Add an SqliteWorker

src/workers/sqlite.ts

@@ -0,0 +1,37 @@
+class SqliteWorker {
+  #path: string;
+  #worker: Worker;
+
+  constructor(path: string) {
+    this.#path = path;
+    this.#worker = new Worker(new URL('./sqlite.worker.ts', import.meta.url).href, { type: 'module' });
+  }
+
+  open(): Promise<void> {
+    return this.#call(['open', [this.#path]]);
+  }
+
+  query(sql: string, params?: any): Promise<unknown[]> {
+    return this.#call(['query', [sql, params]]);
+  }
+
+  #call<T>(msg: [string, unknown[]]): Promise<T> {
+    const id = crypto.randomUUID();
+
+    this.#worker.postMessage([id, msg]);
+
+    // TODO: use a hashmap instead of an event listener for better performance.
+    return new Promise((resolve) => {
+      const handleEvent = (event: MessageEvent<[string, T]>) => {
+        const [_id, result] = event.data;
+        if (_id === id) {
+          this.#worker.removeEventListener('message', handleEvent);
+          resolve(result);
+        }
+      };
+      this.#worker.addEventListener('message', handleEvent);
+    });
+  }
+}
+
+export default SqliteWorker;