import { test } from '@japa/runner'
import { createHash } from 'node:crypto'
import { isPar2, parsePar2 } from '#lib/par2/index'

const md5 = (data: Buffer) => createHash('md5').update(data).digest()

/** Builds one PAR2 packet with a valid checksum. */
function packet(setId: Buffer, type: string, body: Buffer) {
  const padded = Buffer.concat([body, Buffer.alloc((4 - (body.length % 4)) % 4)])
  const length = Buffer.alloc(8)
  length.writeBigUInt64LE(BigInt(64 + padded.length))
  const typeBuf = Buffer.alloc(16)
  typeBuf.write(type, 'latin1')
  const hashed = Buffer.concat([setId, typeBuf, padded])
  return Buffer.concat([Buffer.from('PAR2\0PKT', 'latin1'), length, md5(hashed), hashed])
}

function fileDesc(setId: Buffer, name: string, size: number) {
  const len = Buffer.alloc(8)
  len.writeBigUInt64LE(BigInt(size))
  const md5_16k = md5(Buffer.from(`${name}-16k`))
  const fileId = md5(Buffer.concat([md5_16k, len, Buffer.from(name)]))
  const body = Buffer.concat([fileId, md5(Buffer.from(name)), md5_16k, len, Buffer.from(name, 'utf8')])
  return packet(setId, 'PAR 2.0\0FileDesc', body)
}

test.group('par2 / parsePar2', () => {
  const setId = Buffer.alloc(16, 7)

  test('reads file names and sizes from FileDesc packets', ({ assert }) => {
    const data = Buffer.concat([
      packet(setId, 'PAR 2.0\0Main', Buffer.alloc(12)),
      fileDesc(setId, 'Some.Movie.2024.part01.rar', 104857600),
      fileDesc(setId, 'Some.Movie.2024.part02.rar', 52428800),
      fileDesc(setId, 'Some.Movie.2024.part01.rar', 104857600), // duplicates are common
    ])
    assert.isTrue(isPar2(data))
    const set = parsePar2(data)!
    assert.equal(set.recoverySetId, setId.toString('hex'))
    assert.deepEqual(
      set.files.map((f) => [f.name, f.length]),
      [
        ['Some.Movie.2024.part01.rar', 104857600],
        ['Some.Movie.2024.part02.rar', 52428800],
      ]
    )
  })

  test('skips corrupted packets and resumes at the next one', ({ assert }) => {
    const bad = fileDesc(setId, 'bad.bin', 1)
    bad[100] ^= 0xff
    const data = Buffer.concat([bad, fileDesc(setId, 'good.bin', 12345)])
    assert.deepEqual(parsePar2(data)!.files.map((f) => f.name), ['good.bin'])
  })

  test('returns null for non-par2 data', ({ assert }) => {
    assert.isFalse(isPar2(Buffer.from('Rar!\x1a\x07\x00', 'latin1')))
    assert.isNull(parsePar2(Buffer.from('hello world')))
  })
})