'use strict';

const fs = require('fs').promises;
const path = require('path');
const crypto = require('crypto');

async function writeJsonAtomic(file, value, io = fs) {
  const folder = path.dirname(file), name = path.basename(file);
  const temp = path.join(folder, `.${name}.${crypto.randomUUID()}.tmp`);
  await io.writeFile(temp, JSON.stringify(value, null, 2) + '\n');
  try {
    try { await io.rename(temp, file); return; }
    catch (error) {
      if (!['EPERM', 'EACCES', 'EBUSY', 'EEXIST'].includes(error.code)) throw error;
    }
    // Windows may refuse rename-over-existing. Keep the old JSON recoverable
    // until the replacement is safely in place; never delete it first.
    const backup = path.join(folder, `.old-${name}-${crypto.randomUUID()}`);
    await io.rename(file, backup);
    try { await io.rename(temp, file); }
    catch (error) {
      try { await io.rename(backup, file); }
      catch (restoreError) { error.message += `; previous JSON remains at ${backup}: ${restoreError.message}`; }
      throw error;
    }
    await io.rm(backup, { force: true });
  } finally { await io.rm(temp, { force: true }); }
}

module.exports = { writeJsonAtomic };