import { lstat, mkdir, mkdtemp, readFile, readdir, stat, symlink, writeFile } from 'node:fs/promises'
import { tmpdir } from 'node:os'
import { join } from 'node:path'
import { describe, expect, it } from 'vitest'
import { writeFileAtomic } from '../src/index.ts'

async function scratch(): Promise<string> {
  return mkdtemp(join(tmpdir(), 'dsh-atomic-write-'))
}

describe('writeFileAtomic', () => {
  it('creates the file and its parents with exactly the stated mode', async () => {
    const dir = await scratch()
    const target = join(dir, 'nested', 'deep', 'doc.yaml')
    await writeFileAtomic(target, 'a: 1\n', { mode: 0o600 })
    expect(await readFile(target, 'utf8')).toBe('a: 1\n')
    expect((await stat(target)).mode & 0o777).toBe(0o600)
  })

  it('replaces existing content and narrows a wider-permission file to the stated mode', async () => {
    const dir = await scratch()
    const target = join(dir, 'doc.yaml')
    await writeFile(target, 'old', { mode: 0o644 })
    await writeFileAtomic(target, 'new', { mode: 0o600 })
    expect(await readFile(target, 'utf8')).toBe('new')
    expect((await stat(target)).mode & 0o777).toBe(0o600)
  })

  it('replaces a symlinked target itself without writing through to the referent', async () => {
    const dir = await scratch()
    const victim = join(dir, 'victim')
    await writeFile(victim, 'victim-content')
    const target = join(dir, 'doc.yaml')
    await symlink(victim, target)
    await writeFileAtomic(target, 'replaced', { mode: 0o600 })
    expect((await lstat(target)).isSymbolicLink()).toBe(false)
    expect(await readFile(target, 'utf8')).toBe('replaced')
    expect(await readFile(victim, 'utf8')).toBe('victim-content')
  })

  it('leaves no temp sibling and rethrows when the rename fails', async () => {
    const dir = await scratch()
    const target = join(dir, 'occupied')
    await mkdir(target)
    await expect(writeFileAtomic(target, 'content', { mode: 0o600 })).rejects.toThrow()
    expect((await readdir(dir)).filter(entry => entry.includes('.tmp'))).toEqual([])
  })
})
