# All files / local remote_document_change_buffer.ts

100% Statements 28/28
100% Branches 2/2
100% Functions 7/7
100% Lines 26/26

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    66
    67
    68
    69
    70
    71
    72
    73
    74
    75
    76
    77
    78
    79
    80
    81
    82
    83
    84
    85
    86
    87
    88
    89
    90
    91
    92
    93
    94
    95
    96
    97
    98
    99
    100

    2x

    2x

    2x

    2x
    1566x

    1566x

    2x
    1154x
    1153x

    2x

    1255x

    1254x
    1254x
    89x

    1165x

    1565x
    1565x

    1564x
    1564x
    1140x

    1564x

    1564x

    2x
    3974x
    3971x

    2x
     /**
     * 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 { MaybeDocumentMap, maybeDocumentMap } from '../model/collections';
    import { MaybeDocument } from '../model/document';
    import { DocumentKey } from '../model/document_key';
    import { assert } from '../util/assert';

    import { PersistenceTransaction } from './persistence';
    import { PersistencePromise } from './persistence_promise';
    import { RemoteDocumentCache } from './remote_document_cache';

    /**
     * An in-memory buffer of entries to be written to a RemoteDocumentCache.
     * It can be used to batch up a set of changes to be written to the cache, but
     * additionally supports reading entries back with the `getEntry()` method,
     * falling back to the underlying RemoteDocumentCache if no entry is
     * buffered.
     *
     * NOTE: This class was introduced in iOS to work around a limitation in
     * LevelDB. Given IndexedDb has full transaction support with
     * read-your-own-writes capability, this class is not technically needed, but
     * has been preserved as a convenience and to aid portability.
     */
    export class RemoteDocumentChangeBuffer {
      private changes: MaybeDocumentMap | null = maybeDocumentMap();

      constructor(private remoteDocumentCache: RemoteDocumentCache) {}

      /** Buffers a `RemoteDocumentCache.addEntry()` call. */
      addEntry(maybeDocument: MaybeDocument): void {
        const changes = this.assertChanges();
        this.changes = changes.insert(maybeDocument.key, maybeDocument);
      }

      // NOTE: removeEntry() is not presently necessary and so is omitted.

      /**
       * Looks up an entry in the cache. The buffered changes will first be checked,
       * and if no buffered change applies, this will forward to
       * `RemoteDocumentCache.getEntry()`.
       *
       * @param transaction The transaction in which to perform any persistence
       *     operations.
       * @param documentKey The key of the entry to look up.
       * @return The cached Document or NoDocument entry, or null if we have nothing
       * cached.
       */
      getEntry(
        transaction: PersistenceTransaction,
        documentKey: DocumentKey
      ): PersistencePromise<MaybeDocument | null> {
        const changes = this.assertChanges();

        const bufferedEntry = changes.get(documentKey);
        if (bufferedEntry) {
          return PersistencePromise.resolve(bufferedEntry);
        } else {
          return this.remoteDocumentCache.getEntry(transaction, documentKey);
        }
      }

      /**
       * Applies buffered changes to the underlying RemoteDocumentCache, using
       * the provided transaction.
       */
      apply(transaction: PersistenceTransaction): PersistencePromise<void> {
        const changes = this.assertChanges();

        const promises: Array<PersistencePromise<void>> = [];
        changes.forEach((key, maybeDoc) => {
          promises.push(this.remoteDocumentCache.addEntry(transaction, maybeDoc));
        });

        // We should not be used to buffer any more changes.
        this.changes = null;

        return PersistencePromise.waitFor(promises);
      }

      /** Helper to assert this.changes is not null and return it. */
      private assertChanges(): MaybeDocumentMap {
        assert(this.changes !== null, 'Changes have already been applied.');
        return this.changes!;
      }
    }