System Initiative

import { SqlValue } from "@sqlite.org/sqlite-wasm"; // eslint-disable-next-line @typescript-eslint/no-explicit-any type AnyFn = (...args: any[]) => any; export class ReadWriteLock { name: string; readerCount: number; writeLockAcquired: boolean; constructor(name: string) { this.name = name; this.readerCount = 0; this.writeLockAcquired = false; } isWriteLockAcquired(): boolean { return this.writeLockAcquired; } async readLock(callback: AnyFn): Promise<SqlValue[][]> { return await navigator.locks.request( `${this.name}-reader`, { mode: "shared" }, async () => { this.readerCount++; try { return await callback(); } finally { this.readerCount--; } }, ); } async writeLock(callback: AnyFn): Promise<SqlValue[][]> { try { return await navigator.locks.request( `${this.name}-reader`, { mode: "exclusive" }, async () => { return await navigator.locks.request( `${this.name}-writer`, { mode: "exclusive" }, async () => { this.writeLockAcquired = true; return await callback(); }, ); }, ); } finally { this.writeLockAcquired = false; } } async query() { const state = await navigator.locks.query(); const readerLocks = state.held?.filter( (lock) => lock.name === `${this.name}-reader`, ); const writerLocks = state.held?.filter( (lock) => lock.name === `${this.name}-writer`, ); return { readers: readerLocks?.length ?? 0, writers: writerLocks?.length ?? 0, pending: state.pending?.filter( (lock) => lock.name === `${this.name}-reader` || lock.name === `${this.name}-writer`, ).length ?? 0, }; } }