import 'dart:typed_data';

import 'package:pointycastle/api.dart';
import 'package:pointycastle/src/impl/base_block_cipher.dart';
import 'package:pointycastle/src/registry/registry.dart';

class RC2Engine extends BaseBlockCipher {
  static final FactoryConfig factoryConfig =
      StaticFactoryConfig(BlockCipher, 'RC2', () => RC2Engine());

  static Uint8List piTable = Uint8List.fromList([
    0xd9,
    0x78,
    0xf9,
    0xc4,
    0x19,
    0xdd,
    0xb5,
    0xed,
    0x28,
    0xe9,
    0xfd,
    0x79,
    0x4a,
    0xa0,
    0xd8,
    0x9d,
    0xc6,
    0x7e,
    0x37,
    0x83,
    0x2b,
    0x76,
    0x53,
    0x8e,
    0x62,
    0x4c,
    0x64,
    0x88,
    0x44,
    0x8b,
    0xfb,
    0xa2,
    0x17,
    0x9a,
    0x59,
    0xf5,
    0x87,
    0xb3,
    0x4f,
    0x13,
    0x61,
    0x45,
    0x6d,
    0x8d,
    0x09,
    0x81,
    0x7d,
    0x32,
    0xbd,
    0x8f,
    0x40,
    0xeb,
    0x86,
    0xb7,
    0x7b,
    0x0b,
    0xf0,
    0x95,
    0x21,
    0x22,
    0x5c,
    0x6b,
    0x4e,
    0x82,
    0x54,
    0xd6,
    0x65,
    0x93,
    0xce,
    0x60,
    0xb2,
    0x1c,
    0x73,
    0x56,
    0xc0,
    0x14,
    0xa7,
    0x8c,
    0xf1,
    0xdc,
    0x12,
    0x75,
    0xca,
    0x1f,
    0x3b,
    0xbe,
    0xe4,
    0xd1,
    0x42,
    0x3d,
    0xd4,
    0x30,
    0xa3,
    0x3c,
    0xb6,
    0x26,
    0x6f,
    0xbf,
    0x0e,
    0xda,
    0x46,
    0x69,
    0x07,
    0x57,
    0x27,
    0xf2,
    0x1d,
    0x9b,
    0xbc,
    0x94,
    0x43,
    0x03,
    0xf8,
    0x11,
    0xc7,
    0xf6,
    0x90,
    0xef,
    0x3e,
    0xe7,
    0x06,
    0xc3,
    0xd5,
    0x2f,
    0xc8,
    0x66,
    0x1e,
    0xd7,
    0x08,
    0xe8,
    0xea,
    0xde,
    0x80,
    0x52,
    0xee,
    0xf7,
    0x84,
    0xaa,
    0x72,
    0xac,
    0x35,
    0x4d,
    0x6a,
    0x2a,
    0x96,
    0x1a,
    0xd2,
    0x71,
    0x5a,
    0x15,
    0x49,
    0x74,
    0x4b,
    0x9f,
    0xd0,
    0x5e,
    0x04,
    0x18,
    0xa4,
    0xec,
    0xc2,
    0xe0,
    0x41,
    0x6e,
    0x0f,
    0x51,
    0xcb,
    0xcc,
    0x24,
    0x91,
    0xaf,
    0x50,
    0xa1,
    0xf4,
    0x70,
    0x39,
    0x99,
    0x7c,
    0x3a,
    0x85,
    0x23,
    0xb8,
    0xb4,
    0x7a,
    0xfc,
    0x02,
    0x36,
    0x5b,
    0x25,
    0x55,
    0x97,
    0x31,
    0x2d,
    0x5d,
    0xfa,
    0x98,
    0xe3,
    0x8a,
    0x92,
    0xae,
    0x05,
    0xdf,
    0x29,
    0x10,
    0x67,
    0x6c,
    0xba,
    0xc9,
    0xd3,
    0x00,
    0xe6,
    0xcf,
    0xe1,
    0x9e,
    0xa8,
    0x2c,
    0x63,
    0x16,
    0x01,
    0x3f,
    0x58,
    0xe2,
    0x89,
    0xa9,
    0x0d,
    0x38,
    0x34,
    0x1b,
    0xab,
    0x33,
    0xff,
    0xb0,
    0xbb,
    0x48,
    0x0c,
    0x5f,
    0xb9,
    0xb1,
    0xcd,
    0x2e,
    0xc5,
    0xf3,
    0xdb,
    0x47,
    0xe5,
    0xa5,
    0x9c,
    0x77,
    0x0a,
    0xa6,
    0x20,
    0x68,
    0xfe,
    0x7f,
    0xc1,
    0xad
  ]);

  static const BLOCK_SIZE = 8;

  @override
  String get algorithmName => 'RC2';

  @override
  int get blockSize => BLOCK_SIZE;

  bool forEncryption = false;
  List<int>? workingKey;

  List<int> generateWorkingKey(Uint8List key, int bits) {
    int x;
    var xKey = List<int>.generate(128, (index) => 0);

    for (var i = 0; i != key.length; i++) {
      xKey[i] = key[i] & 0xff;
    }

    // Phase 1: Expand input key to 128 bytes
    var len = key.length;

    if (len < 128) {
      var index = 0;

      x = xKey[len - 1];

      do {
        x = piTable[(x + xKey[index++]) & 255] & 0xff;
        xKey[len++] = x;
      } while (len < 128);
    }

    // Phase 2 - reduce effective key size to "bits"
    len = (bits + 7) >> 3;
    x = piTable[xKey[128 - len] & (255 >> (7 & -bits))] & 0xff;
    xKey[128 - len] = x;

    for (var i = 128 - len - 1; i >= 0; i--) {
      x = piTable[x ^ xKey[i + len]] & 0xff;
      xKey[i] = x;
    }

    // Phase 3 - copy to newKey in little-endian order
    var newKey = List<int>.generate(64, (index) => 0);

    for (var i = 0; i != newKey.length; i++) {
      newKey[i] = xKey[2 * i] + (xKey[2 * i + 1] << 8);
    }

    return newKey;
  }

  @override
  void init(bool forEncryption, CipherParameters? params) {
    this.forEncryption = forEncryption;

    Uint8List key;
    if (params != null) {
      if (params is RC2Parameters) {
        workingKey = generateWorkingKey(params.key, params.effectiveKeyBits);
        key = params.key;
      } else if (params is KeyParameter) {
        key = params.key;
        workingKey = generateWorkingKey(key, key.length * 8);
      }
    }
  }

  @override
  Uint8List process(Uint8List data) {
    var out = Uint8List(blockSize);
    var len = processBlock(data, 0, out, 0);
    return out.sublist(0, len);
  }

  @override
  int processBlock(Uint8List input, int inputOff, Uint8List out, int outOff) {
    if (workingKey == null) {
      throw ArgumentError('RC2 engine not initialised');
    }

    if ((inputOff + BLOCK_SIZE) > input.length) {
      throw ArgumentError('input buffer too short');
    }

    if ((outOff + BLOCK_SIZE) > out.length) {
      throw ArgumentError('output buffer too short');
    }

    if (forEncryption) {
      encryptBlock(input, inputOff, out, outOff);
    } else {
      decryptBlock(input, inputOff, out, outOff);
    }

    return BLOCK_SIZE;
  }

  @override
  void reset() {}

  int rotateWordLeft(int x, int y) {
    x &= 0xffff;
    return (x << y) | (x >> (16 - y));
  }

  void encryptBlock(Uint8List input, int inOff, Uint8List out, int outOff) {
    int x76, x54, x32, x10;

    x76 = ((input[inOff + 7] & 0xff) << 8) + (input[inOff + 6] & 0xff);
    x54 = ((input[inOff + 5] & 0xff) << 8) + (input[inOff + 4] & 0xff);
    x32 = ((input[inOff + 3] & 0xff) << 8) + (input[inOff + 2] & 0xff);
    x10 = ((input[inOff + 1] & 0xff) << 8) + (input[inOff + 0] & 0xff);

    for (var i = 0; i <= 16; i += 4) {
      x10 =
          rotateWordLeft(x10 + (x32 & ~x76) + (x54 & x76) + workingKey![i], 1);
      x32 = rotateWordLeft(
          x32 + (x54 & ~x10) + (x76 & x10) + workingKey![i + 1], 2);
      x54 = rotateWordLeft(
          x54 + (x76 & ~x32) + (x10 & x32) + workingKey![i + 2], 3);
      x76 = rotateWordLeft(
          x76 + (x10 & ~x54) + (x32 & x54) + workingKey![i + 3], 5);
    }

    x10 += workingKey![x76 & 63];
    x32 += workingKey![x10 & 63];
    x54 += workingKey![x32 & 63];
    x76 += workingKey![x54 & 63];

    for (var i = 20; i <= 40; i += 4) {
      x10 =
          rotateWordLeft(x10 + (x32 & ~x76) + (x54 & x76) + workingKey![i], 1);
      x32 = rotateWordLeft(
          x32 + (x54 & ~x10) + (x76 & x10) + workingKey![i + 1], 2);
      x54 = rotateWordLeft(
          x54 + (x76 & ~x32) + (x10 & x32) + workingKey![i + 2], 3);
      x76 = rotateWordLeft(
          x76 + (x10 & ~x54) + (x32 & x54) + workingKey![i + 3], 5);
    }

    x10 += workingKey![x76 & 63];
    x32 += workingKey![x10 & 63];
    x54 += workingKey![x32 & 63];
    x76 += workingKey![x54 & 63];

    for (var i = 44; i < 64; i += 4) {
      x10 =
          rotateWordLeft(x10 + (x32 & ~x76) + (x54 & x76) + workingKey![i], 1);
      x32 = rotateWordLeft(
          x32 + (x54 & ~x10) + (x76 & x10) + workingKey![i + 1], 2);
      x54 = rotateWordLeft(
          x54 + (x76 & ~x32) + (x10 & x32) + workingKey![i + 2], 3);
      x76 = rotateWordLeft(
          x76 + (x10 & ~x54) + (x32 & x54) + workingKey![i + 3], 5);
    }

    out[outOff + 0] = x10;
    out[outOff + 1] = x10 >> 8;
    out[outOff + 2] = x32;
    out[outOff + 3] = x32 >> 8;
    out[outOff + 4] = x54;
    out[outOff + 5] = x54 >> 8;
    out[outOff + 6] = x76;
    out[outOff + 7] = x76 >> 8;
  }

  void decryptBlock(Uint8List input, int inOff, Uint8List out, int outOff) {
    int x76, x54, x32, x10;

    x76 = ((input[inOff + 7] & 0xff) << 8) + (input[inOff + 6] & 0xff);
    x54 = ((input[inOff + 5] & 0xff) << 8) + (input[inOff + 4] & 0xff);
    x32 = ((input[inOff + 3] & 0xff) << 8) + (input[inOff + 2] & 0xff);
    x10 = ((input[inOff + 1] & 0xff) << 8) + (input[inOff + 0] & 0xff);

    for (var i = 60; i >= 44; i -= 4) {
      x76 = rotateWordLeft(x76, 11) -
          ((x10 & ~x54) + (x32 & x54) + workingKey![i + 3]);
      x54 = rotateWordLeft(x54, 13) -
          ((x76 & ~x32) + (x10 & x32) + workingKey![i + 2]);
      x32 = rotateWordLeft(x32, 14) -
          ((x54 & ~x10) + (x76 & x10) + workingKey![i + 1]);
      x10 = rotateWordLeft(x10, 15) -
          ((x32 & ~x76) + (x54 & x76) + workingKey![i]);
    }

    x76 -= workingKey![x54 & 63];
    x54 -= workingKey![x32 & 63];
    x32 -= workingKey![x10 & 63];
    x10 -= workingKey![x76 & 63];

    for (var i = 40; i >= 20; i -= 4) {
      x76 = rotateWordLeft(x76, 11) -
          ((x10 & ~x54) + (x32 & x54) + workingKey![i + 3]);
      x54 = rotateWordLeft(x54, 13) -
          ((x76 & ~x32) + (x10 & x32) + workingKey![i + 2]);
      x32 = rotateWordLeft(x32, 14) -
          ((x54 & ~x10) + (x76 & x10) + workingKey![i + 1]);
      x10 = rotateWordLeft(x10, 15) -
          ((x32 & ~x76) + (x54 & x76) + workingKey![i]);
    }

    x76 -= workingKey![x54 & 63];
    x54 -= workingKey![x32 & 63];
    x32 -= workingKey![x10 & 63];
    x10 -= workingKey![x76 & 63];

    for (var i = 16; i >= 0; i -= 4) {
      x76 = rotateWordLeft(x76, 11) -
          ((x10 & ~x54) + (x32 & x54) + workingKey![i + 3]);
      x54 = rotateWordLeft(x54, 13) -
          ((x76 & ~x32) + (x10 & x32) + workingKey![i + 2]);
      x32 = rotateWordLeft(x32, 14) -
          ((x54 & ~x10) + (x76 & x10) + workingKey![i + 1]);
      x10 = rotateWordLeft(x10, 15) -
          ((x32 & ~x76) + (x54 & x76) + workingKey![i]);
    }

    out[outOff + 0] = x10;
    out[outOff + 1] = x10 >> 8;
    out[outOff + 2] = x32;
    out[outOff + 3] = x32 >> 8;
    out[outOff + 4] = x54;
    out[outOff + 5] = x54 >> 8;
    out[outOff + 6] = x76;
    out[outOff + 7] = x76 >> 8;
  }
}