import { createWriteStream } from "fs";
import fs from "fs/promises";
import { Readable } from "stream";
import { pipeline } from "stream/promises";

export async function writeUploadedFile(file: File, destPath: string) {
  const webStream = file.stream();
  const nodeStream = Readable.fromWeb(webStream as Parameters<typeof Readable.fromWeb>[0]);
  await pipeline(nodeStream, createWriteStream(destPath));
}

export async function moveFile(src: string, dest: string) {
  try {
    await fs.rename(src, dest);
  } catch (err) {
    const code = err && typeof err === "object" && "code" in err ? err.code : null;
    if (code === "EXDEV") {
      await fs.copyFile(src, dest);
      await fs.unlink(src).catch(() => {});
      return;
    }
    throw err;
  }
}

export async function mapWithConcurrency<T, R>(
  items: T[],
  concurrency: number,
  fn: (item: T, index: number) => Promise<R>,
) {
  const results: R[] = new Array(items.length);
  let nextIndex = 0;

  async function worker() {
    while (nextIndex < items.length) {
      const index = nextIndex;
      nextIndex += 1;
      results[index] = await fn(items[index], index);
    }
  }

  const workers = Array.from({ length: Math.min(concurrency, items.length) }, () => worker());
  await Promise.all(workers);
  return results;
}