// Copyright 2012 Google Inc. All Rights Reserved.
//
// 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.google.collide.client.util.dom.eventcapture;

import elemental.events.Event;
import elemental.events.EventListener;
import elemental.events.MouseEvent;

/**
 * Listener that can be used for event capture. Simply add this as a
 * {@link Event#MOUSEDOWN} listener and then you will get mouse capture for
 * moves and mouse up for that element.
 */
public abstract class MouseCaptureListener implements EventListener {

  private int prevClientX;
  private int prevClientY;

  private int deltaX;
  private int deltaY;

  private CaptureReleaser releaser;

  public int getDeltaX() {
    return deltaX;
  }

  public int getDeltaY() {
    return deltaY;
  }

  @Override
  public void handleEvent(Event evt) {
    MouseEvent mouseEvent = (MouseEvent) evt;
    updateXYState(mouseEvent);

    if (evt.getType().equals(Event.MOUSEMOVE)) {
      onMouseMove(mouseEvent);
    } else if (evt.getType().equals(Event.MOUSEUP)) {
      release();
      onMouseUp(mouseEvent);
    } else if (evt.getType().equals(Event.MOUSEDOWN)) {
      if (onMouseDown(mouseEvent)) {
        // Start the capture
        MouseEventCapture.capture(this);
        mouseEvent.preventDefault();
      }
    }
  }

  public void release() {
    if (releaser != null) {
      releaser.release();
    }
  }

  /**
   * Called when the mousedown event is received.
   *
   * @return true if the capture should be initiated for mousemove and mouseup
   *         events.
   */
  protected boolean onMouseDown(MouseEvent evt) {
    return true;
  }

  protected void onMouseMove(MouseEvent evt) {
  }

  protected void onMouseUp(MouseEvent evt) {
  }

  void setCaptureReleaser(CaptureReleaser releaser) {
    this.releaser = releaser;
  }

  private void updateXYState(MouseEvent evt) {
    int x = evt.getClientX();
    int y = evt.getClientY();

    if (evt.getType().equals(Event.MOUSEDOWN)) {
      deltaX = deltaY = 0;
    } else {
      deltaX = x - prevClientX;
      deltaY = y - prevClientY;
    }

    prevClientX = x;
    prevClientY = y;
  }
}
