// Exercise 4.1.3 (Solution published at http://algs4.cs.princeton.edu/)
package algs41;
import stdlib.*;
import algs13.Bag;

/**
 *  The {@code Graph} class represents an undirected graph of vertices
 *  named {@code 0} through {@code V-1}.
 *  It supports the following operations: add an edge to the graph,
 *  iterate over all of the neighbors adjacent to a vertex.
 *  Parallel edges and self-loops are permitted.
 *  <p>
 *  For additional documentation, see <a href="http://algs4.cs.princeton.edu/51undirected">Section 5.1</a> of
 *  <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
 */
public class Graph {
  private final int V;
  private int E;
  private final Bag<Integer>[] adj;

  /**
   * Create an empty graph with V vertices.
   */
  @SuppressWarnings("unchecked")
  public Graph(int V) {
    if (V < 0) throw new Error("Number of vertices must be nonnegative");
    this.V = V;
    this.E = 0;
    this.adj = new Bag[V];
    for (int v = 0; v < V; v++) {
      adj[v] = new Bag<>();
    }
  }
  
  /**
   * Return the number of vertices in the graph.
   */
  public int V() { return V; }

  /**
   * Return the number of edges in the graph.
   */
  public int E() { return E; }


  /**
   * Add the undirected edge v-w to graph.
   * @throws java.lang.IndexOutOfBoundsException unless both {@code 0 <= v < V} and {@code 0 <= w < V}
   */
  public void addEdge(int v, int w) {
    if (v < 0 || v >= V) throw new IndexOutOfBoundsException();
    if (w < 0 || w >= V) throw new IndexOutOfBoundsException();
    E++;
    adj[v].add(w);
    adj[w].add(v);
  }


  /**
   * Return the list of neighbors of vertex v as in Iterable.
   * @throws java.lang.IndexOutOfBoundsException unless {@code 0 <= v < V}
   */
  public Iterable<Integer> adj(int v) {
    if (v < 0 || v >= V) throw new IndexOutOfBoundsException();
    return adj[v];
  }
  
    /**
     * Returns the degree of vertex {@code v}.
     *
     * @param  v the vertex
     * @return the degree of vertex {@code v}
     * @throws IllegalArgumentException unless {@code 0 <= v < V}
     */
    public int degree(int v) {
    if (v < 0 || v >= V) throw new IndexOutOfBoundsException();
    return adj[v].size();
    }

  /**
   * Return a string representation of the graph.
   */
  public String toString() {
    StringBuilder s = new StringBuilder();
    String NEWLINE = System.getProperty("line.separator");
    s.append(V + " vertices, " + E + " edges " + NEWLINE);
    for (int v = 0; v < V; v++) {
      s.append(v + ": ");
      for (int w : adj[v]) {
        s.append(w + " ");
      }
      s.append(NEWLINE);
    }
    return s.toString();
  }

  /**
   * Save a graphviz representation of the graph.
   * See <a href="http://www.graphviz.org/">graphviz.org</a>.
   */
  public void toGraphviz(String filename) {
    GraphvizBuilder gb = new GraphvizBuilder ();
    for (int v = 0; v < V; v++) {
      gb.addNode (v);
      boolean showSelfLoop = false;
      for (int w : adj[v]) {
        if (v < w) // only once each edge
          gb.addEdge (v, w);
        if (v == w) {
          showSelfLoop = !showSelfLoop;
          if (showSelfLoop)
            gb.addEdge (v, w);
        }
      }
    }
    gb.toFileUndirected (filename);
  }

  /**
   * Test client.
   */
  public static void main(String[] args) {
    //args = new String [] { "data/tinyCG.txt" };
    args = new String [] { "data/tinyG.txt" };
    //args = new String [] { "20", "40" };

    Graph G;
    if (args.length == 1) {
      In in = new In(args[0]);
      G = GraphGenerator.fromIn (in);
    } else {
      int V = Integer.parseInt (args[0]);
      int E = Integer.parseInt (args[1]);
      G = GraphGenerator.simple(V, E);
    }
    StdOut.println(G);
    G.toGraphviz ("g.png");
  }
}