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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 { Query } from './query';
import { SyncEngine } from './sync_engine';
import { OnlineState, TargetId } from './types';
import { DocumentViewChange } from './view_snapshot';
import { ChangeType, ViewSnapshot } from './view_snapshot';
import { DocumentSet } from '../model/document_set';
import { assert } from '../util/assert';
import { EventHandler } from '../util/misc';
import { ObjectMap } from '../util/obj_map';
/**
* Holds the listeners and the last received ViewSnapshot for a query being
* tracked by EventManager.
*/
class QueryListenersInfo {
viewSnap: ViewSnapshot | null;
targetId: TargetId;
listeners: QueryListener[] = [];
}
/**
* Interface for handling events from the EventManager.
*/
export interface Observer<T> {
next: EventHandler<T>;
error: EventHandler<Error>;
}
/**
* EventManager is responsible for mapping queries to query event emitters.
* It handles "fan-out". -- Identical queries will re-use the same watch on the
* backend.
*/
export class EventManager {
private queries = new ObjectMap<Query, QueryListenersInfo>(q =>
q.canonicalId()
);
private onlineState: OnlineState = OnlineState.Unknown;
constructor(private syncEngine: SyncEngine) {
this.syncEngine.subscribe(
this.onChange.bind(this),
this.onError.bind(this)
);
}
listen(listener: QueryListener): Promise<TargetId> {
const query = listener.query;
let firstListen = false;
let queryInfo = this.queries.get(query);
if (!queryInfo) {
firstListen = true;
queryInfo = new QueryListenersInfo();
this.queries.set(query, queryInfo);
}
queryInfo.listeners.push(listener);
listener.applyOnlineStateChange(this.onlineState);
if (queryInfo.viewSnap) listener.onViewSnapshot(queryInfo.viewSnap);
if (firstListen) {
return this.syncEngine.listen(query).then(targetId => {
queryInfo!.targetId = targetId;
return targetId;
});
} else {
return Promise.resolve(queryInfo.targetId);
}
}
async unlisten(listener: QueryListener): Promise<void> {
const query = listener.query;
let lastListen = false;
const queryInfo = this.queries.get(query);
if (queryInfo) {
const i = queryInfo.listeners.indexOf(listener);
Eif (i >= 0) {
queryInfo.listeners.splice(i, 1);
lastListen = queryInfo.listeners.length === 0;
}
}
if (lastListen) {
this.queries.delete(query);
return this.syncEngine.unlisten(query);
}
}
onChange(viewSnaps: ViewSnapshot[]): void {
for (const viewSnap of viewSnaps) {
const query = viewSnap.query;
const queryInfo = this.queries.get(query);
Eif (queryInfo) {
for (const listener of queryInfo.listeners) {
listener.onViewSnapshot(viewSnap);
}
queryInfo.viewSnap = viewSnap;
}
}
}
onError(query: Query, error: Error): void {
const queryInfo = this.queries.get(query);
Eif (queryInfo) {
for (const listener of queryInfo.listeners) {
listener.onError(error);
}
}
// Remove all listeners. NOTE: We don't need to call syncEngine.unlisten()
// after an error.
this.queries.delete(query);
}
applyOnlineStateChange(onlineState: OnlineState): void {
this.onlineState = onlineState;
this.queries.forEach((_, queryInfo) => {
for (const listener of queryInfo.listeners) {
listener.applyOnlineStateChange(onlineState);
}
});
}
}
export interface ListenOptions {
/** Raise events when only metadata of documents changes */
readonly includeDocumentMetadataChanges?: boolean;
/** Raise events when only metadata of the query changes */
readonly includeQueryMetadataChanges?: boolean;
/**
* Wait for a sync with the server when online, but still raise events while
* offline.
*/
readonly waitForSyncWhenOnline?: boolean;
}
/**
* QueryListener takes a series of internal view snapshots and determines
* when to raise the event.
*
* It uses an Observer to dispatch events.
*/
export class QueryListener {
/**
* Initial snapshots (e.g. from cache) may not be propagated to the wrapped
* observer. This flag is set to true once we've actually raised an event.
*/
private raisedInitialEvent = false;
private options: ListenOptions;
private snap: ViewSnapshot;
private onlineState: OnlineState = OnlineState.Unknown;
constructor(
readonly query: Query,
private queryObserver: Observer<ViewSnapshot>,
options?: ListenOptions
) {
this.options = options || {};
}
onViewSnapshot(snap: ViewSnapshot): void {
assert(
snap.docChanges.length > 0 || snap.syncStateChanged,
'We got a new snapshot with no changes?'
);
if (!this.options.includeDocumentMetadataChanges) {
// Remove the metadata only changes.
const docChanges: DocumentViewChange[] = [];
for (const docChange of snap.docChanges) {
if (docChange.type !== ChangeType.Metadata) {
docChanges.push(docChange);
}
}
snap = new ViewSnapshot(
snap.query,
snap.docs,
snap.oldDocs,
docChanges,
snap.fromCache,
snap.hasPendingWrites,
snap.syncStateChanged
);
}
if (!this.raisedInitialEvent) {
if (this.shouldRaiseInitialEvent(snap, this.onlineState)) {
this.raiseInitialEvent(snap);
}
} else if (this.shouldRaiseEvent(snap)) {
this.queryObserver.next(snap);
}
this.snap = snap;
}
onError(error: Error): void {
this.queryObserver.error(error);
}
applyOnlineStateChange(onlineState: OnlineState): void {
this.onlineState = onlineState;
if (
this.snap &&
!this.raisedInitialEvent &&
this.shouldRaiseInitialEvent(this.snap, onlineState)
) {
this.raiseInitialEvent(this.snap);
}
}
private shouldRaiseInitialEvent(
snap: ViewSnapshot,
onlineState: OnlineState
): boolean {
assert(
!this.raisedInitialEvent,
'Determining whether to raise first event but already had first event'
);
// Always raise the first event when we're synced
if (!snap.fromCache) {
return true;
}
// NOTE: We consider OnlineState.Unknown as online (it should become Offline
// or Online if we wait long enough).
const maybeOnline = onlineState !== OnlineState.Offline;
// Don't raise the event if we're online, aren't synced yet (checked
// above) and are waiting for a sync.
if (this.options.waitForSyncWhenOnline && maybeOnline) {
assert(
snap.fromCache,
'Waiting for sync, but snapshot is not from cache'
);
return false;
}
// Raise data from cache if we have any documents or we are offline
return !snap.docs.isEmpty() || onlineState === OnlineState.Offline;
}
private shouldRaiseEvent(snap: ViewSnapshot): boolean {
// We don't need to handle includeDocumentMetadataChanges here because
// the Metadata only changes have already been stripped out if needed.
// At this point the only changes we will see are the ones we should
// propagate.
if (snap.docChanges.length > 0) {
return true;
}
const hasPendingWritesChanged =
this.snap && this.snap.hasPendingWrites !== snap.hasPendingWrites;
if (snap.syncStateChanged || hasPendingWritesChanged) {
return this.options.includeQueryMetadataChanges === true;
}
// Generally we should have hit one of the cases above, but it's possible
// to get here if there were only metadata docChanges and they got
// stripped out.
return false;
}
private raiseInitialEvent(snap: ViewSnapshot): void {
assert(
!this.raisedInitialEvent,
'Trying to raise initial events for second time'
);
snap = new ViewSnapshot(
snap.query,
snap.docs,
DocumentSet.emptySet(snap.docs),
QueryListener.getInitialViewChanges(snap),
snap.fromCache,
snap.hasPendingWrites,
true
);
this.raisedInitialEvent = true;
this.queryObserver.next(snap);
}
/** Returns changes as if all documents in the snap were added. */
private static getInitialViewChanges(
snap: ViewSnapshot
): DocumentViewChange[] {
const result: DocumentViewChange[] = [];
snap.docs.forEach(doc => {
result.push({ type: ChangeType.Added, doc });
});
return result;
}
}
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