/*
Copyright (c) 2009, Yahoo! Inc. All rights reserved.
Code licensed under the BSD License:
http://developer.yahoo.net/yui/license.txt
version: 3.0.0
build: 1549
*/
YUI.add('attribute-base', function(Y) {

    /**
     * The State class maintains state for a collection of named items, with 
     * a varying number of properties defined.
     *
     * It avoids the need to create a separate class for the item, and separate instances 
     * of these classes for each item, by storing the state in a 2 level hash table, 
     * improving performance when the number of items is likely to be large.
     *
     * @constructor
     * @class State
     */
    Y.State = function() { 
        /**
         * Hash of attributes
         * @property data
         */
        this.data = {};
    };

    Y.State.prototype = {

        /**
         * Adds a property to an item.
         *
         * @method add
         * @param name {String} The name of the item.
         * @param key {String} The name of the property.
         * @param val {Any} The value of the property.
         */
        add : function(name, key, val) {
            var d = this.data;
            d[key] = d[key] || {};
            d[key][name] = val;
        },

        /**
         * Adds multiple properties to an item.
         *
         * @method addAll
         * @param name {String} The name of the item.
         * @param o {Object} A hash of property/value pairs.
         */
        addAll: function(name, o) {
            var key;
            for (key in o) {
                if (o.hasOwnProperty(key)) {
                    this.add(name, key, o[key]);
                }
            }
        },

        /**
         * Removes a property from an item.
         *
         * @method remove
         * @param name {String} The name of the item.
         * @param key {String} The property to remove.
         */
        remove: function(name, key) {
            var d = this.data;
            if (d[key] && (name in d[key])) {
                delete d[key][name];
            }
        },

        /**
         * Removes multiple properties from an item, or remove the item completely.
         *
         * @method removeAll
         * @param name {String} The name of the item.
         * @param o {Object|Array} Collection of properties to delete. If not provided, the entire item is removed.
         */
        removeAll: function(name, o) {
            var d = this.data;

            Y.each(o || d, function(v, k) {
                if(Y.Lang.isString(k)) {
                    this.remove(name, k);
                } else {
                    this.remove(name, v);
                }
            }, this);
        },

        /**
         * For a given item, returns the value of the property requested, or undefined if not found.
         *
         * @method get
         * @param name {String} The name of the item
         * @param key {String} Optional. The property value to retrieve.
         * @return {Any} The value of the supplied property.
         */
        get: function(name, key) {
            var d = this.data;
            return (d[key] && name in d[key]) ?  d[key][name] : undefined;
        },

        /**
         * For the given item, returns a disposable object with all of the
         * item's property/value pairs.
         *
         * @method getAll
         * @param name {String} The name of the item
         * @return {Object} An object with property/value pairs for the item.
         */
        getAll : function(name) {
            var d = this.data, o;

            Y.each(d, function(v, k) {
                if (name in d[k]) {
                    o = o || {};
                    o[k] = v[name];
                }
            }, this);

            return o;
        }
    };
    /**
     * 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-base submodule provides core attribute handling support, with everything
     * aside from complex attribute handling in the provider's constructor.
     *
     * @module attribute
     * @submodule attribute-base
     */
    var O = Y.Object,
        Lang = Y.Lang,
        EventTarget = Y.EventTarget,

        DOT = ".",
        CHANGE = "Change",

        // Externally configurable props
        GETTER = "getter",
        SETTER = "setter",
        READ_ONLY = "readOnly",
        WRITE_ONCE = "writeOnce",
        VALIDATOR = "validator",
        VALUE = "value",
        VALUE_FN = "valueFn",
        BROADCAST = "broadcast",
        LAZY_ADD = "lazyAdd",
        BYPASS_PROXY = "_bypassProxy",

        // Used for internal state management
        ADDED = "added",
        INITIALIZING = "initializing",
        INIT_VALUE = "initValue",
        PUBLISHED = "published",
        DEF_VALUE = "defaultValue",
        LAZY = "lazy",
        IS_LAZY_ADD = "isLazyAdd",

        INVALID_VALUE,
        MODIFIABLE = {};

        // Properties which can be changed after the attribute has been added.
        MODIFIABLE[READ_ONLY] = 1;
        MODIFIABLE[WRITE_ONCE] = 1;
        MODIFIABLE[GETTER] = 1;
        MODIFIABLE[BROADCAST] = 1;

    /**
     * <p>
     * Attribute provides configurable attribute support along with attribute change events. It is designed to be 
     * augmented on to a host class, and provides the host with the ability to configure attributes to store and retrieve state, 
     * along with attribute change events.
     * </p>
     * <p>For example, attributes added to the host can be configured:</p>
     * <ul>
     *     <li>As read only.</li>
     *     <li>As write once.</li>
     *     <li>With a setter function, which can be used to manipulate
     *     values passed to Attribute's <a href="#method_set">set</a> method, before they are stored.</li>
     *     <li>With a getter function, which can be used to manipulate stored values,
     *     before they are returned by Attribute's <a href="#method_get">get</a> method.</li>
     *     <li>With a validator function, to validate values before they are stored.</li>
     * </ul>
     *
     * <p>See the <a href="#method_addAttr">addAttr</a> method, for the complete set of configuration
     * options available for attributes</p>.
     *
     * <p><strong>NOTE:</strong> Most implementations will be better off extending the <a href="Base.html">Base</a> class, 
     * instead of augmenting Attribute directly. Base augments Attribute and will handle the initial configuration 
     * of attributes for derived classes, accounting for values passed into the constructor.</p>
     *
     * @class Attribute
     * @uses EventTarget
     */
    function Attribute() {

        var host = this, // help compression
            attrs = this.constructor.ATTRS,
            Base = Y.Base;

        // Perf tweak - avoid creating event literals if not required.
        host._ATTR_E_FACADE = {};

        EventTarget.call(host, {emitFacade:true});

        // _conf maintained for backwards compat
        host._conf = host._state = new Y.State();

        host._stateProxy = host._stateProxy || null;
        host._requireAddAttr = host._requireAddAttr || false;

        // ATTRS support for Node, which is not Base based
        if ( attrs && !(Base && host instanceof Base)) {
            host.addAttrs(this._protectAttrs(attrs));
        }
    }

    /**
     * <p>The value to return from an attribute setter in order to prevent the set from going through.</p>
     *
     * <p>You can return this value from your setter if you wish to combine validator and setter 
     * functionality into a single setter function, which either returns the massaged value to be stored or 
     * Attribute.INVALID_VALUE to prevent invalid values from being stored.</p>
     *
     * @property Attribute.INVALID_VALUE
     * @type Object
     * @static
     * @final
     */
    Attribute.INVALID_VALUE = {};
    INVALID_VALUE = Attribute.INVALID_VALUE;

    /**
     * The list of properties which can be configured for 
     * each attribute (e.g. setter, getter, writeOnce etc.).
     *
     * This property is used internally as a whitelist for faster
     * Y.mix operations.
     *
     * @property Attribute._ATTR_CFG
     * @type Array
     * @static
     * @protected
     */
    Attribute._ATTR_CFG = [SETTER, GETTER, VALIDATOR, VALUE, VALUE_FN, WRITE_ONCE, READ_ONLY, LAZY_ADD, BROADCAST, BYPASS_PROXY];

    Attribute.prototype = {
        /**
         * <p>
         * Adds an attribute with the provided configuration to the host object.
         * </p>
         * <p>
         * The config argument object supports the following properties:
         * </p>
         * 
         * <dl>
         *    <dt>value &#60;Any&#62;</dt>
         *    <dd>The initial value to set on the attribute</dd>
         *
         *    <dt>valueFn &#60;Function&#62;</dt>
         *    <dd>A function, which will return the initial value to set on the attribute. This is useful
         *    for cases where the attribute configuration is defined statically, but needs to 
         *    reference the host instance ("this") to obtain an initial value.
         *    If defined, this precedence over the value property.</dd>
         *
         *    <dt>readOnly &#60;boolean&#62;</dt>
         *    <dd>Whether or not the attribute is read only. Attributes having readOnly set to true
         *        cannot be modified by invoking the set method.</dd>
         *
         *    <dt>writeOnce &#60;boolean&#62;</dt>
         *    <dd>Whether or not the attribute is "write once". Attributes having writeOnce set to true, 
         *        can only have their values set once, be it through the default configuration, 
         *        constructor configuration arguments, or by invoking set.</dd>
         *
         *    <dt>setter &#60;Function&#62;</dt>
         *    <dd>The setter function used to massage or normalize the value passed to the set method for the attribute. 
         *    The value returned by the setter will be the final stored value. Returning
         *    <a href="#property_Attribute.INVALID_VALUE">Attribute.INVALID_VALUE</a>, from the setter will prevent
         *    the value from being stored.</dd>
         *
         *    <dt>getter &#60;Function&#62;</dt>
         *    <dd>The getter function used to massage or normalize the value returned by the get method for the attribute.
         *    The value returned by the getter function is the value which will be returned to the user when they 
         *    invoke get.</dd>
         *
         *    <dt>validator &#60;Function&#62;</dt>
         *    <dd>The validator function invoked prior to setting the stored value. Returning
         *    false from the validator function will prevent the value from being stored.</dd>
         *    
         *    <dt>broadcast &#60;int&#62;</dt>
         *    <dd>If and how attribute change events for this attribute should be broadcast. See CustomEvent's <a href="CustomEvent.html#property_broadcast">broadcast</a> property for 
         *    valid values. By default attribute change events are not broadcast.</dd>
         *
         *    <dt>lazyAdd &#60;boolean&#62;</dt>
         *    <dd>Whether or not to delay initialization of the attribute until the first call to get/set it. 
         *    This flag can be used to over-ride lazy initialization on a per attribute basis, when adding multiple attributes through 
         *    the <a href="#method_addAttrs">addAttrs</a> method.</dd>
         *
         * </dl>
         *
         * <p>The setter, getter and validator are invoked with the value and name passed in as the first and second arguments, and with
         * the context ("this") set to the host object.</p>
         *
         * <p>Configuration properties outside of the list mentioned above are considered private properties used internally by attribute, and are not intended for public use.</p>
         * 
         * @method addAttr
         *
         * @param {String} name The name of the attribute.
         * @param {Object} config An object with attribute configuration property/value pairs, specifying the configuration for the attribute.
         *
         * <p>
         * <strong>NOTE:</strong> The configuration object is modified when adding an attribute, so if you need 
         * to protect the original values, you will need to merge the object.
         * </p>
         *
         * @param {boolean} lazy (optional) Whether or not to add this attribute lazily (on the first call to get/set). 
         *
         * @return {Object} A reference to the host object.
         *
         * @chainable
         */
        addAttr: function(name, config, lazy) {


            var host = this, // help compression
                state = host._state,
                value,
                hasValue;

            lazy = (LAZY_ADD in config) ? config[LAZY_ADD] : lazy;

            if (lazy && !host.attrAdded(name)) {
                state.add(name, LAZY, config || {});
                state.add(name, ADDED, true);
            } else {


                if (!host.attrAdded(name) || state.get(name, IS_LAZY_ADD)) {

                    config = config || {};

                    hasValue = (VALUE in config);


                    if(hasValue) {
                        // We'll go through set, don't want to set value in _state directly
                        value = config.value;
                        delete config.value;
                    }

                    config.added = true;
                    config.initializing = true;

                    state.addAll(name, config);

                    if (hasValue) {
                        // Go through set, so that raw values get normalized/validated
                        host.set(name, value);
                    }

                    state.remove(name, INITIALIZING);
                }
            }

            return host;
        },

        /**
         * Checks if the given attribute has been added to the host
         *
         * @method attrAdded
         * @param {String} name The name of the attribute to check.
         * @return {boolean} true if an attribute with the given name has been added, false if it hasn't. This method will return true for lazily added attributes.
         */
        attrAdded: function(name) {
            return !!this._state.get(name, ADDED);
        },

        /**
         * Updates the configuration of an attribute which has already been added.
         * <p>
         * The properties which can be modified through this interface are limited
         * to the following subset of attributes, which can be safely modified
         * after a value has already been set on the attribute: readOnly, writeOnce, 
         * broadcast and getter.
         * </p>
         * @method modifyAttr
         * @param {String} name The name of the attribute whose configuration is to be updated.
         * @param {Object} config An object with configuration property/value pairs, specifying the configuration properties to modify.
         */
        modifyAttr: function(name, config) {
            var host = this, // help compression
                prop, state;

            if (host.attrAdded(name)) {

                if (host._isLazyAttr(name)) {
                    host._addLazyAttr(name);
                }

                state = host._state;
                for (prop in config) {
                    if (MODIFIABLE[prop] && config.hasOwnProperty(prop)) {
                        state.add(name, prop, config[prop]);

                        // If we reconfigured broadcast, need to republish
                        if (prop === BROADCAST) {
                            state.remove(name, PUBLISHED);
                        }
                    }
                }
            }

        },

        /**
         * Removes an attribute from the host object
         *
         * @method removeAttr
         * @param {String} name The name of the attribute to be removed.
         */
        removeAttr: function(name) {
            this._state.removeAll(name);
        },

        /**
         * Returns the current value of the attribute. If the attribute
         * has been configured with a 'getter' function, this method will delegate
         * to the 'getter' to obtain the value of the attribute.
         *
         * @method get
         *
         * @param {String} name The name of the attribute. If the value of the attribute is an Object, 
         * dot notation can be used to obtain the value of a property of the object (e.g. <code>get("x.y.z")</code>)
         *
         * @return {Any} The value of the attribute
         */
        get : function(name) {
            return this._getAttr(name);
        },

        /**
         * Checks whether or not the attribute is one which has been
         * added lazily and still requires initialization.
         *
         * @method _isLazyAttr
         * @private
         * @param {String} name The name of the attribute
         * @return {boolean} true if it's a lazily added attribute, false otherwise.
         */
        _isLazyAttr: function(name) {
            return this._state.get(name, LAZY);
        },

        /**
         * Finishes initializing an attribute which has been lazily added.
         *
         * @method _addLazyAttr
         * @private
         * @param {Object} name The name of the attribute
         */
        _addLazyAttr: function(name) {
            var state = this._state,
                lazyCfg = state.get(name, LAZY);

            state.add(name, IS_LAZY_ADD, true);
            state.remove(name, LAZY);
            this.addAttr(name, lazyCfg);
        },

        /**
         * 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);
        },

        /**
         * Resets the attribute (or all attributes) to its initial value, as long as
         * the attribute is not readOnly, or writeOnce.
         *
         * @method reset
         * @param {String} name Optional. The name of the attribute to reset.  If omitted, all attributes are reset.
         * @return {Object} A reference to the host object.
         * @chainable
         */
        reset : function(name) {
            var host = this,  // help compression
                added;

            if (name) {
                if (host._isLazyAttr(name)) {
                    host._addLazyAttr(name);
                }
                host.set(name, host._state.get(name, INIT_VALUE));
            } else {
                added = host._state.data.added;
                Y.each(added, function(v, n) {
                    host.reset(n);
                }, host);
            }
            return host;
        },

        /**
         * 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);
        },

        /**
         * Provides the common implementation for the public get method,
         * allowing Attribute hosts to over-ride either method.
         *
         * See <a href="#method_get">get</a> for argument details.
         *
         * @method _getAttr
         * @protected
         * @chainable
         *
         * @param {String} name The name of the attribute.
         * @return {Any} The value of the attribute.
         */
        _getAttr : function(name) {
            var host = this, // help compression
                fullName = name,
                state = host._state,
                path,
                getter,
                val,
                cfg;

            if (name.indexOf(DOT) !== -1) {
                path = name.split(DOT);
                name = path.shift();
            }

            // On Demand - Should be rare - handles out of order valueFn references
            if (host._tCfgs && host._tCfgs[name]) {
                cfg = {};
                cfg[name] = host._tCfgs[name];
                delete host._tCfgs[name];
                host._addAttrs(cfg, host._tVals);
            }

            // Lazy Init
            if (host._isLazyAttr(name)) {
                host._addLazyAttr(name);
            }

            val = host._getStateVal(name);
            getter = state.get(name, GETTER);

            val = (getter) ? getter.call(host, val, fullName) : val;
            val = (path) ? O.getValue(val, path) : val;

            return val;
        },

        /**
         * Provides the common implementation for the public set and protected _set methods.
         *
         * See <a href="#method_set">set</a> for argument details.
         *
         * @method _setAttr
         * @protected
         * @chainable
         *
         * @param {String} name The name of the attribute.
         * @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.
         * @param {boolean} force If true, allows the caller to set values for 
         * readOnly or writeOnce attributes which have already been set.
         *
         * @return {Object} A reference to the host object.
         */
        _setAttr : function(name, val, opts, force) {
            var allowSet = true,
                state = this._state,
                stateProxy = this._stateProxy,
                data = state.data,
                initialSet,
                strPath,
                path,
                currVal;

            if (name.indexOf(DOT) !== -1) {
                strPath = name;
                path = name.split(DOT);
                name = path.shift();
            }

            if (this._isLazyAttr(name)) {
                this._addLazyAttr(name);
            }

            initialSet = (!data.value || !(name in data.value));

            if (stateProxy && name in stateProxy && !this._state.get(name, BYPASS_PROXY)) {
                // TODO: Value is always set for proxy. Can we do any better? Maybe take a snapshot as the initial value for the first call to set? 
                initialSet = false;
            }

            if (this._requireAddAttr && !this.attrAdded(name)) {
            } else {

                if (!initialSet && !force) {

                    if (state.get(name, WRITE_ONCE)) {
                        allowSet = false;
                    }

                    if (state.get(name, READ_ONLY)) {
                        allowSet = false;
                    }
                }

                if (allowSet) {
                    // Don't need currVal if initialSet (might fail in custom getter if it always expects a non-undefined/non-null value)
                    if (!initialSet) {
                        currVal =  this.get(name);
                    }

                    if (path) {
                       val = O.setValue(Y.clone(currVal), path, val);

                       if (val === undefined) {
                           allowSet = false;
                       }
                    }

                    if (allowSet) {
                        if (state.get(name, INITIALIZING)) {
                            this._setAttrVal(name, strPath, currVal, val);
                        } else {
                            this._fireAttrChange(name, strPath, currVal, val, opts);
                        }
                    }
                }
            }

            return this;
        },

        /**
         * 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;

            if (!state.get(attrName, PUBLISHED)) {
                host.publish(eventName, {
                    queuable:false, 
                    defaultFn:host._defAttrChangeFn, 
                    silent:true,
                    broadcast : state.get(attrName, BROADCAST)
                });
                state.add(attrName, PUBLISHED, true);
            }

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

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

            host.fire(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)) {
                // Prevent "after" listeners from being invoked since nothing changed.
                e.stopImmediatePropagation();
            } else {
                e.newVal = this._getStateVal(e.attrName);
            }
        },

        /**
         * Gets the stored value for the attribute, from either the 
         * internal state object, or the state proxy if it exits
         * 
         * @method _getStateVal
         * @private
         * @param {String} name The name of the attribute
         * @return {Any} The stored value of the attribute
         */
        _getStateVal : function(name) {
            var stateProxy = this._stateProxy;
            return stateProxy && (name in stateProxy) && !this._state.get(name, BYPASS_PROXY) ? stateProxy[name] : this._state.get(name, VALUE);
        },

        /**
         * Sets the stored value for the attribute, in either the 
         * internal state object, or the state proxy if it exits
         *
         * @method _setStateVal
         * @private
         * @param {String} name The name of the attribute
         * @param {Any} value The value of the attribute
         */
        _setStateVal : function(name, value) {
            var stateProxy = this._stateProxy;
            if (stateProxy && (name in stateProxy) && !this._state.get(name, BYPASS_PROXY)) {
                stateProxy[name] = value;
            } else {
                this._state.add(name, VALUE, value);
            }
        },

        /**
         * Updates the stored value of the attribute in the privately held State object,
         * if validation and setter passes.
         *
         * @method _setAttrVal
         * @private
         * @param {String} attrName The attribute name.
         * @param {String} subAttrName The sub-attribute name, if setting a sub-attribute property ("x.y.z").
         * @param {Any} prevVal The currently stored value of the attribute.
         * @param {Any} newVal The value which is going to be stored.
         * 
         * @return {booolean} true if the new attribute value was stored, false if not.
         */
        _setAttrVal : function(attrName, subAttrName, prevVal, newVal) {

            var host = this,
                allowSet = true,
                state = host._state,

                validator = state.get(attrName, VALIDATOR),
                setter = state.get(attrName, SETTER),
                initializing = state.get(attrName, INITIALIZING),
                prevValRaw = this._getStateVal(attrName),

                name = subAttrName || attrName,
                retVal,
                valid;

            if (validator) {
                valid = validator.call(host, newVal, name);

                if (!valid && initializing) {
                    newVal = state.get(attrName, DEF_VALUE);
                    valid = true; // Assume it's valid, for perf.
                }
            }

            if (!validator || valid) {
                if (setter) {
                    retVal = setter.call(host, newVal, name);

                    if (retVal === INVALID_VALUE) {
                        allowSet = false;
                    } else if (retVal !== undefined){
                        newVal = retVal;
                    }
                }

                if (allowSet) {
                    if(!subAttrName && (newVal === prevValRaw) && !Lang.isObject(newVal)) {
                        allowSet = false;
                    } else {
                        // Store value
                        if (state.get(attrName, INIT_VALUE) === undefined) {
                            state.add(attrName, INIT_VALUE, newVal);
                        }
                        host._setStateVal(attrName, newVal);
                    }
                }

            } else {
                allowSet = false;
            }

            return allowSet;
        },

        /**
         * 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);
        },

        /**
         * Implementation behind the public setAttrs method, to set multiple attribute values.
         *
         * @method _setAttrs
         * @protected
         * @param {Object} attrs  An object with attributes name/value pairs.
         * @return {Object} A reference to the host object.
         * @chainable
         */
        _setAttrs : function(attrs, opts) {
            for (var attr in attrs) {
                if ( attrs.hasOwnProperty(attr) ) {
                    this.set(attr, attrs[attr]);
                }
            }
            return this;
        },

        /**
         * Gets multiple attribute values.
         *
         * @method getAttrs
         * @param {Array | boolean} attrs Optional. An array of attribute names. If omitted, all attribute values are
         * returned. If set to true, all attributes modified from their initial values are returned.
         * @return {Object} An object with attribute name/value pairs.
         */
        getAttrs : function(attrs) {
            return this._getAttrs(attrs);
        },

        /**
         * Implementation behind the public getAttrs method, to get multiple attribute values.
         *
         * @method _getAttrs
         * @protected
         * @param {Array | boolean} attrs Optional. An array of attribute names. If omitted, all attribute values are
         * returned. If set to true, all attributes modified from their initial values are returned.
         * @return {Object} An object with attribute name/value pairs.
         */
        _getAttrs : function(attrs) {
            var host = this,
                o = {}, 
                i, l, attr, val,
                modifiedOnly = (attrs === true);

            attrs = (attrs && !modifiedOnly) ? attrs : O.keys(host._state.data.added);

            for (i = 0, l = attrs.length; i < l; i++) {
                // Go through get, to honor cloning/normalization
                attr = attrs[i];
                val = host.get(attr);

                if (!modifiedOnly || host._getStateVal(attr) != host._state.get(attr, INIT_VALUE)) {
                    o[attr] = host.get(attr); 
                }
            }

            return o;
        },

        /**
         * Configures a group of attributes, and sets initial values.
         *
         * <p>
         * <strong>NOTE:</strong> This method does not isolate the configuration object by merging/cloning. 
         * The caller is responsible for merging/cloning the configuration object if required.
         * </p>
         *
         * @method addAttrs
         * @chainable
         *
         * @param {Object} cfgs An object with attribute name/configuration pairs.
         * @param {Object} values An object with attribute name/value pairs, defining the initial values to apply.
         * Values defined in the cfgs argument will be over-written by values in this argument unless defined as read only.
         * @param {boolean} lazy Whether or not to delay the intialization of these attributes until the first call to get/set.
         * Individual attributes can over-ride this behavior by defining a lazyAdd configuration property in their configuration.
         * See <a href="#method_addAttr">addAttr</a>.
         * 
         * @return {Object} A reference to the host object.
         */
        addAttrs : function(cfgs, values, lazy) {
            var host = this; // help compression
            if (cfgs) {
                host._tCfgs = cfgs;
                host._tVals = host._normAttrVals(values);
                host._addAttrs(cfgs, host._tVals, lazy);
                host._tCfgs = host._tVals = null;
            }

            return host;
        },

        /**
         * Implementation behind the public addAttrs method. 
         * 
         * This method is invoked directly by get if it encounters a scenario 
         * in which an attribute's valueFn attempts to obtain the 
         * value an attribute in the same group of attributes, which has not yet 
         * been added (on demand initialization).
         *
         * @method _addAttrs
         * @private
         * @param {Object} cfgs An object with attribute name/configuration pairs.
         * @param {Object} values An object with attribute name/value pairs, defining the initial values to apply.
         * Values defined in the cfgs argument will be over-written by values in this argument unless defined as read only.
         * @param {boolean} lazy Whether or not to delay the intialization of these attributes until the first call to get/set.
         * Individual attributes can over-ride this behavior by defining a lazyAdd configuration property in their configuration.
         * See <a href="#method_addAttr">addAttr</a>.
         */
        _addAttrs : function(cfgs, values, lazy) {
            var host = this, // help compression
                attr,
                attrCfg,
                value;

            for (attr in cfgs) {
                if (cfgs.hasOwnProperty(attr)) {

                    // Not Merging. Caller is responsible for isolating configs
                    attrCfg = cfgs[attr];
                    attrCfg.defaultValue = attrCfg.value;

                    // Handle simple, complex and user values, accounting for read-only
                    value = host._getAttrInitVal(attr, attrCfg, host._tVals);

                    if (value !== undefined) {
                        attrCfg.value = value;
                    }

                    if (host._tCfgs[attr]) {
                        delete host._tCfgs[attr];
                    }

                    host.addAttr(attr, attrCfg, lazy);
                }
            }
        },

        /**
         * Utility method to protect an attribute configuration
         * hash, by merging the entire object and the individual 
         * attr config objects. 
         *
         * @method _protectAttrs
         * @protected
         * @param {Object} attrs A hash of attribute to configuration object pairs.
         * @return {Object} A protected version of the attrs argument.
         */
        _protectAttrs : function(attrs) {
            if (attrs) {
                attrs = Y.merge(attrs);
                for (var attr in attrs) {
                    if (attrs.hasOwnProperty(attr)) {
                        attrs[attr] = Y.merge(attrs[attr]);
                    }
                }
            }
            return attrs;
        },

        /**
         * Utility method to normalize attribute values. The base implementation 
         * simply merges the hash to protect the original.
         *
         * @method _normAttrVals
         * @param {Object} valueHash An object with attribute name/value pairs
         *
         * @return {Object}
         *
         * @private
         */
        _normAttrVals : function(valueHash) {
            return (valueHash) ? Y.merge(valueHash) : null;
        },

        /**
         * Returns the initial value of the given attribute from
         * either the default configuration provided, or the 
         * over-ridden value if it exists in the set of initValues 
         * provided and the attribute is not read-only.
         *
         * @param {String} attr The name of the attribute
         * @param {Object} cfg The attribute configuration object
         * @param {Object} initValues The object with simple and complex attribute name/value pairs returned from _normAttrVals
         *
         * @return {Any} The initial value of the attribute.
         *
         * @method _getAttrInitVal
         * @private
         */
        _getAttrInitVal : function(attr, cfg, initValues) {

            // init value is provided by the user if it exists, else, provided by the config
            var val = (!cfg[READ_ONLY] && initValues && initValues.hasOwnProperty(attr)) ?
                            val = initValues[attr] :
                            (cfg[VALUE_FN]) ?
                                cfg[VALUE_FN].call(this) : 
                                cfg[VALUE];


            return val;
        }
    };

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

    Y.Attribute = Attribute;


}, '3.0.0' ,{requires:['event-custom']});
