package animation;

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

class animation extends JPanel {
  final int BOX_SIZE = 30;
  // number of frames per second. Movies use 24 frames per second, 
  // but I am using 25 since it evenly divides 1000 milliseconds
  final int FRAMES_PER_SECOND = 25;
  final int FRAME_INTERVAL = 1000 / 25;
  LabeledBox boxes[];
  int num_boxes;
  int num_seconds;
  Timer animationTimer;

  class mover implements ActionListener {
    int pixels_per_move = 4;
    final int UP = 0;
    final int RIGHT = 1;
    final int DOWN = 2;
    // the number of pixels that the boxes move vertically up or down
    final int VERTICAL_DISTANCE = 50;
    int action = UP;
    int startX;
    int endX;
    int startY;
    int endY;
    int totalDist; // total distance the boxes move
    LabeledBox upBox;
    LabeledBox downBox;

    public mover(LabeledBox box1, LabeledBox box2) {
      upBox = box1;
      downBox = box2;
      startX = upBox.getLeft();
      endX = downBox.getLeft();
      startY = upBox.getTop();
      endY = startY - VERTICAL_DISTANCE;
      totalDist = 2*VERTICAL_DISTANCE + (endX - startX);
      pixels_per_move = totalDist / (FRAMES_PER_SECOND * num_seconds);
    }

    public void actionPerformed(ActionEvent evt) {
      int slack = 0;
      if (action == UP) {
        int tentativeTop = upBox.getTop() - pixels_per_move;
	if (tentativeTop > endY) {
	  upBox.setPosition(upBox.getLeft(), tentativeTop);
	  downBox.setPosition(downBox.getLeft(), 
			      downBox.getTop() + pixels_per_move);
	  repaint();
	  return;
	}
	else {
 	  // start moving to the right by pegging the top and
	  // bottom boxes to their maximum vertical extents and
	  // take any additional pixels and add them to the x
	  // direction
	  action = RIGHT;
	  slack = endY - tentativeTop;
	  upBox.setPosition(startX, startY - VERTICAL_DISTANCE);
	  downBox.setPosition(endX, startY + VERTICAL_DISTANCE);
        }
      }
      if (action == RIGHT) {
	int tentativeUpLeft;
	int tentativeDownLeft;
	if (slack != 0) {
	  tentativeUpLeft = upBox.getLeft() + slack;
	  tentativeDownLeft = downBox.getLeft() - slack;
        }
	else {
	  tentativeUpLeft = upBox.getLeft() + pixels_per_move;
	  tentativeDownLeft = downBox.getLeft() - pixels_per_move;
        }
	if (tentativeUpLeft < endX) {
	  upBox.setPosition(tentativeUpLeft, upBox.getTop());
	  downBox.setPosition(tentativeDownLeft, downBox.getTop());
	  repaint();
	  return;
	}
	else {
 	  // peg the rectangles to their final Left positions and
	  // start them moving vertically to their final vertical
	  // positions
	  action = DOWN;
	  slack = tentativeUpLeft - endX;
	  upBox.setPosition(endX, upBox.getTop());
	  downBox.setPosition(startX, downBox.getTop());
	}
      }
      if (action == DOWN) {
 	int tentativeTop;
	int tentativeBottom;
	if (slack == 0) {
	    tentativeTop = upBox.getTop() + pixels_per_move;
	    tentativeBottom = downBox.getTop() - pixels_per_move;
	}
	else {
	    tentativeTop = upBox.getTop() + slack;
	    tentativeBottom = downBox.getTop() - slack;
        }
	if (tentativeTop < startY) {
	  upBox.setPosition(upBox.getLeft(), tentativeTop);
	  downBox.setPosition(downBox.getLeft(), tentativeBottom);
	  repaint();
	  return;
	}
	else {
	  // we are done--peg the boxes to their new vertical positions
	  upBox.setPosition(upBox.getLeft(), startY);
	  downBox.setPosition(downBox.getLeft(), startY);
	  repaint();
	  animationTimer.stop();
	}
      }
    }
  }

  public animation(int number_of_boxes, int seconds) {
    num_seconds = seconds;
    num_boxes = number_of_boxes;
    Dimension size = getPreferredSize();
    int starting_left = ((int)size.getWidth() - (num_boxes * BOX_SIZE)) / 2;
    int top = ((int)size.getHeight() - BOX_SIZE) / 2;

    boxes = new LabeledBox[num_boxes];
    for (int i = 0; i < num_boxes; i++) {
      boxes[i] = new LabeledBox(String.valueOf(i), starting_left, top, 
				BOX_SIZE);
      starting_left += BOX_SIZE;
    }
    ActionListener taskPerformer = new mover(boxes[1], boxes[6]);
    animationTimer = new Timer(FRAME_INTERVAL, taskPerformer);
    addMouseListener(new MouseAdapter() {
	public void mouseClicked(MouseEvent me) {
	  animationTimer.start();
	}
      });
  }

  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D)g;
    for (int i = 0; i < num_boxes; i++)
      boxes[i].draw(g2);
  }

  public Dimension getPreferredSize() {
    return new Dimension(400, 300);
  }
}