/**
     * Provides the augmentable PluginHost interface, which can be added to any class.
     * @module pluginhost
     */

    /**
     * Provides the augmentable PluginHost interface, which can be added to any class.
     * @module pluginhost-base
     */

    /**
     * <p>
     * An augmentable class, which provides the augmented class with the ability to host plugins.
     * It adds <a href="#method_plug">plug</a> and <a href="#method_unplug">unplug</a> methods to the augmented class, which can 
     * be used to add or remove plugins from instances of the class.
     * </p>
     *
     * <p>Plugins can also be added through the constructor configuration object passed to the host class' constructor using
     * the "plugins" property. Supported values for the "plugins" property are those defined by the <a href="#method_plug">plug</a> method. 
     * 
     * For example the following code would add the AnimPlugin and IOPlugin to Overlay (the plugin host):
     * <xmp>
     * var o = new Overlay({plugins: [ AnimPlugin, {fn:IOPlugin, cfg:{section:"header"}}]});
     * </xmp>
     * </p>
     * <p>
     * Plug.Host's protected <a href="#method_initPlugins">_initPlugins</a> and <a href="#method_destroyPlugins">_destroyPlugins</a> 
     * methods should be invoked by the host class at the appropriate point in the host's lifecyle.  
     * </p>
     *
     * @class Plugin.Host
     */

    var L = Y.Lang;

    function PluginHost() {
        this._plugins = {};
    }

    PluginHost.prototype = {

        /**
         * Adds a plugin to the host object. This will instantiate the 
         * plugin and attach it to the configured namespace on the host object.
         *
         * @method plug
         * @chainable
         * @param P {Function | Object |Array} Accepts the plugin class, or an 
         * object with a "fn" property specifying the plugin class and 
         * a "cfg" property specifying the configuration for the Plugin.
         * <p>
         * Additionally an Array can also be passed in, with the above function or 
         * object values, allowing the user to add multiple plugins in a single call.
         * </p>
         * @param config (Optional) If the first argument is the plugin class, the second argument
         * can be the configuration for the plugin.
         * @return {Base} A reference to the host object
         */
        plug: function(Plugin, config) {
            var i, ln, ns;

            if (L.isArray(Plugin)) {
                for (i = 0, ln = Plugin.length; i < ln; i++) {
                    this.plug(Plugin[i]);
                }
            } else {
                if (Plugin && !L.isFunction(Plugin)) {
                    config = Plugin.cfg;
                    Plugin = Plugin.fn;
                }

                // Plugin should be fn by now
                if (Plugin && Plugin.NS) {
                    ns = Plugin.NS;
        
                    config = config || {};
                    config.host = this;
        
                    if (this.hasPlugin(ns)) {
                        // Update config
                        if (this[ns].setAttrs) {
                            this[ns].setAttrs(config);
                        }
                        else { Y.log("Attempt to replug an already attached plugin, and we can't setAttrs, because it's not Attribute based: " + ns); }
                    } else {
                        // Create new instance
                        this[ns] = new Plugin(config);
                        this._plugins[ns] = Plugin;
                    }
                }
                else { Y.log("Attempt to plug in an invalid plugin. Host:" + this + ", Plugin:" + Plugin); }
            }
            return this;
        },

        /**
         * Removes a plugin from the host object. This will destroy the 
         * plugin instance and delete the namespace from the host object. 
         *
         * @method unplug
         * @param {String | Function} plugin The namespace of the plugin, or the plugin class with the static NS namespace property defined. If not provided,
         * all registered plugins are unplugged.
         * @return {Base} A reference to the host object
         * @chainable
         */
        unplug: function(plugin) {
            var ns = plugin, 
                plugins = this._plugins;
            
            if (plugin) {
                if (L.isFunction(plugin)) {
                    ns = plugin.NS;
                    if (ns && (!plugins[ns] || plugins[ns] !== plugin)) {
                        ns = null;
                    }
                }
        
                if (ns) {
                    if (this[ns]) {
                        if (this[ns].destroy) {
                            this[ns].destroy();
                        }
                        delete this[ns];
                    }
                    if (plugins[ns]) {
                        delete plugins[ns];
                    }
                }
            } else {
                for (ns in this._plugins) {
                    if (this._plugins.hasOwnProperty(ns)) {
                        this.unplug(ns);
                    }
                }
            }
            return this;
        },

        /**
         * Determines if a plugin has plugged into this host.
         *
         * @method hasPlugin
         * @param {String} ns The plugin's namespace
         * @return {Plugin} Returns a truthy value (the plugin instance) if present, or undefined if not.
         */
        hasPlugin : function(ns) {
            return (this._plugins[ns] && this[ns]);
        },

        /**
         * Initializes static plugins registered on the host (using the
         * Base.plug static method) and any plugins passed to the 
         * instance through the "plugins" configuration property.
         *
         * @method _initPlugins
         * @param {Config} config The configuration object with property name/value pairs.
         * @private
         */
        
        _initPlugins: function(config) {
            this._plugins = this._plugins || {};

            if (this._initConfigPlugins) {
                this._initConfigPlugins(config);
            }
        },

        /**
         * Unplugs and destroys all plugins on the host
         * @method _destroyPlugins
         * @private
         */
        _destroyPlugins: function() {
            this.unplug();
        }
    };

    Y.namespace("Plugin").Host = PluginHost;