/* Copyright (c) 2008, Marcel Laverdet and Facebook, inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*    * Redistributions of source code must retain the above copyright
*      notice, this list of conditions and the following disclaimer.
*    * Redistributions in binary form must reproduce the above copyright
*      notice, this list of conditions and the following disclaimer in the
*      documentation and/or other materials provided with the distribution.
*    * Neither the name of Facebook, inc. nor the names of its contributors
*      may be used to endorse or promote products derived from this software
*      without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
function Animation(obj) {
 if (this == window) {
   return new Animation(obj);
 } else {
   this.obj = obj;
   this._reset_state();
   this.queue = [];
   this.last_attr = null;
 }
}
Animation.resolution = 20;
Animation.offset = 0;

// Initializes the state to blank values
Animation.prototype._reset_state = function() {
 this.state = {
   attrs: {},
   duration: 500 // default duration
 }
}

// Stops any current animation
Animation.prototype.stop = function() {
 this._reset_state();
 this.queue = [];
 return this;
}

// Builds an overflow:hidden container for this.obj. Used with .blind()
Animation.prototype._build_container = function() {
 if (this.container_div) {
   this._refresh_container();
   return;
 }
 // ref-counting here on the magic container in case someone decides to start two animations with blind() on the same element
 // Either way it's not ideal because if animating to 'auto' the calculations will probably be incorrect... but at least this
 // way it won't tear up your DOM.
 if (this.obj.firstChild && this.obj.firstChild.__animation_refs) {
   this.container_div = this.obj.firstChild;
   this.container_div.__animation_refs++;
   this._refresh_container();
   return;
 }
 var container = document.createElement('div');
 container.style.padding = '0px';
 container.style.margin = '0px';
 container.style.border = '0px';
 container.__animation_refs = 1;
 var children = this.obj.childNodes;
 while (children.length) {
   container.appendChild(children[0]);
 }
 this.obj.appendChild(container);
 this.obj.style.overflow = 'hidden';
 this.container_div = container;
 this._refresh_container();
}

// Refreshes the size of the container. Used on checkpoints and such.
Animation.prototype._refresh_container = function() {
 this.container_div.style.height = 'auto';
 this.container_div.style.width = 'auto';
 this.container_div.style.height = this.container_div.offsetHeight+'px';
 this.container_div.style.width = this.container_div.offsetWidth+'px';
}

// Destroys the container built by _build_container()
Animation.prototype._destroy_container = function() {
 if (!this.container_div) {
   return;
 }
 if (!--this.container_div.__animation_refs) {
   var children = this.container_div.childNodes;
   while (children.length) {
     this.obj.appendChild(children[0]);
   }
   this.obj.removeChild(this.container_div);
 }
 this.container_div = null;
}

// Generalized attr function. Calls to .to, .by, and .from go through this
Animation.ATTR_TO = 1;
Animation.ATTR_BY = 2;
Animation.ATTR_FROM = 3;
Animation.prototype._attr = function(attr, value, mode) {

 // Turn stuff like border-left into borderLeft
 attr = attr.replace(/-[a-z]/gi, function(l) {
   return l.substring(1).toUpperCase();
 });

 var auto = false;
 switch (attr) {
   case 'background':
     this._attr('backgroundColor', value, mode);
     return this;

   case 'margin':
     value = Animation.parse_group(value);
     this._attr('marginBottom', value[0], mode);
     this._attr('marginLeft', value[1], mode);
     this._attr('marginRight', value[2], mode);
     this._attr('marginTop', value[3], mode);
     return this;

   case 'padding':
     value = Animation.parse_group(value);
     this._attr('paddingBottom', value[0], mode);
     this._attr('paddingLeft', value[1], mode);
     this._attr('paddingRight', value[2], mode);
     this._attr('paddingTop', value[3], mode);
     return this;

   case 'backgroundColor':
   case 'borderColor':
   case 'color':
     value = Animation.parse_color(value);
     break;

   case 'opacity':
     value = parseFloat(value, 10);
     break;

   case 'height':
   case 'width':
     if (value == 'auto') {
       auto = true;
     } else {
       value = parseInt(value);
     }
     break;

   case 'borderWidth':
   case 'lineHeight':
   case 'fontSize':
   case 'marginBottom':
   case 'marginLeft':
   case 'marginRight':
   case 'marginTop':
   case 'paddingBottom':
   case 'paddingLeft':
   case 'paddingRight':
   case 'paddingTop':
   case 'bottom':
   case 'left':
   case 'right':
   case 'top':
   case 'scrollTop':
   case 'scrollLeft':
     value = parseInt(value, 10);
     break;

   default:
     throw a+' is not a supported attribute!';
     break;
 }

 if (this.state.attrs[attr] === undefined) {
   this.state.attrs[attr] = {};
 }
 if (auto) {
   this.state.attrs[attr].auto = true;
 }
 switch (mode) {
   case Animation.ATTR_FROM:
     this.state.attrs[attr].start = value;
     break;

   case Animation.ATTR_BY:
     this.state.attrs[attr].by = true;
     // fall through

   case Animation.ATTR_TO:
     this.state.attrs[attr].value = value;
     break;
 }
}


// Explcit animation to a certain value
Animation.prototype.to = function(attr, value) {
 if (value === undefined) {
   this._attr(this.last_attr, attr, Animation.ATTR_TO);
 } else {
   this._attr(attr, value, Animation.ATTR_TO)
   this.last_attr = attr;
 }
 return this;
}

// Animation by a value (i.e. add this value to the current value)
Animation.prototype.by = function(attr, value) {
 if (value === undefined) {
   this._attr(this.last_attr, attr, Animation.ATTR_BY);
 } else {
   this._attr(attr, value, Animation.ATTR_BY)
   this.last_attr = attr;
 }
 return this;
}

// Start the animation from a value instead of the current value
Animation.prototype.from = function(attr, value) {
 if (value === undefined) {
   this._attr(this.last_attr, attr, Animation.ATTR_FROM);
 } else {
   this._attr(attr, value, Animation.ATTR_FROM)
   this.last_attr = attr;
 }
 return this;
}

// How long is this animation supposed to last (in miliseconds)
Animation.prototype.duration = function(duration) {
 this.state.duration = duration ? duration : 0;
 return this;
}

// Checkpoint the animation to start a new one.
Animation.prototype.checkpoint = function(distance /* = 1.0 */, callback) {
 if (distance === undefined) {
   distance = 1;
 }
 this.state.checkpoint = distance;
 this.state.checkpointcb = callback;
 this.queue.push(this.state);
 this._reset_state();
 return this;
}

// This animation requires an overflow container (usually used for width animations)
Animation.prototype.blind = function() {
 this.state.blind = true;
 return this;
}

// Hide this object at the end of the animation
Animation.prototype.hide = function() {
 this.state.hide = true;
 return this;
}

// Show this object at the beginning of the animation
Animation.prototype.show = function() {
 this.state.show = true;
 return this;
}

// Use an easing function to adjust the distribution of the animation state over frames
Animation.prototype.ease = function(ease) {
 this.state.ease = ease;
 return this;
}

// Let the animation begin!
Animation.prototype.go = function() {
 var time = (new Date()).getTime();
 this.queue.push(this.state);

 for (var i = 0; i < this.queue.length; i++) {
   this.queue[i].start = time - Animation.offset;
   if (this.queue[i].checkpoint) {
     time += this.queue[i].checkpoint * this.queue[i].duration;
   }
 }
 Animation.push(this);
 return this;
}

// Draw a frame for this animation
Animation.prototype._frame = function(time) {
 var done = true;
 var still_needs_container = false;
 var whacky_firefox = false;
 for (var i = 0; i < this.queue.length; i++) {

   // If this animation shouldn't start yet we can abort early
   var cur = this.queue[i];
   if (cur.start > time) {
     done = false;
     continue;
   } else if (cur.checkpointcb && (cur.checkpoint * cur.duration + cur.start > time)) {
     this._callback(cur.checkpointcb, time - cur.start - cur.checkpoint * cur.duration);
     cur.checkpointcb = null;
   }

   // We need to initialize an animation on the first frame
   if (cur.started === undefined) {
     if (cur.show) {
       this.obj.style.display = 'block';
     }
     for (var a in cur.attrs) {
       if (cur.attrs[a].start !== undefined) {
         continue;
       }
       switch (a) {
         case 'backgroundColor':
         case 'borderColor':
         case 'color':
           // Defer to the left border color, whatever.
           var val = Animation.parse_color(Animation.get_style(this.obj, a == 'borderColor' ? 'borderLeftColor' : a));

           // I'm not sure why anyone would want to do relative color adjustment... but at least they can
           if (cur.attrs[a].by) {
             cur.attrs[a].value[0] = Math.min(255, Math.max(0, cur.attrs[a].value[0] + val[0]));
             cur.attrs[a].value[1] = Math.min(255, Math.max(0, cur.attrs[a].value[1] + val[1]));
             cur.attrs[a].value[2] = Math.min(255, Math.max(0, cur.attrs[a].value[2] + val[2]));
           }
           break;

         case 'opacity':
           var val = ((val = Animation.get_style(this.obj, 'opacity')) && parseFloat(val)) ||
                     ((val = Animation.get_style(this.obj, 'opacity')) && (val = /(\d+(?:\.\d+)?)/.exec(val)) && parseFloat(val.pop()) / 100) ||
                     1;
           if (cur.attrs[a].by) {
             cur.attrs[a].value = Math.min(1, Math.max(0, cur.attrs[a].value + val));
           }
           break;

         case 'height':
         case 'width':
           var val = Animation['get_'+a](this.obj);
           if (cur.attrs[a].by) {
             cur.attrs[a].value += val;
           }
           break;

         case 'scrollLeft':
         case 'scrollTop':
           var val = (this.obj == document.body) ? (document.documentElement[a] || document.body[a]) : this.obj[a];
           if (cur.attrs[a].by) {
             cur.attrs[a].value += val;
           }
           cur['last'+a] = val;
           break;

         default:
           var val = parseInt(Animation.get_style(this.obj, a), 10);
           if (cur.attrs[a].by) {
             cur.attrs[a].value += val;
           }
           break;
       }
       cur.attrs[a].start = val;
     }

     // If we're animating height or width to "auto" we need to do some DOM-fu to figure out what that means in px
     if ((cur.attrs.height && cur.attrs.height.auto) ||
         (cur.attrs.width && cur.attrs.width.auto)) {

       // This is a silly fix for Firefox's whacky redrawing. This bug can be reproduced with the following code:
       /* <div style="width: 300px; height: 300px; background: red" id="test"></div>
          <script>
            setInterval(function() {
              var obj = document.getElementById('test');
          //    var p = obj.parentNode;
              obj.style.visibility = 'hidden';
              obj.offsetWidth; // request a property, requires a re-render
          //    p.removeChild(obj);
              obj.style.visibility = 'visible';
          //    p.appendChild(obj);
            }, 100);
          </script> */
       // In all browsers that aren't Firefox the div will stay solid red. In Firefox it flickers. The workaround
       // for the bug is included in the code block above, but commented out.
       if (/Firefox\/[12]\./.test(navigator.userAgent)) {
         whacky_firefox = true;
       }

       // Set any attributes that affect element size to their final desired values
       this._destroy_container();
       for (var a in {height: 1, width: 1,
                      fontSize: 1,
                      borderLeftWidth: 1, borderRightWidth: 1, borderTopWidth: 1, borderBottomWidth: 1,
                      paddingLeft: 1, paddingRight: 1, paddingTop: 1, paddingBottom: 1}) {
         if (cur.attrs[a]) {
           this.obj.style[a] = cur.attrs[a].value + (typeof cur.attrs[a].value == 'number' ? 'px' : '');
         }
       }


       // Record the dimensions of what the element will look like after the animation
       if (cur.attrs.height && cur.attrs.height.auto) {
         cur.attrs.height.value = Animation.get_height(this.obj);
       }
       if (cur.attrs.width && cur.attrs.width.auto) {
         cur.attrs.width.value = Animation.get_width(this.obj);
       }

       // We don't need to do anything else with temporarily adjusted style because they're
       // about to be overwritten in the frame loop below
     }

     cur.started = true;
     if (cur.blind) {
       this._build_container();
     }
   }

   // Calculate the animation's progress from 0 - 1
   var p = (time - cur.start) / cur.duration;
   if (p >= 1) {
     p = 1;
     if (cur.hide) {
       this.obj.style.display = 'none';
     }
   } else {
     done = false;
   }
   var pc = cur.ease ? cur.ease(p) : p;

   // If this needs a blind container and doesn't have one, we build it
   if (!still_needs_container && p != 1 && cur.blind) {
     still_needs_container = true;
   }

   // Hack documented above
   if (whacky_firefox && this.obj.parentNode) {
     var parentNode = this.obj.parentNode;
     var nextChild = this.obj.nextSibling;
     parentNode.removeChild(this.obj);
   }

   // Loop through each animated attribute and set it where it needs to be
   for (var a in cur.attrs) {
     switch (a) {
       case 'backgroundColor':
       case 'borderColor':
       case 'color':
         this.obj.style[a] = 'rgb('+
           Animation.calc_tween(pc, cur.attrs[a].start[0], cur.attrs[a].value[0], true)+','+
           Animation.calc_tween(pc, cur.attrs[a].start[1], cur.attrs[a].value[1], true)+','+
           Animation.calc_tween(pc, cur.attrs[a].start[2], cur.attrs[a].value[2], true)+')';
         break;

       case 'opacity':
         var opacity = Animation.calc_tween(pc, cur.attrs[a].start, cur.attrs[a].value);
         try {
           this.obj.style.opacity = (opacity == 1 ? '' : opacity);
           this.obj.style.filter = (opacity == 1 ? '' : 'alpha(opacity=' + opacity * 100 + ')');
         }
         catch (e) {}
         break;

       case 'height':
       case 'width':
         this.obj.style[a] = pc == 1 && cur.attrs[a].auto ? 'auto' :
                             Animation.calc_tween(pc, cur.attrs[a].start, cur.attrs[a].value, true)+'px';
         break;

       case 'scrollLeft':
       case 'scrollTop':
         // Special-case here for scrolling. If the user overrides the scroll we immediately terminate this animation
         var val = (this.obj == document.body) ? (document.documentElement[a] || document.body[a]) : this.obj[a];
         if (cur['last'+a] != val) {
           delete cur.attrs[a];
         } else {
           var diff = Animation.calc_tween(pc, cur.attrs[a].start, cur.attrs[a].value, true) - val;
           if (a == 'scrollLeft') {
             window.scrollBy(diff, 0);
           } else {
             window.scrollBy(0, diff);
           }
           cur['last'+a] = diff + val;
         }
         break;

       default:
         this.obj.style[a] = Animation.calc_tween(pc, cur.attrs[a].start, cur.attrs[a].value, true)+'px';
         break;
     }
   }

   // If this animation is complete remove it from the queue
   if (p == 1) {
     this.queue.splice(i--, 1);
     this._callback(cur.ondone, time - cur.start - cur.duration);
   }
 }

 // Hack documented above
 if (whacky_firefox) {
   parentNode[nextChild ? 'insertBefore' : 'appendChild'](this.obj, nextChild);
 }

 if (!still_needs_container && this.container_div) {
   this._destroy_container();
 }
 return !done;
}

// Add a callback to fire when this animation is finished
Animation.prototype.ondone = function(fn) {
 this.state.ondone = fn;
 return this;
}

// Call a callback with a time offset (for instantiating more animations)
Animation.prototype._callback = function(callback, offset) {
 if (callback) {
   Animation.offset = offset;
   callback.call(this);
   Animation.offset = 0;
 }
}

// Calculates a value in between two values based on a percentage. Basically a weighted average.
Animation.calc_tween = function(p, v1, v2, whole) {
 return (whole ? parseInt : parseFloat)((v2 - v1) * p + v1, 10);
}

// Takes a color like #fff and returns an array of [255, 255, 255].
Animation.parse_color = function(color) {
 var hex = /^#([a-f0-9]{1,2})([a-f0-9]{1,2})([a-f0-9]{1,2})$/i.exec(color);
 if (hex) {
   return [parseInt(hex[1].length == 1 ? hex[1] + hex[1] : hex[1], 16),
           parseInt(hex[2].length == 1 ? hex[2] + hex[2] : hex[2], 16),
           parseInt(hex[3].length == 1 ? hex[3] + hex[3] : hex[3], 16)];
 } else {
   var rgb = /^rgba? *\(([0-9]+), *([0-9]+), *([0-9]+)(?:, *([0-9]+))?\)$/.exec(color);
   if (rgb) {
     if (rgb[4] === '0') {
       return [255, 255, 255]; // transparent
     } else {
       return [parseInt(rgb[1], 10), parseInt(rgb[2], 10), parseInt(rgb[3], 10)];
     }
   } else if (color == 'transparent') {
     return [255, 255, 255]; // not much we can do here...
   } else {
     // When we open this to Platform we'll need a key-value list of names to rgb values
     throw 'Named color attributes are not supported.';
   }
 }
}

// Takes a CSS attribute like padding or margin and returns an explicit array of 4 values
// Ex: '0px 1px' -> ['0px', '1px', '0px', '1px']
Animation.parse_group = function(value) {
 var value = trim(value).split(/ +/);
 if (value.length == 4) {
   return value;
 } else if (value.length == 3) {
   return [value[0], value[1], value[2], value[1]];
 } else if (value.length == 2) {
   return [value[0], value[1], value[0], value[1]];
 } else {
   return [value[0], value[0], value[0], value[0]];
 }
}

// Gets the current height of an element which when used with obj.style.height = height+'px' is a visual NO-OP
Animation.get_height = function(obj) {
 var pT = parseInt(Animation.get_style(obj, 'paddingTop'), 10),
     pB = parseInt(Animation.get_style(obj, 'paddingBottom'), 10),
     bT = parseInt(Animation.get_style(obj, 'borderTopWidth'), 10),
     bW = parseInt(Animation.get_style(obj, 'borderBottomWidth'), 10);
 return obj.offsetHeight - (pT ? pT : 0) - (pB ? pB : 0) - (bT ? bT : 0) - (bW ? bW : 0);
}

// Similar to get_height except for widths
Animation.get_width = function(obj) {
 var pL = parseInt(Animation.get_style(obj, 'paddingLeft'), 10),
     pR = parseInt(Animation.get_style(obj, 'paddingRight'), 10),
     bL = parseInt(Animation.get_style(obj, 'borderLeftWidth'), 10),
     bR = parseInt(Animation.get_style(obj, 'borderRightWidth'), 10);
 return obj.offsetWidth - (pL ? pL : 0) - (pR ? pR : 0) - (bL ? bL : 0) - (bR ? bR : 0);
}

// Gets the computed style of an element
Animation.get_style = function(obj, prop) {
 var temp;
 return (window.getComputedStyle && window.getComputedStyle(obj, null).getPropertyValue(prop.replace(/[A-Z]/g, function(match) { return '-' + match.toLowerCase() }))) ||
        (document.defaultView && document.defaultView.getComputedStyle && (temp = document.defaultView.getComputedStyle(obj, null)) && temp.getPropertyValue(prop.replace(/[A-Z]/g, function(match) { return '-' + match.toLowerCase() }))) ||
        (obj.currentStyle && obj.currentStyle[prop]) ||
        obj.style[prop];
}

// Add this animation object to the global animation stack.
Animation.push = function(instance) {
 if (!Animation.active) {
   Animation.active = [];
 }
 Animation.active.push(instance);
 if (!Animation.timeout) {
   Animation.timeout = setInterval(Animation.animate, Animation.resolution);
 }
}


// Renders a frame from each naimation currently active. By putting all our animations in one
// stack it gives us the advantage of a single setInterval with all style updates in a single
// callback. That means the browser will do less rendering and multiple animations will be
// smoother.
Animation.animate = function() {
 var done = true;
 var time = (new Date()).getTime();
 for (var i = 0; i < Animation.active.length; i++) {
   if (Animation.active[i]._frame(time)) {
     done = false;
   } else {
     Animation.active.splice(i--, 1); // remove from the list
   }
 }
 if (done) {
   clearInterval(Animation.timeout);
   Animation.timeout = null;
 }
}

// Ease functions. These functions all have a domain and (maybe) range of 0 - 1
Animation.ease = {}
Animation.ease.begin = function(p) {
 return p * p;
}
Animation.ease.end = function(p) {
 p -= 1;
 return -(p * p) + 1;
}
Animation.ease.both = function(p) {
 if (p <= 0.5) {
   return (p * p) * 2;
 } else {
   p -= 1;
   return (p * p) * -2 + 1;
 }
}