import { test } from 'node:test'
import assert from 'node:assert/strict'
import { mkdtemp, readFile, readdir, writeFile as plainWrite, rm } from 'node:fs/promises'
import os from 'node:os'
import path from 'node:path'
import { writeFile } from '../server/atomic-write.js'

test('replaces file contents and leaves no temp files', async () => {
  const dir = await mkdtemp(path.join(os.tmpdir(), 'atomic-'))
  const file = path.join(dir, 'a.json')
  await plainWrite(file, 'old')
  await writeFile(file, '{"ok":true}', 'utf8')
  assert.equal(await readFile(file, 'utf8'), '{"ok":true}')
  assert.deepEqual(await readdir(dir), ['a.json'])
  await rm(dir, { recursive: true })
})

test('a failed write keeps the old file and cleans up', async () => {
  const dir = await mkdtemp(path.join(os.tmpdir(), 'atomic-'))
  const file = path.join(dir, 'a.json')
  await plainWrite(file, 'old')
  await assert.rejects(() => writeFile(file, { not: 'a string' }))
  assert.equal(await readFile(file, 'utf8'), 'old')
  assert.deepEqual(await readdir(dir), ['a.json'])
  await rm(dir, { recursive: true })
})