import { randomUUID } from 'node:crypto';
import { chmod, link, mkdir, readFile, rename, rm, writeFile } from 'node:fs/promises';
import { dirname } from 'node:path';
import { canonicalJson } from '../control-plane/snapshots.ts';

export async function readJson<T>(path: string): Promise<T | null> {
  try { return JSON.parse(await readFile(path, 'utf8')) as T; }
  catch (error) { if ((error as NodeJS.ErrnoException).code === 'ENOENT') return null; throw error; }
}

export async function atomicJson(path: string, value: unknown) {
  await mkdir(dirname(path), { recursive: true, mode: 0o700 });
  const temporary = `${path}.${randomUUID()}.tmp`;
  await writeFile(temporary, `${canonicalJson(value)}\n`, { encoding: 'utf8', mode: 0o600 });
  await chmod(temporary, 0o600);
  await rename(temporary, path);
}

export async function immutableJson(path: string, value: unknown) {
  await mkdir(dirname(path), { recursive: true, mode: 0o700 });
  const temporary = `${path}.${randomUUID()}.tmp`;
  await writeFile(temporary, `${canonicalJson(value)}\n`, { encoding: 'utf8', mode: 0o600 });
  await chmod(temporary, 0o600);
  try { await link(temporary, path); }
  catch (error) {
    if ((error as NodeJS.ErrnoException).code !== 'EEXIST') throw error;
    await rm(temporary, { force: true });
    return false;
  }
  await rm(temporary, { force: true });
  return true;
}