lib/ripple/platform/webworks/2.0.0/XMLHttpRequest.js

/*
 *  Copyright 2011 Research In Motion Limited.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
var XHR = window.XMLHttpRequest,
    webworks = require('ripple/platform/webworks/2.0.0/server');

module.exports = function () {
    var _url,
        _async,
        xhr = new XHR(),
        origMethods = {
            open: xhr.open,
            send: xhr.send,
            setRequestHeader: xhr.setRequestHeader
        };

    function onreadystatechange() {
        if (typeof xhr.onreadystatechange === "function") {
            xhr.onreadystatechange();
        }
    }

    function statemachine(getResult) {
        var state = 0,
            incState = function (prev, baton) {
                state++;
                if (_async) {
                    baton.take();
                    setTimeout(baton.pass, 1);
                }
            },
            setResponse = function (result) {
                xhr.__defineGetter__("status", function () {
                    return 200;
                });

                xhr.__defineGetter__("responseText", function () {
                    return result !== null && result !== undefined ?
                        JSON.stringify(result) : null;
                });
            };

        xhr.__defineGetter__("readyState", function () {
            return state;
        });

        jWorkflow.order(incState)
                 .andThen(onreadystatechange)
                 .andThen(incState)
                 .andThen(onreadystatechange)
                 .andThen(incState)
                 .andThen(onreadystatechange)
                 .andThen(getResult)
                 .andThen(setResponse)
                 .andThen(incState)
                 .andThen(onreadystatechange)
                 .start();
    }

    xhr.setRequestHeader = function (header, value) {
        if (!_url.match(/^webworks:\/\//)) {
            origMethods.setRequestHeader.apply(xhr, Array.prototype.slice.call(arguments));
        }
    };

    xhr.open = function (method, url, async, user, password) {
        _url = url;
        _async = async;

        if (!_url.match(/^webworks:\/\//)) {
            origMethods.open.apply(xhr, Array.prototype.slice.call(arguments));
        }
    };

    xhr.send = function (post) {
        if (!_url.match(/^webworks:\/\//)) {
            origMethods.send.apply(xhr, Array.prototype.slice.call(arguments));
            return;
        }

        var params = _url.match(/\?(.*)$/),
            objPath = _url.match(/^webworks:\/\/([^\?]*)/)[1].split("/"),
            apiMethod = objPath.reduce(function (obj, name) {
                return obj[name];
            }, webworks),
            postParams = {},
            get = {};

        if (params) {
            params[1].split("&").forEach(function (param) {
                    var pair = param.split("="),
                        key = decodeURIComponent(pair[0]),
                        value = decodeURIComponent(pair[1]);
                    // parsing undefied with JSON throws exception
                    get[key] = value === "undefined" ? undefined : JSON.parse(value);
                });
        }

        if (post) {
            post.split("&").forEach(function (param) {
                    var pair = param.split("="),
                        value;
                    try {
                        value = JSON.parse(decodeURIComponent(pair[1]));
                    } catch (e) {
                        value = pair[1] === "undefined" ? undefined : pair[1];
                    }

                    postParams[pair[0]] = value;
                });
        }

        statemachine(function (prev, baton) {
            return apiMethod(get, postParams, baton);
        });
    };

    return xhr;
};