();
        private final ValueMap values = new ValueMap ();
        private final CodeMap codeMap = new CodeMap ();
        private final InsideIgnoredMethodMap boolMap = new InsideIgnoredMethodMap ();

        public void monitorContendedEnterEvent (MonitorContendedEnterEvent event) {}
        public void monitorContendedEnteredEvent (MonitorContendedEnteredEvent event) {}
        public void monitorWaitEvent (MonitorWaitEvent event) {}
        public void monitorWaitedEvent (MonitorWaitedEvent event) {}

        public void vmStartEvent (VMStartEvent event) {
                if (Trace.CONSOLE_SHOW_THREADS) println ("|||| VM Started");
        }
        public void vmDeathEvent (VMDeathEvent event) {
                if (Trace.CONSOLE_SHOW_THREADS) println ("|||| VM Stopped");
        }
        public void vmDisconnectEvent (VMDisconnectEvent event) {
                if (Trace.CONSOLE_SHOW_THREADS) println ("|||| VM Disconnected application");
        }
        public void threadStartEvent (ThreadStartEvent event) {
                ThreadReference thr = event.thread ();
                values.stackCreate (thr);
                boolMap.addThread (thr);
                if (Trace.CONSOLE_SHOW_THREADS) println ("|||| thread started: " + thr.name ());
        }
        public void threadDeathEvent (ThreadDeathEvent event) {
                ThreadReference thr = event.thread ();
                values.stackDestroy (thr);
                boolMap.removeThread (thr);
                if (Trace.CONSOLE_SHOW_THREADS) println ("|||| thread stopped: " + thr.name ());
        }
        public void classPrepareEvent (ClassPrepareEvent event) {

                ReferenceType ref = event.referenceType ();

                List<Field> fields = ref.fields ();
                List<Method> methods = ref.methods ();

                String filename;
                try {
                        filename = ref.sourcePaths (null).get (0); // get filename of the class
                        codeMap.addFile (filename);
                } catch (AbsentInformationException e) {
                        filename = "??";
                }

                boolean hasConstructors = false;
                boolean hasObjectMethods = false;
                boolean hasClassMethods = false;
                boolean hasClassFields = false;
                boolean hasObjectFields = false;
                for (Method m : methods) {
                        if (Format.isConstructor (m)) hasConstructors = true;
                        if (Format.isObjectMethod (m)) hasObjectMethods = true;
                        if (Format.isClassMethod (m)) hasClassMethods = true;
                }
                for (Field f : fields) {
                        if (Format.isStaticField (f)) hasClassFields = true;
                        if (Format.isObjectField (f)) hasObjectFields = true;
                }

                if (hasClassFields) {
                        staticClasses.add (ref);
                }
                if (Trace.CONSOLE_SHOW_CLASSES) {
                        println ("|||| loaded class: " + ref.name () + " from " + filename);
                        if (hasClassFields) {
                                println ("||||  class fields: ");
                                for (Field f : fields)
                                        if (Format.isStaticField (f)) println ("||||    " + Format.fieldToString (f));
                        }
                        if (hasClassMethods) {
                                println ("||||  class methods: ");
                                for (Method m : methods)
                                        if (Format.isClassMethod (m)) println ("||||    " + Format.methodToString (m, false));
                        }
                        if (hasConstructors) {
                                println ("||||  constructors: ");
                                for (Method m : methods)
                                        if (Format.isConstructor (m)) println ("||||    " + Format.methodToString (m, false));
                        }
                        if (hasObjectFields) {
                                println ("||||  object fields: ");
                                for (Field f : fields)
                                        if (Format.isObjectField (f)) println ("||||    " + Format.fieldToString (f));
                        }
                        if (hasObjectMethods) {
                                println ("||||  object methods: ");
                                for (Method m : methods)
                                        if (Format.isObjectMethod (m)) println ("||||    " + Format.methodToString (m, false));
                        }
                }
        }
        public void classUnloadEvent (ClassUnloadEvent event) {
                if (Trace.CONSOLE_SHOW_CLASSES) println ("|||| unloaded class: " + event.className ());
        }

        public void methodEntryEvent (MethodEntryEvent event) {
                Method meth = event.method ();
                ThreadReference thr = event.thread ();
                String calledMethodClassname = meth.declaringType ().name ();
                //System.err.println (calledMethodClassname);
                //System.err.println (Trace.GRAPHVIZ_CLASS_NAME);
                if (Format.matchesExcludePrefix (calledMethodClassname)) return;
                if (!Trace.SHOW_SYNTHETIC_METHODS && meth.isSynthetic ()) return;
                if (Trace.GRAPHVIZ_CLASS_NAME.equals (calledMethodClassname)) return;

                if (!Trace.CALLBACK_CLASS_NAME.equals (calledMethodClassname)) {
                        StackFrame currFrame = Format.getFrame (meth, thr);
                        values.stackPushFrame (currFrame, thr);
                        if (Trace.CONSOLE_SHOW_STEPS || Trace.CONSOLE_SHOW_CALLS) {
                                println (thr, ">>>> " + Format.methodToString (meth, true)); // + "[" + thr.name () + "]");
                                printLocals (currFrame, thr);
                        }
                } else {
                        // COPY PASTE HORRORS HERE
                        boolMap.enteringIgnoredMethod (thr);
                        String name = meth.name ();
                        if (Trace.CALLBACK_CLEAR_CALL_TREE.equals (name)) {
                                values.clearCallTree();
                        } else if (Trace.CALLBACK_DRAW_STEPS_OF_METHOD.equals (name)) {
                                List<StackFrame> frames;
                                try {
                                        frames = thr.frames ();
                                } catch (IncompatibleThreadStateException e) {
                                        throw new Error (Trace.BAD_ERROR_MESSAGE);
                                }
                                StackFrame currFrame = Format.getFrame (meth, thr);
                                List<LocalVariable> locals;
                                try {
                                        locals = currFrame.visibleVariables ();
                                } catch (AbsentInformationException e) {
                                        return;
                                }
                                StringReference obj = (StringReference) currFrame.getValue (locals.get (0));
                                Trace.drawStepsOfMethodBegin (obj.value());
                                returnValues.put (thr, null);
                        } else if (Trace.CALLBACK_DRAW_STEPS_OF_METHODS.equals (name)) {
                                List<StackFrame> frames;
                                try {
                                        frames = thr.frames ();
                                } catch (IncompatibleThreadStateException e) {
                                        throw new Error (Trace.BAD_ERROR_MESSAGE);
                                }
                                StackFrame currFrame = Format.getFrame (meth, thr);
                                List<LocalVariable> locals;
                                try {
                                        locals = currFrame.visibleVariables ();
                                } catch (AbsentInformationException e) {
                                        return;
                                }
                                ArrayReference arr = (ArrayReference) currFrame.getValue (locals.get (0)); 
                                for (int i = arr.length() - 1; i >= 0; i--) {
                                        StringReference obj = (StringReference) arr.getValue (i);
                                        Trace.drawStepsOfMethodBegin (obj.value());
                                }
                                returnValues.put (thr, null);
                        } else if (Trace.CALLBACK_DRAW_STEPS_BEGIN.equals (name)) {
                                Trace.GRAPHVIZ_SHOW_STEPS = true;
                                returnValues.put (thr, null);
                        } else if (Trace.CALLBACK_DRAW_STEPS_END.equals (name)) {
                                Trace.drawStepsOfMethodEnd ();
                        } else if (Trace.CALLBACKS.contains (name)) {
                                //System.err.println (calledMethodClassname + ":" + Trace.SPECIAL_METHOD_NAME + ":" + meth.name ());
                                StackFrame frame;
                                try {
                                        frame = thr.frame (1);
                                } catch (IncompatibleThreadStateException e) {
                                        throw new Error (Trace.BAD_ERROR_MESSAGE);
                                }
                                Location loc = frame.location ();
                                String label = Format.methodToString (loc.method (), true, false, "_") + "_" + Integer.toString (loc.lineNumber ());
                                drawGraph (label, thr, meth);
                                if (Trace.GRAPHVIZ_SHOW_FILENAMES_ON_CONSOLE && (Trace.CONSOLE_SHOW_STEPS)) printDrawEvent (thr, Graphviz.peekFilename ());
                        }
                }
        }
        public void methodExitEvent (MethodExitEvent event) {
                ThreadReference thr = event.thread ();
                Method meth = event.method ();
                String calledMethodClassname = meth.declaringType ().name ();
                if (Format.matchesExcludePrefix (calledMethodClassname)) return;
                if (!Trace.SHOW_SYNTHETIC_METHODS && meth.isSynthetic ()) return;
                if (Trace.GRAPHVIZ_CLASS_NAME.equals (calledMethodClassname)) return;
                if (boolMap.leavingIgnoredMethod (thr)) return;
                if (Trace.CONSOLE_SHOW_STEPS || Trace.CONSOLE_SHOW_CALLS) {
                        Type returnType;
                        try {
                                returnType = meth.returnType ();
                        } catch (ClassNotLoadedException e) {
                                returnType = null;
                        }
                        if (returnType instanceof VoidType) {
                                println (thr, "<<<< " + Format.methodToString (meth, true));
                        } else {
                                println (thr, "<<<< " + Format.methodToString (meth, true) + " : " + Format.valueToString (event.returnValue ()));
                        }
                }
                values.stackPopFrame (thr);
                StackFrame currFrame = Format.getFrame (meth, thr);
                if (meth.isConstructor ()) {
                        returnValues.put (thr, currFrame.thisObject ());
                } else {
                        returnValues.put (thr, event.returnValue ());
                }
        }
        public void exceptionEvent (ExceptionEvent event) {
                ThreadReference thr = event.thread ();
                try {
                        StackFrame currentFrame = thr.frame (0);
                } catch (IncompatibleThreadStateException e) {
                        throw new Error (Trace.BAD_ERROR_MESSAGE);
                }
                ObjectReference exception = event.exception ();
                Location catchLocation = event.catchLocation ();
                //String name = Format.objectToStringLong (exception);
                String message = "()";
                Field messageField = exception.referenceType ().fieldByName ("detailMessage");
                if (messageField != null) {
                        Value value = exception.getValue (messageField);
                        if (value != null) {
                                message = "(" + value.toString () + ")";
                        }
                }
                String name = Format.shortenFullyQualifiedName (exception.referenceType ().name ()) + message;

                if (catchLocation == null) {
                        // uncaught exception
                        if (Trace.CONSOLE_SHOW_STEPS) println (thr, "!!!! UNCAUGHT EXCEPTION: " + name);
                        if (Trace.GRAPHVIZ_SHOW_STEPS) Graphviz.drawFramesCheck (null, null, event.exception (), null, staticClasses);
                } else {
                        if (Trace.CONSOLE_SHOW_STEPS) println (thr, "!!!! EXCEPTION: " + name);
                        if (Trace.GRAPHVIZ_SHOW_STEPS) exceptionsMap.put (thr, event.exception ());
                }
        }
        public void stepEvent (StepEvent event) {
                ThreadReference thr = event.thread ();
                if (boolMap.insideIgnoredMethod (thr)) {
                        //System.err.println ("ignored");
                        return;
                }
                values.maybeAdjustAfterException (thr);

                Location loc = event.location ();
                String filename;
                try {
                        filename = loc.sourcePath ();
                } catch (AbsentInformationException e) {
                        return;
                }
                if (Trace.CONSOLE_SHOW_STEPS) {
                        values.stackUpdateFrame (event.location ().method (), thr, this);
                        int lineNumber = loc.lineNumber ();
                        if (Trace.CONSOLE_SHOW_STEPS_VERBOSE) {
                                println (thr, Format.shortenFilename (filename) + ":" + lineNumber + codeMap.show (filename, lineNumber));
                        } else {
                                printLineNum (thr, lineNumber);
                        }
                }
                if (Trace.GRAPHVIZ_SHOW_STEPS) {
                        try {
                                Graphviz.drawFramesCheck (Format.methodToString (loc.method (), true, false, "_") + "_" + Integer.toString (loc.lineNumber ()), returnValues.get (thr),
                                                exceptionsMap.get (thr), thr.frames (), staticClasses);
                                if (Trace.GRAPHVIZ_SHOW_FILENAMES_ON_CONSOLE && (Trace.CONSOLE_SHOW_STEPS)) printDrawEvent (thr, Graphviz.peekFilename ());
                                returnValues.put (thr, null);
                                exceptionsMap.put (thr, null);
                        } catch (IncompatibleThreadStateException e) {
                                throw new Error (Trace.BAD_ERROR_MESSAGE);
                        }
                }

        }
        public void modificationWatchpointEvent (ModificationWatchpointEvent event) {
                ThreadReference thr = event.thread ();
                if (boolMap.insideIgnoredMethod (thr)) return;
                if (!Trace.CONSOLE_SHOW_STEPS) return;
                Field f = event.field ();
                Value value = event.valueToBe (); // value that _will_ be assigned
                String debug = Trace.DEBUG ? "#5" + "[" + thr.name () + "]" : "";
                Type type;
                try {
                        type = f.type ();
                } catch (ClassNotLoadedException e) {
                        type = null; // waiting for class to load
                }

                if (value instanceof ArrayReference) {
                        if (f.isStatic ()) {
                                String name = Format.shortenFullyQualifiedName (f.declaringType ().name ()) + "." + f.name ();
                                if (values.registerStaticArray ((ArrayReference) value, name)) {
                                        println (thr, "  " + debug + "> " + name + " = " + Format.valueToString (value));
                                }
                        }
                        return; // array types are handled separately -- this avoids redundant printing
                }
                ObjectReference objRef = event.object ();
                if (objRef == null) {
                        println (thr, "  " + debug + "> " + Format.shortenFullyQualifiedName (f.declaringType ().name ()) + "." + f.name () + " = " + Format.valueToString (value));
                } else {
                        // changes to array references are printed by updateFrame
                        if (Format.tooManyFields (objRef)) {
                                println (thr, "  " + debug + "> " + Format.objectToStringShort (objRef) + "." + f.name () + " = " + Format.valueToString (value));
                        } else {
                                println (thr, "  " + debug + "> this = " + Format.objectToStringLong (objRef));
                        }
                }

        }

        public void printCallTree () { values.printCallTree(); }
        private void drawGraph (String loc, ThreadReference thr, Method meth) {
                List<StackFrame> frames;
                try {
                        frames = thr.frames ();
                } catch (IncompatibleThreadStateException e) {
                        throw new Error (Trace.BAD_ERROR_MESSAGE);
                }
                //setDrawPrefixFromParameter (Format.getFrame (meth, thr), meth);
                StackFrame currFrame = Format.getFrame (meth, thr);
                List<LocalVariable> locals;
                try {
                        locals = currFrame.visibleVariables ();
                } catch (AbsentInformationException e) {
                        return;
                }
                String name = meth.name ();
                if (Trace.CALLBACK_DRAW_THIS_FRAME.equals (name)) {
                        Graphviz.drawFrames (1, 2, loc, null, null, frames, staticClasses, false);
                } else if (Trace.CALLBACK_DRAW_ALL_FRAMES_AND_STATICS.equals (name)) {
                        Graphviz.drawFrames (1, frames==null?0:frames.size(), loc, null, null, frames, staticClasses, true);
                } else if (Trace.CALLBACK_DRAW_ALL_FRAMES.equals (name) || locals.size () == 0) {
                        Graphviz.drawFrames (1, frames==null?0:frames.size(), loc, null, null, frames, staticClasses, false);
                } else if (Trace.CALLBACK_DRAW_OBJECT.equals (name)) {
                        ObjectReference obj = (ObjectReference) currFrame.getValue (locals.get (0));
                        Map<String, ObjectReference> objects = new HashMap<> ();
                        objects.put (Graphviz.PREFIX_UNUSED_LABEL, obj);
                        Graphviz.drawObjects (loc, objects);
                } else if (Trace.CALLBACK_DRAW_OBJECT_NAMED.equals (name)) {
                        StringReference str = (StringReference) currFrame.getValue (locals.get (0));
                        ObjectReference obj = (ObjectReference) currFrame.getValue (locals.get (1));
                        Map<String, ObjectReference> objects = new HashMap<> ();
                        objects.put (str.value (), obj);
                        Graphviz.drawObjects (loc, objects);
                } else if (Trace.CALLBACK_DRAW_OBJECTS_NAMED.equals (name)) {
                        ArrayReference args = (ArrayReference) currFrame.getValue (locals.get (0));
                        Map<String, ObjectReference> objects = new HashMap<> ();
                        int n = args.length ();
                        if (n % 2 != 0) throw new Error ("\n!!!! " + Trace.CALLBACK_DRAW_OBJECTS_NAMED + " requires an even number of parameters, alternating strings and objects.");
                        for (int i = 0; i < n; i += 2) {
                                Value str = args.getValue (i);
                                if (!(str instanceof StringReference)) throw new Error ("\n!!!! " + Trace.CALLBACK_DRAW_OBJECTS_NAMED
                                                + " requires an even number of parameters, alternating strings and objects.");
                                objects.put (((StringReference) str).value (), (ObjectReference) args.getValue (i + 1));
                        }
                        Graphviz.drawObjects (loc, objects);
                } else {
                        ArrayReference args = (ArrayReference) currFrame.getValue (locals.get (0));
                        Map<String, ObjectReference> objects = new HashMap<> ();
                        int n = args.length ();
                        for (int i = 0; i < n; i++) {
                                objects.put (Graphviz.PREFIX_UNUSED_LABEL + i, (ObjectReference) args.getValue (i));
                        }
                        Graphviz.drawObjects (loc, objects);
                }
        }
        // This method was used to set the filename from the parameter of the draw method.
        // Not using this any more.
        //      private void setDrawPrefixFromParameter (StackFrame currFrame, Method meth) {
        //              String prefix = null;
        //              List<LocalVariable> locals;
        //              try {
        //                      locals = currFrame.visibleVariables ();
        //              } catch (AbsentInformationException e) {
        //                      return;
        //              }
        //              if (locals.size () >= 1) {
        //                      Value v = currFrame.getValue (locals.get (0));
        //                      if (!(v instanceof StringReference)) throw new Error ("\n!!!! " + meth.name () + " must have at most a single parameter."
        //                                      + "\n!!!! The parameter must be of type String");
        //                      prefix = ((StringReference) v).value ();
        //                      if (prefix != null) {
        //                              Graphviz.setOutputFilenamePrefix (prefix);
        //                      }
        //              }
        //      }

        // ---------------------- print locals ----------------------------------

        private void printLocals (StackFrame currFrame, ThreadReference thr) {
                List<LocalVariable> locals;
                try {
                        locals = currFrame.visibleVariables ();
                } catch (AbsentInformationException e) {
                        return;
                }
                String debug = Trace.DEBUG ? "#3" : "";

                ObjectReference objRef = currFrame.thisObject (); // get 'this' object
                if (objRef != null) {
                        if (Format.tooManyFields (objRef)) {
                                println (thr, "  " + debug + "this: " + Format.objectToStringShort (objRef));
                                ReferenceType type = objRef.referenceType (); // get type (class) of object
                                List<Field> fields; // use allFields() to include inherited fields
                                try {
                                        fields = type.fields ();
                                } catch (ClassNotPreparedException e) {
                                        throw new Error (Trace.BAD_ERROR_MESSAGE);
                                }

                                //println (thr, "  fields: ");
                                for (Field f : fields) {
                                        if (!Format.isObjectField (f)) continue;
                                        println (thr, "  " + debug + "| " + Format.objectToStringShort (objRef) + "." + f.name () + " = " + Format.valueToString (objRef.getValue (f)));
                                }
                                if (locals.size () > 0) println (thr, "  locals: ");
                        } else {
                                println (thr, "  " + debug + "| this = " + Format.objectToStringLong (objRef));
                        }
                }
                for (LocalVariable l : locals)
                        println (thr, "  " + debug + "| " + l.name () + " = " + Format.valueToString (currFrame.getValue (l)));
        }

        // ---------------------- indented printing ----------------------------------

        private boolean atNewLine = true;
        private static PrintStream out = System.out;
        public static void setFilename (String s) {
                try {
                        Printer.out = new PrintStream (s);
                } catch (FileNotFoundException e) {
                        System.err.println ("Attempting setFilename \"" + s + "\"");
                        System.err.println ("Cannot open file \"" + s + "\" for writing; using the console for output.");
                }
        }
        public static void setFilename () {
                Printer.out = System.out;
        }
        public void println (String string) {
                if (!atNewLine) {
                        atNewLine = true;
                        Printer.out.println ();
                }
                Printer.out.println (string);
        }
        public void println (ThreadReference thr, String string) {
                if (!atNewLine) {
                        atNewLine = true;
                        Printer.out.println ();
                }
                if (values.numThreads () > 1) Printer.out.format ("%-9s: ", thr.name ());
                int numFrames = (Trace.CONSOLE_SHOW_CALLS || Trace.CONSOLE_SHOW_STEPS) ? values.numFrames (thr) : 0;
                for (int i = 1; i < numFrames; i++)
                        Printer.out.print ("  ");
                Printer.out.println (string);
        }
        private void printLinePrefix (ThreadReference thr, boolean showLinePrompt) {
                if (atNewLine) {
                        atNewLine = false;
                        if (values.numThreads () > 1) Printer.out.format ("%-9s: ", thr.name ());
                        int numFrames = (Trace.CONSOLE_SHOW_CALLS || Trace.CONSOLE_SHOW_STEPS) ? values.numFrames (thr) : 0;
                        for (int i = 1; i < numFrames; i++)
                                Printer.out.print ("  ");
                        if (showLinePrompt) Printer.out.print ("  Line: ");
                }
        }
        public void printLineNum (ThreadReference thr, int lineNumber) {
                printLinePrefix (thr, true);
                Printer.out.print (lineNumber + " ");
        }
        public void printDrawEvent (ThreadReference thr, String filename) {
                printLinePrefix (thr, false);
                Printer.out.print ("#" + filename + "# ");
        }
}

/**
 * Code for formatting values and other static utilities.
 *
 * @author James Riely, jriely@cs.depaul.edu, August 2014
 */
/* private static */class Format {
        private Format () {}; // noninstantiable class

        public static StackFrame getFrame (Method meth, ThreadReference thr) {
                Type methDeclaredType = meth.declaringType ();
                int frameNumber = -1;
                StackFrame currFrame;
                try {
                        do {
                                frameNumber++;
                                currFrame = thr.frame (frameNumber);
                        } while (methDeclaredType != currFrame.location ().declaringType ());
                } catch (IncompatibleThreadStateException e) {
                        throw new Error (Trace.BAD_ERROR_MESSAGE);
                }
                return currFrame;
        }
        // http://stackoverflow.com/questions/1247772/is-there-an-equivalent-of-java-util-regex-for-glob-type-patterns
        public static String glob2regex (String glob) {
                StringBuilder regex = new StringBuilder ("^");
                for(int i = 0; i < glob.length(); ++i) {
                        final char c = glob.charAt(i);
                        switch(c) {
                        case '*': regex.append (".*"); break;
                        case '.': regex.append ("\\."); break;
                        case '$': regex.append ("\\$"); break;
                        default: regex.append (c);
                        }
                }
                regex.append ('$');
                return regex.toString ();
        }
        private static final ArrayList<String> EXCLUDE_REGEX;
        private static final ArrayList<String> DRAWING_INCLUDE_REGEX;
        static {
                EXCLUDE_REGEX = new ArrayList<> ();
                for (String s : Trace.EXCLUDE_GLOBS) {
                        //System.err.println (glob2regex (s));
                        EXCLUDE_REGEX.add (glob2regex (s));
                }
                DRAWING_INCLUDE_REGEX = new ArrayList<> ();
                for (String s : Trace.DRAWING_INCLUDE_GLOBS) {
                        DRAWING_INCLUDE_REGEX.add (glob2regex (s));
                }
        }
        public static boolean matchesExcludePrefix (String typeName) {
                //System.err.println (typeName + ":" + Trace.class.getName());
                if (!Trace.SHOW_STRINGS_AS_PRIMITIVE && "java.lang.String".equals (typeName)) return false;
                // don't explore objects on the exclude list
                for (String regex : Format.EXCLUDE_REGEX)
                        if (typeName.matches (regex)) return true;
                return false;
        }
        public static boolean matchesExcludePrefixShow (String typeName) {
                for (String regex : Format.DRAWING_INCLUDE_REGEX)
                        if (typeName.matches (regex)) return false;
                return matchesExcludePrefix (typeName);
        }
        public static String valueToString (Value value) {
                return valueToString (false, new HashSet<> (), value);
        }
        private static String valueToString (boolean inArray, Set<Value> visited, Value value) {
                if (value == null) return "null";
                if (value instanceof PrimitiveValue) return value.toString ();
                if (Trace.SHOW_STRINGS_AS_PRIMITIVE && value instanceof StringReference) return value.toString ();
                if (Trace.SHOW_BOXED_PRIMITIVES_AS_PRIMITIVE && isWrapper (value.type ())) return wrapperToString ((ObjectReference) value);
                return objectToStringLong (inArray, visited, (ObjectReference) value);
        }
        public static String valueToStringShort (Value value) {
                if (value == null) return "null";
                if (value instanceof PrimitiveValue) return value.toString ();
                if (Trace.SHOW_STRINGS_AS_PRIMITIVE && value instanceof StringReference) return value.toString ();
                if (Trace.SHOW_BOXED_PRIMITIVES_AS_PRIMITIVE && isWrapper (value.type ())) return value.toString (); //wrapperToString ((ObjectReference) value);
                return objectToStringShort ((ObjectReference) value);
        }
        public static boolean isWrapper (Type type) {
                if (!(type instanceof ReferenceType)) return false;
                if (type instanceof ArrayType) return false;
                String fqn = type.name ();
                if (!fqn.startsWith ("java.lang.")) return false;
                String className = fqn.substring (10);
                if (className.equals ("String")) return false;
                return (className.equals ("Integer") || className.equals ("Double") || className.equals ("Float") || className.equals ("Long") || className.equals ("Character")
                                || className.equals ("Short") || className.equals ("Byte") || className.equals ("Boolean"));
        }
        public static String wrapperToString (ObjectReference obj) {
                Object xObject;
                if (obj == null) return "null";
                ReferenceType cz = (ReferenceType) obj.type ();
                String fqn = cz.name ();
                String className = fqn.substring (10);
                Field field = cz.fieldByName ("value");
                return obj.getValue (field).toString ();
        }
        public static String objectToStringShort (ObjectReference objRef) {
                if (Trace.CONSOLE_SHOW_TYPE_IN_OBJECT_NAME) return shortenFullyQualifiedName (objRef.type ().name ()) + "@" + objRef.uniqueID ();
                else return "@" + objRef.uniqueID ();
        }
        private static String emptyArrayToStringShort (ArrayReference arrayRef, int length) {
                if (Trace.CONSOLE_SHOW_TYPE_IN_OBJECT_NAME) {
                        String classname = shortenFullyQualifiedName (arrayRef.type ().name ());
                        return classname.substring (0, classname.indexOf ("[")) + "[" + length + "]@" + arrayRef.uniqueID ();
                } else {
                        return "@" + arrayRef.uniqueID ();
                }
        }
        private static String nonemptyArrayToStringShort (ArrayReference arrayRef, int length) {
                if (Trace.CONSOLE_SHOW_TYPE_IN_OBJECT_NAME) return shortenFullyQualifiedName (arrayRef.getValue (0).type ().name ()) + "[" + length + "]@" + arrayRef.uniqueID ();
                else return "@" + arrayRef.uniqueID ();
        }

        public static String objectToStringLong (ObjectReference objRef) {
                return objectToStringLong (false, new HashSet<> (), objRef);
        }
        private static String objectToStringLong (boolean inArray, Set<Value> visited, ObjectReference objRef) {
                if (!visited.add (objRef)) return objectToStringShort (objRef);
                StringBuilder result = new StringBuilder ();
                if (objRef == null) {
                        return "null";
                } else if (objRef instanceof ArrayReference) {
                        ArrayReference arrayRef = (ArrayReference) objRef;
                        int length = arrayRef.length ();
                        if (length == 0 || arrayRef.getValue (0) == null) {
                                if (!inArray || Trace.CONSOLE_SHOW_NESTED_ARRAY_IDS) {
                                        result.append (emptyArrayToStringShort (arrayRef, length));
                                        result.append (" ");
                                }
                                result.append ("[ ] ");
                        } else {
                                if (!inArray || Trace.CONSOLE_SHOW_NESTED_ARRAY_IDS) {
                                        result.append (nonemptyArrayToStringShort (arrayRef, length));
                                        result.append (" ");
                                }
                                result.append ("[ ");
                                int max = (arrayRef.getValue (0) instanceof PrimitiveValue) ? Trace.CONSOLE_MAX_ARRAY_ELEMENTS_PRIMITIVE : Trace.CONSOLE_MAX_ARRAY_ELEMENTS_OBJECT;
                                int i = 0;
                                while (i < length && i < max) {
                                        result.append (valueToString (true, visited, arrayRef.getValue (i)));
                                        i++;
                                        if (i < length) result.append (", ");
                                }
                                if (i < length) result.append ("...");
                                result.append (" ]");
                        }
                } else {
                        result.append (objectToStringShort (objRef));
                        ReferenceType type = objRef.referenceType (); // get type (class) of object

                        // don't explore objects on the exclude list
                        if (!Format.matchesExcludePrefixShow (type.name ())) {
                                Iterator<Field> fields; // use allFields() to include inherited fields
                                try {
                                        fields = type.fields ().iterator ();
                                } catch (ClassNotPreparedException e) {
                                        throw new Error (Trace.BAD_ERROR_MESSAGE);
                                }
                                if (fields.hasNext ()) {
                                        result.append (" { ");
                                        int i = 0;
                                        while (fields.hasNext () && i < Trace.CONSOLE_MAX_FIELDS) {
                                                Field f = fields.next ();
                                                if (!isObjectField (f)) continue;
                                                if (i != 0) result.append (", ");
                                                result.append (f.name ());
                                                result.append ("=");
                                                result.append (valueToString (inArray, visited, objRef.getValue (f)));
                                                i++;
                                        }
                                        if (fields.hasNext ()) result.append ("...");
                                        result.append (" }");
                                }
                        }
                }
                return result.toString ();
        }

        // ---------------------- static utilities ----------------------------------

        public static boolean ignoreThread (ThreadReference thr) {
                if (thr.name ().equals ("Signal Dispatcher") || thr.name ().equals ("DestroyJavaVM") || thr.name ().startsWith ("AWT-")) return true; // ignore AWT threads
                if (thr.threadGroup ().name ().equals ("system")) return true; // ignore system threads
                return false;
        }

        public static boolean isStaticField (Field f) {
                if (!Trace.SHOW_SYNTHETIC_FIELDS && f.isSynthetic ()) return false;
                return f.isStatic ();
        }
        public static boolean isObjectField (Field f) {
                if (!Trace.SHOW_SYNTHETIC_FIELDS && f.isSynthetic ()) return false;
                return !f.isStatic ();
        }
        public static boolean isConstructor (Method m) {
                if (!Trace.SHOW_SYNTHETIC_METHODS && m.isSynthetic ()) return false;
                return m.isConstructor ();
        }
        public static boolean isObjectMethod (Method m) {
                if (!Trace.SHOW_SYNTHETIC_METHODS && m.isSynthetic ()) return false;
                return !m.isConstructor () && !m.isStatic ();
        }
        public static boolean isClassMethod (Method m) {
                if (!Trace.SHOW_SYNTHETIC_METHODS && m.isSynthetic ()) return false;
                return m.isStatic ();
        }
        public static boolean tooManyFields (ObjectReference objRef) {
                int count = 0;
                ReferenceType type = ((ReferenceType) objRef.type ());
                for (Field field : type.fields ())
                        if (isObjectField (field)) count++;
                return count > Trace.CONSOLE_MAX_FIELDS;
        }
        public static String shortenFullyQualifiedName (String fqn) {
                if (Trace.SHOW_PACKAGE_IN_CLASS_NAME || !fqn.contains (".")) return fqn;
                String className = fqn.substring (1 + fqn.lastIndexOf ("."));
                if (Trace.SHOW_OUTER_CLASS_IN_CLASS_NAME || !className.contains ("$")) return className;
                return className.substring (1 + className.lastIndexOf ("$"));
        }
        public static String shortenFilename (String fn) {
                if (!fn.contains ("/")) return fn;
                return fn.substring (1 + fn.lastIndexOf ("/"));
        }
        public static String fieldToString (Field f) {
                StringBuilder result = new StringBuilder ();
                if (f.isPrivate ()) result.append ("- ");
                if (f.isPublic ()) result.append ("+ ");
                if (f.isPackagePrivate ()) result.append ("~ ");
                if (f.isProtected ()) result.append ("# ");
                result.append (shortenFullyQualifiedName (f.name ()));
                result.append (" : ");
                result.append (shortenFullyQualifiedName (f.typeName ()));
                return result.toString ();
        }
        public static String methodToString (Method m, boolean showClass) {
                return methodToString (m, showClass, true, ".");
        }
        public static String methodToString (Method m, boolean showClass, boolean showParameters, String dotCharacter) {
                String className = shortenFullyQualifiedName (m.declaringType ().name ());
                StringBuilder result = new StringBuilder ();
                if (!showClass && showParameters) {
                        if (m.isPrivate ()) result.append ("- ");
                        if (m.isPublic ()) result.append ("+ ");
                        if (m.isPackagePrivate ()) result.append ("~ ");
                        if (m.isProtected ()) result.append ("# ");
                }
                if (m.isConstructor ()) {
                        result.append (className);
                } else if (m.isStaticInitializer ()) {
                        result.append (className);
                        result.append (".CLASS_INITIALIZER");
                        return result.toString ();
                } else {
                        if (showClass) {
                                result.append (className);
                                result.append (dotCharacter);
                        }
                        result.append (shortenFullyQualifiedName (m.name ()));
                }
                if (showParameters) {
                        result.append ("(");
                        Iterator<LocalVariable> vars;
                        try {
                                vars = m.arguments ().iterator ();
                                while (vars.hasNext ()) {
                                        result.append (shortenFullyQualifiedName (vars.next ().typeName ()));
                                        if (vars.hasNext ()) result.append (", ");
                                }
                        } catch (AbsentInformationException e) {
                                result.append ("??");
                        }
                        result.append (")");
                }
                //result.append (" from ");
                //result.append (m.declaringType ());
                return result.toString ();
        }
}

/**
 * A map from filenames to file contents. Allows lines to be printed.
 *
 * changes: Riely inlined the "ShowLines" class.
 *
 * @author Andrew Davison, March 2009, ad@fivedots.coe.psu.ac.th
 * @author James Riely
 **/
/* private static */class CodeMap {
        private TreeMap<String, ArrayList<String>> listings = new TreeMap<> ();
        private static boolean errorFound = false;
        // add filename-ShowLines pair to map
        public void addFile (String filename) {
                if (listings.containsKey (filename)) {
                        //System.err.println (filename + "already listed");
                        return;
                }

                String srcFilename = null;
                for (var s : Trace.POSSIBLE_SRC_LOCATIONS) {
                        String f = s + File.separator + filename;
                        if (Files.exists(Path.of(f))) {
                                srcFilename = f;
                        }
                }
                if (srcFilename == null) {
                        if (!errorFound) {
                                errorFound = true;
                                System.err.println ("\n!!!! Source not found: " + filename);
                                System.err.println ("\n !!!   Looking in " + Trace.POSSIBLE_SRC_LOCATIONS);
                                System.err.println ("\n !!!   Consider calling Trace.addPossibleSrcLocation(String dirName)");
                        }
                        return;
                }
                ArrayList<String> code = new ArrayList<> ();
                BufferedReader in = null;
                try {
                        in = new BufferedReader (new FileReader (srcFilename));
                        String line;
                        while ((line = in.readLine ()) != null)
                                code.add (line);
                } catch (IOException ex) {
                        System.err.println ("\n!!!! Could not read " + srcFilename);
                } finally {
                        try {
                                if (in != null) in.close ();
                        } catch (IOException e) {
                                throw new Error ("\n!!!! Problem reading " + srcFilename);
                        }
                }
                listings.put (filename, code);
                //println (filename + " added to listings");
        }

        // return the specified line from filename
        public String show (String filename, int lineNumber) {
                ArrayList<String> code = listings.get (filename);
                if (code == null) return (filename + " not listed");
                if ((lineNumber < 1) || (lineNumber > code.size ())) return " [Could not load source file.]";
                return (code.get (lineNumber - 1));
        }

}

/**
 * Map from threads to booleans.
 *
 * @author James Riely, jriely@cs.depaul.edu, August 2014
 */
/* private static */class InsideIgnoredMethodMap {
        // Stack is probably unnecessary here.  A single boolean would do.
        private HashMap<ThreadReference, Stack<Boolean>> map = new HashMap<> ();
        public void removeThread (ThreadReference thr) {
                map.remove (thr);
        }
        public void addThread (ThreadReference thr) {
                Stack<Boolean> st = new Stack<> ();
                st.push (false);
                map.put (thr, st);
        }
        public void enteringIgnoredMethod (ThreadReference thr) {
                Stack<Boolean> insideStack = map.get (thr);
                insideStack.push (true);        
        }
        public boolean leavingIgnoredMethod (ThreadReference thr) {
                Stack<Boolean> insideStack = map.get (thr);
                boolean result = insideStack.peek ();
                if (result) insideStack.pop ();
                return result;
        }
        public boolean insideIgnoredMethod (ThreadReference thr) {
                return map.get (thr).peek ();
        }
}

/** From sedgewick and wayne */
/* private static */class Stack<T> {
        private int N;
        private Node<T> first;
        private static class Node<T> {
                T item;
                Node<T> next;
        }
        public Stack () {
                first = null;
                N = 0;
        }
        public boolean isEmpty () {
                return first == null;
        }
        public int size () {
                return N;
        }
        public void push (T item) {
                Node<T> oldfirst = first;
                first = new Node<> ();
                first.item = item;
                first.next = oldfirst;
                N++;
        }
        public T pop () {
                if (isEmpty ()) throw new NoSuchElementException ("Stack underflow");
                T item = first.item;
                first = first.next;
                N--;
                return item;
        }
        public void pop (int n) {
                for (int i=n; i>0; i--)
                        pop ();
        }
        public T peek () {
                if (isEmpty ()) throw new NoSuchElementException ("Stack underflow");
                return first.item;
        }
}

/**
 * Keeps track of values in order to spot changes. This keeps copies of stack
 * variables (frames) and arrays. Does not store objects, since direct changes
 * to fields can be trapped by the JDI.
 *
 * @author James Riely, jriely@cs.depaul.edu, August 2014
 */
/* private static */class ValueMap {
        private HashMap<ThreadReference, Stack<HashMap<LocalVariable, Value>>> stacks = new HashMap<> ();
        private HashMap<ArrayReference, Object[]> arrays = new HashMap<> ();
        private HashMap<ArrayReference, Object[]> staticArrays = new HashMap<> ();
        private HashMap<ArrayReference, String> staticArrayNames = new HashMap<> ();
        private CallTree callTree = new CallTree ();
        public int numThreads () {
                return stacks.size ();
        }
        public void clearCallTree () {
                callTree = new CallTree ();
        }
        public void printCallTree () {
                callTree.output ();
        }
        private static class CallTree {
                private HashMap<ThreadReference, Stack<String>> frameIdsMap = new HashMap<> ();
                private HashMap<ThreadReference, List<String>> gvStringsMap = new HashMap<> ();
                private int frameNumber = 0;

                public void output () {
                        if (!Trace.SHOW_CALL_TREE) return;
                        Graphviz.drawStuff ("callTree", (out) -> {
                                out.println ("rankdir=LR;");
                                for (List<String> gvStrings : gvStringsMap.values ())
                                        for (String s : gvStrings) {
                                                out.println (s);
                                        }
                        });
                }
                public void pop (ThreadReference thr) {
                        if (!Trace.SHOW_CALL_TREE) return;
                        if (!Trace.drawStepsOfInternal (thr)) return;

                        Stack<String> frameIds = frameIdsMap.get(thr);
                        if (!frameIds.isEmpty ())
                                frameIds.pop ();
                }
                public void push (StackFrame currFrame, ThreadReference thr) {
                        if (!Trace.SHOW_CALL_TREE) return;
                        if (!Trace.drawStepsOfInternal (thr)) return;

                        Stack<String> frameIds = frameIdsMap.get(thr);
                        if (frameIds==null) { frameIds = new Stack<> (); frameIdsMap.put (thr, frameIds); }
                        List<String> gvStrings = gvStringsMap.get (thr);
                        if (gvStrings==null) { gvStrings = new LinkedList<> (); gvStringsMap.put (thr, gvStrings); }

                        String currentFrameId = "f" + frameNumber++;
                        StringBuilder sb = new StringBuilder ();
                        Method method = currFrame.location ().method ();
                        sb.append (currentFrameId);
                        sb.append ("[label=\"");
                        if (method.isSynthetic ()) sb.append ("!");
                        if (!method.isStatic ()) {
                                sb.append (Graphviz.quote (Format.valueToStringShort (currFrame.thisObject ())));
                                sb.append (":");
                        }
                        sb.append (Graphviz.quote (Format.methodToString (method, true, false, ".")));
                        //sb.append (Graphviz.quote (method.name ()));
                        sb.append ("(");
                        List<LocalVariable> locals = null;
                        try { locals = currFrame.visibleVariables (); } catch (AbsentInformationException e) { }
                        if (locals != null) {
                                boolean first = true;
                                for (LocalVariable l : locals)
                                        if (l.isArgument ()) {
                                                if (!first) sb.append (", ");
                                                else first = false;
                                                String valString = Format.valueToString (currFrame.getValue (l));
                                                //Value val = currFrame.getValue (l);
                                                //String valString = val==null ? "null" : val.toString ();
                                                sb.append (Graphviz.quote (valString));
                                        }
                        }
                        sb.append (")\"");
                        sb.append (Trace.GRAPHVIZ_CALL_TREE_BOX_ATTRIBUTES);
                        sb.append ("];");
                        gvStrings.add (sb.toString ());
                        if (!frameIds.isEmpty ()) {
                                gvStrings.add (frameIds.peek () + " -> " + currentFrameId + "[label=\"\"" + Trace.GRAPHVIZ_CALL_TREE_ARROW_ATTRIBUTES + "];");
                        }
                        frameIds.push (currentFrameId);
                }
        }

        public boolean maybeAdjustAfterException (ThreadReference thr) {
                Stack<HashMap<LocalVariable, Value>> stack = stacks.get (thr);

                // count the number of frames left
                int oldCount = stack.size ();
                int currentCount = 0;
                List<StackFrame> frames;
                try {
                        frames = thr.frames ();
                } catch (IncompatibleThreadStateException e) {
                        throw new Error (Trace.BAD_ERROR_MESSAGE);
                }

                for (StackFrame frame : frames) {
                        String calledMethodClassname = frame.location ().declaringType ().name ();
                        if (!Format.matchesExcludePrefix (calledMethodClassname)) currentCount++;
                }

                if (oldCount > currentCount) {
                        for (int i = oldCount - currentCount; i > 0; i--) {
                                stack.pop ();
                                callTree.pop (thr);
                        }
                        return true;
                }
                return false;
        }
        public int numFrames (ThreadReference thr) {
                return stacks.get (thr).size ();
        }
        public void stackCreate (ThreadReference thr) {
                stacks.put (thr, new Stack<> ());
        }
        public void stackDestroy (ThreadReference thr) {
                stacks.remove (thr);
        }
        public void stackPushFrame (StackFrame currFrame, ThreadReference thr) {
                if (!Trace.CONSOLE_SHOW_VARIABLES) return;
                callTree.push (currFrame, thr);
                List<LocalVariable> locals;
                try {
                        locals = currFrame.visibleVariables ();
                } catch (AbsentInformationException e) {
                        return;
                }

                Stack<HashMap<LocalVariable, Value>> stack = stacks.get (thr);
                HashMap<LocalVariable, Value> frame = new HashMap<> ();
                stack.push (frame);

                for (LocalVariable l : locals) {
                        Value v = currFrame.getValue (l);
                        frame.put (l, v);
                        if (v instanceof ArrayReference) registerArray ((ArrayReference) v);
                }
        }

        public void stackPopFrame (ThreadReference thr) {
                if (!Trace.CONSOLE_SHOW_VARIABLES) return;
                callTree.pop (thr);
                Stack<HashMap<LocalVariable, Value>> stack = stacks.get (thr);
                stack.pop ();
                // space leak in arrays HashMap: arrays never removed
        }

        public void stackUpdateFrame (Method meth, ThreadReference thr, IndentPrinter printer) {
                if (!Trace.CONSOLE_SHOW_VARIABLES) return;
                StackFrame currFrame = Format.getFrame (meth, thr);
                List<LocalVariable> locals;
                try {
                        locals = currFrame.visibleVariables ();
                } catch (AbsentInformationException e) {
                        return;
                }
                Stack<HashMap<LocalVariable, Value>> stack = stacks.get (thr);
                if (stack.isEmpty ()) {
                        throw new Error ("\n!!!! Frame empty: " + meth + " : " + thr);
                }
                HashMap<LocalVariable, Value> frame = stack.peek ();

                String debug = Trace.DEBUG ? "#1" : "";
                for (LocalVariable l : locals) {
                        Value oldValue = frame.get (l);
                        Value newValue = currFrame.getValue (l);
                        if (valueHasChanged (oldValue, newValue)) {
                                frame.put (l, newValue);
                                if (newValue instanceof ArrayReference) registerArray ((ArrayReference) newValue);
                                String change = (oldValue == null) ? "|" : ">";
                                printer.println (thr, "  " + debug + change + " " + l.name () + " = " + Format.valueToString (newValue));
                        }
                }

                ObjectReference thisObj = currFrame.thisObject ();
                if (thisObj != null) {
                        boolean show = Format.tooManyFields (thisObj);
                        if (arrayFieldHasChanged (show, thr, thisObj, printer) && !show) printer.println (thr, "  " + debug + "> this = " + Format.objectToStringLong (thisObj));
                }
                arrayStaticFieldHasChanged (true, thr, printer);
        }

        public void registerArray (ArrayReference val) {
                if (!arrays.containsKey (val)) {
                        arrays.put (val, copyArray (val));
                }
        }
        public boolean registerStaticArray (ArrayReference val, String name) {
                if (!staticArrays.containsKey (val)) {
                        staticArrays.put (val, copyArray (val));
                        staticArrayNames.put (val, name);
                        return true;
                }
                return false;
        }
        private static Object[] copyArray (ArrayReference oldArrayReference) {
                Object[] newArray = new Object[oldArrayReference.length ()];
                for (int i = 0; i < newArray.length; i++) {
                        Value val = oldArrayReference.getValue (i);
                        if (val instanceof ArrayReference) newArray[i] = copyArray ((ArrayReference) val);
                        else newArray[i] = val;
                }
                return newArray;
        }

        private boolean valueHasChanged (Value oldValue, Value newValue) {
                if (oldValue == null && newValue == null) return false;
                if (oldValue == null && newValue != null) return true;
                if (oldValue != null && newValue == null) return true;
                if (!oldValue.equals (newValue)) return true;
                if (!(oldValue instanceof ArrayReference)) return false;
                return arrayValueHasChanged ((ArrayReference) oldValue, (ArrayReference) newValue);
        }
        private boolean arrayStaticFieldHasChanged (Boolean show, ThreadReference thr, IndentPrinter printer) {
                boolean result = false;
                boolean print = false;
                String debug = Trace.DEBUG ? "#7" : "";
                String change = ">";
                for (ArrayReference a : staticArrays.keySet ()) {
                        Object[] objArray = staticArrays.get (a);
                        if (arrayValueHasChangedHelper (objArray, a)) {
                                result = true;
                                print = true;
                        }
                        if (show && print) {
                                printer.println (thr, "  " + debug + change + " " + staticArrayNames.get (a) + " = " + Format.valueToString (a));
                        }
                }
                return result;
        }
        private boolean arrayFieldHasChanged (Boolean show, ThreadReference thr, ObjectReference objRef, IndentPrinter printer) {
                ReferenceType type = objRef.referenceType (); // get type (class) of object
                List<Field> fields; // use allFields() to include inherited fields
                try {
                        fields = type.fields ();
                } catch (ClassNotPreparedException e) {
                        throw new Error (Trace.BAD_ERROR_MESSAGE);
                }
                boolean result = false;
                String debug = Trace.DEBUG ? "#2" : "";
                String change = ">";
                for (Field f : fields) {
                        Boolean print = false;
                        Value v = objRef.getValue (f);
                        if (!(v instanceof ArrayReference)) continue;
                        ArrayReference a = (ArrayReference) v;
                        if (!arrays.containsKey (a)) {
                                registerArray (a);
                                change = "|";
                                result = true;
                                print = true;
                        } else {
                                Object[] objArray = arrays.get (a);
                                if (arrayValueHasChangedHelper (objArray, a)) {
                                        result = true;
                                        print = true;
                                }
                        }
                        if (show && print) {
                                printer.println (thr, "  " + debug + change + " " + Format.objectToStringShort (objRef) + "." + f.name () + " = " + Format.valueToString (objRef.getValue (f)));
                        }
                }
                return result;
        }
        private boolean arrayValueHasChanged (ArrayReference oldArray, ArrayReference newArray) {
                if (oldArray.length () != newArray.length ()) return true;
                int len = oldArray.length ();
                if (!arrays.containsKey (newArray)) {
                        return true;
                }
                Object[] oldObjArray = arrays.get (newArray);
                //            if (oldObjArray.length != len)
                //                throw new Error (Trace.BAD_ERROR_MESSAGE);
                return arrayValueHasChangedHelper (oldObjArray, newArray);
        }
        private boolean arrayValueHasChangedHelper (Object[] oldObjArray, ArrayReference newArray) {
                int len = oldObjArray.length;
                boolean hasChanged = false;
                for (int i = 0; i < len; i++) {
                        Object oldObject = oldObjArray[i];
                        Value newVal = newArray.getValue (i);
                        if (oldObject == null && newVal != null) {
                                oldObjArray[i] = newVal;
                                hasChanged = true;
                        }
                        if (oldObject instanceof Value && valueHasChanged ((Value) oldObject, newVal)) {
                                //System.out.println ("BOB:" + i + ":" + oldObject + ":" + newVal);
                                oldObjArray[i] = newVal;
                                hasChanged = true;
                        }
                        if (oldObject instanceof Object[]) {
                                //if (!(newVal instanceof ArrayReference)) throw new Error (Trace.BAD_ERROR_MESSAGE);
                                if (arrayValueHasChangedHelper ((Object[]) oldObject, (ArrayReference) newVal)) {
                                        hasChanged = true;
                                }
                        }
                }
                return hasChanged;
        }
}

/* private static */class Graphviz {
        private Graphviz () {} // noninstantiable class
        //- This code is based on LJV:
        // LJV.java --- Generate a graph of an object, using Graphviz
        // The Lightweight Java Visualizer (LJV)
        // https://www.cs.auckland.ac.nz/~j-hamer/

        //- Author:     John Hamer <J.Hamer@cs.auckland.ac.nz>
        //- Created:    Sat May 10 15:27:48 2003
        //- Time-stamp: <2004-08-23 12:47:06 jham005>

        //- Copyright (C) 2004  John Hamer, University of Auckland
        //-
        //-   This program is free software; you can redistribute it and/or
        //-   modify it under the terms of the GNU General Public License
        //-   as published by the Free Software Foundation; either version 2
        //-   of the License, or (at your option) any later version.
        //-
        //-   This program is distributed in the hope that it will be useful,
        //-   but WITHOUT ANY WARRANTY; without even the implied warranty of
        //-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        //-   GNU General Public License for more details.
        //-
        //-   You should have received a copy of the GNU General Public License along
        //-   with this program; if not, write to the Free Software Foundation, Inc.,
        //-   59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.

        //- $Id: LJV.java,v 1.1 2004/07/14 02:03:45 jham005 Exp $
        //

        /**
         * Graphics files are saved in directory dirName/mainClassName.
         * dirName directory is created if it does not already exist.
         * If dirName/mainClassName exists, then numbers are appended to the directory name:
         * "dirName/mainClassName 1", "dirName/mainClassName 2", etc.
         */
        public static void setOutputDirectory (String dirName, String mainClassName) {
                if (dirName == null || mainClassName == null) {
                        throw new Error ("\n!!!! no nulls please");
                }
                Graphviz.dirName = dirName;
                Graphviz.mainClassName = mainClassName;
        }
        private static String dirName;
        private static String mainClassName;

        public static boolean isWindows () {
                String osName = System.getProperty("os.name");
                if (osName == null) {
                        throw new Error("\n!!! os.name not found");
                }
                osName = osName.toLowerCase(Locale.ENGLISH);
                return osName.contains("windows");
        }
        public static String getDesktop () {
                if (isWindows()) {
                        // Supposedly this selects the windows desktop folder:
                        return javax.swing.filechooser.FileSystemView.getFileSystemView().getHomeDirectory().toString();
                } else {
                        return System.getProperty ("user.home") + File.separator + "Desktop";
                }
        }

        /**
         * The name of the output file is derived from {@code baseFilename} by
         * appending successive integers.
         */

        public static String peekFilename () {
                return String.format ("%03d", nextGraphNumber);
        }
        private static String nextFilename () {
                if (baseFilename == null) setBaseFilename ();           
                ++nextGraphNumber;
                return baseFilename + peekFilename ();          
        }
        private static int nextGraphNumber = -1;
        private static String baseFilename = null;
        private static void setBaseFilename () {
                if (dirName == null || mainClassName == null) {
                        throw new Error ("\n!!!! no call to setOutputDirectory");
                }
                // create dir
                File dir = new File (dirName);
                if (!dir.isAbsolute ()) {
                        dirName = getDesktop() + File.separator + dirName;
                        dir = new File (dirName);
                }
                if (dir.exists ()) {
                        if (!dir.isDirectory ()) 
                                throw new Error ("\n!!!! \"" + dir + "\" is not a directory");
                        if (!dir.canWrite ()) 
                                throw new Error ("\n!!!! Unable to write directory: \"" + dir + "\"");
                } else {
                        dir.mkdirs ();
                }

                // create newDir
                String prefix = dirName + File.separator;
                String[] mainClassPath = mainClassName.split ("\\.");
                mainClassName = mainClassPath[mainClassPath.length-1];
                File newDir = new File (prefix + mainClassName);
                int suffix = 0;
                while (newDir.exists()) { 
                        suffix++; 
                        newDir = new File(prefix + mainClassName + " " + suffix);
                }
                newDir.mkdir ();

                if (!newDir.isDirectory () || !newDir.canWrite ())
                        throw new Error ("Failed setOutputDirectory \"" + newDir + "\"");
                baseFilename = newDir + File.separator;
                nextGraphNumber = -1;
        }
        //      /** @deprecated */
        //      private static void setOutputFilenamePrefix (String s) {
        //              File f = new File (s);
        //              String fCanonical;
        //              try { 
        //                      fCanonical = f.getCanonicalPath ();
        //              } catch (IOException e) {
        //                      throw new Error ("Failed setBaseFilename \"" + f + "\"");
        //              }
        //
        //              String newBaseFilename;
        //              if (f.isDirectory ()) {                         
        //                      if (f.canWrite ()) {
        //                              newBaseFilename = fCanonical + "/trace-"; 
        //                      } else {
        //                              throw new Error ("Failed setBaseFilename \"" + f + "\"");
        //                      }
        //              } else {
        //                      File parent = (f == null) ? null : f.getParentFile ();
        //                      if (parent == null || parent.canWrite ()) {
        //                              newBaseFilename = fCanonical;
        //                      } else {
        //                              System.err.println ("Cannot open directory \"" + f.getParent () + "\" for writing; using the current directory for graphziv output.");
        //                              throw new Error ("Failed setBaseFilename \"" + f + "\"");
        //                      }
        //              }
        //              if (!newBaseFilename.equals (baseFilename)) {
        //                      baseFilename = newBaseFilename;
        //                      nextGraphNumber = -1;
        //              }
        //      }

        public static final HashMap<String, String> objectAttributeMap = new HashMap<> ();
        public static final HashMap<String, String> staticClassAttributeMap = new HashMap<> ();
        public static final HashMap<String, String> frameAttributeMap = new HashMap<> ();
        public static final HashMap<String, String> fieldAttributeMap = new HashMap<> ();

        // ----------------------------------- utilities -----------------------------------------------

        private static boolean canTreatAsPrimitive (Value v) {
                if (v == null || v instanceof PrimitiveValue) return true;
                if (Trace.SHOW_STRINGS_AS_PRIMITIVE && v instanceof StringReference) return true;
                if (Trace.SHOW_BOXED_PRIMITIVES_AS_PRIMITIVE && Format.isWrapper (v.type ())) return true;
                return false;
        }
        private static boolean looksLikePrimitiveArray (ArrayReference obj) {
                try {
                        if (((ArrayType) obj.type ()).componentType () instanceof PrimitiveType) return true;
                } catch (ClassNotLoadedException e) {
                        return false;
                }

                for (int i = 0, len = obj.length (); i < len; i++)
                        if (!canTreatAsPrimitive (obj.getValue (i))) return false;
                return true;
        }
        private static boolean canIgnoreObjectField (Field field) {
                if (!Format.isObjectField (field)) return true;
                for (String ignoredField : Trace.GRAPHVIZ_IGNORED_FIELDS)
                        if (ignoredField.equals (field.name ())) return true;
                return false;
        }
        private static boolean canIgnoreStaticField (Field field) {
                if (!Format.isStaticField (field)) return true;
                for (String ignoredField : Trace.GRAPHVIZ_IGNORED_FIELDS)
                        if (ignoredField.equals (field.name ())) return true;
                return false;
        }

        //private static final String canAppearUnquotedInLabelChars = " /$&*@#!-+()^%;_[],;.=";
        private static boolean canAppearUnquotedInLabel (char c) {
                return true;
                //return canAppearUnquotedInLabelChars.indexOf (c) != -1 || Character.isLetter (c) || Character.isDigit (c);
        }
        private static final String quotable = "\\\"<>{}|";
        protected static String quote (String s) {
                s = unescapeJavaString (s);
                StringBuffer sb = new StringBuffer ();
                for (int i = 0, n = s.length (); i < n; i++) {
                        char c = s.charAt (i);
                        if (quotable.indexOf (c) != -1) sb.append ('\\').append (c);
                        else if (canAppearUnquotedInLabel (c)) sb.append (c);
                        else sb.append ("\\\\u").append (Integer.toHexString (c));
                }
                return sb.toString ();
        }
        /**
         * Unescapes a string that contains standard Java escape sequences.
         * <ul>
         * <li><strong>\\b \\f \\n \\r \\t \\" \\'</strong> :
         * BS, FF, NL, CR, TAB, double and single quote.</li>
         * <li><strong>\\N \\NN \\NNN</strong> : Octal character
         * specification (0 - 377, 0x00 - 0xFF).</li>
         * <li><strong>\\uNNNN</strong> : Hexadecimal based Unicode character.</li>
         * </ul>
         *
         * @param st
         *            A string optionally containing standard java escape sequences.
         * @return The translated string.
         */
        // from http://udojava.com/2013/09/28/unescape-a-string-that-contains-standard-java-escape-sequences/
        private static String unescapeJavaString(String st) {
                StringBuilder sb = new StringBuilder(st.length());
                for (int i = 0; i < st.length(); i++) {
                        char ch = st.charAt(i);
                        if (ch == '\\') {
                                char nextChar = (i == st.length() - 1) ? '\\' : st.charAt(i + 1);
                                // Octal escape?
                                if (nextChar >= '0' && nextChar <= '7') {
                                        String code = "" + nextChar;
                                        i++;
                                        if ((i < st.length() - 1) && st.charAt(i + 1) >= '0' && st.charAt(i + 1) <= '7') {
                                                code += st.charAt(i + 1);
                                                i++;
                                                if ((i < st.length() - 1) && st.charAt(i + 1) >= '0' && st.charAt(i + 1) <= '7') {
                                                        code += st.charAt(i + 1);
                                                        i++;
                                                }
                                        }
                                        sb.append((char) Integer.parseInt(code, 8));
                                        continue;
                                }
                                switch (nextChar) {
                                case '\\': ch = '\\'; break;
                                case 'b': ch = '\b'; break;
                                case 'f': ch = '\f'; break;
                                case 'n': ch = '\n'; break;
                                case 'r': ch = '\r'; break;
                                case 't': ch = '\t'; break;
                                case '\"': ch = '\"'; break;
                                case '\'': ch = '\''; break;
                                // Hex Unicode: u????
                                case 'u':
                                        if (i >= st.length() - 5) { ch = 'u'; break; }
                                        int code = Integer.parseInt(st.substring (i+2,i+6), 16);
                                        sb.append(Character.toChars(code));
                                        i += 5;
                                        continue;
                                }
                                i++;
                        }
                        sb.append(ch);
                }
                return sb.toString();
        }



        // ----------------------------------- values -----------------------------------------------

        protected static final String PREFIX_UNUSED_LABEL = "_____";
        private static final String PREFIX_LABEL = "L";
        private static final String PREFIX_ARRAY = "A";
        private static final String PREFIX_OBJECT = "N";
        private static final String PREFIX_STATIC = "S";
        private static final String PREFIX_FRAME = "F";
        private static final String PREFIX_RETURN = "returnValue";
        private static final String PREFIX_EXCEPTION = "exception";

        private static void processPrimitiveArray (ArrayReference obj, PrintWriter out) {
                out.print (objectGvName (obj) + "[label=\"");
                if (Trace.GRAPHVIZ_SHOW_OBJECT_IDS) out.print (objectName (obj));
                for (int i = 0, len = obj.length (); i < len; i++) {
                        if (Trace.GRAPHVIZ_SHOW_OBJECT_IDS || i != 0) out.print ("|");
                        Value v = obj.getValue (i);
                        if (v != null) processValueInline (Trace.GRAPHVIZ_SHOW_NULL_FIELDS, "", v, out);
                }
                out.println ("\"" + Trace.GRAPHVIZ_ARRAY_BOX_ATTRIBUTES + "];");
        }
        private static void processObjectArray (ArrayReference obj, PrintWriter out, Set<ObjectReference> visited) {
                out.print (objectGvName (obj) + "[label=\"");
                if (Trace.GRAPHVIZ_SHOW_OBJECT_IDS) out.print (objectName (obj));
                int len = obj.length ();
                for (int i = 0; i < len; i++) {
                        if (Trace.GRAPHVIZ_SHOW_OBJECT_IDS || i != 0) out.print ("|");
                        out.print ("<" + PREFIX_ARRAY + i + ">");
                        if (Trace.GRAPHVIZ_SHOW_OBJECT_IDS_REDUNDANTLY) {
                                ObjectReference ref = (ObjectReference) obj.getValue (i);
                                out.print (objectNameOnly (ref));
                        }
                }
                out.println ("\"" + Trace.GRAPHVIZ_ARRAY_BOX_ATTRIBUTES + "];");
                for (int i = 0; i < len; i++) {
                        ObjectReference ref = (ObjectReference) obj.getValue (i);
                        if (ref == null) continue;
                        out.println (objectGvName (obj) + ":" + PREFIX_ARRAY + i + ":c -> " + objectGvName (ref) + "[label=\"" + i + "\"" + Trace.GRAPHVIZ_ARRAY_ARROW_ATTRIBUTES + "];");
                        processObject (ref, out, visited);
                }
        }
        private static void processValueStandalone (String gvSource, String arrowAttributes, String fieldName, Value val, PrintWriter out, Set<ObjectReference> visited) {
                if (canTreatAsPrimitive (val)) throw new Error (Trace.BAD_ERROR_MESSAGE);
                ObjectReference objRef = (ObjectReference) val;
                String GvName = objectGvName (objRef);
                if (isNode (objRef.type())) {
                        arrowAttributes = arrowAttributes + Trace.GRAPHVIZ_NODE_ARROW_ATTRIBUTES;
                }
                out.println (gvSource + " -> " + GvName + "[label=\"" + fieldName + "\"" + arrowAttributes + "];");
                processObject (objRef, out, visited);
        }
        private static boolean processValueInline (boolean showNull, String prefix, Value val, PrintWriter out) {
                if ((!Trace.GRAPHVIZ_SHOW_OBJECT_IDS_REDUNDANTLY) && (!canTreatAsPrimitive (val))) return false;
                if (val == null && !showNull)
                        return false;
                out.print (prefix);
                if (val == null) {
                        out.print (quote ("null"));
                } else if (val instanceof PrimitiveValue) {
                        out.print (quote (val.toString ()));
                } else if (Trace.SHOW_STRINGS_AS_PRIMITIVE && val instanceof StringReference) {
                        out.print (quote (val.toString ()));
                } else if (Trace.SHOW_BOXED_PRIMITIVES_AS_PRIMITIVE && Format.isWrapper (val.type ())) {
                        out.print (quote (Format.wrapperToString ((ObjectReference) val)));
                } else if (Trace.GRAPHVIZ_SHOW_OBJECT_IDS_REDUNDANTLY && val instanceof ObjectReference) {
                        out.print (quote (objectNameOnly (val)));
                }
                return true;
        }
        // val must be primitive, wrapper or string
        private static void processWrapperAsSimple (String gvName, Value val, PrintWriter out, Set<ObjectReference> visited) {
                String cabs = null;
                out.print (gvName + "[label=\"");
                if (Trace.GRAPHVIZ_SHOW_OBJECT_IDS && val instanceof ObjectReference) {
                        out.print (objectNameOnly (val) + " : ");
                }
                if (val instanceof PrimitiveValue) {
                        out.print (quote (val.toString ()));
                } else if (val instanceof StringReference) {
                        out.print (quote (val.toString ()));
                } else {
                        out.print (quote (Format.wrapperToString ((ObjectReference) val)));
                }
                out.println ("\"" + Trace.GRAPHVIZ_WRAPPER_BOX_ATTRIBUTES + (cabs == null ? "" : "," + cabs) + "];");
        }

        // ----------------------------------- objects -----------------------------------------------

        private static String objectNameOnly (Value val) {
                if (val == null) return "null";
                if (!(val instanceof ObjectReference)) return ""; 
                return "@" + ((ObjectReference)val).uniqueID ();
        }
        private static String objectName (ObjectReference obj) {
                if (obj == null) return "";
                String objString = (Trace.GRAPHVIZ_SHOW_OBJECT_IDS) ? "@" + obj.uniqueID () + " : " : "";
                return objString + Format.shortenFullyQualifiedName (obj.type ().name ());
        }
        private static String objectGvName (ObjectReference obj) {
                return PREFIX_OBJECT + obj.uniqueID ();
        }
        private static boolean objectHasPrimitives (List<Field> fs, ObjectReference obj) {
                for (Field f : fs) {
                        if (canIgnoreObjectField (f)) continue;
                        if (canTreatAsPrimitive (obj.getValue (f))) return true;
                        if (Trace.GRAPHVIZ_SHOW_OBJECT_IDS_REDUNDANTLY) return true;
                }
                return false;
        }
        private static boolean objectHasNonNodeReferences (List<Field> fs, ObjectReference obj) {
                for (Field f : fs) {
                        if (isNode (f)) continue;
                        if (canIgnoreObjectField (f)) continue;
                        if (canTreatAsPrimitive (obj.getValue (f))) continue;
                        return true;
                }
                return false;
        }
        private static void labelObjectWithNoPrimitiveFields (ObjectReference obj, PrintWriter out) {
                String cabs = objectAttributeMap.get (obj.type ().name ());
                out.println (objectGvName (obj) + "[label=\"" + objectName (obj) + "\"" + Trace.GRAPHVIZ_OBJECT_BOX_ATTRIBUTES + (cabs == null ? "" : "," + cabs) + "];");
        }
        private static void labelObjectWithSomePrimitiveFields (ObjectReference obj, List<Field> fs, PrintWriter out) {
                out.print (objectGvName (obj) + "[label=\"" + objectName (obj) + "|{");
                String sep = "";
                for (Field f : fs) {
                        String name = Trace.GRAPHVIZ_SHOW_FIELD_NAMES_IN_LABELS ? f.name () + " = " : "";
                        if (!isNode (f) && !canIgnoreObjectField (f)) {
                                if (processValueInline (Trace.GRAPHVIZ_SHOW_NULL_FIELDS, sep + name, obj.getValue (f), out)) sep = "|";
                        } 
                }
                String cabs = objectAttributeMap.get (obj.type ().name ());
                out.println ("}\"" + Trace.GRAPHVIZ_OBJECT_BOX_ATTRIBUTES + (cabs == null ? "" : "," + cabs) + "];");
        }
        private static void labelNodeWithSomePrimitiveFields (ObjectReference obj, List<Field> fs, PrintWriter out) {
                out.print (objectGvName (obj) + "[label=\"");
                String sep = "";
                for (Field f : fs) {
                        String name = Trace.GRAPHVIZ_SHOW_FIELD_NAMES_IN_NODE_LABELS ? f.name () + " = " : "";
                        if (!isNode (f) && !canIgnoreObjectField (f)) {
                                if (processValueInline (Trace.GRAPHVIZ_SHOW_NULL_FIELDS, sep + name, obj.getValue (f), out)) sep = ", ";
                        }
                }
                String cabs = objectAttributeMap.get (obj.type ().name ());
                out.println ("\"" + Trace.GRAPHVIZ_NODE_BOX_ATTRIBUTES + (cabs == null ? "" : "," + cabs) + "];");
        }
        private static void processNodeStandalone (boolean srcIsNode, boolean srcHasNonNodeReferences, String gvSource, String fieldName, Value val, PrintWriter out, Set<ObjectReference> visited) {
                String arrowAttributes = Trace.GRAPHVIZ_OBJECT_ARROW_ATTRIBUTES;
                if (!srcIsNode) {
                        arrowAttributes = arrowAttributes + Trace.GRAPHVIZ_NODE_ARROW_ATTRIBUTES;
                }
                if (srcIsNode && !srcHasNonNodeReferences && !Trace.GRAPHVIZ_SHOW_FIELD_NAMES_IN_NODE_ARROWS) {
                        fieldName = "";
                }
                if (val == null) {
                        addNullDot(gvSource, fieldName, arrowAttributes, out);
                } else {
                        if (canTreatAsPrimitive (val)) throw new Error (Trace.BAD_ERROR_MESSAGE);
                        ObjectReference objRef = (ObjectReference) val;
                        String GvName = objectGvName (objRef);
                        out.println (gvSource + " -> " + GvName + "[label=\"" + fieldName + "\"" + arrowAttributes + "];");
                        processObject (objRef, out, visited);
                }
        }
        private static int nullId = 0;
        private static void addNullDot (String gvSource, String label, String arrowAttributes, PrintWriter out) {
                String id = "null__" + nullId;
                nullId++;
                out.print (id + "[shape=\"point\"];");                  
                out.println (gvSource + " -> " + id + "[label=\"" + label + "\"" + arrowAttributes + "];");
        }
        private static void processObjectWithLabel (String label, ObjectReference obj, PrintWriter out, Set<ObjectReference> visited) {
                processObject (obj, out, visited);
                if (!label.startsWith (PREFIX_UNUSED_LABEL)) {
                        String gvObjName = objectGvName (obj);
                        String gvLabelName = PREFIX_LABEL + label;
                        out.println (gvLabelName + "[label=\"" + label + "\"" + Trace.GRAPHVIZ_LABEL_BOX_ATTRIBUTES + "];");
                        out.println (gvLabelName + " -> " + gvObjName + "[label=\"\"" + Trace.GRAPHVIZ_LABEL_ARROW_ATTRIBUTES + "];");
                }
        }
        private static Value valueByFieldname (ObjectReference obj, String fieldName) {
                ReferenceType type = (ReferenceType) obj.type ();
                Field field = type.fieldByName (fieldName);
                return obj.getValue (field);
        }
        private static boolean isNode (Type type) {
                String typeName = type.name ();
                for (String s : Trace.GRAPHVIZ_NODE_CLASS) {
                        //System.err.printf ("s=%s, typeName=%s\n", s, typeName);
                        if (typeName.endsWith (s)) return true;
                }
                return false;
        }
        private static boolean isNode (Field f) {
                try {
                        return isNode (f.type());
                } catch (ClassNotLoadedException e) {
                        return false; //throw new Error ("\n!!!! Node class not loaded");
                }
        }
        private static void processObject (ObjectReference obj, PrintWriter out, Set<ObjectReference> visited) {
                if (visited.add (obj)) {
                        Type type = obj.type ();
                        String typeName = type.name ();

                        if (!Trace.SHOW_BOXED_PRIMITIVES_AS_PRIMITIVE && Trace.GRAPHVIZ_SHOW_BOXED_PRIMITIVES_SIMPLY && Format.isWrapper (type)) {
                                processWrapperAsSimple (objectGvName (obj), obj, out, visited);
                        } else if (!Trace.SHOW_STRINGS_AS_PRIMITIVE && Trace.GRAPHVIZ_SHOW_BOXED_PRIMITIVES_SIMPLY && obj instanceof StringReference) {
                                processWrapperAsSimple (objectGvName (obj), obj, out, visited);
                        } else if (obj instanceof ArrayReference) {
                                ArrayReference arr = (ArrayReference) obj;
                                if (looksLikePrimitiveArray (arr)) processPrimitiveArray (arr, out);
                                else processObjectArray (arr, out, visited);
                        } else {
                                List<Field> fs = ((ReferenceType) type).fields ();
                                if (isNode (type)) labelNodeWithSomePrimitiveFields (obj, fs, out);
                                else if (objectHasPrimitives (fs, obj)) labelObjectWithSomePrimitiveFields (obj, fs, out);
                                else labelObjectWithNoPrimitiveFields (obj, out);
                                if (!Format.matchesExcludePrefixShow (typeName)) {
                                        //System.err.println (typeName);
                                        String source = objectGvName (obj);
                                        for (Field f : fs) {
                                                Value value = obj.getValue (f);
                                                if (canIgnoreObjectField (f)) {
                                                        continue;
                                                }
                                                if (isNode (f)) {
                                                        processNodeStandalone (isNode (type), objectHasNonNodeReferences (fs, obj), source, f.name (), value, out, visited);
                                                } else if (!canTreatAsPrimitive (value)) {
                                                        processValueStandalone (source, Trace.GRAPHVIZ_OBJECT_ARROW_ATTRIBUTES, f.name (), value, out, visited);
                                                }
                                        }
                                }
                        }
                }
        }

        // ----------------------------------- static classes -----------------------------------------------

        private static String staticClassName (ReferenceType type) {
                return Format.shortenFullyQualifiedName (type.name ());
        }
        private static String staticClassGvName (ReferenceType type) {
                return PREFIX_STATIC + type.classObject ().uniqueID ();
        }
        private static boolean staticClassHasFields (List<Field> fs) {
                for (Field f : fs) {
                        if (!canIgnoreStaticField (f)) return true;
                }
                return false;
        }
        private static boolean staticClassHasPrimitives (List<Field> fs, ReferenceType staticClass) {
                for (Field f : fs) {
                        if (canIgnoreStaticField (f)) continue;
                        if (canTreatAsPrimitive (staticClass.getValue (f))) return true;
                        if (Trace.GRAPHVIZ_SHOW_OBJECT_IDS_REDUNDANTLY) return true;
                }
                return false;
        }
        private static void labelStaticClassWithNoPrimitiveFields (ReferenceType type, PrintWriter out) {
                String cabs = staticClassAttributeMap.get (type.name ());
                out.println (staticClassGvName (type) + "[label=\"" + staticClassName (type) + "\"" + Trace.GRAPHVIZ_STATIC_CLASS_BOX_ATTRIBUTES + (cabs == null ? "" : "," + cabs) + "];");
        }
        private static void labelStaticClassWithSomePrimitiveFields (ReferenceType type, List<Field> fs, PrintWriter out) {
                out.print (staticClassGvName (type) + "[label=\"" + staticClassName (type) + "|{");
                String sep = "";
                for (Field field : fs) {
                        if (!canIgnoreStaticField (field)) {
                                String name = Trace.GRAPHVIZ_SHOW_FIELD_NAMES_IN_LABELS ? field.name () + " = " : "";
                                if (processValueInline (Trace.GRAPHVIZ_SHOW_NULL_FIELDS, sep + name, type.getValue (field), out)) sep = "|";
                        }
                }
                String cabs = staticClassAttributeMap.get (type.name ());
                out.println ("}\"" + Trace.GRAPHVIZ_STATIC_CLASS_BOX_ATTRIBUTES + (cabs == null ? "" : "," + cabs) + "];");
        }
        private static void processStaticClass (ReferenceType type, PrintWriter out, Set<ObjectReference> visited) {
                String typeName = type.name ();
                List<Field> fs = type.fields ();
                if (!staticClassHasFields (fs)) {
                        return;
                }
                if (staticClassHasPrimitives (fs, type)) {
                        labelStaticClassWithSomePrimitiveFields (type, fs, out);
                } else {
                        labelStaticClassWithNoPrimitiveFields (type, out);
                }
                if (!Format.matchesExcludePrefixShow (type.name ())) {
                        String source = staticClassGvName (type);
                        for (Field f : fs) {
                                if (f.isStatic ()) {
                                        Value value = type.getValue (f);
                                        if ((!canIgnoreStaticField (f)) && (!canTreatAsPrimitive (value))) {
                                                String name = f.name ();
                                                processValueStandalone (source, Trace.GRAPHVIZ_STATIC_CLASS_ARROW_ATTRIBUTES, name, value, out, visited);
                                        }
                                }
                        }
                }
        }

        // ----------------------------------- frames -----------------------------------------------
        private static String frameName (int frameNumber, StackFrame frame, Method method, int lineNumber) {
                String objString = (Trace.GRAPHVIZ_SHOW_FRAME_NUMBERS) ? "@" + frameNumber + " : " : "";
                return objString + Format.methodToString (method, true, false, ".") + " # " + lineNumber;
        }
        private static String frameGvName (int frameNumber) {
                return PREFIX_FRAME + frameNumber;
        }
        private static boolean frameHasPrimitives (Map<LocalVariable, Value> ls) {
                for (LocalVariable lv : ls.keySet ()) {
                        Value v = ls.get (lv);
                        if (canTreatAsPrimitive (v)) return true;
                        if (Trace.GRAPHVIZ_SHOW_OBJECT_IDS_REDUNDANTLY) return true;
                }
                return false;
        }
        private static void labelFrameWithNoPrimitiveLocals (int frameNumber, StackFrame frame, PrintWriter out) {
                Location location = frame.location ();
                ReferenceType type = location.declaringType ();
                Method method = location.method ();
                String attributes = frameAttributeMap.get (type.name ());
                out.println (frameGvName (frameNumber) + "[label=\"" + frameName (frameNumber, frame, method, location.lineNumber ()) + "\"" + Trace.GRAPHVIZ_FRAME_BOX_ATTRIBUTES
                                + (attributes == null ? "" : "," + attributes) + "];");
        }
        private static void labelFrameWithSomePrimitiveLocals (int frameNumber, StackFrame frame, Map<LocalVariable, Value> ls, PrintWriter out) {
                Location location = frame.location ();
                ReferenceType type = location.declaringType ();
                Method method = location.method ();
                out.print (frameGvName (frameNumber) + "[label=\"" + frameName (frameNumber, frame, method, location.lineNumber ()) + "|{");
                String sep = "";
                ObjectReference thisObject = frame.thisObject ();
                if (thisObject != null) {
                        String name = Trace.GRAPHVIZ_SHOW_FIELD_NAMES_IN_LABELS ? "this = " : "";
                        if (processValueInline (Trace.GRAPHVIZ_SHOW_NULL_VARIABLES, sep + name, thisObject, out)) sep = "|";
                }
                for (LocalVariable lv : ls.keySet ()) {
                        String name = Trace.GRAPHVIZ_SHOW_FIELD_NAMES_IN_LABELS ? lv.name () + " = " : "";
                        if (processValueInline (Trace.GRAPHVIZ_SHOW_NULL_VARIABLES, sep + name, ls.get (lv), out)) sep = "|";
                }
                String cabs = frameAttributeMap.get (type.name ());
                out.println ("}\"" + Trace.GRAPHVIZ_FRAME_BOX_ATTRIBUTES + (cabs == null ? "" : "," + cabs) + "];");
        }
        private static boolean processFrame (int frameNumber, StackFrame frame, PrintWriter out, Set<ObjectReference> visited) {
                Location location = frame.location ();
                ReferenceType type = location.declaringType ();
                Method method = location.method ();
                if (Format.matchesExcludePrefixShow (type.name ())) return false;

                Map<LocalVariable, Value> ls;
                try {
                        ls = frame.getValues (frame.visibleVariables ());
                } catch (AbsentInformationException e) {
                        return false;
                }
                if (frameHasPrimitives (ls)) {
                        labelFrameWithSomePrimitiveLocals (frameNumber, frame, ls, out);
                } else {
                        labelFrameWithNoPrimitiveLocals (frameNumber, frame, out);
                }
                ObjectReference thisObject = frame.thisObject ();
                if (!canTreatAsPrimitive (thisObject)) {
                        processValueStandalone (frameGvName (frameNumber), Trace.GRAPHVIZ_FRAME_OBJECT_ARROW_ATTRIBUTES, "this", thisObject, out, visited);
                }
                for (LocalVariable lv : ls.keySet ()) {
                        Value value = ls.get (lv);
                        if (!canTreatAsPrimitive (value)) {
                                processValueStandalone (frameGvName (frameNumber), Trace.GRAPHVIZ_FRAME_OBJECT_ARROW_ATTRIBUTES, lv.name (), value, out, visited);
                        }
                }
                return true;
        }

        // ----------------------------------- top level -----------------------------------------------

        public static void drawFramesCheck (String loc, Value returnVal, Value exnVal, List<StackFrame> frames, Set<ReferenceType> staticClasses) {
                if (Trace.drawStepsOfInternal (frames, returnVal)) {
                        int len = 0;
                        if (frames!=null) len = (Trace.GRAPHVIZ_SHOW_ONLY_TOP_FRAME)? 2 : frames.size();
                        drawFrames (0, len, loc, returnVal, exnVal, frames, staticClasses, false);
                }
        }
        public static void drawFrames (int start, int len, String loc, Value returnVal, Value exnVal, List<StackFrame> frames, Set<ReferenceType> staticClasses, boolean overrideShowStatics) {
                drawStuff (loc, (out) -> {
                        Set<ObjectReference> visited = new HashSet<> ();
                        if ((overrideShowStatics || Trace.GRAPHVIZ_SHOW_STATIC_CLASSES) && staticClasses != null) {
                                for (ReferenceType staticClass : staticClasses) {
                                        processStaticClass (staticClass, out, visited);
                                }
                        }
                        if (frames != null) {
                                for (int i = len - 1, prev = i; i >= start; i--) {
                                        StackFrame currentFrame = frames.get (i);
                                        Method meth = currentFrame.location ().method ();
                                        if (!Trace.SHOW_SYNTHETIC_METHODS && meth.isSynthetic ()) continue;
                                        if (processFrame (len - i, currentFrame, out, visited)) {
                                                if (prev != i) {
                                                        out.println (frameGvName (len - i) + " -> " + frameGvName (len - prev) + "[label=\"\"" + Trace.GRAPHVIZ_FRAME_FRAME_ARROW_ATTRIBUTES + "];");
                                                        prev = i;
                                                }
                                        }
                                }
                                // show the return value -- without this, it mysteriously disappears when drawing all steps
                                if (!Trace.GRAPHVIZ_SHOW_ONLY_TOP_FRAME && returnVal != null && !(returnVal instanceof VoidValue)) {
                                        String objString = (Trace.GRAPHVIZ_SHOW_FRAME_NUMBERS) ? "@" + (len + 1) + " : " : "";
                                        //TODO
                                        if (canTreatAsPrimitive (returnVal) || Trace.GRAPHVIZ_SHOW_OBJECT_IDS_REDUNDANTLY) {
                                                out.print (PREFIX_RETURN + " [label=\"" + objString + "returnValue = ");
                                                processValueInline (true, "", returnVal, out);
                                                out.println ("\"" + Trace.GRAPHVIZ_FRAME_RETURN_ATTRIBUTES + "];");
                                        } else {
                                                out.println (PREFIX_RETURN + " [label=\"" + objString + "returnValue\"" + Trace.GRAPHVIZ_FRAME_RETURN_ATTRIBUTES + "];");
                                        }
                                        if (!canTreatAsPrimitive (returnVal)) {
                                                processValueStandalone (PREFIX_RETURN, Trace.GRAPHVIZ_FRAME_OBJECT_ARROW_ATTRIBUTES, "", returnVal, out, visited);
                                        }
                                        out.println (PREFIX_RETURN + " -> " + frameGvName (len) + "[label=\"\"" + Trace.GRAPHVIZ_FRAME_FRAME_ARROW_ATTRIBUTES + "];");
                                }
                        }
                        // show the exception value
                        if (exnVal != null && !(exnVal instanceof VoidValue)) {
                                if (canTreatAsPrimitive (exnVal)) {
                                        out.print (PREFIX_EXCEPTION + " [label=\"exception = ");
                                        processValueInline (true, "", exnVal, out);
                                        out.println ("\"" + Trace.GRAPHVIZ_FRAME_EXCEPTION_ATTRIBUTES + "];");
                                        if (len != 0) out.println (PREFIX_EXCEPTION + " -> " + frameGvName (len) + "[label=\"\"" + Trace.GRAPHVIZ_FRAME_FRAME_ARROW_ATTRIBUTES + "];");
                                } else {
                                        out.println (PREFIX_EXCEPTION + " [label=\"exception\"" + Trace.GRAPHVIZ_FRAME_EXCEPTION_ATTRIBUTES + "];");
                                        processValueStandalone (PREFIX_EXCEPTION, Trace.GRAPHVIZ_FRAME_OBJECT_ARROW_ATTRIBUTES, "", exnVal, out, visited);
                                        if (len != 0) out.println (PREFIX_EXCEPTION + " -> " + frameGvName (len) + "[label=\"\"" + Trace.GRAPHVIZ_FRAME_FRAME_ARROW_ATTRIBUTES + "];");
                                }
                        }
                });
        }
        public static void drawObjects (String loc, Map<String, ObjectReference> objects) {
                drawStuff (loc, (out) -> {
                        Set<ObjectReference> visited = new HashSet<> ();
                        for (String key : objects.keySet ()) {
                                processObjectWithLabel (key, objects.get (key), out, visited);
                        }
                });
        }
        protected static void drawStuff (String loc, Consumer<PrintWriter> consumer) {
                String filenamePrefix = nextFilename ();
                String theLoc = (loc != null && Trace.GRAPHVIZ_PUT_LINE_NUMBER_IN_FILENAME) ? "-" + loc : "";
                File gvFile = new File (filenamePrefix + theLoc + ".gv");
                PrintWriter out;
                try {
                        out = new PrintWriter (new FileWriter (gvFile));
                } catch (IOException e) {
                        throw new Error ("\n!!!! Cannot open " + gvFile + "for writing");
                }
                out.println ("digraph Java {");
                consumer.accept (out);
                out.println ("}");
                out.close ();
                //System.err.println (gvFile);
                if (!Trace.GRAPHVIZ_RUN_GRAPHVIZ) {
                        System.err.println ("\n!!!! Not running graphviz because Trace.GRAPHVIZ_RUN_GRAPHVIZ is false.");                       
                } else {
                        String executable = null;
                        for (String s : Trace.GRAPHVIZ_POSSIBLE_DOT_LOCATIONS) {
                                if (new File (s).canExecute ()) executable = s;
                        }
                        if (executable == null) {
                                System.err.println ("\n!!!! Make sure Graphviz is installed.  Go to https://www.graphviz.org/download/");                                                       
                                System.err.println ("\n!!!! Graphviz executable not found in: " + Trace.GRAPHVIZ_POSSIBLE_DOT_LOCATIONS);                                                       
                        } else {
                                ProcessBuilder pb = new ProcessBuilder (executable, "-T", Trace.GRAPHVIZ_OUTPUT_FORMAT);
                                File outFile = new File (filenamePrefix + theLoc + "." + Trace.GRAPHVIZ_OUTPUT_FORMAT);
                                pb.redirectInput (gvFile);
                                pb.redirectOutput (outFile);
                                int result = -1;
                                try {
                                        result = pb.start ().waitFor ();
                                } catch (IOException e) {
                                        throw new Error ("\n!!!! Cannot execute " + executable + "\n!!!! Make sure you have installed http://www.graphviz.org/"
                                                        + "\n!!!! Check the value of GRAPHVIZ_POSSIBLE_DOT_LOCATIONS in " + Trace.class.getCanonicalName ());
                                } catch (InterruptedException e) {
                                        throw new Error ("\n!!!! Execution of " + executable + "interrupted");
                                }
                                if (result == 0) {
                                        if (Trace.GRAPHVIZ_REMOVE_GV_FILES) {
                                                gvFile.delete ();
                                        }
                                } else {
                                        outFile.delete ();
                                }
                        }
                }
        }

        //    public static void drawFrames (int start, String loc, Value returnVal, Value exnVal, List<StackFrame> frames, Set<ReferenceType> staticClasses, Map<String, ObjectReference> objects) {
        //        String filenamePrefix = nextFilename ();
        //        String theLoc = (loc != null && Trace.GRAPHVIZ_PUT_LINE_NUMBER_IN_FILENAME) ? "-" + loc : "";
        //        File gvFile = new File (filenamePrefix + theLoc + ".gv");
        //        PrintWriter out;
        //        try {
        //            out = new PrintWriter (new FileWriter (gvFile));
        //        } catch (IOException e) {
        //            throw new Error ("\n!!!! Cannot open " + gvFile + "for writing");
        //        }
        //        processFrames (start, returnVal, exnVal, frames, staticClasses, objects, out);
        //        out.close ();
        //        //System.err.println (gvFile);
        //        if (Trace.GRAPHVIZ_RUN_DOT) {
        //            String executable = null;
        //            for (String s : Trace.GRAPHVIZ_POSSIBLE_DOT_LOCATIONS) {
        //                if (new File (s).canExecute ())
        //                    executable = s;
        //            }
        //            if (executable != null) {
        //                ProcessBuilder pb = new ProcessBuilder (executable, "-T", Trace.GRAPHVIZ_DOT_OUTPUT_FORMAT);
        //                File outFile = new File (filenamePrefix + theLoc + "." + Trace.GRAPHVIZ_DOT_OUTPUT_FORMAT);
        //                pb.redirectInput (gvFile);
        //                pb.redirectOutput(outFile);
        //                int result = -1;
        //                try {
        //                    result = pb.start ().waitFor ();
        //                } catch (IOException e) {
        //                    throw new Error ("\n!!!! Cannot execute " + executable +
        //                            "\n!!!! Make sure you have installed http://www.graphviz.org/" +
        //                            "\n!!!! Check the value of GRAPHVIZ_DOT_COMMAND in " + Trace.class.getCanonicalName ());
        //                } catch (InterruptedException e) {
        //                    throw new Error ("\n!!!! Execution of " + executable + "interrupted");
        //                }
        //                if (result == 0) {
        //                    if (Trace.GRAPHVIZ_REMOVE_GV_FILES) {
        //                        gvFile.delete ();
        //                    }
        //                } else {
        //                    outFile.delete ();
        //                }
        //            }
        //        }
        //    }
}