package edu.hws.eck.mdb;

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

/**
 * A MandelbrotPanel contains a MandelbrotDisplay and a status bar.  The display
 * computes and displays a visualization of the Mandelbrot Set.  The status bar is
 * a JLabel that is used to display information that the user might be interested
 * in.  A mouse listener is installed on the display that enables the user to
 * zoom in and out on the image.  Nothing is done to stop the user from zooming
 * in beyond the limited accuracy of numbers of type double -- when this happens,
 * the picture will first become "blocky" and with even further zooms will become
 * meaningless.
 * 
 * <p>Mouse actions on the display:
 * <ul>
 * <li>Moving or dragging the mouse shows image coordinates corresponding to mouse location.
 * <li>Clicking the mouse zooms in on or out from a point.  If shift or meta is down when the
 * mouse was pressed, or if the right mouse button is used, then zoom out by a factor of 2;
 * otherwise, zoom in by a factor of 2.  If alt is down when the mouse is pressed, or if
 * the middle mouse button is used, then the point that was clicked is moved to the center
 * of the image; otherwise, it stays where it is and the rest of the picture moves toward
 * that point or away from it.
 * <li>Dragging the mouse will draw a box around a region of the image.  The box is forced
 * to have the same aspect ratio (shape) as the display.  The box is not drawn if it would
 * be too narrow.  If the box is there when the mouse is released, then the image is
 * zoomed.  With no modifier keys and using the left mouse button, the inside of the
 * box is zoomed to fill the entire display (this zooms in on the image, which is usually
 * what you want).  If the shift or meta key is down, or if the right mouse button is used, 
 * then the entire display is shrunk down into the box (this zooms out).
 * </ul>
 */
public class MandelbrotPanel extends JPanel {
    
    private MandelbrotDisplay display;
    private JLabel statusBar;

    /**
     * Create a panel containing a MandelbrotDisplay and the label that
     * is used as a status bar.  Also add a mouse listener of type
     * MouseHandler (defined in this class).  A ComponentListener
     * is added that will respond to a change in the size of the
     * display by reporting the new size in the status bar.
     */
    public MandelbrotPanel() {
        setLayout(new BorderLayout());
        display = new MandelbrotDisplay();
        statusBar = new JLabel(I18n.tr("Idle"));
        add(display,BorderLayout.CENTER);
        add(statusBar,BorderLayout.SOUTH);
        MouseHandler mouser = new MouseHandler();
        display.addMouseListener(mouser);
        display.addMouseMotionListener(mouser);
        display.addComponentListener( new ComponentAdapter() {
            public void componentResized(ComponentEvent evt) {
                   // Called when the display changes size; report the new
                   // size in the status bar.  Note that this is also
                   // called when the display gets its initial size, so
                   // when the program opens, the image size will be shown
                   // in the status bar.
                String w = "" + display.getWidth();
                String h = "" + display.getHeight();
                statusBar.setText(I18n.tr("status.imageSize",w,h));
            }
        });
    }
    
    
    /**
     * Returns the MandelbrotDisplay that is contained in this panel.
     */
    public MandelbrotDisplay getDisplay() {
        return display;
    }
    
    /**
     * Zoom in on or out from a point in the image.
     * @param x x-coordinate of the point at the center of the zoom
     * @param y y-coordinate of the point at the center of the zoom
     * @param factor magnification or shrinking factor.  If factor is
     *   greater than 1, zoom out.  If factor is less than 1, zoom in.
     *   For example, factor=0.5 shrinks the x,y ranges in the image
     *   to half their previous size.
     * @param movePointToCenter if true, then the image point at pixel
     *   position (x,y) is moved to the center pixel of the image after
     *   the zoom; if false, the point is not moved so that the pixel
     *   at (x,y) represents the same point after the zoom as before
     *   and all the other points move towards or away from that one.
     */
    public void zoom(int x, int y, double factor, boolean movePointToCenter) {
        double xmin = display.getXmin();
        double xmax = display.getXmax();
        double ymin = display.getYmin();
        double ymax = display.getYmax();
        double newWidth = factor*(xmax-xmin);
        double newHeight = factor*(ymax-ymin);
        double centerX = xmin + ((double)x)/display.getWidth()*(xmax-xmin);
        double centerY = ymax - ((double)y)/display.getHeight()*(ymax-ymin);
        if (movePointToCenter) {
            display.setLimits(centerX-newWidth/2,centerX+newWidth/2,
                    centerY-newHeight/2,centerY+newHeight/2);
        }
        else {
            double newXmin = centerX - newWidth*(centerX-xmin)/(xmax-xmin);
            double newYmin = centerY - newHeight*(centerY-ymin)/(ymax-ymin);
            display.setLimits(newXmin,newXmin+newWidth,newYmin,newYmin+newHeight);
        }
    }
    
    /**
     * Display the coordinates of the image point that corresponds
     * to pixel coordinates (x,y).
     */
    private void doShowCoordsInStatusBar(int x, int y) {
        double xmin = display.getXmin();
        double xmax = display.getXmax();
        double ymin = display.getYmin();
        double ymax = display.getYmax();
        double width = display.getWidth();
        double height = display.getHeight();
        double xCoord = xmin + x/width*(xmax-xmin);
        double yCoord = ymax - y/height*(ymax-ymin);
          // The next 10 lines try to avoid more digits after the decimal
          // points than makes sense.  If it succeeds the coordinates
          // that are shown should differ only in their last few digits.
        double diff = xmax - xmin;
        int scale = 4;
        if (diff > 0) {
            while (diff < 1) {
                scale++;
                diff *= 10;
            }
        }
        String xStr = String.format("%1." + scale + "f", xCoord);
        String yStr = String.format("%1." + scale + "f", yCoord);
        statusBar.setText(I18n.tr("status.mouseCoords",xStr,yStr));
    }
     
    
    /**
     * Defines the listener that responds to user mouse actions on the display.
     * Note that the (x,y) coordinates for the events refer to the display, since
     * the listeners are registered to respond to events on the display, not on
     * this panel.  Mouse drags and clicks are used for zooming the image.  Dragging
     * and mouse motion also show the current mouse coordinates in the status bar.
     */
    private class MouseHandler implements MouseListener, MouseMotionListener {
        
        int startX, startY;  // Location of mousePressed event.
        
        boolean dragging;  // True if a drag operation is in progress.

        boolean zoomOut;   // True if the action will be a zoom out rather than
                           // a zoom in.  This is set to true if the shift key
                           // or meta key is down for the mousePressed action.
                           // (Also true if the right-mouse button is used.)
        
        boolean moved;     // During a drag operation, this becomes true if
                           // the mouse actually moves at least a few pixels.
                           // If so, the mouse action is interpreted as a
                           // click rather than a drag.

        boolean movePointToCenter;   // True if the click point for a click
                                     // operation should be moved to the center
                                     // of the image; false if it should not
                                     // be moved.  This is set in the mousePressed
                                     // routine to be true if the alt/option key
                                     // is down (or the middle mouse button is used).

        public void mousePressed(MouseEvent evt) {
            doShowCoordsInStatusBar(startX,startY);
            dragging = false;
            if (display.getStatus() == MandelbrotDisplay.STATUS_OUT_OF_MEMORY) {
                   // If there is not enough memory to have an image in the display,
                   // don't try to zoom it!
                return;
            }
            startX = evt.getX();
            startY = evt.getY();
            zoomOut = evt.isShiftDown() || evt.isMetaDown();
            dragging = true;
            moved = false;
            movePointToCenter = evt.isAltDown();
        }

        
        public void mouseReleased(MouseEvent evt) {
            if (!dragging)
                return;
            if (moved)  // If moved is true, this is a drag operation, otherwise, a click.
                display.applyZoom(zoomOut);  // zoom into or out of zoom rect that user has drawn
            else if (zoomOut)
                zoom(startX,startY,2,movePointToCenter); // zoom out from point
            else
                zoom(startX,startY,0.5,movePointToCenter); // zoom in on point
            dragging = false;
        }

        public void mouseDragged(MouseEvent evt) {
            int x = evt.getX();
            int y = evt.getY();
            doShowCoordsInStatusBar(x,y);
            if (!dragging)
                return;
            int width = Math.abs(x-startX);
            int height = Math.abs(y-startY);
            if (Math.abs(width) < 3 || Math.abs(height) < 3) {
                   // Too close to start point to have a zoom box.
                if (!display.drawZoomBox(null)) {
                       // display.drawZoomBox() returns false if there is
                       // some error, such as not having an image, that
                       // prevents having a zoom box.  This is unlikely to
                       // happen, but if it does, we should cancel the zoom.
                    dragging = false;
                }
                return;
            }
            moved = true;  // Mouse has moved more than 2 pixels away from start position.
               // During a draw operation, a zoom box is drawn with one corner at the
               // mouse's starting position.  When the mouse is released, the image
               // is zoomed out form this box or into this box.
               // The next 6 lines adjust the shape of the zoom box so that it matches
               // the shape of the window.  This is so that zooming will use the same
               // magnification factor in both directions.
            double aspect = (double)width/height;
            double imageAspect = (double)display.getWidth()/display.getHeight();
            if (aspect < imageAspect)
                width = (int)(width*imageAspect/aspect+0.49);
            else if (aspect > imageAspect)
                height = (int)(height*aspect/imageAspect+0.49);
               // The next 9 lines compute the upper left corner of the rectangle,
               // so that it has one corner at the start position of the mouse;
               // width and height represent the size of the zoom rect.
            int x1,y1;
            if (x < startX)
                x1 = startX - width;
            else
                x1 = startX;
            if (y < startY)
                y1 = startY - height;
            else
                y1 = startY;
            Rectangle rect = new Rectangle(x1,y1,width,height);
            if (!display.drawZoomBox(rect))
                dragging = false;
        }

        public void mouseMoved(MouseEvent evt) { 
            doShowCoordsInStatusBar(evt.getX(),evt.getY());
        }
        
        public void mouseExited(MouseEvent evt) { 
               // When mouse moves out of the display, get rid of the coordinate
               // display in the status bar.
            statusBar.setText("Idle");
        }
        
        public void mouseEntered(MouseEvent evt) { }
        public void mouseClicked(MouseEvent evt) { }
        
    } // end nested class MouseHandler
    
    
} // end class MandelbrotPanel