import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

// This class represents a canvas on which a graph is edited and displayed
public class GraphEditor  extends JPanel implements MouseListener, KeyListener, MouseMotionListener {
    // Keep the model (i.e. the graph)
    private Graph  aGraph;
    private Node   dragNode;
    private Edge   dragEdge;
    private Point  elasticEndLocation, dragPoint;	

    public GraphEditor() { this(new Graph()); }
    public GraphEditor(Graph g) {
        aGraph = g;
        setBackground(Color.white);
		addEventHandlers();
    }
    
    public Graph getGraph() { return aGraph; }
    public void setGraph(Graph g) { aGraph = g; update(); }

    // This is the method that is responsible for displaying the graph
    public void paintComponent(Graphics aPen) {
        super.paintComponent(aPen);
        aGraph.draw(aPen);
		if (dragNode != null)
			if (!dragNode.isSelected())
				aPen.drawLine(dragNode.getLocation().x, dragNode.getLocation().y,
                              elasticEndLocation.x, elasticEndLocation.y);
    }
	
    public void mouseClicked(MouseEvent event) {
    	// If this was a double-click, then add/select a node or select an edge
    	if (event.getClickCount() == 2) {
			Node     aNode = aGraph.nodeAt(event.getPoint());
			if (aNode == null) {
				// We missed a node, now try for an edge midpoint
				Edge anEdge = aGraph.edgeAt(event.getPoint());
				if (anEdge == null)
					aGraph.addNode(new Node(event.getPoint()));
				else
					anEdge.toggleSelected();
			}
			else
				aNode.toggleSelected();		

    		// We have changed the model, so now we update
    		update();
    	}
    }
	
	// Mouse press event handler
	public void mousePressed(MouseEvent event) {
		// First check to see if we are about to drag a node
		Node     aNode = aGraph.nodeAt(event.getPoint());
		if (aNode != null) {
			// If we pressed on a node, store it
			dragNode = aNode;
		}
		else
			dragEdge = aGraph.edgeAt(event.getPoint());
		dragPoint = event.getPoint();
	}
	
	// Mouse drag event handler
	public void mouseDragged(MouseEvent event) {
		if (dragNode != null)  {
			if (dragNode.isSelected()) {
				for (Node n:  aGraph.selectedNodes()) {
					n.getLocation().translate(
						event.getPoint().x - dragPoint.x,
						event.getPoint().y - dragPoint.y);
				}	
				dragPoint = event.getPoint();
			}
			else
				elasticEndLocation = event.getPoint();
		}	
				
		if (dragEdge != null) {
			if (dragEdge.isSelected()) {
				dragEdge.getStartNode().getLocation().translate(
						event.getPoint().x - dragPoint.x,
						event.getPoint().y - dragPoint.y);
				dragEdge.getEndNode().getLocation().translate(
						event.getPoint().x - dragPoint.x,
						event.getPoint().y - dragPoint.y);
				dragPoint = event.getPoint();
			}
		}
		
		// We have changed the model, so now update
		update();
	}

	// Mouse release event handler (i.e. stop dragging process)
	public void mouseReleased(MouseEvent event) {
		// Check to see if we have let go on a node
		Node     aNode = aGraph.nodeAt(event.getPoint());
		if ((aNode != null) && (aNode != dragNode))
			aGraph.addEdge(dragNode, aNode);

		// Refresh the panel either way
		dragNode = null;
		update();
	}
	 
    public void mouseEntered(MouseEvent event) {}
    public void mouseExited(MouseEvent event) {}
    public void mouseMoved(MouseEvent event) {}
	
	public void keyTyped(KeyEvent event) {}
	public void keyReleased(KeyEvent event) {}

	public void keyPressed(KeyEvent event) {
		if (event.getKeyCode() == KeyEvent.VK_DELETE) {
			// First remove the selected edges
			for(Edge e:  aGraph.selectedEdges())
				aGraph.deleteEdge(e);
	
			// Now remove the selected nodes
			for (Node n:  aGraph.selectedNodes())
				aGraph.deleteNode(n);
			update();
		}
	}
	 
	public void update() {
		requestFocus();
		removeEventHandlers();
		repaint();
		addEventHandlers();
	}
	public void addEventHandlers() {
		addMouseMotionListener(this);
		addMouseListener(this);
		addKeyListener(this);
	}
	public void removeEventHandlers() {
		removeMouseMotionListener(this);
		removeMouseListener(this);
		removeKeyListener(this);
	}
}