import { execFile } from 'node:child_process'
import { mkdtemp, rm, writeFile } from 'node:fs/promises'
import { tmpdir } from 'node:os'
import path from 'node:path'
import { promisify } from 'node:util'
import { storedEntryData, type RarEntry } from './parse.js'

const run = promisify(execFile)

/** Tools that print one archive entry to stdout, tried in order. */
const EXTRACTORS: [string, (archive: string, entry: string) => string[]][] = [
  ['bsdtar', (archive, entry) => ['-xOf', archive, entry]],
  ['unrar', (archive, entry) => ['p', '-inul', '-p-', '--', archive, entry]],
]

/**
 * The unpacked data of one entry of a complete (single-volume) archive:
 * copied out when stored, else unpacked with bsdtar (libarchive, in the
 * Docker image) or unrar. Null when that is not possible.
 */
export async function extractEntry(
  archive: Buffer,
  entry: RarEntry,
  maxBytes = 64 * 1024 * 1024,
  warn: (message: string) => void = () => {}
): Promise<Buffer | null> {
  const stored = storedEntryData(archive, entry)
  if (stored) return stored
  if (entry.encrypted || entry.directory || entry.splitBefore || entry.splitAfter) return null
  if (entry.size !== null && entry.size > maxBytes) return null

  const dir = await mkdtemp(path.join(tmpdir(), 'rar-'))
  try {
    const file = path.join(dir, 'archive.rar')
    await writeFile(file, archive)
    for (const [tool, args] of EXTRACTORS) {
      try {
        const { stdout } = await run(tool, args(file, entry.name), { encoding: 'buffer', maxBuffer: maxBytes, timeout: 60_000 })
        if (stdout.length > 0) return stdout
      } catch (error: any) {
        if (error.code !== 'ENOENT') warn(`${tool} could not extract "${entry.name}": ${error.message}`)
      }
    }
    return null
  } finally {
    await rm(dir, { recursive: true, force: true })
  }
}