// This file contains excerpts from the textbook Concrete
// Abstractions: An Introduction to Computer Science Using Scheme, by
// Max Hailperin, Barbara Kaiser, and Karl Knight, Copyright (c) 1998
// by the authors. Full text is available for free at
// http://www.gustavus.edu/+max/concrete-abstractions.html

import java.awt.*;

public class Puzzle extends java.applet.Applet {

  private int size = 4;         // how many buttons wide and high
  private Button[][] buttons;
  private int blankRow, blankCol;  // position of the blank space

  public void init(){
    setLayout(new GridLayout(size, size));
    buttons = new Button[size][size];
    int buttonCount = 0;
    for(int row = 0; row < size; row++){
      for(int col = 0; col < size; col++){
        Button b = new Button();
        buttons[row][col] = b;
        b.addActionListener(new TileActionListener
                            (this, row, col));
        buttonCount++;
        b.setLabel("" + buttonCount);
        add(b);
      }
    }
    blankRow = size - 1;
    blankCol = size - 1;
    buttons[blankRow][blankCol].setLabel("");
  }

  public void pushTile(int row, int col){
    if(row == blankRow){
      for( ; blankCol < col; blankCol++){
        buttons[blankRow][blankCol].setLabel
          (buttons[blankRow][blankCol+1].getLabel());
      }
      for( ; blankCol > col; blankCol--){
        buttons[blankRow][blankCol].setLabel
          (buttons[blankRow][blankCol-1].getLabel());
      }
    } else if(col == blankCol){
      for( ; blankRow < row; blankRow++){
        buttons[blankRow][blankCol].setLabel
          (buttons[blankRow+1][blankCol].getLabel());
      }
      for( ; blankRow > row; blankRow--){
        buttons[blankRow][blankCol].setLabel
          (buttons[blankRow-1][blankCol].getLabel());
      }
    }
    buttons[blankRow][blankCol].setLabel("");
  }
}