/*
 * Metadata - jQuery plugin for parsing metadata from elements
 *
 * Copyright (c) 2006 John Resig, Yehuda Katz, J�örn Zaefferer, Paul McLanahan
 *
 * Dual licensed under the MIT and GPL licenses:
 *   http://www.opensource.org/licenses/mit-license.php
 *   http://www.gnu.org/licenses/gpl.html
 *
 * Revision: $Id$
 *
 */

/**
 * Sets the type of metadata to use. Metadata is encoded in JSON, and each property
 * in the JSON will become a property of the element itself.
 *
 * There are three supported types of metadata storage:
 *
 *   attr:  Inside an attribute. The name parameter indicates *which* attribute.
 *
 *   class: Inside the class attribute, wrapped in curly braces: { }
 *
 *   elem:  Inside a child element (e.g. a script tag). The
 *          name parameter indicates *which* element.
 *
 * The metadata for an element is loaded the first time the element is accessed via jQuery.
 *
 * As a result, you can define the metadata type, use $(expr) to load the metadata into the elements
 * matched by expr, then redefine the metadata type and run another $(expr) for other elements.
 *
 * @name $.metadata.setType
 *
 * @example <p id="one" class="some_class {item_id: 1, item_label: 'Label'}">This is a p</p>
 * @before $.metadata.setType("class")
 * @after $("#one").metadata().item_id == 1; $("#one").metadata().item_label == "Label"
 * @desc Reads metadata from the class attribute
 *
 * @example <p id="one" class="some_class" data="{item_id: 1, item_label: 'Label'}">This is a p</p>
 * @before $.metadata.setType("attr", "data")
 * @after $("#one").metadata().item_id == 1; $("#one").metadata().item_label == "Label"
 * @desc Reads metadata from a "data" attribute
 *
 * @example <p id="one" class="some_class"><script>{item_id: 1, item_label: 'Label'}</script>This is a p</p>
 * @before $.metadata.setType("elem", "script")
 * @after $("#one").metadata().item_id == 1; $("#one").metadata().item_label == "Label"
 * @desc Reads metadata from a nested script element
 *
 * @param String type The encoding type
 * @param String name The name of the attribute to be used to get metadata (optional)
 * @cat Plugins/Metadata
 * @descr Sets the type of encoding to be used when loading metadata for the first time
 * @type undefined
 * @see metadata()
 */

(function ($) {

    $.extend({
        metadata: {
            defaults: {
                type: 'class',
                name: 'metadata',
                cre: /({.*})/,
                single: 'metadata'
            },
            setType: function (type, name) {
                this.defaults.type = type;
                this.defaults.name = name;
            },
            get: function (elem, opts) {
                var settings = $.extend({}, this.defaults, opts);
                // check for empty string in single property
                if (!settings.single.length) settings.single = 'metadata';

                var data = $.data(elem, settings.single);
                // returned cached data if it already exists
                if (data) return data;

                data = "{}";

                if (settings.type == "class") {
                    var m = settings.cre.exec(elem.className);
                    if (m)
                        data = m[1];
                } else if (settings.type == "elem") {
                    if (!elem.getElementsByTagName)
                        return undefined;
                    var e = elem.getElementsByTagName(settings.name);
                    if (e.length)
                        data = $.trim(e[0].innerHTML);
                } else if (elem.getAttribute != undefined) {
                    var attr = elem.getAttribute(settings.name);
                    if (attr)
                        data = attr;
                }

                if (data.indexOf('{') < 0)
                    data = "{" + data + "}";

                data = eval("(" + data + ")");

                $.data(elem, settings.single, data);
                return data;
            }
        }
    });

    /**
     * Returns the metadata object for the first member of the jQuery object.
     *
     * @name metadata
     * @descr Returns element's metadata object
     * @param Object opts An object contianing settings to override the defaults
     * @type jQuery
     * @cat Plugins/Metadata
     */
    $.fn.metadata = function (opts) {
        return $.metadata.get(this[0], opts);
    };

})(jQuery);