var _mods = {},

    ROOT_LANG = "yuiRootLang",
    ACTIVE_LANG = "yuiActiveLang",
    NONE = [];

/**
 * Provides utilities to support the management of localized resources (strings and formatting patterns).
 *
 * @module intl
 */

/**
 * The Intl utility provides a central location for managing sets of localized resources (strings and formatting patterns).
 *
 * @class Intl
 * @uses EventTarget
 * @static
 */
Y.mix(Y.namespace("Intl"), {

    /**
     * Private method to retrieve the language hash for a given module.
     *
     * @method _mod
     * @private
     *
     * @param {String} module The name of the module
     * @return {Object} The hash of localized resources for the module, keyed by BCP language tag
     */
    _mod : function(module) {
        if (!_mods[module]) {
            _mods[module] = {};
        }
        return _mods[module];
    },

    /**
     * Sets the active language for the given module.
     *
     * Returns false on failure, which would happen if the language had not been registered through the <a href="#method_add">add()</a> method.
     *
     * @method setLang
     *
     * @param {String} module The module name.
     * @param {String} lang The BCP 47 language tag.
     * @return boolean true if successful, false if not.
     */
    setLang : function(module, lang) {
        var langs = this._mod(module),
            currLang = langs[ACTIVE_LANG],
            exists = !!langs[lang];

        if (exists && lang !== currLang) {
            langs[ACTIVE_LANG] = lang;
            this.fire("intl:langChange", {module: module, prevVal: currLang, newVal: (lang === ROOT_LANG) ? "" : lang});
        }

        return exists;
    },

    /**
     * Get the currently active language for the given module.
     *
     * @method getLang
     *
     * @param {String} module The module name.
     * @return {String} The BCP 47 language tag.
     */
    getLang : function(module) {
        var lang = this._mod(module)[ACTIVE_LANG];
        return (lang === ROOT_LANG) ? "" : lang;
    },

    /**
     * Register a hash of localized resources for the given module and language
     *
     * @method add
     *
     * @param {String} module The module name.
     * @param {String} lang The BCP 47 language tag.
     * @param {Object} strings The hash of localized values, keyed by the string name.
     */
    add : function(module, lang, strings) {
        lang = lang || ROOT_LANG;
        this._mod(module)[lang] = strings;
        this.setLang(module, lang);
    },

    /**
     * Gets the module's localized resources for the currently active language (as provided by the <a href="#method_getLang">getLang</a> method).
     * <p>
     * Optionally, the localized resources for alternate languages which have been added to Intl (see the <a href="#method_add">add</a> method) can
     * be retrieved by providing the BCP 47 language tag as the lang parameter.
     * </p>
     * @method get
     *
     * @param {String} module The module name.
     * @param {String} key Optional. A single resource key. If not provided, returns a copy (shallow clone) of all resources.
     * @param {String} lang Optional. The BCP 47 language tag. If not provided, the module's currently active language is used.
     * @return String | Object A copy of the module's localized resources, or a single value if key is provided.
     */
    get : function(module, key, lang) {
        var mod = this._mod(module),
            strs;

        lang = lang || mod[ACTIVE_LANG];
        strs = mod[lang] || {};

        return (key) ? strs[key] : Y.merge(strs);
    },

    /**
     * Gets the list of languages for which localized resources are available for a given module, based on the module
     * meta-data (part of loader). If loader is not on the page, returns an empty array.
     *
     * @method getAvailableLangs
     * @param {String} module The name of the module
     * @return {Array} The array of languages available.
     */
    getAvailableLangs : function(module) {
        var loader = Y.Env._loader,
            mod = loader && loader.moduleInfo[module],
            langs = mod && mod.lang;
        return (langs) ? langs.concat() : NONE;

    }
});

Y.augment(Y.Intl, Y.EventTarget);

/**
 * Notification event to indicate when the lang for a module has changed. There is no default behavior associated with this event,
 * so the on and after moments are equivalent.
 *
 * @event intl:langChange
 * @param {EventFacade} e The event facade
 * <p>The event facade contains:</p>
 * <dl>
 *     <dt>module</dt><dd>The name of the module for which the language changed</dd>
 *     <dt>newVal</dt><dd>The new language tag</dd>
 *     <dt>prevVal</dt><dd>The current language tag</dd>
 * </dl>
 */
Y.Intl.publish("intl:langChange", {emitFacade:true});