# All files / core firestore_client.ts

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     /**
     * Copyright 2017 Google Inc.
     *
     * 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 { CredentialsProvider } from '../api/credentials';
    import { User } from '../auth/user';
    import {
      EventManager,
      ListenOptions,
      Observer,
      QueryListener
    } from './event_manager';
    import { SyncEngine } from './sync_engine';
    import { EagerGarbageCollector } from '../local/eager_garbage_collector';
    import { GarbageCollector } from '../local/garbage_collector';
    import { IndexedDbPersistence } from '../local/indexeddb_persistence';
    import { LocalStore } from '../local/local_store';
    import { MemoryPersistence } from '../local/memory_persistence';
    import { NoOpGarbageCollector } from '../local/no_op_garbage_collector';
    import { Persistence } from '../local/persistence';
    import { Mutation } from '../model/mutation';
    import { Platform } from '../platform/platform';
    import { Datastore } from '../remote/datastore';
    import { RemoteStore } from '../remote/remote_store';
    import { JsonProtoSerializer } from '../remote/serializer';
    import { AsyncQueue } from '../util/async_queue';
    import { Code, FirestoreError } from '../util/error';
    import { debug } from '../util/log';
    import { Deferred } from '../util/promise';

    import { DatabaseId, DatabaseInfo } from './database_info';
    import { Query } from './query';
    import { Transaction } from './transaction';
    import { OnlineState } from './types';
    import { ViewSnapshot } from './view_snapshot';

    const LOG_TAG = 'FirestoreClient';

    /**
     * FirestoreClient is a top-level class that constructs and owns all of the
     * pieces of the client SDK architecture. It is responsible for creating the
     * async queue that is shared by all of the other components in the system.
     */
    export class FirestoreClient {
      // NOTE: These should technically have '|undefined' in the types, since
      // they're initialized asynchronously rather than in the constructor, but
      // given that all work is done on the async queue and we assert that
      // initialization completes before any other work is queued, we're cheating
      // with the types rather than littering the code with '!' or unnecessary
      // undefined checks.
      private eventMgr: EventManager;
      private garbageCollector: GarbageCollector;
      private persistence: Persistence;
      private localStore: LocalStore;
      private remoteStore: RemoteStore;
      private syncEngine: SyncEngine;

      constructor(
        private platform: Platform,
        private databaseInfo: DatabaseInfo,
        private credentials: CredentialsProvider,
        /**
         * Asynchronous queue responsible for all of our internal processing. When
         * we get incoming work from the user (via public API) or the network
         * (incoming GRPC messages), we should always schedule onto this queue.
         * This ensures all of our work is properly serialized (e.g. we don't
         * start processing a new operation while the previous one is waiting for
         * an async I/O to complete).
         */
        private asyncQueue: AsyncQueue
      ) {}

      /**
       * Starts up the FirestoreClient, returning only whether or not enabling
       * persistence succeeded.
       *
       * The intent here is to "do the right thing" as far as users are concerned.
       * Namely, in cases where offline persistence is requested and possible,
       * enable it, but otherwise fall back to persistence disabled. For the most
       * part we expect this to succeed one way or the other so we don't expect our
       * users to actually wait on the firestore.enablePersistence Promise since
       * they generally won't care.
       *
       * Of course some users actually do care about whether or not persistence
       * was successfully enabled, so the Promise returned from this method
       * indicates this outcome.
       *
       * This presents a problem though: even before enablePersistence resolves or
       * rejects, users may have made calls to e.g. firestore.collection() which
       * means that the FirestoreClient in there will be available and will be
       * enqueuing actions on the async queue.
       *
       * Meanwhile any failure of an operation on the async queue causes it to
       * panic and reject any further work, on the premise that unhandled errors
       * are fatal.
       *
       * Consequently the fallback is handled internally here in start, and if the
       * fallback succeeds we signal success to the async queue even though the
       * start() itself signals failure.
       *
       * @param usePersistence Whether or not to attempt to enable persistence.
       * @returns A deferred result indicating the user-visible result of enabling
       *     offline persistence. This method will reject this if IndexedDB fails to
       *     start for any reason. If usePersistence is false this is
       *     unconditionally resolved.
       */
      start(usePersistence: boolean): Promise<void> {
        // We defer our initialization until we get the current user from
        // setUserChangeListener(). We block the async queue until we got the
        // initial user and the initialization is completed. This will prevent
        // any scheduled work from happening before initialization is completed.
        //
        // If initializationDone resolved then the FirestoreClient is in a usable
        // state.
        const initializationDone = new Deferred<void>();

        // If usePersistence is true, certain classes of errors while starting are
        // recoverable but only by falling back to persistence disabled.
        //
        // If there's an error in the first case but not in recovery we cannot
        // reject the promise blocking the async queue because this will cause the
        // async queue to panic.
        const persistenceResult = new Deferred<void>();

        let initialized = false;
        this.credentials.setUserChangeListener(user => {
          Eif (!initialized) {
            initialized = true;

            this.initializePersistence(usePersistence, persistenceResult)
              .then(() => this.initializeRest(user))
              .then(initializationDone.resolve, initializationDone.reject);
          } else {
            this.asyncQueue.enqueue(() => {
              return this.handleUserChange(user);
            });
          }
        });

        // Block the async queue until initialization is done
        this.asyncQueue.enqueue(() => {
          return initializationDone.promise;
        });

        // Return only the result of enabling persistence. Note that this does not
        // need to await the completion of initializationDone because the result of
        // this method should not reflect any other kind of failure to start.
        return persistenceResult.promise;
      }

      /** Enables the network connection and requeues all pending operations. */
      enableNetwork(): Promise<void> {
        return this.asyncQueue.enqueue(() => {
          return this.remoteStore.enableNetwork();
        });
      }

      /**
       * Initializes persistent storage, attempting to use IndexedDB if
       * usePersistence is true or memory-only if false.
       *
       * If IndexedDB fails because it's already open in another tab or because the
       * platform can't possibly support our implementation then this method rejects
       * the persistenceResult and falls back on memory-only persistence.
       *
       * @param usePersistence indicates whether or not to use offline persistence
       * @param persistenceResult A deferred result indicating the user-visible
       *     result of enabling offline persistence. This method will reject this if
       *     IndexedDB fails to start for any reason. If usePersistence is false
       *     this is unconditionally resolved.
       * @returns a Promise indicating whether or not initialization should
       *     continue, i.e. that one of the persistence implementations actually
       *     succeeded.
       */
      private initializePersistence(
        usePersistence: boolean,
        persistenceResult: Deferred<void>
      ): Promise<void> {
        if (usePersistence) {
          return this.startIndexedDbPersistence()
            .then(persistenceResult.resolve)
            .catch((error: FirestoreError) => {
              // Regardless of whether or not the retry succeeds, from an user
              // perspective, offline persistence has failed.
              persistenceResult.reject(error);

              // An unknown failure on the first stage shuts everything down.
              if (!this.canFallback(error)) {
                return Promise.reject(error);
              }

              console.warn(
                'Error enabling offline storage. Falling back to' +
                  ' storage disabled: ' +
                  error
              );
              return this.startMemoryPersistence();
            });
        } else {
          // When usePersistence == false, enabling offline persistence is defined
          // to unconditionally succeed. This allows start() to have the same
          // signature for both cases, despite the fact that the returned promise
          // is only used in the enablePersistence call.
          persistenceResult.resolve();
          return this.startMemoryPersistence();
        }
      }

      private canFallback(error: FirestoreError): boolean {
        return (
          error.code === Code.FAILED_PRECONDITION ||
          error.code === Code.UNIMPLEMENTED
        );
      }

      /**
       * Starts IndexedDB-based persistence.
       *
       * @returns A promise indicating success or failure.
       */
      private startIndexedDbPersistence(): Promise<void> {
        // TODO(http://b/33384523): For now we just disable garbage collection
        // when persistence is enabled.
        this.garbageCollector = new NoOpGarbageCollector();
        const storagePrefix = IndexedDbPersistence.buildStoragePrefix(
          this.databaseInfo
        );
        // Opt to use proto3 JSON in case the platform doesn't support Uint8Array.
        const serializer = new JsonProtoSerializer(this.databaseInfo.databaseId, {
          useProto3Json: true
        });
        this.persistence = new IndexedDbPersistence(storagePrefix, serializer);
        return this.persistence.start();
      }

      /**
       * Starts Memory-backed persistence. In practice this cannot fail.
       *
       * @returns A promise that will successfully resolve.
       */
      private startMemoryPersistence(): Promise<void> {
        this.garbageCollector = new EagerGarbageCollector();
        this.persistence = new MemoryPersistence();
        return this.persistence.start();
      }

      /**
       * Initializes the rest of the FirestoreClient, assuming the initial user
       * has been obtained from the credential provider and some persistence
       * implementation is available in this.persistence.
       */
      private initializeRest(user: User): Promise<void> {
        return this.platform
          .loadConnection(this.databaseInfo)
          .then(connection => {
            this.localStore = new LocalStore(
              this.persistence,
              user,
              this.garbageCollector
            );
            const serializer = this.platform.newSerializer(
              this.databaseInfo.databaseId
            );
            const datastore = new Datastore(
              this.asyncQueue,
              connection,
              this.credentials,
              serializer
            );

            const onlineStateChangedHandler = (onlineState: OnlineState) => {
              this.syncEngine.applyOnlineStateChange(onlineState);
              this.eventMgr.applyOnlineStateChange(onlineState);
            };

            this.remoteStore = new RemoteStore(
              this.localStore,
              datastore,
              this.asyncQueue,
              onlineStateChangedHandler
            );

            this.syncEngine = new SyncEngine(
              this.localStore,
              this.remoteStore,
              user
            );

            // Setup wiring between sync engine and remote store
            this.remoteStore.syncEngine = this.syncEngine;

            this.eventMgr = new EventManager(this.syncEngine);

            // NOTE: RemoteStore depends on LocalStore (for persisting stream
            // tokens, refilling mutation queue, etc.) so must be started after
            // LocalStore.
            return this.localStore.start();
          })
          .then(() => {
            return this.remoteStore.start();
          });
      }

      private handleUserChange(user: User): Promise<void> {
        this.asyncQueue.verifyOperationInProgress();

        debug(LOG_TAG, 'User Changed: ' + user.uid);
        return this.syncEngine.handleUserChange(user);
      }

      /** Disables the network connection. Pending operations will not complete. */
      disableNetwork(): Promise<void> {
        return this.asyncQueue.enqueue(() => {
          return this.remoteStore.disableNetwork();
        });
      }

      shutdown(): Promise<void> {
        return this.asyncQueue
          .enqueue(() => {
            this.credentials.removeUserChangeListener();
            return this.remoteStore.shutdown();
          })
          .then(() => {
            // PORTING NOTE: LocalStore does not need an explicit shutdown on web.
            return this.persistence.shutdown();
          });
      }

      listen(
        query: Query,
        observer: Observer<ViewSnapshot>,
        options: ListenOptions
      ): QueryListener {
        const listener = new QueryListener(query, observer, options);
        this.asyncQueue.enqueue(() => {
          return this.eventMgr.listen(listener);
        });
        return listener;
      }

      unlisten(listener: QueryListener): void {
        this.asyncQueue.enqueue(() => {
          return this.eventMgr.unlisten(listener);
        });
      }

      write(mutations: Mutation[]): Promise<void> {
        const deferred = new Deferred<void>();
        this.asyncQueue.enqueue(() => this.syncEngine.write(mutations, deferred));
        return deferred.promise;
      }

      databaseId(): DatabaseId {
        return this.databaseInfo.databaseId;
      }

      transaction<T>(
        updateFunction: (transaction: Transaction) => Promise<T>
      ): Promise<T> {
        // We have to wait for the async queue to be sure syncEngine is initialized.
        return this.asyncQueue
          .enqueue(async () => {})
          .then(() => this.syncEngine.runTransaction(updateFunction));
      }
    }