// Copyright (c) 2020
// Author: Hugo Pointcheval
import 'dart:async';
import 'dart:developer';
import 'dart:typed_data';

import 'package:flutter/services.dart';

class NativeCrypto {
  static const String _tag = 'fr.pointcheval.native_crypto';
  static const MethodChannel _channel =
      const MethodChannel('native.crypto.helper');

  /// Generates AES key.
  ///
  /// Size of **256 bits** by design.
  /// And returns `Uint8List`.
  Future<Uint8List> symKeygen() async {
    final Uint8List aesKey = await _channel.invokeMethod('symKeygen');

    log('AES Key Length: ${aesKey.length}', name: _tag);
    print('AES Key: $aesKey');

    return aesKey;
  }

  /// Encrypts passed data with a given AES key.
  ///
  /// Generates a random **IV**. Returns a list
  /// of `Uint8List` with encrypted cipher as first
  /// and IV as second member.
  Future<List<Uint8List>> symEncrypt(
      Uint8List payloadbytes, Uint8List aesKey) async {
    final List<Uint8List> encryptedPayload =
        await _channel.invokeListMethod('symEncrypt', <String, dynamic>{
      'payload': payloadbytes,
      'aesKey': aesKey,
    });

    log('Payload Length: ${payloadbytes.length}', name: _tag);
    log('Cipher Length: ${encryptedPayload.first.length}', name: _tag);
    print('Cipher: ${encryptedPayload.first}');
    log('IV Length: ${encryptedPayload.last.length}', name: _tag);
    print('IV: ${encryptedPayload.last}');

    return encryptedPayload;
  }

  /// Decrypts a passed payload with a given AES key.
  ///
  /// The payload must be a list of `Uint8List`
  /// with encrypted cipher as first and IV as second member.
  Future<Uint8List> symDecrypt(
      List<Uint8List> payloadbytes, Uint8List aesKey) async {
    final Uint8List decryptedPayload =
        await _channel.invokeMethod('symDecrypt', <String, dynamic>{
      'payload': payloadbytes,
      'aesKey': aesKey,
    });

    return decryptedPayload;
  }
}

class TypeHelper {
  /// Returns bytes `Uint8List` from a `String`.
  Uint8List stringToBytes(String source) {
    var list = source.codeUnits;
    var bytes = Uint8List.fromList(list);
    return bytes;
  }

  /// Returns a `String` from bytes `Uint8List`.
  String bytesToString(Uint8List bytes) {
    var string = String.fromCharCodes(bytes);
    return string;
  }
}