// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

/**
 * @fileoverview
 * OAuth2 class that handles retrieval/storage of an OAuth2 token.
 *
 * Uses a content script to trampoline the OAuth redirect page back into the
 * extension context.  This works around the lack of native support for
 * chrome-extensions in OAuth2.
 */

// TODO(jamiewalch): Delete this code once Chromoting is a v2 app and uses the
// identity API (http://crbug.com/ 134213).

'use strict';

/** @suppress {duplicate} */
var remoting = remoting || {};

/** @type {remoting.OAuth2} */
remoting.oauth2 = null;


/** @constructor */
remoting.OAuth2 = function() {
};

// Constants representing keys used for storing persistent state.
/** @private */
remoting.OAuth2.prototype.KEY_REFRESH_TOKEN_ = 'oauth2-refresh-token';
/** @private */
remoting.OAuth2.prototype.KEY_REFRESH_TOKEN_REVOKABLE_ =
    'oauth2-refresh-token-revokable';
/** @private */
remoting.OAuth2.prototype.KEY_ACCESS_TOKEN_ = 'oauth2-access-token';
/** @private */
remoting.OAuth2.prototype.KEY_XSRF_TOKEN_ = 'oauth2-xsrf-token';
/** @private */
remoting.OAuth2.prototype.KEY_EMAIL_ = 'remoting-email';

// Constants for parameters used in retrieving the OAuth2 credentials.
/** @private */
remoting.OAuth2.prototype.SCOPE_ =
      'https://www.googleapis.com/auth/chromoting ' +
      'https://www.googleapis.com/auth/googletalk ' +
      'https://www.googleapis.com/auth/userinfo#email';

// Configurable URLs/strings.
/** @private
 *  @return {string} OAuth2 redirect URI.
 */
remoting.OAuth2.prototype.getRedirectUri_ = function() {
  return remoting.settings.OAUTH2_REDIRECT_URL;
};

/** @private
 *  @return {string} API client ID.
 */
remoting.OAuth2.prototype.getClientId_ = function() {
  return remoting.settings.OAUTH2_CLIENT_ID;
};

/** @private
 *  @return {string} API client secret.
 */
remoting.OAuth2.prototype.getClientSecret_ = function() {
  return remoting.settings.OAUTH2_CLIENT_SECRET;
};

/** @private
 *  @return {string} OAuth2 authentication URL.
 */
remoting.OAuth2.prototype.getOAuth2AuthEndpoint_ = function() {
  return remoting.settings.OAUTH2_BASE_URL + '/auth';
};

/** @return {boolean} True if the app is already authenticated. */
remoting.OAuth2.prototype.isAuthenticated = function() {
  if (this.getRefreshToken_()) {
    return true;
  }
  return false;
};

/**
 * Removes all storage, and effectively unauthenticates the user.
 *
 * @return {void} Nothing.
 */
remoting.OAuth2.prototype.clear = function() {
  window.localStorage.removeItem(this.KEY_EMAIL_);
  this.clearAccessToken_();
  this.clearRefreshToken_();
};

/**
 * Sets the refresh token.
 *
 * This method also marks the token as revokable, so that this object will
 * revoke the token when it no longer needs it.
 *
 * @param {string} token The new refresh token.
 * @return {void} Nothing.
 * @private
 */
remoting.OAuth2.prototype.setRefreshToken_ = function(token) {
  window.localStorage.setItem(this.KEY_REFRESH_TOKEN_, escape(token));
  window.localStorage.setItem(this.KEY_REFRESH_TOKEN_REVOKABLE_, true);
  window.localStorage.removeItem(this.KEY_EMAIL_);
  this.clearAccessToken_();
};

/**
 * Gets the refresh token.
 *
 * This method also marks the refresh token as not revokable, so that this
 * object will not revoke the token when it no longer needs it. After this
 * object has exported the token, it cannot know whether it is still in use
 * when this object no longer needs it.
 *
 * @return {?string} The refresh token, if authenticated, or NULL.
 */
remoting.OAuth2.prototype.exportRefreshToken = function() {
  window.localStorage.removeItem(this.KEY_REFRESH_TOKEN_REVOKABLE_);
  return this.getRefreshToken_();
};

/**
 * @return {?string} The refresh token, if authenticated, or NULL.
 * @private
 */
remoting.OAuth2.prototype.getRefreshToken_ = function() {
  var value = window.localStorage.getItem(this.KEY_REFRESH_TOKEN_);
  if (typeof value == 'string') {
    return unescape(value);
  }
  return null;
};

/**
 * Clears the refresh token.
 *
 * @return {void} Nothing.
 * @private
 */
remoting.OAuth2.prototype.clearRefreshToken_ = function() {
  if (window.localStorage.getItem(this.KEY_REFRESH_TOKEN_REVOKABLE_)) {
    this.revokeToken_(this.getRefreshToken_());
  }
  window.localStorage.removeItem(this.KEY_REFRESH_TOKEN_);
  window.localStorage.removeItem(this.KEY_REFRESH_TOKEN_REVOKABLE_);
};

/**
 * @param {string} token The new access token.
 * @param {number} expiration Expiration time in milliseconds since epoch.
 * @return {void} Nothing.
 * @private
 */
remoting.OAuth2.prototype.setAccessToken_ = function(token, expiration) {
  // Offset expiration by 120 seconds so that we can guarantee that the token
  // we return will be valid for at least 2 minutes.
  // If the access token is to be useful, this object must make some
  // guarantee as to how long the token will be valid for.
  // The choice of 2 minutes is arbitrary, but that length of time
  // is part of the contract satisfied by callWithToken().
  // Offset by a further 30 seconds to account for RTT issues.
  var access_token = {
    'token': token,
    'expiration': (expiration - (120 + 30)) * 1000 + Date.now()
  };
  window.localStorage.setItem(this.KEY_ACCESS_TOKEN_,
                              JSON.stringify(access_token));
};

/**
 * Returns the current access token, setting it to a invalid value if none
 * existed before.
 *
 * @private
 * @return {{token: string, expiration: number}} The current access token, or
 * an invalid token if not authenticated.
 */
remoting.OAuth2.prototype.getAccessTokenInternal_ = function() {
  if (!window.localStorage.getItem(this.KEY_ACCESS_TOKEN_)) {
    // Always be able to return structured data.
    this.setAccessToken_('', 0);
  }
  var accessToken = window.localStorage.getItem(this.KEY_ACCESS_TOKEN_);
  if (typeof accessToken == 'string') {
    var result = jsonParseSafe(accessToken);
    if (result && 'token' in result && 'expiration' in result) {
      return /** @type {{token: string, expiration: number}} */ result;
    }
  }
  console.log('Invalid access token stored.');
  return {'token': '', 'expiration': 0};
};

/**
 * Returns true if the access token is expired, or otherwise invalid.
 *
 * Will throw if !isAuthenticated().
 *
 * @return {boolean} True if a new access token is needed.
 * @private
 */
remoting.OAuth2.prototype.needsNewAccessToken_ = function() {
  if (!this.isAuthenticated()) {
    throw 'Not Authenticated.';
  }
  var access_token = this.getAccessTokenInternal_();
  if (!access_token['token']) {
    return true;
  }
  if (Date.now() > access_token['expiration']) {
    return true;
  }
  return false;
};

/**
 * @return {void} Nothing.
 * @private
 */
remoting.OAuth2.prototype.clearAccessToken_ = function() {
  window.localStorage.removeItem(this.KEY_ACCESS_TOKEN_);
};

/**
 * Update state based on token response from the OAuth2 /token endpoint.
 *
 * @param {function(string):void} onOk Called with the new access token.
 * @param {string} accessToken Access token.
 * @param {number} expiresIn Expiration time for the access token.
 * @return {void} Nothing.
 * @private
 */
remoting.OAuth2.prototype.onAccessToken_ =
    function(onOk, accessToken, expiresIn) {
  this.setAccessToken_(accessToken, expiresIn);
  onOk(accessToken);
};

/**
 * Update state based on token response from the OAuth2 /token endpoint.
 *
 * @param {function():void} onOk Called after the new tokens are stored.
 * @param {string} refreshToken Refresh token.
 * @param {string} accessToken Access token.
 * @param {number} expiresIn Expiration time for the access token.
 * @return {void} Nothing.
 * @private
 */
remoting.OAuth2.prototype.onTokens_ =
    function(onOk, refreshToken, accessToken, expiresIn) {
  this.setAccessToken_(accessToken, expiresIn);
  this.setRefreshToken_(refreshToken);
  onOk();
};

/**
 * Redirect page to get a new OAuth2 Refresh Token.
 *
 * @return {void} Nothing.
 */
remoting.OAuth2.prototype.doAuthRedirect = function() {
  var xsrf_token = remoting.generateXsrfToken();
  window.localStorage.setItem(this.KEY_XSRF_TOKEN_, xsrf_token);
  var GET_CODE_URL = this.getOAuth2AuthEndpoint_() + '?' +
    remoting.xhr.urlencodeParamHash({
          'client_id': this.getClientId_(),
          'redirect_uri': this.getRedirectUri_(),
          'scope': this.SCOPE_,
          'state': xsrf_token,
          'response_type': 'code',
          'access_type': 'offline',
          'approval_prompt': 'force'
        });
  window.location.replace(GET_CODE_URL);
};

/**
 * Asynchronously exchanges an authorization code for a refresh token.
 *
 * @param {string} code The OAuth2 authorization code.
 * @param {string} state The state parameter received from the OAuth redirect.
 * @param {function():void} onDone Callback to invoke on completion.
 * @return {void} Nothing.
 */
remoting.OAuth2.prototype.exchangeCodeForToken = function(code, state, onDone) {
  var xsrf_token = window.localStorage.getItem(this.KEY_XSRF_TOKEN_);
  window.localStorage.removeItem(this.KEY_XSRF_TOKEN_);
  if (xsrf_token == undefined || state != xsrf_token) {
    // Invalid XSRF token, or unexpected OAuth2 redirect. Abort.
    onDone();
  }
  /** @param {remoting.Error} error */
  var onError = function(error) {
    console.error('Unable to exchange code for token: ', error);
  };

  remoting.OAuth2Api.exchangeCodeForTokens(
      this.onTokens_.bind(this, onDone), onError,
      this.getClientId_(), this.getClientSecret_(), code,
      this.getRedirectUri_());
};

/**
 * Revokes a refresh or an access token.
 *
 * @param {string?} token An access or refresh token.
 * @return {void} Nothing.
 * @private
 */
remoting.OAuth2.prototype.revokeToken_ = function(token) {
  if (!token || (token.length == 0)) {
    return;
  }

  remoting.OAuth2Api.revokeToken(function() {}, function() {}, token);
};

/**
 * Call a function with an access token, refreshing it first if necessary.
 * The access token will remain valid for at least 2 minutes.
 *
 * @param {function(string):void} onOk Function to invoke with access token if
 *     an access token was successfully retrieved.
 * @param {function(remoting.Error):void} onError Function to invoke with an
 *     error code on failure.
 * @return {void} Nothing.
 */
remoting.OAuth2.prototype.callWithToken = function(onOk, onError) {
  var refreshToken = this.getRefreshToken_();
  if (refreshToken) {
    if (this.needsNewAccessToken_()) {
      remoting.OAuth2Api.refreshAccessToken(
          this.onAccessToken_.bind(this, onOk), onError,
          this.getClientId_(), this.getClientSecret_(),
          refreshToken);
    } else {
      onOk(this.getAccessTokenInternal_()['token']);
    }
  } else {
    onError(remoting.Error.NOT_AUTHENTICATED);
  }
};

/**
 * Get the user's email address.
 *
 * @param {function(string):void} onOk Callback invoked when the email
 *     address is available.
 * @param {function(remoting.Error):void} onError Callback invoked if an
 *     error occurs.
 * @return {void} Nothing.
 */
remoting.OAuth2.prototype.getEmail = function(onOk, onError) {
  var cached = window.localStorage.getItem(this.KEY_EMAIL_);
  if (typeof cached == 'string') {
    onOk(cached);
    return;
  }
  /** @type {remoting.OAuth2} */
  var that = this;
  /** @param {string} email */
  var onResponse = function(email) {
    window.localStorage.setItem(that.KEY_EMAIL_, email);
    onOk(email);
  };

  this.callWithToken(
      remoting.OAuth2Api.getEmail.bind(null, onResponse, onError), onError);
};

/**
 * If the user's email address is cached, return it, otherwise return null.
 *
 * @return {?string} The email address, if it has been cached by a previous call
 *     to getEmail, otherwise null.
 */
remoting.OAuth2.prototype.getCachedEmail = function() {
  var value = window.localStorage.getItem(this.KEY_EMAIL_);
  if (typeof value == 'string') {
    return value;
  }
  return null;
};