feat(api): allow bots to search messages within a single community (#1660)

fluxer_api/src/api/utils/ConcurrencyUtils.ts

@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+export async function mapWithConcurrency<T, TResult>(
+	items: ReadonlyArray<T>,
+	concurrency: number,
+	mapper: (item: T, index: number) => Promise<TResult>,
+): Promise<Array<TResult>> {
+	const results = new Array<TResult>(items.length);
+	let nextIndex = 0;
+	async function worker(): Promise<void> {
+		for (;;) {
+			const index = nextIndex++;
+			if (index >= items.length) return;
+			results[index] = await mapper(items[index]!, index);
+		}
+	}
+	await Promise.all(Array.from({length: Math.min(concurrency, items.length)}, () => worker()));
+	return results;
+}