/*
 * @Describe: 鼠标滚动监听事件
 */
(function ($) {
    var toFix = ['wheel', 'mousewheel', 'DOMMouseScroll', 'MozMousePixelScroll'],
        toBind = ('onwheel' in document || document.documentMode >= 9) ?
            ['wheel'] : ['mousewheel', 'DomMouseScroll', 'MozMousePixelScroll'],
        slice = Array.prototype.slice,
        nullLowestDeltaTimeout, lowestDelta;

    if ($.event.fixHooks) {
        for (var i = toFix.length; i;) {
            $.event.fixHooks[toFix[--i]] = $.event.mouseHooks;
        }
    }

    var special = $.event.special.mousewheel = {
        setup: function () {
            if (this.addEventListener) {
                for (var i = toBind.length; i;) {
                    this.addEventListener(toBind[--i], handler, false);
                }
            } else {
                this.onmousewheel = handler;
            }
            // Store the line height and page height for this particular element
            $.data(this, 'mousewheel-line-height', special.getLineHeight(this));
            $.data(this, 'mousewheel-page-height', special.getPageHeight(this));
        },
        teardown: function () {
            if (this.removeEventListener) {
                for (var i = toBind.length; i;) {
                    this.removeEventListener(toBind[--i], handler, false);
                }
            } else {
                this.onmousewheel = null;
            }
        },
        getLineHeight: function (elem) {
            return parseInt($(elem)['offsetParent' in $.fn ? 'offsetParent' : 'parent']().css('fontSize'), 10);
        },
        getPageHeight: function (elem) {
            return $(elem).height();
        },
        settings: {
            adjustOldDeltas: true
        }
    };

    $.fn.extend({
        mousewheel: function (fn) {
            return fn ? this.bind('mousewheel', fn) : this.trigger('mousewheel');
        },
        unmousewheel: function (fn) {
            return this.unbind('mousewheel', fn);
        }
    });


    function handler(event) {
        var orgEvent = event || window.event,
            args = slice.call(arguments, 1),
            delta = 0,
            deltaX = 0,
            deltaY = 0,
            absDelta = 0;
        event = $.event.fix(orgEvent);
        event.type = 'mousewheel';

        // Old school scrollwheel delta
        if ('detail' in orgEvent) { deltaY = orgEvent.detail * -1; }
        if ('wheelDelta' in orgEvent) { deltaY = orgEvent.wheelDelta; }
        if ('wheelDeltaY' in orgEvent) { deltaY = orgEvent.wheelDeltaY; }
        if ('wheelDeltaX' in orgEvent) { deltaX = orgEvent.wheelDeltaX * -1; }

        // Firefox < 17 horizontal scrolling related to DOMMouseScroll event
        if ('axis' in orgEvent && orgEvent.axis === orgEvent.HORIZONTAL_AXIS) {
            deltaX = deltaY * -1;
            deltaY = 0;
        }

        // Set delta to be deltaY or deltaX if deltaY is 0 for backwards compatabilitiy
        delta = deltaY === 0 ? deltaX : deltaY;

        // New school wheel delta (wheel event)
        if ('deltaY' in orgEvent) {
            deltaY = orgEvent.deltaY * -1;
            delta = deltaY;
        }
        if ('deltaX' in orgEvent) {
            deltaX = orgEvent.deltaX;
            if (deltaY === 0) { delta = deltaX * -1; }
        }

        // No change actually happened, no reason to go any further
        if (deltaY === 0 && deltaX === 0) { return; }

        // Need to convert lines and pages to pixels if we aren't already in pixels
        // There are three delta modes:
        //   * deltaMode 0 is by pixels, nothing to do
        //   * deltaMode 1 is by lines
        //   * deltaMode 2 is by pages
        if (orgEvent.deltaMode === 1) {
            var lineHeight = $.data(this, 'mousewheel-line-height');
            delta *= lineHeight;
            deltaY *= lineHeight;
            deltaX *= lineHeight;
        } else if (orgEvent.deltaMode === 2) {
            var pageHeight = $.data(this, 'mousewheel-page-height');
            delta *= pageHeight;
            deltaY *= pageHeight;
            deltaX *= pageHeight;
        }

        // Store lowest absolute delta to normalize the delta values
        absDelta = Math.max(Math.abs(deltaY), Math.abs(deltaX));

        if (!lowestDelta || absDelta < lowestDelta) {
            lowestDelta = absDelta;

            // Adjust older deltas if necessary
            if (shouldAdjustOldDeltas(orgEvent, absDelta)) {
                lowestDelta /= 40;
            }
        }

        // Adjust older deltas if necessary
        if (shouldAdjustOldDeltas(orgEvent, absDelta)) {
            // Divide all the things by 40!
            delta /= 40;
            deltaX /= 40;
            deltaY /= 40;
        }

        // Get a whole, normalized value for the deltas
        delta = Math[delta >= 1 ? 'floor' : 'ceil'](delta / lowestDelta);
        deltaX = Math[deltaX >= 1 ? 'floor' : 'ceil'](deltaX / lowestDelta);
        deltaY = Math[deltaY >= 1 ? 'floor' : 'ceil'](deltaY / lowestDelta);

        // Add information to the event object
        event.deltaX = deltaX;
        event.deltaY = deltaY;
        event.deltaFactor = lowestDelta;
        // Go ahead and set deltaMode to 0 since we converted to pixels
        // Although this is a little odd since we overwrite the deltaX/Y
        // properties with normalized deltas.
        event.deltaMode = 0;

        // Add event and delta to the front of the arguments
        args.unshift(event, delta, deltaX, deltaY);

        // Clearout lowestDelta after sometime to better
        // handle multiple device types that give different
        // a different lowestDelta
        // Ex: trackpad = 3 and mouse wheel = 120
        if (nullLowestDeltaTimeout) { clearTimeout(nullLowestDeltaTimeout); }
        nullLowestDeltaTimeout = setTimeout(nullLowestDelta, 200);

        return ($.event.dispatch || $.event.handle).apply(this, args);
    }
    function nullLowestDelta() {
        lowestDelta = null;
    }
    function shouldAdjustOldDeltas(orgEvent, absDelta) {
        return special.settings.adjustOldDeltas && orgEvent.type === 'mousewheel' && absDelta % 120 === 0;
    }
})(window.jQuery);