Template loader wrapper

/**
 * The templates tool loads a template with view data. It caches template scripts.
 *
 * Example: loader.load('/path/to/template.html', 'selector', container, data);
 */
(function ($, M) {
    'use strict';
    var templates = {},
        data = {};
 
    /**
     * Render a template
     * @param {Object} template {id: id, html: template}
     */
    function renderTemplate(template) {
        var viewData = data[template.id].viewData,
            $container = data[template.id].$templateContainer,
            output = M.render(template.html, viewData);
        // clear and fill the container
        $container.html('').html(output);
 
    }
 
    /**
     * get template by url
     * @param {String} templateUrl Location of the template
     * @param {String} templateId  ID of template
     */
    function getTemplate(templateUrl, templateId) {
        var templateDefer = new $.Deferred();
 
        // get template
        $.get(templateUrl, function (file) {
            var html = $(file).filter('#' + templateId).html();
            templates[templateId] = templateDefer.promise();
            templateDefer.resolve({id: templateId, html: html});
        });
        return templateDefer.promise();
    }
 
    /**
     * Load a template and put it in a container.
     * @param {String} templateUrl        The absolute path to the template
     * @param {String} templateId         The id of the chosen template
     * @param {jQuery} $templateContainer Empty container where the template will be placed in
     * @param {Object} viewData           The data that is loaded in the template
     */
    function load(templateUrl, templateId, $templateContainer, viewData) {
        var templateRendered = $.Deferred();
        data[templateId] = {
            $templateContainer: $templateContainer,
            viewData: viewData
        };
        function resolveLoad() {
            templateRendered.resolve($templateContainer);
        }
        if (templates[templateId]) {
            // template already in cache
            templates[templateId].done(renderTemplate, resolveLoad);
        } else {
            getTemplate(templateUrl, templateId).done(renderTemplate, resolveLoad);
        }
        return templateRendered.promise();
    }
 
    loader = {
        load: load
    };
}(jQuery, Mustache));