import { mkdir, open, rename, rm, stat } from 'node:fs/promises';
import { dirname } from 'node:path';

const STALE_LOCK_MS = 30_000;

function errnoCode(error: unknown): string | undefined {
  return error instanceof Error && 'code' in error
    ? (error as NodeJS.ErrnoException).code
    : undefined;
}

export async function withCinemaFileLock<T>(path: string, operation: () => Promise<T>): Promise<T> {
  const lockPath = `${path}.lock`;
  const deadline = Date.now() + 10_000;
  await mkdir(dirname(path), { recursive: true });
  let release: (() => Promise<void>) | null = null;
  while (!release) {
    try {
      const handle = await open(lockPath, 'wx');
      await handle.writeFile(JSON.stringify({ pid: process.pid, createdAt: new Date().toISOString() }));
      release = async () => {
        await handle.close();
        await rm(lockPath, { force: true });
      };
    } catch (error) {
      if (errnoCode(error) !== 'EEXIST') throw error;
      try {
        if (Date.now() - (await stat(lockPath)).mtimeMs > STALE_LOCK_MS) {
          const claimed = `${lockPath}.stale-${process.pid}-${Date.now()}`;
          try {
            await rename(lockPath, claimed);
            await rm(claimed, { force: true });
          } catch (claimError) {
            if (errnoCode(claimError) !== 'ENOENT') throw claimError;
          }
        }
      } catch (statError) {
        if (errnoCode(statError) !== 'ENOENT') throw statError;
      }
      if (Date.now() >= deadline) throw new Error(`timed out waiting for Cinema file lock: ${lockPath}`);
      await new Promise((resolve) => setTimeout(resolve, 20));
    }
  }
  try {
    return await operation();
  } finally {
    await release();
  }
}