import 'dart:math';
import 'dart:typed_data';

import 'package:nanga_kathai/offline/song_cipher.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  test('decrypting any range after a seek returns the original bytes', () {
    final r = Random(1);
    final plain = Uint8List.fromList(List.generate(100000, (_) => r.nextInt(256)));
    final cipher = SongCipher(SongCipher.newKey());
    final nonce = SongCipher.newNonce();

    // Encrypt in uneven chunks, the way a download arrives.
    final enc = Uint8List.fromList(plain);
    for (var off = 0; off < enc.length; off += 7777) {
      final end = min(off + 7777, enc.length);
      final part = Uint8List.sublistView(enc, off, end);
      cipher.apply(part, off, nonce);
    }
    expect(enc, isNot(equals(plain)));

    for (final (start, end) in [(0, 100000), (5, 21), (16, 32), (99990, 100000), (12345, 67891)]) {
      final chunk = Uint8List.fromList(enc.sublist(start, end));
      cipher.apply(chunk, start, nonce);
      expect(chunk, equals(plain.sublist(start, end)), reason: 'range $start-$end');
    }
  });

  test('a different key cannot decrypt', () {
    final plain = Uint8List.fromList(List.generate(64, (i) => i));
    final nonce = SongCipher.newNonce();
    final enc = Uint8List.fromList(plain);
    SongCipher(SongCipher.newKey()).apply(enc, 0, nonce);
    SongCipher(SongCipher.newKey()).apply(enc, 0, nonce);
    expect(enc, isNot(equals(plain)));
  });
}