class Graph {
  ArrayList edges;
  ArrayList nodes;

  PImage img; // buffer for drawing static graph

  Graph() {
    edges = new ArrayList();
    nodes = new ArrayList();
    createRectGraph();
    paintGraph();

    // stunt: capture the edges as an image
    img = get();
  }
  void paint() {
    image(img,0,0);
    //background(img);
  }
  void paintGraph() {
    background(200);
    for(int i = 0; i<edges.size(); i++) ((Edge)edges.get(i)).paint();
    for(int i = 0; i<nodes.size(); i++) ((Node)nodes.get(i)).paint();
  }

  void createRectGraph() {
    int dx = 25;
    int nx = (width/dx) - 1;
    int dy = 25;
    int ny = (height/dy) - 1;
    println ("Geography: dx=" + dx + " nx=" + nx + " dy=" + dy + " ny=" + ny + " nx*ny=" + nx*ny);
    for(int j = 0; j<ny; j++) {
      for(int i = 0; i<nx; i++) {
        int numNodes = nodes.size();
        Node n = new Node((i+1)*dx, (j+1)*dy);
        nodes.add(n);
        if(i>0) edges.add(new Edge(n,(Node)nodes.get(numNodes-1)));
        if(j>0) edges.add(new Edge(n,(Node)nodes.get(numNodes-nx)));
      }
    }
    println ("Graph: Nodes=" + nodes.size() + " Edges=" + edges.size());
  }
}