package algs13;
import stdlib.*;
import java.util.Iterator;
public class XFixedCapacityIterableStack<T> implements Iterable<T> {
  T[] a; // holds the items
  int N; // number of items in stack

  @SuppressWarnings("unchecked")
  public XFixedCapacityIterableStack (int capacity) {
    this.a = (T[]) new Object[capacity]; // no generic array creation
    this.N = 0;
  }
  public int size ()        { return N; }
  public boolean isEmpty () { return (N == 0); }
  public void push (T item) {
    if (item == null) throw new IllegalArgumentException ();
    a[N] = item;
    N++;
  }
  public T pop () {
    N--;
    T result = a[N];
    a[N] = null;
    return result;
  }
  public Iterator<T> iterator () {
    return new ReverseArrayIterator ();
  }
  public class ReverseArrayIterator implements Iterator<T> {
    private int i;
    public ReverseArrayIterator() { 
      int numOccupied = N;
      this.i = numOccupied - 1; 
    }
    public boolean hasNext () { return i >= 0; }
    public T next () {
      T result = a[i];
      i--;
      return result;
    }
  }
  public static void main (String[] args) {
    //Trace.showBuiltInObjects (true);
    //Trace.drawStepsOfMethod ("main");
    //Trace.drawStepsOfMethod ("next");
    //Trace.drawSteps();
    //Trace.run ();
    
    XFixedCapacityIterableStack<Integer> s1 = new XFixedCapacityIterableStack<> (5);
    XFixedCapacityIterableStack<String> s2 = new XFixedCapacityIterableStack<> (3);
    s1.push (11);
    s1.push (21);
    s1.push (31);
    s2.push ("duck");
    s2.push ("goose");

    
    // Here's a nicer version
    StdOut.print ("What's on the stack: ");
    for (Integer k : s1) {
      StdOut.print (k + " ");
    }
    StdOut.println ();
  }
}