# All files / helpers refresh-auth-token.ts

95.16% Statements 59/62
92.11% Branches 35/38
100% Functions 11/11
94.64% Lines 53/56

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     /**
     * @license
     * Copyright 2019 Google LLC
     *
     * 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.
     */

    import { generateAuthTokenRequest } from '../api/generate-auth-token-request';
    import { AppConfig } from '../interfaces/app-config';
    import { FirebaseDependencies } from '../interfaces/firebase-dependencies';
    import {
      AuthToken,
      CompletedAuthToken,
      InProgressAuthToken,
      InstallationEntry,
      RegisteredInstallationEntry,
      RequestStatus
    } from '../interfaces/installation-entry';
    import { PENDING_TIMEOUT_MS, TOKEN_EXPIRATION_BUFFER } from '../util/constants';
    import { ERROR_FACTORY, ErrorCode, isServerError } from '../util/errors';
    import { sleep } from '../util/sleep';
    import { remove, set, update } from './idb-manager';

    /**
     * Returns a valid authentication token for the installation. Generates a new
     * token if one doesn't exist, is expired or about to expire.
     *
     * Should only be called if the Firebase Installation is registered.
     */
    export async function refreshAuthToken(
      dependencies: FirebaseDependencies,
      forceRefresh = false
    ): Promise<CompletedAuthToken> {
      let tokenPromise: Promise<CompletedAuthToken> | undefined;
      const entry = await update(dependencies.appConfig, oldEntry => {
        if (!isEntryRegistered(oldEntry)) {
          throw ERROR_FACTORY.create(ErrorCode.NOT_REGISTERED);
        }

        const oldAuthToken = oldEntry.authToken;
        if (!forceRefresh && isAuthTokenValid(oldAuthToken)) {
          // There is a valid token in the DB.
          return oldEntry;
        } else if (oldAuthToken.requestStatus === RequestStatus.IN_PROGRESS) {
          // There already is a token request in progress.
          tokenPromise = waitUntilAuthTokenRequest(dependencies, forceRefresh);
          return oldEntry;
        } else {
          // No token or token expired.
          if (!navigator.onLine) {
            throw ERROR_FACTORY.create(ErrorCode.APP_OFFLINE);
          }

          const inProgressEntry = makeAuthTokenRequestInProgressEntry(oldEntry);
          tokenPromise = fetchAuthTokenFromServer(dependencies, inProgressEntry);
          return inProgressEntry;
        }
      });

      const authToken = tokenPromise
        ? await tokenPromise
        : (entry.authToken as CompletedAuthToken);
      return authToken;
    }

    /**
     * Call only if FID is registered and Auth Token request is in progress.
     *
     * Waits until the current pending request finishes. If the request times out,
     * tries once in this thread as well.
     */
    async function waitUntilAuthTokenRequest(
      dependencies: FirebaseDependencies,
      forceRefresh: boolean
    ): Promise<CompletedAuthToken> {
      // Unfortunately, there is no way of reliably observing when a value in
      // IndexedDB changes (yet, see https://github.com/WICG/indexed-db-observers),
      // so we need to poll.

      let entry = await updateAuthTokenRequest(dependencies.appConfig);
      while (entry.authToken.requestStatus === RequestStatus.IN_PROGRESS) {
        // generateAuthToken still in progress.
        await sleep(100);

        entry = await updateAuthTokenRequest(dependencies.appConfig);
      }

      const authToken = entry.authToken;
      Iif (authToken.requestStatus === RequestStatus.NOT_STARTED) {
        // The request timed out or failed in a different call. Try again.
        return refreshAuthToken(dependencies, forceRefresh);
      } else {
        return authToken;
      }
    }

    /**
     * Called only if there is a GenerateAuthToken request in progress.
     *
     * Updates the InstallationEntry in the DB based on the status of the
     * GenerateAuthToken request.
     *
     * Returns the updated InstallationEntry.
     */
    function updateAuthTokenRequest(
      appConfig: AppConfig
    ): Promise<RegisteredInstallationEntry> {
      return update(appConfig, oldEntry => {
        Iif (!isEntryRegistered(oldEntry)) {
          throw ERROR_FACTORY.create(ErrorCode.NOT_REGISTERED);
        }

        const oldAuthToken = oldEntry.authToken;
        Iif (hasAuthTokenRequestTimedOut(oldAuthToken)) {
          return {
            ...oldEntry,
            authToken: { requestStatus: RequestStatus.NOT_STARTED }
          };
        }

        return oldEntry;
      });
    }

    async function fetchAuthTokenFromServer(
      dependencies: FirebaseDependencies,
      installationEntry: RegisteredInstallationEntry
    ): Promise<CompletedAuthToken> {
      try {
        const authToken = await generateAuthTokenRequest(
          dependencies,
          installationEntry
        );
        const updatedInstallationEntry: RegisteredInstallationEntry = {
          ...installationEntry,
          authToken
        };
        await set(dependencies.appConfig, updatedInstallationEntry);
        return authToken;
      } catch (e) {
        if (isServerError(e) && (e.serverCode === 401 || e.serverCode === 404)) {
          // Server returned a "FID not found" or a "Invalid authentication" error.
          // Generate a new ID next time.
          await remove(dependencies.appConfig);
        } else {
          const updatedInstallationEntry: RegisteredInstallationEntry = {
            ...installationEntry,
            authToken: { requestStatus: RequestStatus.NOT_STARTED }
          };
          await set(dependencies.appConfig, updatedInstallationEntry);
        }
        throw e;
      }
    }

    function isEntryRegistered(
      installationEntry: InstallationEntry | undefined
    ): installationEntry is RegisteredInstallationEntry {
      return (
        installationEntry !== undefined &&
        installationEntry.registrationStatus === RequestStatus.COMPLETED
      );
    }

    function isAuthTokenValid(authToken: AuthToken): boolean {
      return (
        authToken.requestStatus === RequestStatus.COMPLETED &&
        !isAuthTokenExpired(authToken)
      );
    }

    function isAuthTokenExpired(authToken: CompletedAuthToken): boolean {
      const now = Date.now();
      return (
        now < authToken.creationTime ||
        authToken.creationTime + authToken.expiresIn < now + TOKEN_EXPIRATION_BUFFER
      );
    }

    /** Returns an updated InstallationEntry with an InProgressAuthToken. */
    function makeAuthTokenRequestInProgressEntry(
      oldEntry: RegisteredInstallationEntry
    ): RegisteredInstallationEntry {
      const inProgressAuthToken: InProgressAuthToken = {
        requestStatus: RequestStatus.IN_PROGRESS,
        requestTime: Date.now()
      };
      return {
        ...oldEntry,
        authToken: inProgressAuthToken
      };
    }

    function hasAuthTokenRequestTimedOut(authToken: AuthToken): boolean {
      return (
        authToken.requestStatus === RequestStatus.IN_PROGRESS &&
        authToken.requestTime + PENDING_TIMEOUT_MS < Date.now()
      );
    }