import 'package:crypto/crypto.dart';
import 'dart:convert';

class Sha1Encryptor {
  /// This method will change the List<int> into a Big Int.
  /// I did not write this myself
  ///
  /// Source: https://github.com/PointyCastle/pointycastle/blob/master/lib/src/utils.dart
  BigInt _decodeBigInt(List<int> bytes) {
    var result = BigInt.from(0);
    for (var i = 0; i < bytes.length; i++) {
      result += BigInt.from(bytes[bytes.length - i - 1]) << (8 * i);
    }
    return result;
  }

  String _removeFirstZeros(String str) {
    var split = str.split('');

    for (var i = 0; i < split.length; i++) {
      if (split[i] == '0') {
        str = str.replaceFirst('0', '');
      } else {
        if(i >1){
          print('wtf : ' + i.toString());
        }
        break;
      }
    }
    return str;
  }

  String getEncrypted(String str) {
    //First we convert the string into bytes (UTF-8) and then encrypt them with the SHA-1 algrorithm.
    var digest = sha1.convert(utf8.encode(str));

    //If the first byte is smaller than 128, it should be seen as a negative number.
    if (digest.bytes[0] < 128) {
      return _removeFirstZeros(digest.toString());
    }

    //We turn the result from the encryption into a big int.
    var bytesAsBigInt = _decodeBigInt(digest.bytes);

    //As we want to perform two's complement, we first have to turn the big int into bits and then changing
    //all the 0's to 1's and the other way around.
    var bytesReversed = bytesAsBigInt
        .toRadixString(2)
        .replaceAll('0', '2')
        .replaceAll('1', '0')
        .replaceAll('2', '1');

    //Since we need to add 1 to the bit series (two's complement), we will split each bit from eachother into a List.
    var split = bytesReversed.split('');

    //We will loop through every bit in the list to make sure we correctly add the bit.
    //The is a very small chance of carry overloading, but the chance is too small to care about it.
    //A better developer would've looked into that.
    var addedOne = '';
    var carry = true;
    for (var i = split.length - 1; i >= 0; i--) {
      var char = split[i];

      if (carry) {
        if (char == '0') {
          char = '1';
          carry = false;
        } else {
          //Keep the carry
          char = '0';
        }
      }
      addedOne = (char + addedOne);
    }

//Return the bit series as HEX values
    return '-' +
        _removeFirstZeros(BigInt.parse(addedOne, radix: 2).toRadixString(16));
  }

    String getServerHash(String serverID, List PublicKey, List SecretKey)
        {



            byte[] hash = digest(new byte[][] {  Encoding.GetEncoding("iso-8859-1").GetBytes(serverID), SecretKey, PublicKey });
            bool negative = (hash[0] & 0x80) == 0x80;
            if (negative) { hash = TwosComplementLittleEndian(hash); }
            string result = GetHexString(hash).TrimStart('0');
            if (negative) { result = "-" + result; }
            return result;
        }

}