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/*
Spacebar: A FOSS re-implementation and extension of the Discord.com backend.
Copyright (C) 2026 Spacebar and Spacebar Contributors
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published
by the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
import { TimeSpan } from "./Timespan";
import { sleep } from "./index";
export class SingletonCache<T> {
private expiry: TimeSpan;
private lastUpdated: Date = new Date(0);
private isLocked: boolean = false;
private cachedValue: T;
constructor(expiry: TimeSpan) {
this.expiry = expiry;
}
async getOrUpdate(factory: () => Promise<T>): Promise<T> {
if (new TimeSpan(this.lastUpdated.getTime(), Date.now()).totalMillis < this.expiry.totalMillis) return this.cachedValue;
if (this.isLocked) {
// avoid running the factory twice (async)
while (this.isLocked) await sleep(50);
return this.cachedValue;
}
this.isLocked = true;
try {
const result = await factory();
this.cachedValue = result;
return result;
} catch (e) {
console.log(`[SingletonCache] Factory method failed, returning stale value:`, e);
return this.cachedValue;
} finally {
this.isLocked = false;
}
}
}
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