94 lines
3.2 KiB
TypeScript
94 lines
3.2 KiB
TypeScript
/*
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Copyright 2020 The Matrix.org Foundation C.I.C.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import { MatrixClient } from "matrix-js-sdk/src/matrix";
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import { EventEmitter } from "events";
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import { EchoContext } from "./EchoContext";
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import { EchoTransaction, RunFn, TransactionStatus } from "./EchoTransaction";
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export async function implicitlyReverted(): Promise<void> {
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// do nothing :D
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}
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export const PROPERTY_UPDATED = "property_updated";
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export abstract class GenericEchoChamber<C extends EchoContext, K, V> extends EventEmitter {
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private cache = new Map<K, { txn: EchoTransaction; val: V }>();
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protected matrixClient: MatrixClient | null = null;
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protected constructor(public readonly context: C, private lookupFn: (key: K) => V) {
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super();
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}
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public setClient(client: MatrixClient | null): void {
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const oldClient = this.matrixClient;
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this.matrixClient = client;
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this.onClientChanged(oldClient, client);
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}
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protected abstract onClientChanged(oldClient: MatrixClient | null, newClient: MatrixClient | null): void;
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/**
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* Gets a value. If the key is in flight, the cached value will be returned. If
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* the key is not in flight then the lookupFn provided to this class will be
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* called instead.
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* @param key The key to look up.
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* @returns The value for the key.
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*/
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public getValue(key: K): V {
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return this.cache.has(key) ? this.cache.get(key)!.val : this.lookupFn(key);
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}
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private cacheVal(key: K, val: V, txn: EchoTransaction): void {
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this.cache.set(key, { txn, val });
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this.emit(PROPERTY_UPDATED, key);
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}
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private decacheKey(key: K): void {
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if (this.cache.has(key)) {
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this.context.disownTransaction(this.cache.get(key)!.txn);
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this.cache.delete(key);
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this.emit(PROPERTY_UPDATED, key);
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}
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}
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protected markEchoReceived(key: K): void {
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if (this.cache.has(key)) {
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const txn = this.cache.get(key)!.txn;
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this.context.disownTransaction(txn);
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txn.cancel();
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}
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this.decacheKey(key);
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}
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public setValue(auditName: string, key: K, targetVal: V, runFn: RunFn, revertFn: RunFn): void {
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// Cancel any pending transactions for the same key
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if (this.cache.has(key)) {
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this.cache.get(key)!.txn.cancel();
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}
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const ctxn = this.context.beginTransaction(auditName, runFn);
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this.cacheVal(key, targetVal, ctxn); // set the cache now as it won't be updated by the .when() ladder below.
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ctxn.when(TransactionStatus.Pending, () => this.cacheVal(key, targetVal, ctxn)).when(
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TransactionStatus.Error,
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() => revertFn(),
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);
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ctxn.run();
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}
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}
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