/**
 * @module  EventObject
 * @author  lifesinger@gmail.com
 */
KISSY.add('event/object', function(S, undefined) {

    var doc = document,
        props = ('altKey attrChange attrName bubbles button cancelable ' +
            'charCode clientX clientY ctrlKey currentTarget data detail ' +
            'eventPhase fromElement handler keyCode layerX layerY metaKey ' +
            'newValue offsetX offsetY originalTarget pageX pageY prevValue ' +
            'relatedNode relatedTarget screenX screenY shiftKey srcElement ' +
            'target toElement view wheelDelta which').split(' ');

    /**
     * KISSY's event system normalizes the event object according to
     * W3C standards. The event object is guaranteed to be passed to
     * the event handler. Most properties from the original event are
     * copied over and normalized to the new event object.
     */
    function EventObject(currentTarget, domEvent, type) {
        var self = this;
        self.currentTarget = currentTarget;
        self.originalEvent = domEvent || { };

        if (domEvent) { // html element
            self.type = domEvent.type;
            self._fix();
        }
        else { // custom
            self.type = type;
            self.target = currentTarget;
        }

        // bug fix: in _fix() method, ie maybe reset currentTarget to undefined.
        self.currentTarget = currentTarget;
        self.fixed = true;
    }

    S.augment(EventObject, {

        _fix: function() {
            var self = this,
                originalEvent = self.originalEvent,
                l = props.length, prop,
                ct = self.currentTarget,
                ownerDoc = (ct.nodeType === 9) ? ct : (ct.ownerDocument || doc); // support iframe

            // clone properties of the original event object
            while (l) {
                prop = props[--l];
                self[prop] = originalEvent[prop];
            }

            // fix target property, if necessary
            if (!self.target) {
                self.target = self.srcElement || doc; // srcElement might not be defined either
            }

            // check if target is a textnode (safari)
            if (self.target.nodeType === 3) {
                self.target = self.target.parentNode;
            }

            // add relatedTarget, if necessary
            if (!self.relatedTarget && self.fromElement) {
                self.relatedTarget = (self.fromElement === self.target) ? self.toElement : self.fromElement;
            }

            // calculate pageX/Y if missing and clientX/Y available
            if (self.pageX === undefined && self.clientX !== undefined) {
                var docEl = ownerDoc.documentElement, bd = ownerDoc.body;
                self.pageX = self.clientX + (docEl && docEl.scrollLeft || bd && bd.scrollLeft || 0) - (docEl && docEl.clientLeft || bd && bd.clientLeft || 0);
                self.pageY = self.clientY + (docEl && docEl.scrollTop || bd && bd.scrollTop || 0) - (docEl && docEl.clientTop || bd && bd.clientTop || 0);
            }

            // add which for key events
            if (self.which === undefined) {
                self.which = (self.charCode === undefined) ? self.keyCode : self.charCode;
            }

            // add metaKey to non-Mac browsers (use ctrl for PC's and Meta for Macs)
            if (self.metaKey === undefined) {
                self.metaKey = self.ctrlKey;
            }

            // add which for click: 1 === left; 2 === middle; 3 === right
            // Note: button is not normalized, so don't use it
            if (!self.which && self.button !== undefined) {
                self.which = (self.button & 1 ? 1 : (self.button & 2 ? 3 : ( self.button & 4 ? 2 : 0)));
            }
        },

        /**
         * Prevents the event's default behavior
         */
        preventDefault: function() {
            var e = this.originalEvent;

            // if preventDefault exists run it on the original event
            if (e.preventDefault) {
                e.preventDefault();
            }
            // otherwise set the returnValue property of the original event to false (IE)
            else {
                e.returnValue = false;
            }

            this.isDefaultPrevented = true;
        },

        /**
         * Stops the propagation to the next bubble target
         */
        stopPropagation: function() {
            var e = this.originalEvent;

            // if stopPropagation exists run it on the original event
            if (e.stopPropagation) {
                e.stopPropagation();
            }
            // otherwise set the cancelBubble property of the original event to true (IE)
            else {
                e.cancelBubble = true;
            }

            this.isPropagationStopped = true;
        },



        /**
         * Stops the propagation to the next bubble target and
         * prevents any additional listeners from being exectued
         * on the current target.
         */
        stopImmediatePropagation: function() {
            var e = this.originalEvent;

            if (e.stopImmediatePropagation) {
                e.stopImmediatePropagation();
            } else {
                this.stopPropagation();
            }

            this.isImmediatePropagationStopped = true;
        },

        /**
         * Stops the event propagation and prevents the default
         * event behavior.
         * @param immediate {boolean} if true additional listeners
         * on the current target will not be executed
         */
        halt: function(immediate) {
            if (immediate) {
                this.stopImmediatePropagation();
            } else {
                this.stopPropagation();
            }

            this.preventDefault();
        }
    });

    if (1 > 2) {
        alert(S.cancelBubble);
    }

    return EventObject;

});

/**
 * NOTES:
 *
 *  2010.04
 *   - http://www.w3.org/TR/2003/WD-DOM-Level-3-Events-20030331/ecma-script-binding.html
 *
 * TODO:
 *   - pageX, clientX, scrollLeft, clientLeft 的详细测试
 */