/* 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/. */

var EXPORTED_SYMBOLS = ["FxAccountsClient"];

ChromeUtils.import("resource://gre/modules/Services.jsm");
ChromeUtils.import("resource://services-common/utils.js");
ChromeUtils.import("resource://services-common/hawkclient.js");
ChromeUtils.import("resource://services-common/hawkrequest.js");
ChromeUtils.import("resource://services-crypto/utils.js");
ChromeUtils.import("resource://gre/modules/FxAccountsCommon.js");
ChromeUtils.import("resource://gre/modules/Credentials.jsm");

const HOST_PREF = "identity.fxaccounts.auth.uri";

const SIGNIN = "/account/login";
const SIGNUP = "/account/create";

var FxAccountsClient = function(host = Services.prefs.getCharPref(HOST_PREF)) {
  this.host = host;

  // The FxA auth server expects requests to certain endpoints to be authorized
  // using Hawk.
  this.hawk = new HawkClient(host);
  this.hawk.observerPrefix = "FxA:hawk";

  // Manage server backoff state. C.f.
  // https://github.com/mozilla/fxa-auth-server/blob/master/docs/api.md#backoff-protocol
  this.backoffError = null;
};

this.FxAccountsClient.prototype = {

  /**
   * Return client clock offset, in milliseconds, as determined by hawk client.
   * Provided because callers should not have to know about hawk
   * implementation.
   *
   * The offset is the number of milliseconds that must be added to the client
   * clock to make it equal to the server clock.  For example, if the client is
   * five minutes ahead of the server, the localtimeOffsetMsec will be -300000.
   */
  get localtimeOffsetMsec() {
    return this.hawk.localtimeOffsetMsec;
  },

  /*
   * Return current time in milliseconds
   *
   * Not used by this module, but made available to the FxAccounts.jsm
   * that uses this client.
   */
  now() {
    return this.hawk.now();
  },

  /**
   * Common code from signIn and signUp.
   *
   * @param path
   *        Request URL path. Can be /account/create or /account/login
   * @param email
   *        The email address for the account (utf8)
   * @param password
   *        The user's password
   * @param [getKeys=false]
   *        If set to true the keyFetchToken will be retrieved
   * @param [retryOK=true]
   *        If capitalization of the email is wrong and retryOK is set to true,
   *        we will retry with the suggested capitalization from the server
   * @return Promise
   *        Returns a promise that resolves to an object:
   *        {
   *          authAt: authentication time for the session (seconds since epoch)
   *          email: the primary email for this account
   *          keyFetchToken: a key fetch token (hex)
   *          sessionToken: a session token (hex)
   *          uid: the user's unique ID (hex)
   *          unwrapBKey: used to unwrap kB, derived locally from the
   *                      password (not revealed to the FxA server)
   *          verified (optional): flag indicating verification status of the
   *                               email
   *        }
   */
  _createSession(path, email, password, getKeys = false,
                 retryOK = true) {
    return Credentials.setup(email, password).then((creds) => {
      let data = {
        authPW: CommonUtils.bytesAsHex(creds.authPW),
        email,
      };
      let keys = getKeys ? "?keys=true" : "";

      return this._request(path + keys, "POST", null, data).then(
        // Include the canonical capitalization of the email in the response so
        // the caller can set its signed-in user state accordingly.
        result => {
          result.email = data.email;
          result.unwrapBKey = CommonUtils.bytesAsHex(creds.unwrapBKey);

          return result;
        },
        error => {
          log.debug("Session creation failed", error);
          // If the user entered an email with different capitalization from
          // what's stored in the database (e.g., Greta.Garbo@gmail.COM as
          // opposed to greta.garbo@gmail.com), the server will respond with a
          // errno 120 (code 400) and the expected capitalization of the email.
          // We retry with this email exactly once.  If successful, we use the
          // server's version of the email as the signed-in-user's email. This
          // is necessary because the email also serves as salt; so we must be
          // in agreement with the server on capitalization.
          //
          // API reference:
          // https://github.com/mozilla/fxa-auth-server/blob/master/docs/api.md
          if (ERRNO_INCORRECT_EMAIL_CASE === error.errno && retryOK) {
            if (!error.email) {
              log.error("Server returned errno 120 but did not provide email");
              throw error;
            }
            return this._createSession(path, error.email, password, getKeys,
                                       false);
          }
          throw error;
        }
      );
    });
  },

  /**
   * Create a new Firefox Account and authenticate
   *
   * @param email
   *        The email address for the account (utf8)
   * @param password
   *        The user's password
   * @param [getKeys=false]
   *        If set to true the keyFetchToken will be retrieved
   * @return Promise
   *        Returns a promise that resolves to an object:
   *        {
   *          uid: the user's unique ID (hex)
   *          sessionToken: a session token (hex)
   *          keyFetchToken: a key fetch token (hex),
   *          unwrapBKey: used to unwrap kB, derived locally from the
   *                      password (not revealed to the FxA server)
   *        }
   */
  signUp(email, password, getKeys = false) {
    return this._createSession(SIGNUP, email, password, getKeys,
                               false /* no retry */);
  },

  /**
   * Authenticate and create a new session with the Firefox Account API server
   *
   * @param email
   *        The email address for the account (utf8)
   * @param password
   *        The user's password
   * @param [getKeys=false]
   *        If set to true the keyFetchToken will be retrieved
   * @return Promise
   *        Returns a promise that resolves to an object:
   *        {
   *          authAt: authentication time for the session (seconds since epoch)
   *          email: the primary email for this account
   *          keyFetchToken: a key fetch token (hex)
   *          sessionToken: a session token (hex)
   *          uid: the user's unique ID (hex)
   *          unwrapBKey: used to unwrap kB, derived locally from the
   *                      password (not revealed to the FxA server)
   *          verified: flag indicating verification status of the email
   *        }
   */
  signIn: function signIn(email, password, getKeys = false) {
    return this._createSession(SIGNIN, email, password, getKeys,
                               true /* retry */);
  },

  /**
   * Check the status of a session given a session token
   *
   * @param sessionTokenHex
   *        The session token encoded in hex
   * @return Promise
   *        Resolves with a boolean indicating if the session is still valid
   */
  sessionStatus(sessionTokenHex) {
    return this._request("/session/status", "GET",
      deriveHawkCredentials(sessionTokenHex, "sessionToken")).then(
        () => Promise.resolve(true),
        error => {
          if (isInvalidTokenError(error)) {
            return Promise.resolve(false);
          }
          throw error;
        }
      );
  },

  /**
   * Destroy the current session with the Firefox Account API server and its
   * associated device.
   *
   * @param sessionTokenHex
   *        The session token encoded in hex
   * @return Promise
   */
  signOut(sessionTokenHex, options = {}) {
    let path = "/session/destroy";
    if (options.service) {
      path += "?service=" + encodeURIComponent(options.service);
    }
    return this._request(path, "POST",
      deriveHawkCredentials(sessionTokenHex, "sessionToken"));
  },

  /**
   * Check the verification status of the user's FxA email address
   *
   * @param sessionTokenHex
   *        The current session token encoded in hex
   * @return Promise
   */
  recoveryEmailStatus(sessionTokenHex, options = {}) {
    let path = "/recovery_email/status";
    if (options.reason) {
      path += "?reason=" + encodeURIComponent(options.reason);
    }

    return this._request(path, "GET",
      deriveHawkCredentials(sessionTokenHex, "sessionToken"));
  },

  /**
   * Resend the verification email for the user
   *
   * @param sessionTokenHex
   *        The current token encoded in hex
   * @return Promise
   */
  resendVerificationEmail(sessionTokenHex) {
    return this._request("/recovery_email/resend_code", "POST",
      deriveHawkCredentials(sessionTokenHex, "sessionToken"));
  },

  /**
   * Retrieve encryption keys
   *
   * @param keyFetchTokenHex
   *        A one-time use key fetch token encoded in hex
   * @return Promise
   *        Returns a promise that resolves to an object:
   *        {
   *          kA: an encryption key for recevorable data (bytes)
   *          wrapKB: an encryption key that requires knowledge of the
   *                  user's password (bytes)
   *        }
   */
  accountKeys(keyFetchTokenHex) {
    let creds = deriveHawkCredentials(keyFetchTokenHex, "keyFetchToken");
    let keyRequestKey = creds.extra.slice(0, 32);
    let morecreds = CryptoUtils.hkdf(keyRequestKey, undefined,
                                     Credentials.keyWord("account/keys"), 3 * 32);
    let respHMACKey = morecreds.slice(0, 32);
    let respXORKey = morecreds.slice(32, 96);

    return this._request("/account/keys", "GET", creds).then(resp => {
      if (!resp.bundle) {
        throw new Error("failed to retrieve keys");
      }

      let bundle = CommonUtils.hexToBytes(resp.bundle);
      let mac = bundle.slice(-32);

      let hasher = CryptoUtils.makeHMACHasher(Ci.nsICryptoHMAC.SHA256,
        CryptoUtils.makeHMACKey(respHMACKey));

      let bundleMAC = CryptoUtils.digestBytes(bundle.slice(0, -32), hasher);
      if (mac !== bundleMAC) {
        throw new Error("error unbundling encryption keys");
      }

      let keyAWrapB = CryptoUtils.xor(respXORKey, bundle.slice(0, 64));

      return {
        kA: keyAWrapB.slice(0, 32),
        wrapKB: keyAWrapB.slice(32),
      };
    });
  },

  /**
   * Sends a public key to the FxA API server and returns a signed certificate
   *
   * @param sessionTokenHex
   *        The current session token encoded in hex
   * @param serializedPublicKey
   *        A public key (usually generated by jwcrypto)
   * @param lifetime
   *        The lifetime of the certificate
   * @return Promise
   *        Returns a promise that resolves to the signed certificate.
   *        The certificate can be used to generate a Persona assertion.
   * @throws a new Error
   *         wrapping any of these HTTP code/errno pairs:
   *           https://github.com/mozilla/fxa-auth-server/blob/master/docs/api.md#response-12
   */
  signCertificate(sessionTokenHex, serializedPublicKey, lifetime) {
    let creds = deriveHawkCredentials(sessionTokenHex, "sessionToken");

    let body = { publicKey: serializedPublicKey,
                 duration: lifetime };
    return Promise.resolve()
      .then(_ => this._request("/certificate/sign", "POST", creds, body))
      .then(resp => resp.cert,
            err => {
              log.error("HAWK.signCertificate error: " + JSON.stringify(err));
              throw err;
            });
  },

  /**
   * Determine if an account exists
   *
   * @param email
   *        The email address to check
   * @return Promise
   *        The promise resolves to true if the account exists, or false
   *        if it doesn't. The promise is rejected on other errors.
   */
  accountExists(email) {
    return this.signIn(email, "").then(
      (cantHappen) => {
        throw new Error("How did I sign in with an empty password?");
      },
      (expectedError) => {
        switch (expectedError.errno) {
          case ERRNO_ACCOUNT_DOES_NOT_EXIST:
            return false;
          case ERRNO_INCORRECT_PASSWORD:
            return true;
          default:
            // not so expected, any more ...
            throw expectedError;
        }
      }
    );
  },

  /**
   * Given the uid of an existing account (not an arbitrary email), ask
   * the server if it still exists via /account/status.
   *
   * Used for differentiating between password change and account deletion.
   */
  accountStatus(uid) {
    return this._request("/account/status?uid=" + uid, "GET").then(
      (result) => {
        return result.exists;
      },
      (error) => {
        log.error("accountStatus failed with: " + error);
        return Promise.reject(error);
      }
    );
  },

  /**
   * Register a new device
   *
   * @method registerDevice
   * @param  sessionTokenHex
   *         Session token obtained from signIn
   * @param  name
   *         Device name
   * @param  type
   *         Device type (mobile|desktop)
   * @param  [options]
   *         Extra device options
   * @param  [options.availableCommands]
   *         Available commands for this device
   * @param  [options.pushCallback]
   *         `pushCallback` push endpoint callback
   * @param  [options.pushPublicKey]
   *         `pushPublicKey` push public key (URLSafe Base64 string)
   * @param  [options.pushAuthKey]
   *         `pushAuthKey` push auth secret (URLSafe Base64 string)
   * @return Promise
   *         Resolves to an object:
   *         {
   *           id: Device identifier
   *           createdAt: Creation time (milliseconds since epoch)
   *           name: Name of device
   *           type: Type of device (mobile|desktop)
   *         }
   */
  registerDevice(sessionTokenHex, name, type, options = {}) {
    let path = "/account/device";

    let creds = deriveHawkCredentials(sessionTokenHex, "sessionToken");
    let body = { name, type };

    if (options.pushCallback) {
      body.pushCallback = options.pushCallback;
    }
    if (options.pushPublicKey && options.pushAuthKey) {
      body.pushPublicKey = options.pushPublicKey;
      body.pushAuthKey = options.pushAuthKey;
    }
    body.availableCommands = options.availableCommands;

    return this._request(path, "POST", creds, body);
  },

  /**
   * Sends a message to other devices. Must conform with the push payload schema:
   * https://github.com/mozilla/fxa-auth-server/blob/master/docs/pushpayloads.schema.json
   *
   * @method notifyDevice
   * @param  sessionTokenHex
   *         Session token obtained from signIn
   * @param  deviceIds
   *         Devices to send the message to. If null, will be sent to all devices.
   * @param  excludedIds
   *         Devices to exclude when sending to all devices (deviceIds must be null).
   * @param  payload
   *         Data to send with the message
   * @return Promise
   *         Resolves to an empty object:
   *         {}
   */
  notifyDevices(sessionTokenHex, deviceIds, excludedIds, payload, TTL = 0) {
    if (deviceIds && excludedIds) {
      throw new Error("You cannot specify excluded devices if deviceIds is set.");
    }
    const body = {
      to: deviceIds || "all",
      payload,
      TTL,
    };
    if (excludedIds) {
      body.excluded = excludedIds;
    }
    return this._request("/account/devices/notify", "POST",
      deriveHawkCredentials(sessionTokenHex, "sessionToken"), body);
  },

  /**
   * Retrieves pending commands for our device.
   *
   * @method getCommands
   * @param  sessionTokenHex - Session token obtained from signIn
   * @param  [index] - If specified, only messages received after the one who
   *                   had that index will be retrieved.
   * @param  [limit] - Maximum number of messages to retrieve.
   */
  getCommands(sessionTokenHex, {index, limit}) {
    const params = new URLSearchParams();
    if (index != undefined) {
      params.set("index", index);
    }
    if (limit != undefined) {
      params.set("limit", limit);
    }
    const path = `/account/device/commands?${params.toString()}`;
    return this._request(path, "GET",
      deriveHawkCredentials(sessionTokenHex, "sessionToken"));
  },

  /**
   * Invokes a command on another device.
   *
   * @method invokeCommand
   * @param  sessionTokenHex - Session token obtained from signIn
   * @param  command - Name of the command to invoke
   * @param  target - Recipient device ID.
   * @param  payload
   * @return Promise
   *         Resolves to the request's response, (which should be an empty object)
   */
  invokeCommand(sessionTokenHex, command, target, payload) {
    const body = {
      command,
      target,
      payload,
    };
    return this._request("/account/devices/invoke_command", "POST",
      deriveHawkCredentials(sessionTokenHex, "sessionToken"), body);
  },

  /**
   * Update the session or name for an existing device
   *
   * @method updateDevice
   * @param  sessionTokenHex
   *         Session token obtained from signIn
   * @param  id
   *         Device identifier
   * @param  name
   *         Device name
   * @param  [options]
   *         Extra device options
   * @param  [options.availableCommands]
   *         Available commands for this device
   * @param  [options.pushCallback]
   *         `pushCallback` push endpoint callback
   * @param  [options.pushPublicKey]
   *         `pushPublicKey` push public key (URLSafe Base64 string)
   * @param  [options.pushAuthKey]
   *         `pushAuthKey` push auth secret (URLSafe Base64 string)
   * @return Promise
   *         Resolves to an object:
   *         {
   *           id: Device identifier
   *           name: Device name
   *         }
   */
  updateDevice(sessionTokenHex, id, name, options = {}) {
    let path = "/account/device";

    let creds = deriveHawkCredentials(sessionTokenHex, "sessionToken");
    let body = { id, name };
    if (options.pushCallback) {
      body.pushCallback = options.pushCallback;
    }
    if (options.pushPublicKey && options.pushAuthKey) {
      body.pushPublicKey = options.pushPublicKey;
      body.pushAuthKey = options.pushAuthKey;
    }
    body.availableCommands = options.availableCommands;

    return this._request(path, "POST", creds, body);
  },

  /**
   * Get a list of currently registered devices
   *
   * @method getDeviceList
   * @param  sessionTokenHex
   *         Session token obtained from signIn
   * @return Promise
   *         Resolves to an array of objects:
   *         [
   *           {
   *             id: Device id
   *             isCurrentDevice: Boolean indicating whether the item
   *                              represents the current device
   *             name: Device name
   *             type: Device type (mobile|desktop)
   *           },
   *           ...
   *         ]
   */
  getDeviceList(sessionTokenHex) {
    let path = "/account/devices";
    let creds = deriveHawkCredentials(sessionTokenHex, "sessionToken");

    return this._request(path, "GET", creds, {});
  },

  _clearBackoff() {
      this.backoffError = null;
  },

  /**
   * A general method for sending raw API calls to the FxA auth server.
   * All request bodies and responses are JSON.
   *
   * @param path
   *        API endpoint path
   * @param method
   *        The HTTP request method
   * @param credentials
   *        Hawk credentials
   * @param jsonPayload
   *        A JSON payload
   * @return Promise
   *        Returns a promise that resolves to the JSON response of the API call,
   *        or is rejected with an error. Error responses have the following properties:
   *        {
   *          "code": 400, // matches the HTTP status code
   *          "errno": 107, // stable application-level error number
   *          "error": "Bad Request", // string description of the error type
   *          "message": "the value of salt is not allowed to be undefined",
   *          "info": "https://docs.dev.lcip.og/errors/1234" // link to more info on the error
   *        }
   */
  async _request(path, method, credentials, jsonPayload) {
    // We were asked to back off.
    if (this.backoffError) {
      log.debug("Received new request during backoff, re-rejecting.");
      throw this.backoffError;
    }
    let response;
    try {
      response = await this.hawk.request(path, method, credentials, jsonPayload);
    } catch (error) {
      log.error("error " + method + "ing " + path + ": " + JSON.stringify(error));
      if (error.retryAfter) {
        log.debug("Received backoff response; caching error as flag.");
        this.backoffError = error;
        // Schedule clearing of cached-error-as-flag.
        CommonUtils.namedTimer(
          this._clearBackoff,
          error.retryAfter * 1000,
          this,
          "fxaBackoffTimer"
         );
      }
      throw error;
    }
    try {
      return JSON.parse(response.body);
    } catch (error) {
      log.error("json parse error on response: " + response.body);
      // eslint-disable-next-line no-throw-literal
      throw {error};
    }
  },
};

function isInvalidTokenError(error) {
  if (error.code != 401) {
    return false;
  }
  switch (error.errno) {
    case ERRNO_INVALID_AUTH_TOKEN:
    case ERRNO_INVALID_AUTH_TIMESTAMP:
    case ERRNO_INVALID_AUTH_NONCE:
      return true;
  }
  return false;
}