database.js

/**
 * Copyright 2025 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.
 */

/**
 * @fileoverview Service that handles database operations.
 */

import {Firestore} from '@google-cloud/firestore';

// The prefix used by the Google Chat API in the User resource name.
const USERS_PREFIX = 'users/';

// The name of the users collection in the database.
const USERS_COLLECTION = 'users';

// Initialize the Firestore database using Application Default Credentials.
const db = new Firestore({ databaseId: 'auth-data' });

// Service that saves and loads OAuth user credentials on Firestore.
export const DatabaseService = {
  /**
   * Saves the user's OAuth2 credentials to storage.
   * 
   * @param {!string} userName The resource name of the user.
   * @param {!Credentials} credentials The OAuth2 credentials.
   * @return {Promise<void>}
   */
  saveUserCredentials: async function(userName, credentials) {
    const docRef = db
        .collection(USERS_COLLECTION)
        .doc(userName.replace(USERS_PREFIX, ''));
    await docRef.set(credentials);
  },

  /**
   * Fetches the user's OAuth2 credentials from storage.
   * 
   * @param {!string} userName The resource name of the user.
   * @return {Promise<Credentials | null>} The credentials or null if the
   *     user is not found in the database.
   */
  getUserCredentials: async function(userName) {
    const doc = await db
        .collection(USERS_COLLECTION)
        .doc(userName.replace(USERS_PREFIX, ''))
        .get();
    if (doc.exists) {
      return doc.data();
    }
    return null;
  },
  
  /**
   * Deletes the user's OAuth2 credentials from storage.
   *
   * @param {!string} userName The resource name of the user.
   * @return {Promise<void>}
   */
  deleteUserCredentials: async function(userName) {
    const docRef = db
        .collection(USERS_COLLECTION)
        .doc(userName.replace(USERS_PREFIX, ''));
    await docRef.delete();
  }
};