/**
 * Support for Widget UI Events (Custom Events fired by the widget, which wrap the underlying DOM events - e.g. widget:click, widget:mousedown)
 *
 * @module widget
 * @submodule widget-uievents
 */

var BOUNDING_BOX = "boundingBox",
    Widget = Y.Widget,
    RENDER = "render",
    L = Y.Lang,
    EVENT_PREFIX_DELIMITER = ":",

    //  Map of Node instances serving as a delegation containers for a specific
    //  event type to Widget instances using that delegation container.
    _uievts = Y.Widget._uievts = Y.Widget._uievts || {};

Y.mix(Widget.prototype, {

    /**
     * Destructor logic for UI event infrastructure,
     * invoked during Widget destruction.
     *
     * @method _destroyUIEvents
     * @for Widget
     * @private
     */
    _destroyUIEvents: function() {

        var widgetGuid = Y.stamp(this, true);

        Y.each(_uievts, function (info, key) {
            if (info.instances[widgetGuid]) {
                //  Unregister this Widget instance as needing this delegated
                //  event listener.
                delete info.instances[widgetGuid];

                //  There are no more Widget instances using this delegated
                //  event listener, so detach it.

                if (Y.Object.isEmpty(info.instances)) {
                    info.handle.detach();

                    if (_uievts[key]) {
                        delete _uievts[key];
                    }
                }
            }
        });
    },

    /**
     * Map of DOM events that should be fired as Custom Events by the
     * Widget instance.
     *
     * @property UI_EVENTS
     * @for Widget
     * @type Object
     */
    UI_EVENTS: Y.Node.DOM_EVENTS,

    /**
     * Returns the node on which to bind delegate listeners.
     *
     * @method _getUIEventNode
     * @for Widget
     * @protected
     */
    _getUIEventNode: function () {
        return this.get(BOUNDING_BOX);
    },

    /**
     * Binds a delegated DOM event listener of the specified type to the
     * Widget's outtermost DOM element to facilitate the firing of a Custom
     * Event of the same type for the Widget instance.
     *
     * @method _createUIEvent
     * @for Widget
     * @param type {String} String representing the name of the event
     * @private
     */
    _createUIEvent: function (type) {

        var uiEvtNode = this._getUIEventNode(),
            key = (Y.stamp(uiEvtNode) + type),
            info = _uievts[key],
            handle;

        //  For each Node instance: Ensure that there is only one delegated
        //  event listener used to fire Widget UI events.

        if (!info) {

            handle = uiEvtNode.delegate(type, function (evt) {

                var widget = Widget.getByNode(this);

                // Widget could be null if node instance belongs to
                // another Y instance.

                if (widget) {
                    if (widget._filterUIEvent(evt)) {
                        widget.fire(evt.type, { domEvent: evt });
                    }
                }

            }, "." + Y.Widget.getClassName());

            _uievts[key] = info = { instances: {}, handle: handle };
        }

        //  Register this Widget as using this Node as a delegation container.
        info.instances[Y.stamp(this)] = 1;
    },

    /**
     * This method is used to determine if we should fire
     * the UI Event or not. The default implementation makes sure
     * that for nested delegates (nested unrelated widgets), we don't
     * fire the UI event listener more than once at each level.
     *
     * <p>For example, without the additional filter, if you have nested
     * widgets, each widget will have a delegate listener. If you
     * click on the inner widget, the inner delegate listener's
     * filter will match once, but the outer will match twice
     * (based on delegate's design) - once for the inner widget,
     * and once for the outer.</p>
     *
     * @method _filterUIEvent
     * @for Widget
     * @param {DOMEventFacade} evt
     * @return {boolean} true if it's OK to fire the custom UI event, false if not.
     * @private
     *
     */
    _filterUIEvent: function(evt) {
        // Either it's hitting this widget's delegate container (and not some other widget's),
        // or the container it's hitting is handling this widget's ui events.
        return (evt.currentTarget.compareTo(evt.container) || evt.container.compareTo(this._getUIEventNode()));
    },

    /**
     * Determines if the specified event is a UI event.
     *
     * @private
     * @method _isUIEvent
     * @for Widget
     * @param type {String} String representing the name of the event
     * @return {String} Event Returns the name of the UI Event, otherwise
     * undefined.
     */
    _getUIEvent: function (type) {

        if (L.isString(type)) {
            var sType = this.parseType(type)[1],
                iDelim,
                returnVal;

            if (sType) {
                // TODO: Get delimiter from ET, or have ET support this.
                iDelim = sType.indexOf(EVENT_PREFIX_DELIMITER);
                if (iDelim > -1) {
                    sType = sType.substring(iDelim + EVENT_PREFIX_DELIMITER.length);
                }

                if (this.UI_EVENTS[sType]) {
                    returnVal = sType;
                }
            }

            return returnVal;
        }
    },

    /**
     * Sets up infrastructure required to fire a UI event.
     *
     * @private
     * @method _initUIEvent
     * @for Widget
     * @param type {String} String representing the name of the event
     * @return {String}
     */
    _initUIEvent: function (type) {
        var sType = this._getUIEvent(type),
            queue = this._uiEvtsInitQueue || {};

        if (sType && !queue[sType]) {
            Y.log("Deferring creation of " + type + " delegate until render.", "info", "widget");

            this._uiEvtsInitQueue = queue[sType] = 1;

            this.after(RENDER, function() {
                this._createUIEvent(sType);
                delete this._uiEvtsInitQueue[sType];
            });
        }
    },

    //  Override of "on" from Base to facilitate the firing of Widget events
    //  based on DOM events of the same name/type (e.g. "click", "mouseover").
    //  Temporary solution until we have the ability to listen to when
    //  someone adds an event listener (bug 2528230)
    on: function (type) {
        this._initUIEvent(type);
        return Widget.superclass.on.apply(this, arguments);
    },

    //  Override of "publish" from Base to facilitate the firing of Widget events
    //  based on DOM events of the same name/type (e.g. "click", "mouseover").
    //  Temporary solution until we have the ability to listen to when
    //  someone publishes an event (bug 2528230)
    publish: function (type, config) {
        var sType = this._getUIEvent(type);
        if (sType && config && config.defaultFn) {
            this._initUIEvent(sType);
        }
        return Widget.superclass.publish.apply(this, arguments);
    }

}, true); // overwrite existing EventTarget methods
