Fx.Shake = new Class({

Extends: Fx.Tween,

options: {
times: 5
},

initialize: function(){
this.parent.apply(this, arguments);
if (this.options.property) {
this.property = this.options.property;
delete this.options.property;
}
this._start = this.start;
this.start = this.shake;
this.duration = this.options.duration;
this.shakeChain = new Chain();
},

complete: function(){
if (!this.shakeChain.$chain.length && this.stopTimer()) this.onComplete();
else if (this.shakeChain.$chain.length) this.shakeChain.callChain();
return this;
},

shake: function(property, distance, times){
if (!this.check(arguments.callee, property, distance)) return this;
var args = Array.link(arguments, {property: String.type, distance: $defined, times: $defined});
property = this.property || args.property;
times = args.times || this.options.times;
// dbug.log(times);
this.stepDur = this.duration / (times + 1);
this._getTransition = this.getTransition;
this.origin = this.element.getStyle(property).toInt()||0;
this.shakeChain.chain(
function(){
this.shakeChain.chain(
function() {
this.stopTimer();
this.getTransition = this._getTransition;
this.options.duration = this.stepDur / 2;
//stage three, return to origin
this._start(property, this.origin);
}.bind(this)
);
this.getTransition = function(){
return function(p){
return (1 + Math.sin( times*p*Math.PI - Math.PI/2 )) / 2;
}.bind(this);
}.bind(this);
this.stopTimer();
this.options.duration = this.stepDur * times;
//stage 2: offset to the other side using the shake transition
this._start(property, this.origin - args.distance);
}.bind(this)
);
this.options.duration = this.stepDur / 2;
//stage 1: offset to one side
return this._start(property, this.origin + args.distance);
},

onCancel: function(){
this.parent();
this.shakeChain.clearChain();
return this;
}

});

Element.Properties.shake = {

set: function(options){
var shake = this.retrieve('shake');
if (shake) shake.cancel();
return this.eliminate('shake').store('shake:options', $extend({link: 'cancel'}, options));
},

get: function(options){
if (options || !this.retrieve('shake')){
if (options || !this.retrieve('shake:options')) this.set('shake', options);
this.store('shake', new Fx.Shake(this, this.retrieve('shake:options')));
}
return this.retrieve('shake');
}

};

Element.implement({

shake: function(property, distance, times, options){
var args = Array.link(arguments, {property: String.type, distance: Number.type, times: Number.type, options: Object.type});
if (args.options) this.set('shake', args.options);
this.get('shake').start(args.property, args.distance, args.times);
return this;
}

})