// Animated Marker Movement. Robert Gerlach 2012-2013 https://github.com/combatwombat/marker-animate
// MIT license
//
// params:
// newPosition        - the new Position as google.maps.LatLng()
// options            - optional options object (optional)
// options.duration   - animation duration in ms (default 1000)
// options.easing     - easing function from jQuery and/or the jQuery easing plugin (default 'linear')
// options.complete   - callback function. Gets called, after the animation has finished
google.maps.Marker.prototype.animateTo = function(newPosition, options) {
    defaultOptions = {
      duration: 1000,
      easing: 'linear',
      complete: null
    }
    options = options || {};
  
    // complete missing options
    for (key in defaultOptions) {
      options[key] = options[key] || defaultOptions[key];
    }
  
    // throw exception if easing function doesn't exist
    if (options.easing != 'linear') {            
      if (typeof jQuery == 'undefined' || !jQuery.easing[options.easing]) {
        throw '"' + options.easing + '" easing function doesn\'t exist. Include jQuery and/or the jQuery easing plugin and use the right function name.';
        return;
      }
    }
    
    window.requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame || window.msRequestAnimationFrame;
    window.cancelAnimationFrame = window.cancelAnimationFrame || window.mozCancelAnimationFrame;
  
    // save current position. prefixed to avoid name collisions. separate for lat/lng to avoid calling lat()/lng() in every frame
    this.AT_startPosition_lat = this.getPosition().lat();
    this.AT_startPosition_lng = this.getPosition().lng();
    var newPosition_lat = newPosition.lat();
    var newPosition_lng = newPosition.lng();
    
    // crossing the 180° meridian and going the long way around the earth?
    if (Math.abs(newPosition_lng - this.AT_startPosition_lng) > 180) {
      if (newPosition_lng > this.AT_startPosition_lng) {      
        newPosition_lng -= 360;      
      } else {
        newPosition_lng += 360;
      }
    }
  
    var animateStep = function(marker, startTime) {            
      var ellapsedTime = (new Date()).getTime() - startTime;
      var durationRatio = ellapsedTime / options.duration; // 0 - 1
      var easingDurationRatio = durationRatio;
  
      // use jQuery easing if it's not linear
      if (options.easing !== 'linear') {
        easingDurationRatio = jQuery.easing[options.easing](durationRatio, ellapsedTime, 0, 1, options.duration);
      }
      
      if (durationRatio < 1) {
        var deltaPosition = new google.maps.LatLng( marker.AT_startPosition_lat + (newPosition_lat - marker.AT_startPosition_lat)*easingDurationRatio,
                                                    marker.AT_startPosition_lng + (newPosition_lng - marker.AT_startPosition_lng)*easingDurationRatio);
        marker.setPosition(deltaPosition);
  
        // use requestAnimationFrame if it exists on this browser. If not, use setTimeout with ~60 fps
        if (window.requestAnimationFrame) {
          marker.AT_animationHandler = window.requestAnimationFrame(function() {animateStep(marker, startTime)});                
        } else {
          marker.AT_animationHandler = setTimeout(function() {animateStep(marker, startTime)}, 17); 
        }
  
      } else {
        
        marker.setPosition(newPosition);
  
        if (typeof options.complete === 'function') {
          options.complete();
        }
  
      }            
    }
  
    // stop possibly running animation
    if (window.cancelAnimationFrame) {
      window.cancelAnimationFrame(this.AT_animationHandler);
    } else {
      clearTimeout(this.AT_animationHandler); 
    }
    
    animateStep(this, (new Date()).getTime());
  }