import { writeFile as fsWriteFile, rename, unlink } from 'node:fs/promises'
import { randomBytes } from 'node:crypto'

// Drop-in replacement for fs.promises.writeFile that never leaves a truncated
// file behind: the data goes to a sibling temp file which is then renamed over
// the target (atomic on the same filesystem). A crash mid-write leaves the
// previous version intact instead of a half-written JSON file.
export async function writeFile(file, data, options) {
  const tmp = `${file}.${process.pid}.${randomBytes(4).toString('hex')}.tmp`
  try {
    await fsWriteFile(tmp, data, options)
    await rename(tmp, file)
  } catch (err) {
    await unlink(tmp).catch(() => {})
    throw err
  }
}