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1/**
2 * Async utilities for controlled concurrency and parallel execution.
3 */
4
5/**
6 * Map over an array with limited concurrency.
7 * Similar to Promise.all but limits how many promises run simultaneously.
8 *
9 * @param items - Array of items to process
10 * @param fn - Async function to apply to each item
11 * @param concurrency - Maximum number of concurrent operations (default: 10)
12 * @returns Array of results in the same order as input
13 *
14 * @example
15 * const results = await mapWithConcurrency(urls, fetchUrl, 5)
16 */
17export async function mapWithConcurrency<T, R>(
18 items: T[],
19 fn: (item: T, index: number) => Promise<R>,
20 concurrency = 10,
21): Promise<R[]> {
22 const results: R[] = Array.from({ length: items.length }) as R[]
23 let currentIndex = 0
24
25 async function worker(): Promise<void> {
26 while (currentIndex < items.length) {
27 const index = currentIndex++
28 results[index] = await fn(items[index]!, index)
29 }
30 }
31
32 // Start workers up to concurrency limit
33 const workers = Array.from({ length: Math.min(concurrency, items.length) }, () => worker())
34 await Promise.all(workers)
35
36 return results
37}