sebastian-software/core

/*
==================================================================================================
  Core - JavaScript Foundation
  Copyright 2010-2012 Zynga Inc.
  Copyright 2012-2014 Sebastian Werner
==================================================================================================
*/

"use strict";

(function(global)
{
    var doc = global.document;

    // the following is a feature sniff for the ability to set async=false on dynamically created script elements, as proposed to the W3C
    // RE: http://wiki.whatwg.org/wiki/Dynamic_Script_Execution_Order
    var supportsScriptAsync = doc && doc.createElement("script").async === true;

    // Dynamic URI can be shared because we do not support reloading files
    var dynamicExtension = "?r=" + Date.now();

    // Used for shorten calls
    var assignCallback = function(elem, value) {
        elem.onload = elem.onerror = elem.onreadystatechange = value;
    };

    // If native, try to use importScripts; if not available shim importScripts via use of eval and readFileSync.
    if (jasy.Env.isSet("runtime", "native"))
    {
        var importScripts = global.importScripts ? global.importScripts : (function() {
            var Fs = require("fs");
            return function() {
                for (var i=0,ii=arguments.length; i<ii; i++) {
                    var uri = arguments[i];
                    eval("//@ sourceURL=" + uri + "\n" + Fs.readFileSync(uri, "utf-8"));
                }
            };
        })();
    }

    /**
     * Generic script loader for features. Could be used for loading feature/class packages after initial load.
     *
     * (though limited feature set and file registration not useful for data transaction)
     */
    core.Module("core.io.Script",
    {
        /** Whether the loader supports parallel requests */
        SUPPORTS_PARALLEL : supportsScriptAsync || jasy.Env.isSet("engine", "gecko") || jasy.Env.isSet("engine", "opera"),

        /** {String|null} URL prefix to prepend to given relative URL. Used by worker script loading */
        URL_PREFIX : null,


        /**
         * Loads a JavaScript file from the given @uri {String} and fires a
         * @callback {Function} (in @context {Object?}) when the script was loaded.
         * Optionally appends an random `GET` parameter to omit caching when
         * @nocache {Boolean?false} is enabled..
         */
        load : function(uri, callback, context, nocache)
        {
            if (jasy.Env.isSet("debug"))
            {
                core.Assert.isType(uri, "String");

                if (callback != null) {
                    core.Assert.isType(callback, "Function", "Invalid callback method!");
                }

                if (context != null) {
                    core.Assert.isType(context, "Object", "Invalid callback context!");
                }

                if (nocache != null) {
                    core.Assert.isType(nocache, "Boolean");
                }
            }

            if (jasy.Env.isSet("debug") && nocache == null) {
                nocache = true;
            }

            if (core.io.Util.isRelativeUrl(uri)) {
                uri = jasy.Env.getValue("jasy.url") + uri;
            }

            // Browser-less (e.g. NodeJS) support
            if (jasy.Env.isSet("runtime", "native"))
            {
                importScripts(uri);
                if (callback) {
                    callback.call(context||global, uri, false);
                }

                return;
            }
            else if (jasy.Env.isSet("runtime", "worker"))
            {
                if (core.io.Script.URL_PREFIX != null && uri[0] != "/" && uri.indexOf(":/") < 0) {
                    uri = core.io.Script.URL_PREFIX + uri;
                }
                try {
                    importScripts(uri);
                } catch (e) {
                    e.fileName = uri;
                    throw e;
                }
                if (callback) {
                    callback.call(context||global, uri, false);
                }
            }
            else
            {
                var head = doc.head;
                var elem = doc.createElement("script");

                // load script via 'src' attribute, set onload/onreadystatechange listeners
                assignCallback(elem, function(e)
                {
                    if (!e) {
                        e = global.event;
                    }

                    var errornous = e.type === "error";
                    if (errornous)
                    {
                        console.warn("Could not load script: " + uri);
                    }
                    else if (e.type == "load" || (/loaded|complete/.test(elem.readyState) && (!doc.documentMode || doc.documentMode < 9)))
                    {
                        // ready
                        // jshint -W035
                    }
                    else
                    {
                        // not yet ready
                        return;
                    }

                    // Prevent memory leaks
                    assignCallback(elem, null);

                    // Execute callback
                    if (callback) {
                        callback.call(context||global, uri, errornous, elem);
                    }
                });

                elem.src = nocache ? uri + dynamicExtension : uri;

                if (supportsScriptAsync) {
                    elem.async = false;
                }

                head.insertBefore(elem, head.firstChild);
            }
        }
    });
})(core.Main.getGlobal());