/*
    * Copyright 2012 Daniel Kurka
    * 
    * 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.googlecode.mgwt.dom.client.recognizer.swipe;
  
  import com.google.gwt.core.client.GWT;
  import com.google.gwt.event.shared.HasHandlers;
  import com.googlecode.mgwt.dom.client.event.touch.Touch;
  import com.googlecode.mgwt.dom.client.event.touch.TouchCancelEvent;
  import com.googlecode.mgwt.dom.client.event.touch.TouchEndEvent;
  import com.googlecode.mgwt.dom.client.event.touch.TouchHandler;
  import com.googlecode.mgwt.dom.client.event.touch.TouchMoveEvent;
  import com.googlecode.mgwt.dom.client.event.touch.TouchStartEvent;
  import com.googlecode.mgwt.dom.client.recognizer.EventPropagator;
  import com.googlecode.mgwt.dom.client.recognizer.swipe.SwipeEvent.DIRECTION;
  
  public class SwipeRecognizer implements TouchHandler {
  
    private static EventPropagator DEFAULT_EVENT_PROPAGATOR;
  
    private final HasHandlers source;
  
    private EventPropagator eventPropagator;
  
    private final int minDistance;
  
    private final int threshold;
  
    private int touchCount;
  
    private enum State {
      INVALID, READY, FINDER_DOWN, FOUND_DIRECTION
    }
  
    private State state;
  
    private DIRECTION direction;
  
    private int lastDistance;
  
    private int x;
  
    private int y;
  
    /**
     * construct a swipe recognizer
     * 
     * @param source the source to fire events on
     */
    public SwipeRecognizer(HasHandlers source) {
      this(source, 40);
    }
  
    /**
     * construct a swipe recognizer
     * 
     * @param source the source to fire events on
     * @param minDistance the minimum distance to cover before this counts as a swipe
     */
    public SwipeRecognizer(HasHandlers source, int minDistance) {
      this(source, minDistance, 10);
    }
  
    /**
     * construct a swipe recognizer
     * 
     * @param source the source to fire events on
     * @param minDistance the minimum distance to cover before this counts as a swipe
     * @param threshold the initial threshold before swipe start is fired
     */
    public SwipeRecognizer(HasHandlers source, int minDistance, int threshold) {
      if (source == null)
        throw new IllegalArgumentException("source can not be null");
  
      if (minDistance <= 0 || minDistance < threshold) {
        throw new IllegalArgumentException("minDistance > 0 and minDistance > threshold");
      }
  
      if (threshold <= 0) {
        throw new IllegalArgumentException("threshold > 0");
      }
  
      this.source = source;
      this.minDistance = minDistance;
      this.threshold = threshold;
      this.touchCount = 0;
      state = State.READY;
    }
  
   /*
    * (non-Javadoc)
    * 
    * @see
    * com.googlecode.mgwt.dom.client.event.touch.TouchStartHandler#onTouchStart(com.googlecode.mgwt
    * .dom.client.event.touch.TouchStartEvent)
    */
   @Override
   public void onTouchStart(TouchStartEvent event) {
     touchCount++;
 
     switch (state) {
       case INVALID:
         break;
 
       case READY:
         state = State.FINDER_DOWN;
 
         x = event.getTouches().get(0).getPageX();
         y = event.getTouches().get(0).getPageY();
         break;
 
       case FINDER_DOWN:
       default:
         state = State.INVALID;
         break;
     }
 
   }
 
   /*
    * (non-Javadoc)
    * 
    * @see
    * com.googlecode.mgwt.dom.client.event.touch.TouchMoveHandler#onTouchMove(com.googlecode.mgwt
    * .dom.client.event.touch.TouchMoveEvent)
    */
   @Override
   public void onTouchMove(TouchMoveEvent event) {
     Touch touch = event.getTouches().get(0);
 
     switch (state) {
       case INVALID:
 
         break;
       case READY:
         // WTF?
         state = State.INVALID;
         break;
       case FINDER_DOWN:
 
         // log(" X: " + touch.getPageX() + " old: " + touchStart.getPageX() + " test: " + x);
 
         if (Math.abs(touch.getPageX() - x) >= threshold) {
           state = State.FOUND_DIRECTION;
 
           direction = touch.getPageX() - x > 0 ? DIRECTION.LEFT_TO_RIGHT : DIRECTION.RIGHT_TO_LEFT;
 
           SwipeStartEvent swipeStartEvent = new SwipeStartEvent(touch, touch.getPageX() - x, direction);
 
           getEventPropagator().fireEvent(source, swipeStartEvent);
 
         } else {
           if (Math.abs(touch.getPageY() - y) >= threshold) {
             state = State.FOUND_DIRECTION;
 
             direction = touch.getPageY() - y > 0 ? DIRECTION.TOP_TO_BOTTOM : DIRECTION.BOTTOM_TO_TOP;
 
             SwipeStartEvent swipeStartEvent = new SwipeStartEvent(touch, touch.getPageY() - y, direction);
 
             getEventPropagator().fireEvent(source, swipeStartEvent);
 
           }
 
         }
         break;
 
       case FOUND_DIRECTION:
 
         switch (direction) {
           case TOP_TO_BOTTOM:
           case BOTTOM_TO_TOP:
             lastDistance = Math.abs(touch.getPageY() - y);
             getEventPropagator().fireEvent(source, new SwipeMoveEvent(touch, lastDistance > minDistance, lastDistance, direction));
             break;
 
           case LEFT_TO_RIGHT:
           case RIGHT_TO_LEFT:
             lastDistance = Math.abs(touch.getPageX() - x);
             getEventPropagator().fireEvent(source, new SwipeMoveEvent(touch, lastDistance > minDistance, lastDistance, direction));
 
             break;
 
           default:
             break;
         }
 
         break;
 
       default:
         break;
     }
 
   }
 
   public native void log(String l)/*-{
 		$wnd.console.log(l);
   }-*/;
 
   /*
    * (non-Javadoc)
    * 
    * @see
    * com.googlecode.mgwt.dom.client.event.touch.TouchEndHandler#onTouchEnd(com.googlecode.mgwt.dom
    * .client.event.touch.TouchEndEvent)
    */
   @Override
   public void onTouchEnd(TouchEndEvent event) {
     touchCount--;
 
     switch (state) {
       case FOUND_DIRECTION:
         getEventPropagator().fireEvent(source, new SwipeEndEvent(lastDistance > minDistance, lastDistance, direction));
         reset();
         break;
 
       default:
         reset();
         break;
     }
 
   }
 
   /*
    * (non-Javadoc)
    * 
    * @see
    * com.googlecode.mgwt.dom.client.event.touch.TouchCancelHandler#onTouchCanceled(com.googlecode
    * .mgwt.dom.client.event.touch.TouchCancelEvent)
    */
   @Override
   public void onTouchCanceled(TouchCancelEvent event) {
     touchCount--;
     if (touchCount <= 0)
       reset();
 
   }
 
   /**
    * the threshold before an event is fired (deadzone)
    * 
    * @return the threshold in px
    */
   public int getThreshold() {
     return threshold;
   }
 
   /**
    * the distance that needs to be covered before counting as a swipe
    * 
    * @return the distance in px
    */
   public int getMinDistance() {
     return minDistance;
   }
 
   protected EventPropagator getEventPropagator() {
     if (eventPropagator == null) {
       if (DEFAULT_EVENT_PROPAGATOR == null) {
         DEFAULT_EVENT_PROPAGATOR = GWT.create(EventPropagator.class);
       }
       eventPropagator = DEFAULT_EVENT_PROPAGATOR;
     }
     return eventPropagator;
   }
 
   protected void setEventPropagator(EventPropagator eventPropagator) {
     this.eventPropagator = eventPropagator;
 
   }
 
   private void reset() {
     state = State.READY;
     touchCount = 0;
 
   }
 
 }