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Extract store subscription management into separate module
Reviewed By: josephsavona, kassens Differential Revision: D24964756 fbshipit-source-id: ef93462be9bb745f0cff47dd2500f72763820d43
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packages/relay-runtime/store/RelayStoreSubscriptions.js
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| /** | ||
| * Copyright (c) Facebook, Inc. and its affiliates. | ||
| * | ||
| * This source code is licensed under the MIT license found in the | ||
| * LICENSE file in the root directory of this source tree. | ||
| * | ||
| * @flow strict-local | ||
| * @format | ||
| */ | ||
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| // flowlint ambiguous-object-type:error | ||
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| 'use strict'; | ||
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| const RelayReader = require('./RelayReader'); | ||
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| const deepFreeze = require('../util/deepFreeze'); | ||
| const hasOverlappingIDs = require('./hasOverlappingIDs'); | ||
| const isEmptyObject = require('../util/isEmptyObject'); | ||
| const recycleNodesInto = require('../util/recycleNodesInto'); | ||
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| import type {Disposable} from '../util/RelayRuntimeTypes'; | ||
| import type { | ||
| RecordSource, | ||
| RequestDescriptor, | ||
| Snapshot, | ||
| UpdatedRecords, | ||
| } from './RelayStoreTypes'; | ||
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| export type Subscription = {| | ||
| callback: (snapshot: Snapshot) => void, | ||
| snapshot: Snapshot, | ||
| stale: boolean, | ||
| backup: ?Snapshot, | ||
| |}; | ||
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| class RelayStoreSubscriptions { | ||
| _subscriptions: Set<Subscription>; | ||
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| constructor() { | ||
| this._subscriptions = new Set(); | ||
| } | ||
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| subscribe( | ||
| snapshot: Snapshot, | ||
| callback: (snapshot: Snapshot) => void, | ||
| ): Disposable { | ||
| const subscription = {backup: null, callback, snapshot, stale: false}; | ||
| const dispose = () => { | ||
| this._subscriptions.delete(subscription); | ||
| }; | ||
| this._subscriptions.add(subscription); | ||
| return {dispose}; | ||
| } | ||
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| snapshotSubscriptions(source: RecordSource) { | ||
| this._subscriptions.forEach(subscription => { | ||
| // Backup occurs after writing a new "final" payload(s) and before (re)applying | ||
| // optimistic changes. Each subscription's `snapshot` represents what was *last | ||
| // published to the subscriber*, which notably may include previous optimistic | ||
| // updates. Therefore a subscription can be in any of the following states: | ||
| // - stale=true: This subscription was restored to a different value than | ||
| // `snapshot`. That means this subscription has changes relative to its base, | ||
| // but its base has changed (we just applied a final payload): recompute | ||
| // a backup so that we can later restore to the state the subscription | ||
| // should be in. | ||
| // - stale=false: This subscription was restored to the same value than | ||
| // `snapshot`. That means this subscription does *not* have changes relative | ||
| // to its base, so the current `snapshot` is valid to use as a backup. | ||
| if (!subscription.stale) { | ||
| subscription.backup = subscription.snapshot; | ||
| return; | ||
| } | ||
| const snapshot = subscription.snapshot; | ||
| const backup = RelayReader.read(source, snapshot.selector); | ||
| const nextData = recycleNodesInto(snapshot.data, backup.data); | ||
| (backup: $FlowFixMe).data = nextData; // backup owns the snapshot and can safely mutate | ||
| subscription.backup = backup; | ||
| }); | ||
| } | ||
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| restoreSubscriptions() { | ||
| this._subscriptions.forEach(subscription => { | ||
| const backup = subscription.backup; | ||
| subscription.backup = null; | ||
| if (backup) { | ||
| if (backup.data !== subscription.snapshot.data) { | ||
| subscription.stale = true; | ||
| } | ||
| subscription.snapshot = { | ||
| data: subscription.snapshot.data, | ||
| isMissingData: backup.isMissingData, | ||
| seenRecords: backup.seenRecords, | ||
| selector: backup.selector, | ||
| missingRequiredFields: backup.missingRequiredFields, | ||
| }; | ||
| } else { | ||
| subscription.stale = true; | ||
| } | ||
| }); | ||
| } | ||
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| updateSubscriptions( | ||
| source: RecordSource, | ||
| updatedRecordIDs: UpdatedRecords, | ||
| updatedOwners: Array<RequestDescriptor>, | ||
| ) { | ||
| const hasUpdatedRecords = !isEmptyObject(updatedRecordIDs); | ||
| this._subscriptions.forEach(subscription => { | ||
| const owner = this._updateSubscription( | ||
| source, | ||
| subscription, | ||
| updatedRecordIDs, | ||
| hasUpdatedRecords, | ||
| ); | ||
| if (owner != null) { | ||
| updatedOwners.push(owner); | ||
| } | ||
| }); | ||
| } | ||
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| // Returns the owner (RequestDescriptor) if the subscription was affected by the | ||
| // latest update, or null if it was not affected. | ||
| _updateSubscription( | ||
| source: RecordSource, | ||
| subscription: Subscription, | ||
| updatedRecordIDs: UpdatedRecords, | ||
| hasUpdatedRecords: boolean, | ||
| ): ?RequestDescriptor { | ||
| const {backup, callback, snapshot, stale} = subscription; | ||
| const hasOverlappingUpdates = | ||
| hasUpdatedRecords && | ||
| hasOverlappingIDs(snapshot.seenRecords, updatedRecordIDs); | ||
| if (!stale && !hasOverlappingUpdates) { | ||
| return; | ||
| } | ||
| let nextSnapshot: Snapshot = | ||
| hasOverlappingUpdates || !backup | ||
| ? RelayReader.read(source, snapshot.selector) | ||
| : backup; | ||
| const nextData = recycleNodesInto(snapshot.data, nextSnapshot.data); | ||
| nextSnapshot = ({ | ||
| data: nextData, | ||
| isMissingData: nextSnapshot.isMissingData, | ||
| seenRecords: nextSnapshot.seenRecords, | ||
| selector: nextSnapshot.selector, | ||
| missingRequiredFields: nextSnapshot.missingRequiredFields, | ||
| }: Snapshot); | ||
| if (__DEV__) { | ||
| deepFreeze(nextSnapshot); | ||
| } | ||
| subscription.snapshot = nextSnapshot; | ||
| subscription.stale = false; | ||
| if (nextSnapshot.data !== snapshot.data) { | ||
| callback(nextSnapshot); | ||
| return snapshot.selector.owner; | ||
| } | ||
| } | ||
| } | ||
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| module.exports = RelayStoreSubscriptions; |