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

/****************************************************************
*    Canvas class. Accpets inputs and draws the graph.		*
*	- initialize():	Initializes the whole graph;		*
*	- mouseDown():	Reacts to clicks or shift-clicks;	*
*	- mouseDrag():  Reacts to mouse drags;			*
*	- addPoint():	Add a point and update display;		*
*	- deletePoint():Delete a point and update display;	*
*	- run():	Show animation;				*
*	- paint():	Draw graphs.				*
****************************************************************/

class DrawingArea 
    extends Canvas 
    implements MouseListener, MouseMotionListener {

    private BSPCell root;

    private Node prevMousePos, selectPos;
    private Image   img;
    private Graphics gc;

    private int numLinksToHighlight;

    /* these are accessed by the Controls object */
    boolean polygonMode;
    boolean closeMode;

    public static final int nodeSize = 6; // assume this to be even
    public static final int nodeSizeDiv2 = nodeSize/2;

    public DrawingArea(int x, int y) 
    {
	super();
	preferredSize = new Dimension(x, y);
	setBackground(Color.white);
	addMouseListener(this);
	addMouseMotionListener(this);
	initialize();
    }

    Dimension preferredSize;
    public Dimension getPreferredSize() 
    {
	return preferredSize;
    }

    void setImageAndGC(Image i, Graphics g) 
    {
	img = i; gc = g;
	repaint();
    }

    // Initialize data structure
    void initialize() 
    {
	root = new BSPCell(preferredSize.width, 
			   preferredSize.height);

	eyePoint    = new Node(preferredSize.width/2,
			       preferredSize.height/2);
	anchorPoint = null;
	setEnabled(true);
	prevMousePos = null;
	repaint();
    }

    /* need to make eye, which is draggable */
    Node eyePoint;
    Node anchorPoint;

    public void mousePressed(MouseEvent e) {
	int x        = e.getX();
	int y        = e.getY();
	int modifier = e.getModifiers();

	Util.dbgPrintln("mpressed: "+modifier+" "+MouseEvent.BUTTON3_MASK);
	
	// checking MouseEvent.BUTTON1_MASK doesn't work for netscape,
	// so check for button3 and reverse the if-condition claues instead
	if ((modifier & MouseEvent.BUTTON3_MASK) > 0) {
	    Util.dbgPrintln("Adding point at (" +x+","+y+").");
	    anchorPoint = new Node(x, y);
	    prevMousePos = new Node(x, y); 
	}
	else { 
	    eyePoint.setLocation(x,y);
	    prevMousePos = eyePoint;
	}

	selectPos = (Node) prevMousePos.clone();
	repaint();
    }

    private boolean isVerticalDisplacement(int x, int y)
    {
	Util.assert(selectPos != null, 
		    "DrawingArea::isVerticalDisplacement");
	double slope = (double) (x - selectPos.x)/(y - selectPos.y);
	return Math.abs(slope) >= 1.0;
    }

    public void mouseDragged(MouseEvent e) 
    {
	int x        = e.getX();
	int y        = e.getY();
	int modifier = e.getModifiers();

	/* to restrict displacement to either HORIZONTAL or VERTICAL */
	if ((modifier & MouseEvent.SHIFT_MASK) > 0) {
	    if(isVerticalDisplacement(x, y))
		y = selectPos.y;
	    else
		x = selectPos.x;
	}

	int xx = Math.max(Math.min(x, getPreferredSize().width-nodeSizeDiv2), nodeSizeDiv2);
	int yy = Math.max(Math.min(y, getPreferredSize().height-nodeSizeDiv2), nodeSizeDiv2);

	Util.assert(prevMousePos != null, "DrawingArea::mouseDragged()");
	Util.dbgPrintln("Dragging: (" + xx + ", " + yy + ")");
	prevMousePos.setLocation(xx, yy);
	repaint();
    }

    public void mouseReleased(MouseEvent e) 
    {
	if(anchorPoint != null) {
	    BSPCell.insert(root, new Segment(anchorPoint, prevMousePos));
	    anchorPoint = null;
	    repaint();
	}
    }

    public void mouseClicked(MouseEvent e) { return; }
    public void mouseEntered(MouseEvent e) { return; }
    public void mouseExited(MouseEvent e) { return; }
    public void mouseMoved(MouseEvent e) { return; }
    
    public void clear()
    {
	initialize();
    }

    public void update(Graphics g)
    {
	//double buffering to avoid flickering
	if(img != null) {
	    gc = img.getGraphics();
	    paint(gc);
	    g.drawImage(img, 0, 0, this);
	}
    }

    public void paint(Graphics g) 
    {
	super.paint(g);
	g.clearRect(0, 0, 
		    getPreferredSize().width, 
		    getPreferredSize().height);

	if(eyePoint != null) {
	    BSPCell c = BSPCell.Locate(root, eyePoint);
	    c.draw(g, Color.cyan);
	    eyePoint.draw(g, Color.red);
	    g.drawString("E", eyePoint.x+3, eyePoint.y-3);
	    BSPCell.resetOrder();
	    BSPCell.Traverse(g, root, eyePoint);
	}
	
	if(anchorPoint != null) {
	    // dragging
	    anchorPoint.draw(g, Color.blue);
	    prevMousePos.draw(g, Color.blue);
	    g.drawLine(anchorPoint.x, anchorPoint.y,
		       prevMousePos.x, prevMousePos.y);
	}
    }
}