/**
     * The attribute module provides an augmentable Attribute implementation, which 
     * adds configurable attributes and attribute change events to the class being 
     * augmented. It also provides a State class, which is used internally by Attribute,
     * but can also be used independently to provide a name/property/value data structure to
     * store state.
     *
     * @module attribute
     */

    /**
     * The attribute-events submodule provides augmentable attribute change event support 
     * for AttributeCore based implementations.
     *
     * @module attribute
     * @submodule attribute-events
     */
    var EventTarget = Y.EventTarget,

        CHANGE = "Change",
        BROADCAST = "broadcast",
        PUBLISHED = "published";

    /**
     * Provides an augmentable implementation of attribute change events for 
     * AttributeCore. 
     *
     * @class AttributeEvents
     * @uses EventTarget
     */
    function AttributeEvents() {
        // Perf tweak - avoid creating event literals if not required.
        this._ATTR_E_FACADE = {};
        EventTarget.call(this, {emitFacade:true});
    }

    AttributeEvents._ATTR_CFG = [BROADCAST];

    AttributeEvents.prototype = {

        /**
         * Sets the value of an attribute.
         *
         * @method set
         * @chainable
         *
         * @param {String} name The name of the attribute. If the 
         * current value of the attribute is an Object, dot notation can be used
         * to set the value of a property within the object (e.g. <code>set("x.y.z", 5)</code>).
         *
         * @param {Any} value The value to set the attribute to.
         *
         * @param {Object} opts (Optional) Optional event data to be mixed into
         * the event facade passed to subscribers of the attribute's change event. This 
         * can be used as a flexible way to identify the source of a call to set, allowing 
         * the developer to distinguish between set called internally by the host, vs. 
         * set called externally by the application developer.
         *
         * @return {Object} A reference to the host object.
         */
        set : function(name, val, opts) {
            return this._setAttr(name, val, opts);
        },

        /**
         * Allows setting of readOnly/writeOnce attributes. See <a href="#method_set">set</a> for argument details.
         *
         * @method _set
         * @protected
         * @chainable
         * 
         * @param {String} name The name of the attribute.
         * @param {Any} val The value to set the attribute to.
         * @param {Object} opts (Optional) Optional event data to be mixed into
         * the event facade passed to subscribers of the attribute's change event.
         * @return {Object} A reference to the host object.
         */
        _set : function(name, val, opts) {
            return this._setAttr(name, val, opts, true);
        },

        /**
         * Sets multiple attribute values.
         *
         * @method setAttrs
         * @param {Object} attrs  An object with attributes name/value pairs.
         * @return {Object} A reference to the host object.
         * @chainable
         */
        setAttrs : function(attrs, opts) {
            return this._setAttrs(attrs, opts);
        },

        /**
         * Utility method to help setup the event payload and fire the attribute change event.
         * 
         * @method _fireAttrChange
         * @private
         * @param {String} attrName The name of the attribute
         * @param {String} subAttrName The full path of the property being changed, 
         * if this is a sub-attribute value being change. Otherwise null.
         * @param {Any} currVal The current value of the attribute
         * @param {Any} newVal The new value of the attribute
         * @param {Object} opts Any additional event data to mix into the attribute change event's event facade.
         */
        _fireAttrChange : function(attrName, subAttrName, currVal, newVal, opts) {
            var host = this,
                eventName = attrName + CHANGE,
                state = host._state,
                facade,
                broadcast,
                evtCfg;

            if (!state.get(attrName, PUBLISHED)) {
                
                evtCfg = {
                    queuable:false,
                    defaultTargetOnly: true, 
                    defaultFn:host._defAttrChangeFn, 
                    silent:true
                };

                broadcast = state.get(attrName, BROADCAST);
                if (broadcast !== undefined) {
                    evtCfg.broadcast = broadcast;
                }

                host.publish(eventName, evtCfg);
                
                state.add(attrName, PUBLISHED, true);
            }

            facade = (opts) ? Y.merge(opts) : host._ATTR_E_FACADE;

            // Not using the single object signature for fire({type:..., newVal:...}), since 
            // we don't want to override type. Changed to the fire(type, {newVal:...}) signature.

            // facade.type = eventName;
            facade.attrName = attrName;
            facade.subAttrName = subAttrName;
            facade.prevVal = currVal;
            facade.newVal = newVal;

            // host.fire(facade);
            host.fire(eventName, facade);
        },

        /**
         * Default function for attribute change events.
         *
         * @private
         * @method _defAttrChangeFn
         * @param {EventFacade} e The event object for attribute change events.
         */
        _defAttrChangeFn : function(e) {
            if (!this._setAttrVal(e.attrName, e.subAttrName, e.prevVal, e.newVal)) {
                Y.log('State not updated and stopImmediatePropagation called for attribute: ' + e.attrName + ' , value:' + e.newVal, 'warn', 'attribute');
                // Prevent "after" listeners from being invoked since nothing changed.
                e.stopImmediatePropagation();
            } else {
                e.newVal = this.get(e.attrName);
            }
        }
    };

    // Basic prototype augment - no lazy constructor invocation.
    Y.mix(AttributeEvents, EventTarget, false, null, 1);

    Y.AttributeEvents = AttributeEvents;