# All files / local indexeddb_mutation_queue.ts

97.24% Statements 211/217
90% Branches 36/40
98.33% Functions 59/60
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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 { Timestamp } from '../api/timestamp';
    import { User } from '../auth/user';
    import { Query } from '../core/query';
    import { BatchId, ProtoByteString } from '../core/types';
    import { DocumentKey } from '../model/document_key';
    import { Mutation } from '../model/mutation';
    import { BATCHID_UNKNOWN, MutationBatch } from '../model/mutation_batch';
    import { ResourcePath } from '../model/path';
    import { assert, fail } from '../util/assert';
    import { immediatePredecessor, primitiveComparator } from '../util/misc';
    import { SortedSet } from '../util/sorted_set';

    import * as EncodedResourcePath from './encoded_resource_path';
    import { GarbageCollector } from './garbage_collector';
    import {
      DbDocumentMutation,
      DbDocumentMutationKey,
      DbMutationBatch,
      DbMutationBatchKey,
      DbMutationQueue,
      DbMutationQueueKey
    } from './indexeddb_schema';
    import { LocalSerializer } from './local_serializer';
    import { MutationQueue } from './mutation_queue';
    import { PersistenceTransaction } from './persistence';
    import { PersistencePromise } from './persistence_promise';
    import { SimpleDbStore, SimpleDbTransaction } from './simple_db';

    /** A mutation queue for a specific user, backed by IndexedDB. */
    export class IndexedDbMutationQueue implements MutationQueue {
      /**
       * Next value to use when assigning sequential IDs to each mutation batch.
       *
       * NOTE: There can only be one IndexedDbMutationQueue for a given db at a
       * time, hence it is safe to track nextBatchID as an instance-level property.
       * Should we ever relax this constraint we'll need to revisit this.
       */
      private nextBatchId: BatchId;

      /**
       * A write-through cache copy of the metadata describing the current queue.
       */
      private metadata: DbMutationQueue;

      private garbageCollector: GarbageCollector | null = null;

      constructor(
        /**
         * The normalized userId (e.g. null UID => "" userId) used to store /
         * retrieve mutations.
         */
        private userId: string,
        private serializer: LocalSerializer
      ) {}

      /**
       * Creates a new mutation queue for the given user.
       * @param user The user for which to create a mutation queue.
       * @param serializer The serializer to use when persisting to IndexedDb.
       */
      static forUser(user: User, serializer: LocalSerializer) {
        // TODO(mcg): Figure out what constraints there are on userIDs
        // In particular, are there any reserved characters? are empty ids allowed?
        // For the moment store these together in the same mutations table assuming
        // that empty userIDs aren't allowed.
        assert(user.uid !== '', 'UserID must not be an empty string.');
        const userId = user.isAuthenticated() ? user.uid! : '';
        return new IndexedDbMutationQueue(userId, serializer);
      }

      start(transaction: PersistenceTransaction): PersistencePromise<void> {
        return IndexedDbMutationQueue.loadNextBatchIdFromDb(transaction)
          .next(nextBatchId => {
            this.nextBatchId = nextBatchId;
            return mutationQueuesStore(transaction).get(this.userId);
          })
          .next((metadata: DbMutationQueue | null) => {
            if (!metadata) {
              metadata = new DbMutationQueue(
                this.userId,
                BATCHID_UNKNOWN,
                /*lastStreamToken=*/ ''
              );
            }
            this.metadata = metadata;

            // On restart, nextBatchId may end up lower than
            // lastAcknowledgedBatchId since it's computed from the queue
            // contents, and there may be no mutations in the queue. In this
            // case, we need to reset lastAcknowledgedBatchId (which is safe
            // since the queue must be empty).
            if (this.metadata.lastAcknowledgedBatchId >= this.nextBatchId) {
              return this.checkEmpty(transaction).next(empty => {
                assert(
                  empty,
                  'Reset nextBatchID is only possible when the queue is empty'
                );

                this.metadata.lastAcknowledgedBatchId = BATCHID_UNKNOWN;
                return mutationQueuesStore(transaction).put(this.metadata);
              });
            } else {
              return PersistencePromise.resolve();
            }
          });
      }

      /**
       * Returns one larger than the largest batch ID that has been stored. If there
       * are no mutations returns 0. Note that batch IDs are global.
       */
      static loadNextBatchIdFromDb(
        txn: PersistenceTransaction
      ): PersistencePromise<BatchId> {
        let maxBatchId = BATCHID_UNKNOWN;
        return mutationsStore(txn)
          .iterate({ reverse: true }, (key, batch, control) => {
            const [userId, batchId] = key;
            if (batchId > maxBatchId) {
              maxBatchId = batch.batchId;
            }

            if (userId === '') {
              // We can't compute a predecessor for the empty string, since it
              // is lexographically first. That also means that no other
              // userIds can come before this one, so we can just exit early.
              control.done();
            } else {
              const nextUser = immediatePredecessor(userId);
              control.skip([nextUser]);
            }
          })
          .next(() => maxBatchId + 1);
      }

      checkEmpty(transaction: PersistenceTransaction): PersistencePromise<boolean> {
        let empty = true;
        const range = IDBKeyRange.bound(
          this.keyForBatchId(Number.NEGATIVE_INFINITY),
          this.keyForBatchId(Number.POSITIVE_INFINITY)
        );
        return mutationsStore(transaction)
          .iterate({ range }, (key, value, control) => {
            empty = false;
            control.done();
          })
          .next(() => empty);
      }

      getNextBatchId(
        transaction: PersistenceTransaction
      ): PersistencePromise<BatchId> {
        return PersistencePromise.resolve(this.nextBatchId);
      }

      getHighestAcknowledgedBatchId(
        transaction: PersistenceTransaction
      ): PersistencePromise<BatchId> {
        return PersistencePromise.resolve(this.metadata.lastAcknowledgedBatchId);
      }

      acknowledgeBatch(
        transaction: PersistenceTransaction,
        batch: MutationBatch,
        streamToken: ProtoByteString
      ): PersistencePromise<void> {
        const batchId = batch.batchId;
        assert(
          batchId > this.metadata.lastAcknowledgedBatchId,
          'Mutation batchIDs must be acknowledged in order'
        );

        this.metadata.lastAcknowledgedBatchId = batchId;
        this.metadata.lastStreamToken = validateStreamToken(streamToken);

        return mutationQueuesStore(transaction).put(this.metadata);
      }

      getLastStreamToken(
        transaction: PersistenceTransaction
      ): PersistencePromise<ProtoByteString> {
        return PersistencePromise.resolve(this.metadata.lastStreamToken);
      }

      setLastStreamToken(
        transaction: PersistenceTransaction,
        streamToken: ProtoByteString
      ): PersistencePromise<void> {
        this.metadata.lastStreamToken = validateStreamToken(streamToken);
        return mutationQueuesStore(transaction).put(this.metadata);
      }

      addMutationBatch(
        transaction: PersistenceTransaction,
        localWriteTime: Timestamp,
        mutations: Mutation[]
      ): PersistencePromise<MutationBatch> {
        const batchId = this.nextBatchId;
        this.nextBatchId++;
        const batch = new MutationBatch(batchId, localWriteTime, mutations);

        const dbBatch = this.serializer.toDbMutationBatch(this.userId, batch);

        return mutationsStore(transaction)
          .put(dbBatch)
          .next(() => {
            const promises: Array<PersistencePromise<void>> = [];
            for (const mutation of mutations) {
              const indexKey = DbDocumentMutation.key(
                this.userId,
                mutation.key.path,
                batchId
              );
              promises.push(
                documentMutationsStore(transaction).put(
                  indexKey,
                  DbDocumentMutation.PLACEHOLDER
                )
              );
            }
            return PersistencePromise.waitFor(promises);
          })
          .next(() => {
            return batch;
          });
      }

      lookupMutationBatch(
        transaction: PersistenceTransaction,
        batchId: BatchId
      ): PersistencePromise<MutationBatch | null> {
        return mutationsStore(transaction)
          .get(this.keyForBatchId(batchId))
          .next(
            dbBatch =>
              dbBatch ? this.serializer.fromDbMutationBatch(dbBatch) : null
          );
      }

      getNextMutationBatchAfterBatchId(
        transaction: PersistenceTransaction,
        batchId: BatchId
      ): PersistencePromise<MutationBatch | null> {
        // All batches with batchId <= this.metadata.lastAcknowledgedBatchId have
        // been acknowledged so the first unacknowledged batch after batchID will
        // have a batchID larger than both of these values.
        const nextBatchId =
          Math.max(batchId, this.metadata.lastAcknowledgedBatchId) + 1;

        const range = IDBKeyRange.lowerBound(this.keyForBatchId(nextBatchId));
        let foundBatch: MutationBatch | null = null;
        return mutationsStore(transaction)
          .iterate({ range }, (key, dbBatch, control) => {
            if (dbBatch.userId === this.userId) {
              assert(
                dbBatch.batchId >= nextBatchId,
                'Should have found mutation after ' + nextBatchId
              );
              foundBatch = this.serializer.fromDbMutationBatch(dbBatch);
            }
            control.done();
          })
          .next(() => foundBatch);
      }

      getAllMutationBatches(
        transaction: PersistenceTransaction
      ): PersistencePromise<MutationBatch[]> {
        const range = IDBKeyRange.bound(
          this.keyForBatchId(BATCHID_UNKNOWN),
          this.keyForBatchId(Number.POSITIVE_INFINITY)
        );
        return mutationsStore(transaction)
          .loadAll(range)
          .next(dbBatches =>
            dbBatches.map(dbBatch => this.serializer.fromDbMutationBatch(dbBatch))
          );
      }

      getAllMutationBatchesThroughBatchId(
        transaction: PersistenceTransaction,
        batchId: BatchId
      ): PersistencePromise<MutationBatch[]> {
        const range = IDBKeyRange.bound(
          this.keyForBatchId(BATCHID_UNKNOWN),
          this.keyForBatchId(batchId)
        );
        return mutationsStore(transaction)
          .loadAll(range)
          .next(dbBatches =>
            dbBatches.map(dbBatch => this.serializer.fromDbMutationBatch(dbBatch))
          );
      }

      getAllMutationBatchesAffectingDocumentKey(
        transaction: PersistenceTransaction,
        documentKey: DocumentKey
      ): PersistencePromise<MutationBatch[]> {
        // Scan the document-mutation index starting with a prefix starting with
        // the given documentKey.
        const indexPrefix = DbDocumentMutation.prefixForPath(
          this.userId,
          documentKey.path
        );
        const indexStart = IDBKeyRange.lowerBound(indexPrefix);

        const results: MutationBatch[] = [];
        return documentMutationsStore(transaction)
          .iterate({ range: indexStart }, (indexKey, _, control) => {
            const [userID, encodedPath, batchID] = indexKey;

            // Only consider rows matching exactly the specific key of
            // interest. Note that because we order by path first, and we
            // order terminators before path separators, we'll encounter all
            // the index rows for documentKey contiguously. In particular, all
            // the rows for documentKey will occur before any rows for
            // documents nested in a subcollection beneath documentKey so we
            // can stop as soon as we hit any such row.
            const path = EncodedResourcePath.decode(encodedPath);
            if (userID !== this.userId || !documentKey.path.isEqual(path)) {
              control.done();
              return;
            }
            const mutationKey = this.keyForBatchId(batchID);
            // Look up the mutation batch in the store.
            // PORTING NOTE: because iteration is callback driven in the web,
            // we just look up the key instead of keeping an open iterator
            // like iOS.
            return mutationsStore(transaction)
              .get(mutationKey)
              .next(dbBatch => {
                Iif (dbBatch === null) {
                  fail(
                    'Dangling document-mutation reference found: ' +
                      indexKey +
                      ' which points to ' +
                      mutationKey
                  );
                }
                results.push(this.serializer.fromDbMutationBatch(dbBatch!));
              });
          })
          .next(() => results);
      }

      getAllMutationBatchesAffectingQuery(
        transaction: PersistenceTransaction,
        query: Query
      ): PersistencePromise<MutationBatch[]> {
        assert(
          !query.isDocumentQuery(),
          "Document queries shouldn't go down this path"
        );

        const queryPath = query.path;
        const immediateChildrenLength = queryPath.length + 1;

        // TODO(mcg): Actually implement a single-collection query
        //
        // This is actually executing an ancestor query, traversing the whole
        // subtree below the collection which can be horrifically inefficient for
        // some structures. The right way to solve this is to implement the full
        // value index, but that's not in the cards in the near future so this is
        // the best we can do for the moment.
        //
        // Since we don't yet index the actual properties in the mutations, our
        // current approach is to just return all mutation batches that affect
        // documents in the collection being queried.
        const indexPrefix = DbDocumentMutation.prefixForPath(
          this.userId,
          queryPath
        );
        const indexStart = IDBKeyRange.lowerBound(indexPrefix);

        // Collect up unique batchIDs encountered during a scan of the index. Use a
        // SortedSet to accumulate batch IDs so they can be traversed in order in a
        // scan of the main table.
        let uniqueBatchIDs = new SortedSet<BatchId>(primitiveComparator);
        return documentMutationsStore(transaction)
          .iterate({ range: indexStart }, (indexKey, _, control) => {
            const [userID, encodedPath, batchID] = indexKey;
            const path = EncodedResourcePath.decode(encodedPath);
            if (userID !== this.userId || !queryPath.isPrefixOf(path)) {
              control.done();
              return;
            }
            // Rows with document keys more than one segment longer than the
            // query path can't be matches. For example, a query on 'rooms'
            // can't match the document /rooms/abc/messages/xyx.
            // TODO(mcg): we'll need a different scanner when we implement
            // ancestor queries.
            if (path.length !== immediateChildrenLength) {
              return;
            }
            uniqueBatchIDs = uniqueBatchIDs.add(batchID);
          })
          .next(() => {
            const results: MutationBatch[] = [];
            const promises: Array<PersistencePromise<void>> = [];
            // TODO(rockwood): Implement this using iterate.
            uniqueBatchIDs.forEach(batchID => {
              const mutationKey = this.keyForBatchId(batchID);
              promises.push(
                mutationsStore(transaction)
                  .get(mutationKey)
                  .next(mutation => {
                    Iif (mutation === null) {
                      fail(
                        'Dangling document-mutation reference found, ' +
                          'which points to ' +
                          mutationKey
                      );
                    }
                    results.push(this.serializer.fromDbMutationBatch(mutation!));
                  })
              );
            });
            return PersistencePromise.waitFor(promises).next(() => results);
          });
      }

      removeMutationBatches(
        transaction: PersistenceTransaction,
        batches: MutationBatch[]
      ): PersistencePromise<void> {
        const txn = mutationsStore(transaction);
        const indexTxn = documentMutationsStore(transaction);
        const promises: Array<PersistencePromise<void>> = [];

        for (const batch of batches) {
          const range = IDBKeyRange.only(this.keyForBatchId(batch.batchId));
          let numDeleted = 0;
          const removePromise = txn.iterate({ range }, (key, value, control) => {
            numDeleted++;
            return control.delete();
          });
          promises.push(
            removePromise.next(() => {
              assert(
                numDeleted === 1,
                'Dangling document-mutation reference found: Missing batch ' +
                  batch.batchId
              );
            })
          );
          for (const mutation of batch.mutations) {
            const indexKey = DbDocumentMutation.key(
              this.userId,
              mutation.key.path,
              batch.batchId
            );
            promises.push(indexTxn.delete(indexKey));
            if (this.garbageCollector !== null) {
              this.garbageCollector.addPotentialGarbageKey(mutation.key);
            }
          }
        }
        return PersistencePromise.waitFor(promises);
      }

      performConsistencyCheck(
        txn: PersistenceTransaction
      ): PersistencePromise<void> {
        return this.checkEmpty(txn).next(empty => {
          if (!empty) {
            return PersistencePromise.resolve();
          }

          // Verify that there are no entries in the documentMutations index if
          // the queue is empty.
          const startRange = IDBKeyRange.lowerBound(
            DbDocumentMutation.prefixForUser(this.userId)
          );
          const danglingMutationReferences: ResourcePath[] = [];
          return documentMutationsStore(txn)
            .iterate({ range: startRange }, (key, _, control) => {
              const userID = key[0];
              Eif (userID !== this.userId) {
                control.done();
                return;
              } else {
                const path = EncodedResourcePath.decode(key[1]);
                danglingMutationReferences.push(path);
              }
            })
            .next(() => {
              assert(
                danglingMutationReferences.length === 0,
                'Document leak -- detected dangling mutation references when queue is empty. Dangling keys: ' +
                  danglingMutationReferences.map(p => p.canonicalString())
              );
            });
        });
      }

      setGarbageCollector(gc: GarbageCollector | null): void {
        this.garbageCollector = gc;
      }

      containsKey(
        txn: PersistenceTransaction,
        key: DocumentKey
      ): PersistencePromise<boolean> {
        const indexKey = DbDocumentMutation.prefixForPath(this.userId, key.path);
        const encodedPath = indexKey[1];
        const startRange = IDBKeyRange.lowerBound(indexKey);
        let containsKey = false;
        return documentMutationsStore(txn)
          .iterate({ range: startRange, keysOnly: true }, (key, value, control) => {
            const [userID, keyPath, /*batchID*/ _] = key;
            if (userID === this.userId && keyPath === encodedPath) {
              containsKey = true;
            }
            control.done();
          })
          .next(() => containsKey);
      }

      /**
       * Creates a [userId, batchId] key for use with the DbMutationQueue object
       * store.
       */
      private keyForBatchId(batchId: BatchId): DbMutationBatchKey {
        return [this.userId, batchId];
      }
    }

    function validateStreamToken(token: ProtoByteString): string {
      assert(
        typeof token === 'string',
        'Persisting non-string stream token not supported.'
      );
      return token as string;
    }

    /**
     * Helper to get a typed SimpleDbStore for the mutations object store.
     */
    function mutationsStore(
      txn: PersistenceTransaction
    ): SimpleDbStore<DbMutationBatchKey, DbMutationBatch> {
      return getStore<DbMutationBatchKey, DbMutationBatch>(
        txn,
        DbMutationBatch.store
      );
    }

    /**
     * Helper to get a typed SimpleDbStore for the mutationQueues object store.
     */
    function documentMutationsStore(
      txn: PersistenceTransaction
    ): SimpleDbStore<DbDocumentMutationKey, DbDocumentMutation> {
      return getStore<DbDocumentMutationKey, DbDocumentMutation>(
        txn,
        DbDocumentMutation.store
      );
    }

    /**
     * Helper to get a typed SimpleDbStore for the mutationQueues object store.
     */
    function mutationQueuesStore(
      txn: PersistenceTransaction
    ): SimpleDbStore<DbMutationQueueKey, DbMutationQueue> {
      return getStore<DbMutationQueueKey, DbMutationQueue>(
        txn,
        DbMutationQueue.store
      );
    }

    /**
     * Helper to get a typed SimpleDbStore from a transaction.
     */
    function getStore<KeyType extends IDBValidKey, ValueType>(
      txn: PersistenceTransaction,
      store: string
    ): SimpleDbStore<KeyType, ValueType> {
      Eif (txn instanceof SimpleDbTransaction) {
        return txn.store<KeyType, ValueType>(store);
      } else {
        return fail('Invalid transaction object provided!');
      }
    }