/* 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/. */

/**
 * Firefox Accounts Web Channel.
 *
 * Uses the WebChannel component to receive messages
 * about account state changes.
 */

this.EXPORTED_SYMBOLS = ["EnsureFxAccountsWebChannel"];

const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;

Cu.import("resource://gre/modules/XPCOMUtils.jsm");
Cu.import("resource://gre/modules/FxAccountsCommon.js");

XPCOMUtils.defineLazyModuleGetter(this, "Services",
                                  "resource://gre/modules/Services.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "WebChannel",
                                  "resource://gre/modules/WebChannel.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "fxAccounts",
                                  "resource://gre/modules/FxAccounts.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "FxAccountsStorageManagerCanStoreField",
                                  "resource://gre/modules/FxAccountsStorage.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "Weave",
                                  "resource://services-sync/main.js");

const COMMAND_PROFILE_CHANGE       = "profile:change";
const COMMAND_CAN_LINK_ACCOUNT     = "fxaccounts:can_link_account";
const COMMAND_LOGIN                = "fxaccounts:login";
const COMMAND_LOGOUT               = "fxaccounts:logout";
const COMMAND_DELETE               = "fxaccounts:delete";
const COMMAND_SYNC_PREFERENCES     = "fxaccounts:sync_preferences";
const COMMAND_CHANGE_PASSWORD      = "fxaccounts:change_password";
const COMMAND_FXA_STATUS           = "fxaccounts:fxa_status";

const PREF_LAST_FXA_USER           = "identity.fxaccounts.lastSignedInUserHash";

// These engines were added years after Sync had been introduced, they need
// special handling since they are system add-ons and are un-available on
// older versions of Firefox.
const EXTRA_ENGINES = ["addresses", "creditcards"];

/**
 * A helper function that extracts the message and stack from an error object.
 * Returns a `{ message, stack }` tuple. `stack` will be null if the error
 * doesn't have a stack trace.
 */
function getErrorDetails(error) {
  let details = { message: String(error), stack: null };

  // Adapted from Console.jsm.
  if (error.stack) {
    let frames = [];
    for (let frame = error.stack; frame; frame = frame.caller) {
      frames.push(String(frame).padStart(4));
    }
    details.stack = frames.join("\n");
  }

  return details;
}

/**
 * Create a new FxAccountsWebChannel to listen for account updates
 *
 * @param {Object} options Options
 *   @param {Object} options
 *     @param {String} options.content_uri
 *     The FxA Content server uri
 *     @param {String} options.channel_id
 *     The ID of the WebChannel
 *     @param {String} options.helpers
 *     Helpers functions. Should only be passed in for testing.
 * @constructor
 */
this.FxAccountsWebChannel = function(options) {
  if (!options) {
    throw new Error("Missing configuration options");
  }
  if (!options["content_uri"]) {
    throw new Error("Missing 'content_uri' option");
  }
  this._contentUri = options.content_uri;

  if (!options["channel_id"]) {
    throw new Error("Missing 'channel_id' option");
  }
  this._webChannelId = options.channel_id;

  // options.helpers is only specified by tests.
  XPCOMUtils.defineLazyGetter(this, "_helpers", () => {
    return options.helpers || new FxAccountsWebChannelHelpers(options);
  });

  this._setupChannel();
};

this.FxAccountsWebChannel.prototype = {
  /**
   * WebChannel that is used to communicate with content page
   */
  _channel: null,

  /**
   * Helpers interface that does the heavy lifting.
   */
  _helpers: null,

  /**
   * WebChannel ID.
   */
  _webChannelId: null,
  /**
   * WebChannel origin, used to validate origin of messages
   */
  _webChannelOrigin: null,

  /**
   * Release all resources that are in use.
   */
  tearDown() {
    this._channel.stopListening();
    this._channel = null;
    this._channelCallback = null;
  },

  /**
   * Configures and registers a new WebChannel
   *
   * @private
   */
  _setupChannel() {
    // if this.contentUri is present but not a valid URI, then this will throw an error.
    try {
      this._webChannelOrigin = Services.io.newURI(this._contentUri);
      this._registerChannel();
    } catch (e) {
      log.error(e);
      throw e;
    }
  },

  _receiveMessage(message, sendingContext) {
    let command = message.command;
    let data = message.data;

    switch (command) {
      case COMMAND_PROFILE_CHANGE:
        Services.obs.notifyObservers(null, ON_PROFILE_CHANGE_NOTIFICATION, data.uid);
        break;
      case COMMAND_LOGIN:
        this._helpers.login(data).catch(error =>
          this._sendError(error, message, sendingContext));
        break;
      case COMMAND_LOGOUT:
      case COMMAND_DELETE:
        this._helpers.logout(data.uid).catch(error =>
          this._sendError(error, message, sendingContext));
        break;
      case COMMAND_CAN_LINK_ACCOUNT:
        let canLinkAccount = this._helpers.shouldAllowRelink(data.email);

        let response = {
          command,
          messageId: message.messageId,
          data: { ok: canLinkAccount }
        };

        log.debug("FxAccountsWebChannel response", response);
        this._channel.send(response, sendingContext);
        break;
      case COMMAND_SYNC_PREFERENCES:
        this._helpers.openSyncPreferences(sendingContext.browser, data.entryPoint);
        break;
      case COMMAND_CHANGE_PASSWORD:
        this._helpers.changePassword(data).catch(error =>
          this._sendError(error, message, sendingContext));
        break;
      case COMMAND_FXA_STATUS:
        log.debug("fxa_status received");

        const service = data && data.service;
        this._helpers.getFxaStatus(service, sendingContext)
          .then(fxaStatus => {
            let response = {
              command,
              messageId: message.messageId,
              data: fxaStatus
            };
            this._channel.send(response, sendingContext);
          }).catch(error =>
            this._sendError(error, message, sendingContext)
          );
        break;
      default:
        log.warn("Unrecognized FxAccountsWebChannel command", command);
        break;
    }
  },

  _sendError(error, incomingMessage, sendingContext) {
    log.error("Failed to handle FxAccountsWebChannel message", error);
    this._channel.send({
      command: incomingMessage.command,
      messageId: incomingMessage.messageId,
      data: {
        error: getErrorDetails(error),
      },
    }, sendingContext);
  },

  /**
   * Create a new channel with the WebChannelBroker, setup a callback listener
   * @private
   */
  _registerChannel() {
    /**
     * Processes messages that are called back from the FxAccountsChannel
     *
     * @param webChannelId {String}
     *        Command webChannelId
     * @param message {Object}
     *        Command message
     * @param sendingContext {Object}
     *        Message sending context.
     *        @param sendingContext.browser {browser}
     *               The <browser> object that captured the
     *               WebChannelMessageToChrome.
     *        @param sendingContext.eventTarget {EventTarget}
     *               The <EventTarget> where the message was sent.
     *        @param sendingContext.principal {Principal}
     *               The <Principal> of the EventTarget where the message was sent.
     * @private
     *
     */
    let listener = (webChannelId, message, sendingContext) => {
      if (message) {
        log.debug("FxAccountsWebChannel message received", message.command);
        if (logPII) {
          log.debug("FxAccountsWebChannel message details", message);
        }
        try {
          this._receiveMessage(message, sendingContext);
        } catch (error) {
          this._sendError(error, message, sendingContext);
        }
      }
    };

    this._channelCallback = listener;
    this._channel = new WebChannel(this._webChannelId, this._webChannelOrigin);
    this._channel.listen(listener);
    log.debug("FxAccountsWebChannel registered: " + this._webChannelId + " with origin " + this._webChannelOrigin.prePath);
  }
};

this.FxAccountsWebChannelHelpers = function(options) {
  options = options || {};

  this._fxAccounts = options.fxAccounts || fxAccounts;
};

this.FxAccountsWebChannelHelpers.prototype = {
  // If the last fxa account used for sync isn't this account, we display
  // a modal dialog checking they really really want to do this...
  // (This is sync-specific, so ideally would be in sync's identity module,
  // but it's a little more seamless to do here, and sync is currently the
  // only fxa consumer, so...
  shouldAllowRelink(acctName) {
    return !this._needRelinkWarning(acctName) ||
            this._promptForRelink(acctName);
  },

  /**
   * stores sync login info it in the fxaccounts service
   *
   * @param accountData the user's account data and credentials
   */
  login(accountData) {

    // We don't act on customizeSync anymore, it used to open a dialog inside
    // the browser to selecte the engines to sync but we do it on the web now.
    delete accountData.customizeSync;

    if (accountData.offeredSyncEngines) {
      EXTRA_ENGINES.forEach(engine => {
        if (accountData.offeredSyncEngines.includes(engine) &&
            !accountData.declinedSyncEngines.includes(engine)) {
          // These extra engines are disabled by default.
          Services.prefs.setBoolPref(`services.sync.engine.${engine}`, true);
        }
      });
      delete accountData.offeredSyncEngines;
    }

    if (accountData.declinedSyncEngines) {
      let declinedSyncEngines = accountData.declinedSyncEngines;
      log.debug("Received declined engines", declinedSyncEngines);
      Weave.Service.engineManager.setDeclined(declinedSyncEngines);
      declinedSyncEngines.forEach(engine => {
        Services.prefs.setBoolPref("services.sync.engine." + engine, false);
      });
      delete accountData.declinedSyncEngines;
    }

    // the user has already been shown the "can link account"
    // screen. No need to keep this data around.
    delete accountData.verifiedCanLinkAccount;

    // Remember who it was so we can log out next time.
    this.setPreviousAccountNameHashPref(accountData.email);

    // A sync-specific hack - we want to ensure sync has been initialized
    // before we set the signed-in user.
    let xps = Cc["@mozilla.org/weave/service;1"]
              .getService(Ci.nsISupports)
              .wrappedJSObject;
    return xps.whenLoaded().then(() => {
      return this._fxAccounts.setSignedInUser(accountData);
    });
  },

  /**
   * logout the fxaccounts service
   *
   * @param the uid of the account which have been logged out
   */
  logout(uid) {
    return fxAccounts.getSignedInUser().then(userData => {
      if (userData && userData.uid === uid) {
        // true argument is `localOnly`, because server-side stuff
        // has already been taken care of by the content server
        return fxAccounts.signOut(true);
      }
      return null;
    });
  },

  /**
   * Check if `sendingContext` is in private browsing mode.
   */
  isPrivateBrowsingMode(sendingContext) {
    if (!sendingContext ||
        !sendingContext.browser ||
        !sendingContext.browser.docShell ||
        sendingContext.browser.docShell.usePrivateBrowsing === undefined) {
      log.error("Unable to check for private browsing mode, assuming true");
      return true;
    }

    const isPrivateBrowsing = sendingContext.browser.docShell.usePrivateBrowsing;
    log.debug("is private browsing", isPrivateBrowsing);
    return isPrivateBrowsing;
  },

  /**
   * Check whether sending fxa_status data should be allowed.
   */
  shouldAllowFxaStatus(service, sendingContext) {
    // Return user data for any service in non-PB mode. In PB mode,
    // only return user data if service==="sync".
    //
    // This behaviour allows users to click the "Manage Account"
    // link from about:preferences#sync while in PB mode and things
    // "just work". While in non-PB mode, users can sign into
    // Pocket w/o entering their password a 2nd time, while in PB
    // mode they *will* have to enter their email/password again.
    //
    // The difference in behaviour is to try to match user
    // expectations as to what is and what isn't part of the browser.
    // Sync is viewed as an integral part of the browser, interacting
    // with FxA as part of a Sync flow should work all the time. If
    // Sync is broken in PB mode, users will think Firefox is broken.
    // See https://bugzilla.mozilla.org/show_bug.cgi?id=1323853
    log.debug("service", service);
    return !this.isPrivateBrowsingMode(sendingContext) || service === "sync";
  },

  /**
   * Get fxa_status information. Resolves to { signedInUser: <user_data> }.
   * If returning status information is not allowed or no user is signed into
   * Sync, `user_data` will be null.
   */
  async getFxaStatus(service, sendingContext) {
    let signedInUser = null;

    if (this.shouldAllowFxaStatus(service, sendingContext)) {
      const userData = await this._fxAccounts.getSignedInUser();
      if (userData) {
        signedInUser = {
          email: userData.email,
          sessionToken: userData.sessionToken,
          uid: userData.uid,
          verified: userData.verified
        };
      }
    }

    return {
      signedInUser,
      capabilities: {
        engines: this._getAvailableExtraEngines()
      }
    };
  },

  _getAvailableExtraEngines() {
    return EXTRA_ENGINES.filter(engineName => {
      try {
        return Services.prefs.getBoolPref(`services.sync.engine.${engineName}.available`);
      } catch (e) {
        return false;
      }
    });
  },

  changePassword(credentials) {
    // If |credentials| has fields that aren't handled by accounts storage,
    // updateUserAccountData will throw - mainly to prevent errors in code
    // that hard-codes field names.
    // However, in this case the field names aren't really in our control.
    // We *could* still insist the server know what fields names are valid,
    // but that makes life difficult for the server when Firefox adds new
    // features (ie, new fields) - forcing the server to track a map of
    // versions to supported field names doesn't buy us much.
    // So we just remove field names we know aren't handled.
    let newCredentials = {
      deviceId: null
    };
    for (let name of Object.keys(credentials)) {
      if (name == "email" || name == "uid" || FxAccountsStorageManagerCanStoreField(name)) {
        newCredentials[name] = credentials[name];
      } else {
        log.info("changePassword ignoring unsupported field", name);
      }
    }
    return this._fxAccounts.updateUserAccountData(newCredentials)
      .then(() => this._fxAccounts.updateDeviceRegistration());
  },

  /**
   * Get the hash of account name of the previously signed in account
   */
  getPreviousAccountNameHashPref() {
    try {
      return Services.prefs.getStringPref(PREF_LAST_FXA_USER);
    } catch (_) {
      return "";
    }
  },

  /**
   * Given an account name, set the hash of the previously signed in account
   *
   * @param acctName the account name of the user's account.
   */
  setPreviousAccountNameHashPref(acctName) {
    Services.prefs.setStringPref(PREF_LAST_FXA_USER, this.sha256(acctName));
  },

  /**
   * Given a string, returns the SHA265 hash in base64
   */
  sha256(str) {
    let converter = Cc["@mozilla.org/intl/scriptableunicodeconverter"]
                      .createInstance(Ci.nsIScriptableUnicodeConverter);
    converter.charset = "UTF-8";
    // Data is an array of bytes.
    let data = converter.convertToByteArray(str, {});
    let hasher = Cc["@mozilla.org/security/hash;1"]
                   .createInstance(Ci.nsICryptoHash);
    hasher.init(hasher.SHA256);
    hasher.update(data, data.length);

    return hasher.finish(true);
  },

  /**
   * Open Sync Preferences in the current tab of the browser
   *
   * @param {Object} browser the browser in which to open preferences
   * @param {String} [entryPoint] entryPoint to use for logging
   */
  openSyncPreferences(browser, entryPoint) {
    let uri = "about:preferences";
    if (entryPoint) {
      uri += "?entrypoint=" + encodeURIComponent(entryPoint);
    }
    uri += "#sync";

    browser.loadURI(uri);
  },

  /**
   * If a user signs in using a different account, the data from the
   * previous account and the new account will be merged. Ask the user
   * if they want to continue.
   *
   * @private
   */
  _needRelinkWarning(acctName) {
    let prevAcctHash = this.getPreviousAccountNameHashPref();
    return prevAcctHash && prevAcctHash != this.sha256(acctName);
  },

  /**
   * Show the user a warning dialog that the data from the previous account
   * and the new account will be merged.
   *
   * @private
   */
  _promptForRelink(acctName) {
    let sb = Services.strings.createBundle("chrome://browser/locale/syncSetup.properties");
    let continueLabel = sb.GetStringFromName("continue.label");
    let title = sb.GetStringFromName("relinkVerify.title");
    let description = sb.formatStringFromName("relinkVerify.description",
                                              [acctName], 1);
    let body = sb.GetStringFromName("relinkVerify.heading") +
               "\n\n" + description;
    let ps = Services.prompt;
    let buttonFlags = (ps.BUTTON_POS_0 * ps.BUTTON_TITLE_IS_STRING) +
                      (ps.BUTTON_POS_1 * ps.BUTTON_TITLE_CANCEL) +
                      ps.BUTTON_POS_1_DEFAULT;

    // If running in context of the browser chrome, window does not exist.
    var targetWindow = typeof window === "undefined" ? null : window;
    let pressed = Services.prompt.confirmEx(targetWindow, title, body, buttonFlags,
                                       continueLabel, null, null, null,
                                       {});
    return pressed === 0; // 0 is the "continue" button
  }
};

var singleton;
// The entry-point for this module, which ensures only one of our channels is
// ever created - we require this because the WebChannel is global in scope
// (eg, it uses the observer service to tell interested parties of interesting
// things) and allowing multiple channels would cause such notifications to be
// sent multiple times.
this.EnsureFxAccountsWebChannel = function() {
  let contentUri = Services.urlFormatter.formatURLPref("identity.fxaccounts.remote.webchannel.uri");
  if (singleton && singleton._contentUri !== contentUri) {
    singleton.tearDown();
    singleton = null;
  }
  if (!singleton) {
    try {
      if (contentUri) {
        // The FxAccountsWebChannel listens for events and updates
        // the state machine accordingly.
        singleton = new this.FxAccountsWebChannel({
          content_uri: contentUri,
          channel_id: WEBCHANNEL_ID,
        });
      } else {
        log.warn("FxA WebChannel functionaly is disabled due to no URI pref.");
      }
    } catch (ex) {
      log.error("Failed to create FxA WebChannel", ex);
    }
  }
}