(function() {
    'use strict';

    var XModule = {};

    XModule.Descriptor = (function() {
        /*
         * Bind the module to an element. This may be called multiple times,
         * if the element content has changed and so the module needs to be rebound
         *
         * @method: constructor
         * @param {html element} the .xmodule_edit section containing all of the descriptor content
         */
        var Descriptor = function(element) {
            this.element = element;
            this.update = _.bind(this.update, this);
        };

        /*
         * Register a callback method to be called when the state of this
         * descriptor is updated. The callback will be passed the results
         * of calling the save method on this descriptor.
         */
        Descriptor.prototype.onUpdate = function(callback) {
            if (!this.callbacks) {
                this.callbacks = [];
            }

            this.callbacks.push(callback);
        };

        /*
         * Notify registered callbacks that the state of this descriptor has changed
         */
        Descriptor.prototype.update = function() {
            var data, callbacks, i, length;

            data = this.save();
            callbacks = this.callbacks;
            length = callbacks.length;

            $.each(callbacks, function(index, callback) {
                callback(data);
            });
        };

        /*
         * Return the current state of the descriptor (to be written to the module store)
         *
         * @method: save
         * @returns {object} An object containing children and data attributes (both optional).
         *                   The contents of the attributes will be saved to the server
         */
        Descriptor.prototype.save = function() {
            return {};
        };

        return Descriptor;
    }());

    this.XBlockToXModuleShim = function(runtime, element, initArgs) {
        /*
         * Load a single module (either an edit module or a display module)
         * from the supplied element, which should have a data-type attribute
         * specifying the class to load
         */
        var moduleType, module;

        if (initArgs) {
            moduleType = initArgs['xmodule-type'];
        }
        if (!moduleType) {
            moduleType = $(element).data('type');
        }

        if (moduleType === 'None') {
            return;
        }

        try {
            module = new window[moduleType](element, runtime);

            if ($(element).hasClass('xmodule_edit')) {
                $(document).trigger('XModule.loaded.edit', [element, module]);
            }

            if ($(element).hasClass('xmodule_display')) {
                $(document).trigger('XModule.loaded.display', [element, module]);
            }

            return module;
        } catch (error) {
            console.error('Unable to load ' + moduleType + ': ' + error.message);
        }
    };

    // Export this module. We do it at the end when everything is ready
    // because some RequireJS scripts require this module. If
    // `window.XModule` appears as defined before this file has a chance
    // to execute fully, then there is a chance that RequireJS will execute
    // some script prematurely.
    this.XModule = XModule;
}).call(this);