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package josx.platform.rcx;

/**
 * Abstraction for an RCX button.
 * Example:<p>
 * <code><pre>
 *    Button.RUN.waitForPressAndRelease();
 *    Sound.playTone (1000, 1);
 * </pre></code>
 */
public class Button implements ListenerCaller
{
  /**
   * The Run button.
   */
  public static final
  Button RUN = new Button (0x01);
  /**
   * The View button.
   */
  public static final
  Button VIEW = new Button (0x02);
  /**
   * The Prgm button.
   */
  public static final
  Button PRGM = new Button (0x04);
  
  /**
   * Array containing VIEW, PRGM and RUN, in that order.
   */
  public static final
  Button[] BUTTONS =
  { Button.RUN, Button.VIEW, Button.PRGM };
  
  private int iCode;
  private
  ButtonListener[] iListeners =
  new ButtonListener[4];
  private int iNumListeners;
  
  private Button (int aCode)
  {
    iCode = aCode;
  }

  /**
   * Return the ID of the button.
   * One of 1, 2 or 4.
   */
  public final int getId()
  {
    return iCode;
  }
    
  /**
   * @return <code>true</code> if
   * button is pressed,
   * <code>false</code> otherwise.
   */
  public final boolean isPressed()
  {
    return (readButtons() & iCode) != 0;
  }

  static Poll poller = new Poll();

  /**
   * Wait until the button is released.
   */
  public final void waitForPressAndRelease()
      throws InterruptedException
  {
    do {
        poller.poll(iCode <<
                    Poll.BUTTON_MASK_SHIFT, 0);
    } while (isPressed());
  }

  /**
   * Adds a listener of button events.
   * Each button can serve at most
   * 4 listeners.
   */
  public synchronized
  void addButtonListener (ButtonListener aListener)
  {
    if (iListeners == null)
    {
      iListeners = new ButtonListener[4];
    }
    iListeners[iNumListeners++] = aListener;
    ListenerThread.get().addButtonToMask(iCode, this);
  }

  /**
   * <i>Low-level API</i> that reads
   * status of buttons.
   * @return An integer with possibly
   * some bits set:
   * 0x02 (view button pressed)
   * 0x04 (prgm button pressed),
   * 0x01 (run button pressed). If all buttons 
   * are released, this method returns 0.
   */
  public static int readButtons() {
      synchronized (Memory.MONITOR) {
          int pAddr = Memory.iAuxDataAddr;
          ROM.call ((short) 0x1fb6,
                    (short) 0x3000,
                    (short) pAddr);
          return Memory.readShort (pAddr);
      }
  }

  public synchronized void callListeners()
  {
    for( int i = 0;
         i < iNumListeners; i++) {
        if( isPressed())
            iListeners[i].buttonPressed( this);
        else
            iListeners[i].buttonReleased( this);
    }
  }
}