# All files / local indexeddb_query_cache.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 { Timestamp } from '../api/timestamp';
    import { Query } from '../core/query';
    import { SnapshotVersion } from '../core/snapshot_version';
    import { TargetId } from '../core/types';
    import { DocumentKeySet, documentKeySet } from '../model/collections';
    import { DocumentKey } from '../model/document_key';
    import { assert, fail } from '../util/assert';
    import { immediateSuccessor } from '../util/misc';

    import * as EncodedResourcePath from './encoded_resource_path';
    import { GarbageCollector } from './garbage_collector';
    import {
      DbTarget,
      DbTargetDocument,
      DbTargetDocumentKey,
      DbTargetGlobal,
      DbTargetGlobalKey,
      DbTargetKey
    } from './indexeddb_schema';
    import { LocalSerializer } from './local_serializer';
    import { PersistenceTransaction } from './persistence';
    import { PersistencePromise } from './persistence_promise';
    import { QueryCache } from './query_cache';
    import { QueryData } from './query_data';
    import { SimpleDbStore, SimpleDbTransaction } from './simple_db';

    export class IndexedDbQueryCache implements QueryCache {
      constructor(private serializer: LocalSerializer) {}

      /**
       * The last received snapshot version. We store this seperately from the
       * metadata to avoid the extra conversion to/from DbTimestamp.
       */
      private lastRemoteSnapshotVersion = SnapshotVersion.MIN;

      /**
       * A cached copy of the metadata for the query cache.
       */
      private metadata = null;

      /** The garbage collector to notify about potential garbage keys. */
      private garbageCollector: GarbageCollector | null = null;

      start(transaction: PersistenceTransaction): PersistencePromise<void> {
        return globalTargetStore(transaction)
          .get(DbTargetGlobal.key)
          .next(metadata => {
            assert(
              metadata !== null,
              'Missing metadata row that should be added by schema migration.'
            );
            this.metadata = metadata;
            const lastSavedVersion = metadata.lastRemoteSnapshotVersion;
            this.lastRemoteSnapshotVersion = SnapshotVersion.fromTimestamp(
              new Timestamp(lastSavedVersion.seconds, lastSavedVersion.nanoseconds)
            );
            return PersistencePromise.resolve();
          });
      }

      getHighestTargetId(): TargetId {
        return this.metadata.highestTargetId;
      }

      getLastRemoteSnapshotVersion(): SnapshotVersion {
        return this.lastRemoteSnapshotVersion;
      }

      setLastRemoteSnapshotVersion(
        transaction: PersistenceTransaction,
        snapshotVersion: SnapshotVersion
      ): PersistencePromise<void> {
        this.lastRemoteSnapshotVersion = snapshotVersion;
        this.metadata.lastRemoteSnapshotVersion = snapshotVersion.toTimestamp();
        return globalTargetStore(transaction).put(
          DbTargetGlobal.key,
          this.metadata
        );
      }

      addQueryData(
        transaction: PersistenceTransaction,
        queryData: QueryData
      ): PersistencePromise<void> {
        return this.saveQueryData(transaction, queryData).next(() => {
          this.metadata.targetCount += 1;
          this.updateMetadataFromQueryData(queryData);
          return this.saveMetadata(transaction);
        });
      }

      updateQueryData(
        transaction: PersistenceTransaction,
        queryData: QueryData
      ): PersistencePromise<void> {
        return this.saveQueryData(transaction, queryData).next(() => {
          Iif (this.updateMetadataFromQueryData(queryData)) {
            return this.saveMetadata(transaction);
          } else {
            return PersistencePromise.resolve();
          }
        });
      }

      removeQueryData(
        transaction: PersistenceTransaction,
        queryData: QueryData
      ): PersistencePromise<void> {
        assert(this.metadata.targetCount > 0, 'Removing from an empty query cache');
        return this.removeMatchingKeysForTargetId(transaction, queryData.targetId)
          .next(() => targetsStore(transaction).delete(queryData.targetId))
          .next(() => {
            this.metadata.targetCount -= 1;
            return this.saveMetadata(transaction);
          });
      }

      private saveMetadata(
        transaction: PersistenceTransaction
      ): PersistencePromise<void> {
        return globalTargetStore(transaction).put(
          DbTargetGlobal.key,
          this.metadata
        );
      }

      private saveQueryData(
        transaction: PersistenceTransaction,
        queryData: QueryData
      ): PersistencePromise<void> {
        return targetsStore(transaction).put(this.serializer.toDbTarget(queryData));
      }

      /**
       * Updates the in-memory version of the metadata to account for values in the
       * given QueryData. Saving is done separately. Returns true if there were any
       * changes to the metadata.
       */
      private updateMetadataFromQueryData(queryData: QueryData): boolean {
        let needsUpdate = false;
        if (queryData.targetId > this.metadata.highestTargetId) {
          this.metadata.highestTargetId = queryData.targetId;
          needsUpdate = true;
        }

        // TODO(GC): add sequence number check
        return needsUpdate;
      }

      get count(): number {
        return this.metadata.targetCount;
      }

      getQueryData(
        transaction: PersistenceTransaction,
        query: Query
      ): PersistencePromise<QueryData | null> {
        // Iterating by the canonicalId may yield more than one result because
        // canonicalId values are not required to be unique per target. This query
        // depends on the queryTargets index to be efficent.
        const canonicalId = query.canonicalId();
        const range = IDBKeyRange.bound(
          [canonicalId, Number.NEGATIVE_INFINITY],
          [canonicalId, Number.POSITIVE_INFINITY]
        );
        let result: QueryData | null = null;
        return targetsStore(transaction)
          .iterate(
            { range, index: DbTarget.queryTargetsIndexName },
            (key, value, control) => {
              const found = this.serializer.fromDbTarget(value);
              // After finding a potential match, check that the query is
              // actually equal to the requested query.
              if (query.isEqual(found.query)) {
                result = found;
                control.done();
              }
            }
          )
          .next(() => result);
      }

      addMatchingKeys(
        txn: PersistenceTransaction,
        keys: DocumentKeySet,
        targetId: TargetId
      ): PersistencePromise<void> {
        // PORTING NOTE: The reverse index (documentsTargets) is maintained by
        // Indexeddb.
        const promises: Array<PersistencePromise<void>> = [];
        const store = documentTargetStore(txn);
        keys.forEach(key => {
          const path = EncodedResourcePath.encode(key.path);
          promises.push(store.put(new DbTargetDocument(targetId, path)));
        });
        return PersistencePromise.waitFor(promises);
      }

      removeMatchingKeys(
        txn: PersistenceTransaction,
        keys: DocumentKeySet,
        targetId: TargetId
      ): PersistencePromise<void> {
        // PORTING NOTE: The reverse index (documentsTargets) is maintained by
        // IndexedDb.
        const promises: Array<PersistencePromise<void>> = [];
        const store = documentTargetStore(txn);
        keys.forEach(key => {
          const path = EncodedResourcePath.encode(key.path);
          promises.push(store.delete([targetId, path]));
          if (this.garbageCollector !== null) {
            this.garbageCollector.addPotentialGarbageKey(key);
          }
        });
        return PersistencePromise.waitFor(promises);
      }

      removeMatchingKeysForTargetId(
        txn: PersistenceTransaction,
        targetId: TargetId
      ): PersistencePromise<void> {
        const store = documentTargetStore(txn);
        const range = IDBKeyRange.bound(
          [targetId],
          [targetId + 1],
          /*lowerOpen=*/ false,
          /*upperOpen=*/ true
        );
        return this.notifyGCForRemovedKeys(txn, range).next(() =>
          store.delete(range)
        );
      }

      private notifyGCForRemovedKeys(
        txn: PersistenceTransaction,
        range: IDBKeyRange
      ): PersistencePromise<void> {
        const store = documentTargetStore(txn);
        if (this.garbageCollector !== null && this.garbageCollector.isEager) {
          // In order to generate garbage events properly, we need to read these
          // keys before deleting.
          return store.iterate({ range, keysOnly: true }, (key, _, control) => {
            const path = EncodedResourcePath.decode(key[1]);
            const docKey = new DocumentKey(path);
            // Paranoid assertion in case the the collector is set to null
            // during the iteration.
            assert(
              this.garbageCollector !== null,
              'GarbageCollector for query cache set to null during key removal.'
            );
            this.garbageCollector!.addPotentialGarbageKey(docKey);
          });
        } else {
          return PersistencePromise.resolve();
        }
      }

      getMatchingKeysForTargetId(
        txn: PersistenceTransaction,
        targetId: TargetId
      ): PersistencePromise<DocumentKeySet> {
        const range = IDBKeyRange.bound(
          [targetId],
          [targetId + 1],
          /*lowerOpen=*/ false,
          /*upperOpen=*/ true
        );
        const store = documentTargetStore(txn);
        let result = documentKeySet();

        return store
          .iterate({ range, keysOnly: true }, (key, _, control) => {
            const path = EncodedResourcePath.decode(key[1]);
            const docKey = new DocumentKey(path);
            result = result.add(docKey);
          })
          .next(() => result);
      }

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

      containsKey(
        txn: PersistenceTransaction | null,
        key: DocumentKey
      ): PersistencePromise<boolean> {
        assert(
          txn !== null,
          'Persistence Transaction cannot be null for query cache containsKey'
        );
        const path = EncodedResourcePath.encode(key.path);
        const range = IDBKeyRange.bound(
          [path],
          [immediateSuccessor(path)],
          /*lowerOpen=*/ false,
          /*upperOpen=*/ true
        );
        let count = 0;
        return documentTargetStore(txn!)
          .iterate(
            {
              index: DbTargetDocument.documentTargetsIndex,
              keysOnly: true,
              range
            },
            (key, _, control) => {
              count++;
              control.done();
            }
          )
          .next(() => count > 0);
      }
    }

    /**
     * Helper to get a typed SimpleDbStore for the queries object store.
     */
    function targetsStore(
      txn: PersistenceTransaction
    ): SimpleDbStore<DbTargetKey, DbTarget> {
      return getStore<DbTargetKey, DbTarget>(txn, DbTarget.store);
    }

    /**
     * Helper to get a typed SimpleDbStore for the target globals object store.
     */
    function globalTargetStore(
      txn: PersistenceTransaction
    ): SimpleDbStore<DbTargetGlobalKey, DbTargetGlobal> {
      return getStore<DbTargetGlobalKey, DbTargetGlobal>(txn, DbTargetGlobal.store);
    }

    /**
     * Helper to get a typed SimpleDbStore for the document target object store.
     */
    function documentTargetStore(
      txn: PersistenceTransaction
    ): SimpleDbStore<DbTargetDocumentKey, DbTargetDocument> {
      return getStore<DbTargetDocumentKey, DbTargetDocument>(
        txn,
        DbTargetDocument.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!');
      }
    }