/*
** Pairs sample applet
**
** by (c) Copyright 2001 Simon Huggins
** 
** For demonstration purposes only.
**
** You may use this applet on your web site, but it cannot be
** sold in either its original or altered state.
** This original notice must be included in all versions of
** the applet distributed, even if altered.
**
** The author accepts no liability for any difficulties or loss
** arising from use of this applet. It is primarily intended for
** demonstration purposes.
**
** Change History
** ~~~~~~~~~~~~~~
** 01-Oct-2001  v1.0  Release version
*/


/*
** Import section - tells the compiler where to look for different classes
** used within this file
*/
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;

/*
** Defines a class called Pairs which takes the basic JApplet
** class as a template, and adds to it to create our Applet.
** Also implementing ActionListener interface for mouse clicks
*/
public class Pairs extends JApplet implements ActionListener {

  JButton buttons[];  // array of buttons to appear on grid
  int buttonValues[];  // values of those buttons (hidden)
  int squaresAcross = 4, squaresDown = 4;  // default grid size
  int firstSelection = -1;  // first value index selected of pair
  boolean oneSelected = false;  // has first of pair been selected?

  JButton firstButton,secondButton; // last pair of buttons selected

  /*
  ** Initialize the applet - i.e. set up any values before processing begins
  */
  public void init() {
    /* Get number of buttons across and down from HTML parameters */
    String squaresAcrossString = getParameter("squaresAcross");
    if(squaresAcrossString != null) // check if the parameter was used
      squaresAcross = Integer.parseInt(squaresAcrossString);

    String squaresDownString = getParameter("squaresDown");
    if(squaresDownString != null) // check if the parameter was used
      squaresDown = Integer.parseInt(squaresDownString);

    /* Set up a grid layout holding the given number of squares across and down */
    getContentPane().setLayout(new GridLayout(squaresDown,squaresAcross));

    int buttonCount = squaresDown * squaresAcross;  // store this for easy reference

    /* Set up the arrays to hold JButtons and their hidden values to match the grid */
    buttons = new JButton[buttonCount];
    buttonValues = new int[buttonCount];

    /* Set up pairs of numbers in the buttonValues array in sequential order */
    for (int i=0 ; i < buttonCount ; i++) buttonValues[i] = (int)((i+2)/2.0);

    /* Randomize the ordering of buttonValues by swapping values around */
    for (int i=0 ; i < buttonCount ; i++) {
      int swapFirst = (int)(Math.random() * buttonCount);
      int swapSecond = (int)(Math.random() * buttonCount);
      int swapValue = buttonValues[swapFirst];
      buttonValues[swapFirst] = buttonValues[swapSecond];
      buttonValues[swapSecond] = swapValue;
    }

    /* Add all the buttons to the content pane from the buttons array.
       Note that each button is givena name buttonx where x is the number
       corresponding to the buttonValues array - this is used later */
    for (int i=0;i<buttonCount;i++) {
      buttons[i] = new JButton("?");
      buttons[i].setName("button"+Integer.toString(i));
      buttons[i].addActionListener(this);
      getContentPane().add(buttons[i]);
    }
  }

  /*
  ** ActionListener Interface method triggered by mouse clicks
  */
  public void actionPerformed(ActionEvent event) {

    /* First, check that the source that originated the action is a JButton */
    if (event.getSource() instanceof JButton) {

      /* It is, so put it into a variable called clickedButton for easy reference */
      JButton clickedButton = (JButton)event.getSource();

      /* Extract the buttonValue index from the name of the button (7th char to end) */
      int buttonIndex = Integer.parseInt(clickedButton.getName().substring(6));
      /* ... and put the hidden value into a variable called buttonValue*/
      int buttonValue = buttonValues[buttonIndex];

      /* if the text on the button is -MATCH- then this button has already been matched */
      if (clickedButton.getText()=="-MATCH-") return;

      /* if oneSelected is set to false, then pair or nothing selected */
      if (!oneSelected) {
        /* if pair selected (firstSelection no longer default value of -1)... */
        if (firstSelection != - 1)
          /* ... then if the text on the first button of the pair is -MATCH- */
          if (firstButton.getText()!="-MATCH-") {
            /* ... then clear the previous two buttons of their text */
            firstButton.setText("?"); secondButton.setText("?");
          }

        /* remember the buttonValues index no of the first selection */
        firstSelection = buttonIndex;
        /* ... and the button itself */
        firstButton = clickedButton;
        /* Reveal the button's number - convert it to a string first */
        clickedButton.setText(Integer.toString(buttonValue));
        /* So now one button has been selected - remember this */
        oneSelected = true;
        return;  // and return from the actionPerformed method - don't go any further.
      }

      /* However, if one button HAS been previously selected... */
      /* if the button was pressed twice, ignore the click */
      if (buttonIndex == firstSelection) return;
      
      oneSelected = false;  // reset back to false, as another has now been selected

      /* if the button value from the first button is the same as the second button */
      if (buttonValues[firstSelection]==buttonValue) {
        /* It's a match, so set the first and second button's text to -MATCH- */
        clickedButton.setText("-MATCH-");
        firstButton.setText("-MATCH-");
        return;  // ... and return back from the actionPerformed method.
      }

      /* So the first and second buttons didn't match...
         Reveal the number behind the second button (just clicked)... */
      clickedButton.setText(Integer.toString(buttonValue));
      /* ... and remember what the second button was, so we can clear its text later */
      secondButton = clickedButton;
    }
  }

  /*
  ** Define information about the applet - in Appletviewer, see Applet | Info menu
  */
  public String getAppletInfo() {
    return "Title: Pairs\nAuthor: Simon Huggins\nSimple Pairs Applet"; }

}