/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
"use strict";

const { Trait } = require('../traits');
const { EventEmitter, EventEmitterTrait } = require('../events');
const { Ci, Cu, Cc } = require('chrome');
const timer = require('../timer');
const { URL } = require('../url');
const unload = require('../unload');
const observers = require('../observer-service');
const { Cortex } = require('../cortex');
const self = require("self");
const { sandbox, evaluate, load } = require("../sandbox");
const { merge } = require('../utils/object');

const CONTENT_PROXY_URL = self.data.url("content-proxy.js");
const CONTENT_WORKER_URL = self.data.url("worker.js");

const JS_VERSION = '1.8';

const ERR_DESTROYED =
  "The page has been destroyed and can no longer be used.";

/**
 * This key is not exported and should only be used for proxy tests.
 * The following `PRIVATE_KEY` is used in addon module scope in order to tell
 * Worker API to expose `UNWRAP_ACCESS_KEY` in content script.
 * This key allows test-content-proxy.js to unwrap proxy with valueOf:
 *   let xpcWrapper = proxyWrapper.valueOf(UNWRAP_ACCESS_KEY);
 */
const PRIVATE_KEY = {};


const WorkerSandbox = EventEmitter.compose({

  /**
   * Emit a message to the worker content sandbox
   */
  emit: function emit() {
    // First ensure having a regular array
    // (otherwise, `arguments` would be mapped to an object by `stringify`)
    let array = Array.slice(arguments);
    // JSON.stringify is buggy with cross-sandbox values,
    // it may return "{}" on functions. Use a replacer to match them correctly.
    function replacer(k, v) {
      return typeof v === "function" ? undefined : v;
    }
    // Ensure having an asynchronous behavior
    let self = this;
    timer.setTimeout(function () {
      self._emitToContent(JSON.stringify(array, replacer));
    }, 0);
  },

  /**
   * Synchronous version of `emit`.
   * /!\ Should only be used when it is strictly mandatory /!\
   *     Doesn't ensure passing only JSON values.
   *     Mainly used by context-menu in order to avoid breaking it.
   */
  emitSync: function emitSync() {
    return this._emitToContent(Array.slice(arguments));
  },

  /**
   * Tells if content script has at least one listener registered for one event,
   * through `self.on('xxx', ...)`.
   * /!\ Shouldn't be used. Implemented to avoid breaking context-menu API.
   */
  hasListenerFor: function hasListenerFor(name) {
    return this._hasListenerFor(name);
  },

  /**
   * Method called by the worker sandbox when it needs to send a message
   */
  _onContentEvent: function onContentEvent(args) {
    // As `emit`, we ensure having an asynchronous behavior
    let self = this;
    timer.setTimeout(function () {
      // We emit event to chrome/addon listeners
      self._emit.apply(self, JSON.parse(args));
    }, 0);
  },

  /**
   * Configures sandbox and loads content scripts into it.
   * @param {Worker} worker
   *    content worker
   */
  constructor: function WorkerSandbox(worker) {
    this._addonWorker = worker;

    // Ensure that `emit` has always the right `this`
    this.emit = this.emit.bind(this);
    this.emitSync = this.emitSync.bind(this);

    // We receive a wrapped window, that may be an xraywrapper if it's content
    let window = worker._window;
    let proto = window;

    // Instantiate trusted code in another Sandbox in order to prevent content
    // script from messing with standard classes used by proxy and API code.
    let apiSanbox = sandbox(window, { wantXrays: true });

    // Build content proxies only if the document has a non-system principal
    if (window.wrappedJSObject) {
      apiSanbox.console = console;
      // Execute the proxy code
      load(apiSanbox, CONTENT_PROXY_URL);
      // Get a reference of the window's proxy
      proto = apiSanbox.create(window);
    }

    // Create the sandbox and bind it to window in order for content scripts to
    // have access to all standard globals (window, document, ...)
    let content = this._sandbox = sandbox(window, {
      sandboxPrototype: proto,
      wantXrays: true
    });
    merge(content, {
      // We need "this === window === top" to be true in toplevel scope:
      get window() content,
      get top() content,
      // Use the Greasemonkey naming convention to provide access to the
      // unwrapped window object so the content script can access document
      // JavaScript values.
      // NOTE: this functionality is experimental and may change or go away
      // at any time!
      get unsafeWindow() window.wrappedJSObject
    });

    // Load trusted code that will inject content script API.
    // We need to expose JS objects defined in same principal in order to
    // avoid having any kind of wrapper.
    load(apiSanbox, CONTENT_WORKER_URL);

    // Then call `inject` method and communicate with this script
    // by trading two methods that allow to send events to the other side:
    //   - `onEvent` called by content script
    //   - `result.emitToContent` called by addon script
    let chromeAPI = {
      timers: {
        setTimeout: timer.setTimeout,
        setInterval: timer.setInterval,
        clearTimeout: timer.clearTimeout,
        clearInterval: timer.clearInterval
      }
    };
    let onEvent = this._onContentEvent.bind(this);
    // `ContentWorker` is defined in CONTENT_WORKER_URL file
    let result = apiSanbox.ContentWorker.inject(content, chromeAPI, onEvent);
    this._emitToContent = result.emitToContent;
    this._hasListenerFor = result.hasListenerFor;

    // Handle messages send by this script:
    let self = this;
    // console.xxx calls
    this.on("console", function consoleListener(kind) {
      console[kind].apply(console, Array.slice(arguments, 1));
    });

    // self.postMessage calls
    this.on("message", function postMessage(data) {
      self._addonWorker._emit('message', data);
    });

    // self.port.emit calls
    this.on("event", function portEmit(name, args) {
      self._addonWorker._onContentScriptEvent.apply(self._addonWorker, arguments);
    });

    // Internal feature that is only used by SDK tests:
    // Expose unlock key to content script context.
    // See `PRIVATE_KEY` definition for more information.
    if (apiSanbox && worker._expose_key)
      content.UNWRAP_ACCESS_KEY = apiSanbox.UNWRAP_ACCESS_KEY;

    // Inject `addon` global into target document if document is trusted,
    // `addon` in document is equivalent to `self` in content script.
    if (worker._injectInDocument) {
      let win = window.wrappedJSObject ? window.wrappedJSObject : window;
      Object.defineProperty(win, "addon", {
          value: content.self
        }
      );
    }

    // The order of `contentScriptFile` and `contentScript` evaluation is
    // intentional, so programs can load libraries like jQuery from script URLs
    // and use them in scripts.
    let contentScriptFile = ('contentScriptFile' in worker) ? worker.contentScriptFile
          : null,
        contentScript = ('contentScript' in worker) ? worker.contentScript : null;

    if (contentScriptFile) {
      if (Array.isArray(contentScriptFile))
        this._importScripts.apply(this, contentScriptFile);
      else
        this._importScripts(contentScriptFile);
    }
    if (contentScript) {
      this._evaluate(
        Array.isArray(contentScript) ? contentScript.join(';\n') : contentScript
      );
    }
  },
  destroy: function destroy() {
    this.emitSync("destroy");
    this._sandbox = null;
    this._addonWorker = null;
  },
  
  /**
   * JavaScript sandbox where all the content scripts are evaluated.
   * {Sandbox}
   */
  _sandbox: null,
  
  /**
   * Reference to the addon side of the worker.
   * @type {Worker}
   */
  _addonWorker: null,
  
  /**
   * Evaluates code in the sandbox.
   * @param {String} code
   *    JavaScript source to evaluate.
   * @param {String} [filename='javascript:' + code]
   *    Name of the file
   */
  _evaluate: function(code, filename) {
    try {
      evaluate(this._sandbox, code, filename || 'javascript:' + code);
    }
    catch(e) {
      this._addonWorker._emit('error', e);
    }
  },
  /**
   * Imports scripts to the sandbox by reading files under urls and
   * evaluating its source. If exception occurs during evaluation
   * `"error"` event is emitted on the worker.
   * This is actually an analog to the `importScript` method in web
   * workers but in our case it's not exposed even though content
   * scripts may be able to do it synchronously since IO operation
   * takes place in the UI process.
   */
  _importScripts: function _importScripts(url) {
    let urls = Array.slice(arguments, 0);
    for each (let contentScriptFile in urls) {
      try {
        let uri = URL(contentScriptFile);
        if (uri.scheme === 'resource')
          load(this._sandbox, String(uri));
        else
          throw Error("Unsupported `contentScriptFile` url: " + String(uri));
      }
      catch(e) {
        this._addonWorker._emit('error', e);
      }
    }
  }
});

/**
 * Message-passing facility for communication between code running
 * in the content and add-on process.
 * @see https://jetpack.mozillalabs.com/sdk/latest/docs/#module/api-utils/content/worker
 */
const Worker = EventEmitter.compose({
  on: Trait.required,
  _removeAllListeners: Trait.required,
  
  /**
   * Sends a message to the worker's global scope. Method takes single
   * argument, which represents data to be sent to the worker. The data may
   * be any primitive type value or `JSON`. Call of this method asynchronously
   * emits `message` event with data value in the global scope of this
   * symbiont.
   *
   * `message` event listeners can be set either by calling
   * `self.on` with a first argument string `"message"` or by
   * implementing `onMessage` function in the global scope of this worker.
   * @param {Number|String|JSON} data
   */
  postMessage: function postMessage(data) {
    if (!this._contentWorker)
      throw new Error(ERR_DESTROYED);
    this._contentWorker.emit("message", data);
  },
  
  /**
   * EventEmitter, that behaves (calls listeners) asynchronously.
   * A way to send customized messages to / from the worker.
   * Events from in the worker can be observed / emitted via 
   * worker.on / worker.emit.
   */
  get port() {
    // We generate dynamically this attribute as it needs to be accessible
    // before Worker.constructor gets called. (For ex: Panel)
    
    // create an event emitter that receive and send events from/to the worker
    let self = this;
    this._port = EventEmitterTrait.create({
      emit: function () self._emitEventToContent(Array.slice(arguments))
    });

    // expose wrapped port, that exposes only public properties:
    // We need to destroy this getter in order to be able to set the
    // final value. We need to update only public port attribute as we never 
    // try to access port attribute from private API.
    delete this._public.port;
    this._public.port = Cortex(this._port);
    // Replicate public port to the private object
    delete this.port;
    this.port = this._public.port;
    
    return this._port;
  },
  
  /**
   * Same object than this.port but private API.
   * Allow access to _emit, in order to send event to port.
   */
  _port: null,
  
  /**
   * Emit a custom event to the content script, 
   * i.e. emit this event on `self.port`
   */
  _emitEventToContent: function _emitEventToContent(args) {
    // We need to save events that are emitted before the worker is 
    // initialized
    if (!this._inited) {
      this._earlyEvents.push(args);
      return;
    }

    // We throw exception when the worker has been destroyed
    if (!this._contentWorker) {
      throw new Error(ERR_DESTROYED);
    }

    // Forward the event to the WorkerSandbox object
    this._contentWorker.emit.apply(null, ["event"].concat(args));
  },
  
  // Is worker connected to the content worker sandbox ?
  _inited: false,
  
  // List of custom events fired before worker is initialized
  get _earlyEvents() {
    delete this._earlyEvents;
    this._earlyEvents = [];
    return this._earlyEvents;
  },
  
  constructor: function Worker(options) {
    options = options || {};

    if ('window' in options)
      this._window = options.window;
    if ('contentScriptFile' in options)
      this.contentScriptFile = options.contentScriptFile;
    if ('contentScript' in options)
      this.contentScript = options.contentScript;
    if ('onError' in options)
      this.on('error', options.onError);
    if ('onMessage' in options)
      this.on('message', options.onMessage);
    if ('onDetach' in options)
      this.on('detach', options.onDetach);

    // Internal feature that is only used by SDK unit tests.
    // See `PRIVATE_KEY` definition for more information.
    if ('exposeUnlockKey' in options && options.exposeUnlockKey === PRIVATE_KEY)
      this._expose_key = true;

    // Track document unload to destroy this worker.
    // We can't watch for unload event on page's window object as it 
    // prevents bfcache from working: 
    // https://developer.mozilla.org/En/Working_with_BFCache
    this._windowID = this._window.
                     QueryInterface(Ci.nsIInterfaceRequestor).
                     getInterface(Ci.nsIDOMWindowUtils).
                     currentInnerWindowID;
    observers.add("inner-window-destroyed", 
                  this._documentUnload = this._documentUnload.bind(this));
    
    unload.ensure(this._public, "destroy");
    
    // Ensure that worker._port is initialized for contentWorker to be able
    // to send use event during WorkerSandbox(this)
    this.port;
    
    // will set this._contentWorker pointing to the private API:
    this._contentWorker = WorkerSandbox(this);
    
    // Mainly enable worker.port.emit to send event to the content worker
    this._inited = true;
    
    // Flush all events that have been fired before the worker is initialized.
    this._earlyEvents.forEach((function (args) this._emitEventToContent(args)).
                              bind(this));
  },
  
  _documentUnload: function _documentUnload(subject, topic, data) {
    let innerWinID = subject.QueryInterface(Ci.nsISupportsPRUint64).data;
    if (innerWinID != this._windowID) return false;
    this._workerCleanup();
    return true;
  },

  get url() {
    // this._window will be null after detach
    return this._window ? this._window.document.location.href : null;
  },
  
  get tab() {
    if (this._window) {
      let tab = require("../tabs/tab");
      // this._window will be null after detach
      return tab.getTabForWindow(this._window);
    }
    return null;
  },
  
  /**
   * Tells content worker to unload itself and 
   * removes all the references from itself.
   */
  destroy: function destroy() {
    this._workerCleanup();
    this._removeAllListeners();
  },
  
  /**
   * Remove all internal references to the attached document
   * Tells _port to unload itself and removes all the references from itself.
   */
  _workerCleanup: function _workerCleanup() {
    // maybe unloaded before content side is created
    // As Symbiont call worker.constructor on document load
    if (this._contentWorker) 
      this._contentWorker.destroy();
    this._contentWorker = null;
    this._window = null;
    // This method may be called multiple times,
    // avoid dispatching `detach` event more than once
    if (this._windowID) {
      this._windowID = null;
      observers.remove("inner-window-destroyed", this._documentUnload);
      this._earlyEvents.slice(0, this._earlyEvents.length);
      this._emit("detach");
    }
  },
  
  /**
   * Receive an event from the content script that need to be sent to 
   * worker.port. Provide a way for composed object to catch all events.
   */
  _onContentScriptEvent: function _onContentScriptEvent() {
    this._port._emit.apply(this._port, arguments);
  },
  
  /**
   * Reference to the content side of the worker.
   * @type {WorkerGlobalScope}
   */
  _contentWorker: null,

  /**
   * Reference to the window that is accessible from
   * the content scripts.
   * @type {Object}
   */
  _window: null,

  /**
   * Flag to enable `addon` object injection in document. (bug 612726)
   * @type {Boolean}
   */
  _injectInDocument: false
});
exports.Worker = Worker;
