'use strict';

// Ox.js Developer Version

/*
Usage:
    Ox.load(callback)
    Ox.load(module, callback)
    Ox.load(module, options, callback)
    Ox.load({module: options, module: options}, callback)
*/

window.Ox = {

    load: function() {

        var args = arguments,
            callback = args[args.length - 1],
            path = getPath();

        loadJSON(function(data) {
            loadScripts(data, function() {
                if (args.length == 1) {
                    callback()
                } else {
                    Ox.load.apply(null, args);
                }
            });
        });

        function getPath() {
            var i, path, scripts = document.getElementsByTagName('script');
            for (i = 0; i < scripts.length; i++) {
                if (/Ox\.js$/.test(scripts[i].src)) {
                    path = scripts[i].src.replace(/Ox\.js$/, '');
                }
            }
            return path;
        }

        function loadJSON(callback) {
            var req = new XMLHttpRequest();
            req.open('GET', path + 'Ox/json/Ox.json?' + Ox.random(1000000), true);
            req.onreadystatechange = function() {
                if (req.readyState == 4) {
                    if (req.status == 200) {
                        callback(JSON.parse(req.responseText));
                    } else {
                        // ...
                    }
                }
            };
            req.send();
        }

        function loadScripts(scripts, callback) {
            loadScriptsOrdered(scripts[0], function() {
                loadScriptsUnordered(scripts[1], function() {
                    loadScriptsUnordered(scripts[2], callback);
                });
            });
        }

        function loadScriptsOrdered(scripts, callback) {
            loadScript(scripts.shift(), function() {
                if (scripts.length) {
                    loadScriptsOrdered(scripts, callback);
                } else {
                    callback();
                }
            });
        }

        function loadScriptsUnordered(scripts, callback) {
            var counter = 0, i, length = scripts.length;
            for (i = 0; i < length; i++) {
                loadScript(scripts[i], function() {
                    ++counter == length && callback();
                });
            }
        }

        function loadScript(script, callback) {
            var element = document.createElement('script'),
                head = document.head || document.getElementsByTagName( "head" )[0] || document.documentElement;
            element.onload = callback;
            element.src = path + script + '?' + parseInt(Math.random() * 1000000);
            element.type = 'text/javascript';
            head.appendChild(element);
        }

    }

};