/*
 * Copyright 2000-2011 JetBrains s.r.o.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.intellij.openapi.wm.impl;

import com.intellij.openapi.application.ApplicationManager;
import com.intellij.util.containers.ContainerUtil;

import java.awt.*;
import java.awt.event.AWTEventListener;
import java.awt.event.KeyEvent;
import java.util.List;

/**
 * @author pegov
 */
public class AltStateManager implements AWTEventListener {

  private static final AltStateManager ourInstance;

  static {
    ourInstance = new AltStateManager();
    if (!ApplicationManager.getApplication().isUnitTestMode()) {
      Toolkit.getDefaultToolkit().addAWTEventListener(ourInstance, AWTEvent.KEY_EVENT_MASK);
    }
  }

  private final List<AltListener> myListeners = ContainerUtil.createLockFreeCopyOnWriteList();

  public interface AltListener {
    void altPressed();

    void altReleased();
  }

  private AltStateManager() {
  }

  public static AltStateManager getInstance() {
    return ourInstance;
  }

  public void addListener(AltListener listener) {
    myListeners.add(listener);
  }

  public void removeListener(AltListener listener) {
    myListeners.remove(listener);
  }

  @Override
  public void eventDispatched(AWTEvent event) {
    KeyEvent keyEvent = (KeyEvent)event;
    if ((keyEvent.getKeyCode() == KeyEvent.VK_ALT)) {
      if (keyEvent.getID() == KeyEvent.KEY_PRESSED) {
        firePressed();
      }
      else if (keyEvent.getID() == KeyEvent.KEY_RELEASED) {
        fireReleased();
      }
    }
  }

  private void fireReleased() {
    for (AltListener listener : myListeners) {
      listener.altReleased();
    }
  }

  private void firePressed() {
    for (AltListener listener : myListeners) {
      listener.altPressed();
    }
  }
}