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

/**
 * Class RectDrawingListener extends Java's MouseInputAdpater to provide
 * handlers for three mouse events: mouse pressed, mouse dragged, and mouse
 * released.  The comments for the event-handling methods describe in
 * detail what each method does to allow the user to draw rectangles.
 *                                                                      <p>
 * The general drawing strategy is to add and remove rectangles from the
 * canvas shapeList as the mouse is being dragged, repainting the canvas at
 * each addition.  Since repainting is done efficiently by Java, this
 * technique is visually OK even if the canvas shapeList contains a large
 * number of other rectangles to be drawn.
 */
public class RectDrawingListener extends MouseInputAdapter {

    private DrawingCanvas canvas;
    private WorkSpace workSpace;
    /** The starting x-axis position for drawing a shape */
    private int startX;

    /** The starting y-axis position for drawing a shape */
    private int startY;

    /** Quadrant-I normalized value of startY */
    private int nStartY;

    /** True if the user is moving the mouse. */
    private boolean moving = false;


    public RectDrawingListener(DrawingCanvas canvas, WorkSpace workSpace) {
        this.canvas = canvas;
        this.workSpace = workSpace;
    }

    /**
     * Record the initial mouse press as the starting point of the
     * rectangle to be drawn.  Add a single-point rectangle to the
     * shapeList to start off the add/remove drawing process.  In this way,
     * mouseDragged will do a remove first, then add a new rect.
     */
    public void mousePressed(MouseEvent e) {
        Shape selection = workSpace.getSelection();
        if (selection != null) {
            selection.selected = false;
        }

        int ch = canvas.getHeight();
        startX = e.getX();
        startY = e.getY();
        nStartY = ch - startY;
//      System.out.println("startX=" + startX + ", startY=" + startY);
        workSpace.add(new Rectangle(0, 0, new Point(startX, nStartY),
            Color.BLACK, false));
        moving = true;
    }

    /**
     * Remove the previously drawn rect and add a new one that extends from
     * the starting point to the current mouse position.  Then call
     * canvas.repaint, which will efficiently redraw the entire canvas,
     * including all of the other items in the shapeList.
     */
    public void mouseDragged(MouseEvent e) {
        int x = e.getX();
        int y = e.getY();
        int ch = canvas.getHeight();
        int ny = ch - y;
        int width = x - startX;
        int height = y - startY;

//          System.out.println(
//              "Mouse dragged in panel at " + e.getX() + "," + e.getY());

        workSpace.remove(workSpace.size() - 1);
        workSpace.add(new Rectangle(
            width >= 0 ? width : -width,
            height >= 0 ? height : -height,
            new Point(
                width >= 0 ? startX : x,
                height >= 0 ? nStartY : ny),
            Color.BLACK,
            false));
        canvas.repaint();

        /*
         * The following might look like an alternative implementation,
         * however it produces a smearing effect, since rects drawn in 
         * previous invocations of mouseDragged are not erased.
         *
        g2.drawRect(
            startX, startY, e.getX() - startX, e.getY() - startY);
         *
         */
    }

    /**
     * Remove the previously drawn rect and add a new rect in its final
     * position.  Then call repaint.
     */
    public void mouseReleased(MouseEvent e) {
        int x = e.getX();
        int y = e.getY();
        int ch = canvas.getHeight();
        int ny = ch - y;
        int width = x - startX;
        int height = y - startY;
        Rectangle rect;

        workSpace.remove(workSpace.size() - 1);
        workSpace.add(rect = new Rectangle(
            width >= 0 ? width : -width,
            height >= 0 ? height : -height,
            new Point(
                width >= 0 ? startX : x,
                height >= 0 ? nStartY : ny),
            Color.BLACK,
            false));

//      System.out.println(x + "," + y + ","  + width + ","  + height);
        moving = false;
        rect.selected = true;
        workSpace.setSelection(rect);
        canvas.repaint();
    }

}