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

import 'package:pointycastle/export.dart';

class EncryptedVideoPayload {
  final Uint8List encryptedFileBytes;
  final String contentId;
  final String contentKeyHex;
  final String encryptedFileName;

  EncryptedVideoPayload({
    required this.encryptedFileBytes,
    required this.contentId,
    required this.contentKeyHex,
    required this.encryptedFileName,
  });
}

Future<EncryptedVideoPayload> encryptVideoForUpload(
  Uint8List sourceBytes,
) async {
  final random = Random.secure();
  final keyBytes = Uint8List.fromList(
    List<int>.generate(16, (_) => random.nextInt(256)),
  );
  final nonceBytes = Uint8List.fromList(
    List<int>.generate(8, (_) => random.nextInt(256)),
  );

  final contentId = _generateUuidV4(random);
  final contentIdBytes = _uuidToBytes(contentId);
  final contentKeyHex = _bytesToHex(keyBytes);

  final counterBlock = Uint8List(16);
  counterBlock.setRange(0, nonceBytes.length, nonceBytes);

  final cipher = CTRStreamCipher(AESEngine())
    ..init(
      true,
      ParametersWithIV<KeyParameter>(KeyParameter(keyBytes), counterBlock),
    );
  final encryptedData = cipher.process(sourceBytes);

  final magic = Uint8List.fromList('MYPLR1'.codeUnits);
  const version = 1;
  final headerSize = magic.length + 1 + contentIdBytes.length + nonceBytes.length;
  final finalBytes = Uint8List(headerSize + encryptedData.length);

  var offset = 0;
  finalBytes.setRange(offset, offset + magic.length, magic);
  offset += magic.length;
  finalBytes[offset] = version;
  offset += 1;
  finalBytes.setRange(offset, offset + contentIdBytes.length, contentIdBytes);
  offset += contentIdBytes.length;
  finalBytes.setRange(offset, offset + nonceBytes.length, nonceBytes);
  offset += nonceBytes.length;
  finalBytes.setRange(offset, offset + encryptedData.length, encryptedData);

  return EncryptedVideoPayload(
    encryptedFileBytes: finalBytes,
    contentId: contentId,
    contentKeyHex: contentKeyHex,
    encryptedFileName: '$contentId.spot',
  );
}

String _bytesToHex(Uint8List bytes) {
  final buffer = StringBuffer();
  for (final byte in bytes) {
    buffer.write(byte.toRadixString(16).padLeft(2, '0'));
  }
  return buffer.toString();
}

Uint8List _uuidToBytes(String uuid) {
  final hex = uuid.replaceAll('-', '');
  final output = Uint8List(16);
  for (var i = 0; i < 16; i++) {
    output[i] = int.parse(hex.substring(i * 2, i * 2 + 2), radix: 16);
  }
  return output;
}

String _generateUuidV4(Random random) {
  final bytes = List<int>.generate(16, (_) => random.nextInt(256));
  bytes[6] = (bytes[6] & 0x0f) | 0x40;
  bytes[8] = (bytes[8] & 0x3f) | 0x80;

  final hex = bytes
      .map((b) => b.toRadixString(16).padLeft(2, '0'))
      .join();
  return '${hex.substring(0, 8)}-'
      '${hex.substring(8, 12)}-'
      '${hex.substring(12, 16)}-'
      '${hex.substring(16, 20)}-'
      '${hex.substring(20, 32)}';
}