/**
 * HIGEWheel - remove dependencies of mouse wheel on each browser.
 *
 * Copyright (c) 2008 Takanobu Izukawa (humming.via-kitchen.com) and
 *                    Spark project    (www.libspark.org)
 *
 * Dual licensed under the MIT (MIT-LICENSE.txt)
 * and GPL (GPL-LICENSE.txt) licenses.
 *
 */
(function ()
{
    // do nothing if already defined `HIGEWheel`.
    if (window.HIGEWheel) return;

    var win = window,
        doc = document,
        nav = navigator;

    var HIGEWheel = window.HIGEWheel = function (id)
    {
        this.setUp(id);
        if (HIGEWheel.browser.msie)
            this.bind4msie();
        else
            this.bind();
    };

    HIGEWheel.prototype = {
        setUp: function (id)
        {
            var el = doc.getElementById(id);
            if (HIGEWheel.browser.safari||HIGEWheel.browser.msie)
                el = el.parentNode;
            this.target = el;
            this.eventType = HIGEWheel.browser.mozilla ? 'DOMMouseScroll' : 'mousewheel';
        },

        bind: function ()
        {
            this.target.addEventListener(this.eventType, function (evt)
            {
                // retrieve real node from XPCNativeWrapper.
                var target = evt.constructor ? evt.target : doc.getElementById(evt.target.id),
                    delta = 0,
                    n = target.nodeName.toLowerCase();
                // check target node.
                if (n != 'object' && n != 'embed') return;
                // kill process.
                evt.preventDefault();
                evt.returnValue = false;
                // execute wheel event if exists.
                if (!target.externalMouseEvent) return;
                // fix delta value.
                switch (true)
                {
                    case HIGEWheel.browser.mozilla:
                        delta = -evt.detail;
                        break;

                    case HIGEWheel.browser.safari:
                    case HIGEWheel.browser.opera:
                        delta = evt.wheelDelta / 80;
                        break;

                    default:
                        break;
                }
                target.externalMouseEvent(delta);
            }, false);
        },

        bind4msie: function ()
        {
            this.target.attachEvent('onmousewheel', function ()
            {
                var evt = win.event;
                var n = evt.srcElement.nodeName.toLowerCase();
                if (n != 'object' && n != 'embed') return;
                evt.returnValue = false;
            });
        }
    };

    //  utilities. ------------------------------------------------------------
    HIGEWheel.browser = (function (ua)
    {
        return {
            safari: /webkit/.test(ua),
            opera: /opera/.test(ua),
            msie: /msie/.test(ua) && !/opera/.test(ua),
            mozilla: /mozilla/.test(ua) && !/(compatible|webkit)/.test(ua)
        }
    })(nav.userAgent.toLowerCase());

    HIGEWheel.join = function (id)
    {
        var t = setInterval(function ()
        {
            if (doc.getElementById(id))
            {
                clearInterval(t);
                new HIGEWheel(id);
            }
        }, 0);
    }

})();