var Slider = Class.create();

Slider.prototype = {

    options: {

        shift: 500

    },

    

    initialize: function(container, controlLeft, controlRight){

        this.animating = false;

        this.containerSize = {

            width: $(container).offsetWidth,

            height: $(container).offsetHeight

        },

        this.content = $(container).down();

        this.controlLeft = $(controlLeft);

        this.controlRight = $(controlRight);

        

        this.initControls();

    },

    

    initControls: function(){

        this.controlLeft.href = this.controlRight.href = 'javascript:void(0)';

        Event.observe(this.controlLeft,  'click', this.shiftLeft.bind(this));

        Event.observe(this.controlRight, 'click', this.shiftRight.bind(this));

        this.updateControls(1, 0);

    },

    

    shiftRight: function(){

        if (this.animating)

            return;

        

        var left = isNaN(parseInt(this.content.style.left)) ? 0 : parseInt(this.content.style.left);

        

        if ((left + this.options.shift) < 0) {

            var shift = this.options.shift;

            this.updateControls(1, 1);

        } else {

            var shift = Math.abs(left);

            this.updateControls(1, 0);

        }

        this.moveTo(shift);

    },

    

    shiftLeft: function(){

        if (this.animating)

            return;

        

        var left = isNaN(parseInt(this.content.style.left)) ? 0 : parseInt(this.content.style.left);

        

        var lastItemLeft = this.content.childElements().last().positionedOffset()[0];

        var lastItemWidth = this.content.childElements().last().down('img').width;

        var contentWidth = lastItemLeft + lastItemWidth + 8;

        

        if ((contentWidth + left - this.options.shift) > this.containerSize.width) {

            var shift = this.options.shift;

            this.updateControls(1, 1);

        } else {

            var shift = contentWidth + left - this.containerSize.width;

            this.updateControls(0, 1);

        } 

        this.moveTo(-shift);

    },

    

    moveTo: function(shift){

        var scope = this;

                     

        this.animating = true;

        

        new Effect.Move(this.content, {

            x: shift,

            duration: 0.4,

            delay: 0,

            afterFinish: function(){

                scope.animating = false;

            }

        });

    },

    

    updateControls: function(left, right){

        if (!left)

            this.controlLeft.addClassName('disabled');

        else

            this.controlLeft.removeClassName('disabled');

        

        if (!right)

            this.controlRight.addClassName('disabled');

        else

            this.controlRight.removeClassName('disabled');

    }

}