/**
Adds touch event facade normalization properties (touches, changedTouches, targetTouches etc.) to the DOM event facade. Adds
touch events to the DOM events whitelist. 

@example
    YUI().use('event-touch', function (Y) {
        Y.one('#myDiv').on('touchstart', function(e) {
            ...
        });
    });
@module event
@submodule event-touch
 */
var SCALE = "scale",
    ROTATION = "rotation",
    IDENTIFIER = "identifier",
    win = Y.config.win,
    GESTURE_MAP = {};

/**
 * Adds touch event facade normalization properties to the DOM event facade
 *
 * @method _touch
 * @for DOMEventFacade
 * @private
 * @param ev {Event} the DOM event
 * @param currentTarget {HTMLElement} the element the listener was attached to
 * @param wrapper {Event.Custom} the custom event wrapper for this DOM event
 */
Y.DOMEventFacade.prototype._touch = function(e, currentTarget, wrapper) {

    var i,l, etCached, et,touchCache;

    Y.log("Calling facade._touch() with e = " + e, "info", "event-touch");

    if (e.touches) {
        Y.log("Found e.touches. Replicating on facade");

        /**
         * Array of individual touch events for touch points that are still in
         * contact with the touch surface.
         *
         * @property touches
         * @type {DOMEventFacade[]}
         */
        this.touches = [];
        touchCache = {};

        for (i = 0, l = e.touches.length; i < l; ++i) {
            et = e.touches[i];
            touchCache[Y.stamp(et)] = this.touches[i] = new Y.DOMEventFacade(et, currentTarget, wrapper);
        }
    }

    if (e.targetTouches) {
        Y.log("Found e.targetTouches. Replicating on facade", "info", "event-touch");

        /**
         * Array of individual touch events still in contact with the touch
         * surface and whose `touchstart` event occurred inside the same taregt
         * element as the current target element.
         *
         * @property targetTouches
         * @type {DOMEventFacade[]}
         */
        this.targetTouches = [];

        for (i = 0, l = e.targetTouches.length; i < l; ++i) {
            et = e.targetTouches[i];
            etCached = touchCache && touchCache[Y.stamp(et, true)];

            this.targetTouches[i] = etCached || new Y.DOMEventFacade(et, currentTarget, wrapper);
            
            if (etCached) { Y.log("Found native event in touches. Using same facade in targetTouches", "info", "event-touch"); }
        }
    }

    if (e.changedTouches) {
        Y.log("Found e.changedTouches. Replicating on facade", "info", "event-touch");

        /**
        An array of event-specific touch events.

        For `touchstart`, the touch points that became active with the current
        event.

        For `touchmove`, the touch points that have changed since the last
        event.
        
        For `touchend`, the touch points that have been removed from the touch
        surface.

        @property changedTouches
        @type {DOMEventFacade[]}
        **/
        this.changedTouches = [];

        for (i = 0, l = e.changedTouches.length; i < l; ++i) {
            et = e.changedTouches[i];
            etCached = touchCache && touchCache[Y.stamp(et, true)];

            this.changedTouches[i] = etCached || new Y.DOMEventFacade(et, currentTarget, wrapper);
            
            if (etCached) { Y.log("Found native event in touches. Using same facade in changedTouches", "info", "event-touch"); }
        }
    }

    if (SCALE in e) {
        this[SCALE] = e[SCALE];
    }

    if (ROTATION in e) {
        this[ROTATION] = e[ROTATION];
    }

    if (IDENTIFIER in e) {
        this[IDENTIFIER] = e[IDENTIFIER];
    }
};

//Adding MSPointer events to whitelisted DOM Events. MSPointer event payloads
//have the same properties as mouse events.
if (Y.Node.DOM_EVENTS) {
    Y.mix(Y.Node.DOM_EVENTS, {
        touchstart:1,
        touchmove:1,
        touchend:1,
        touchcancel:1,
        gesturestart:1,
        gesturechange:1,
        gestureend:1,
        MSPointerDown:1, 
        MSPointerUp:1,
        MSPointerMove:1
    });
}

//Add properties to Y.EVENT.GESTURE_MAP based on feature detection.
if ((win && ("ontouchstart" in win)) && !(Y.UA.chrome && Y.UA.chrome < 6)) {
    GESTURE_MAP.start = "touchstart";
    GESTURE_MAP.end = "touchend";
    GESTURE_MAP.move = "touchmove";
    GESTURE_MAP.cancel = "touchcancel";
}



else if (win && ("msPointerEnabled" in win.navigator)) {
    GESTURE_MAP.start = "MSPointerDown";
    GESTURE_MAP.end = "MSPointerUp";
    GESTURE_MAP.move = "MSPointerMove";
    GESTURE_MAP.cancel = "MSPointerCancel";
}

else {
    GESTURE_MAP.start = "mousedown";
    GESTURE_MAP.end = "mouseup";
    GESTURE_MAP.move = "mousemove";
    GESTURE_MAP.cancel = "mousecancel";
}

/**
 * A object literal with keys "start", "end", and "move". The value for each key is a
 * string representing the event for that environment. For touch environments, the respective
 * values are "touchstart", "touchend" and "touchmove". Mouse and MSPointer environments are also
 * supported via feature detection.
 *
 * @property _GESTURE_MAP
 * @type Object
 * @static
 */
Y.Event._GESTURE_MAP = GESTURE_MAP;