import 'package:flutter/material.dart';
import 'package:pointycastle/export.dart' as crypto;
import 'dart:math';
import 'dart:convert';
import 'dart:typed_data';
import 'package:asn1lib/asn1lib.dart';

class GenerationNouvellePaireClesPage extends StatelessWidget {
  const GenerationNouvellePaireClesPage({super.key});

  Future<Map<String, String>> _generateKeyPair() async {
    // key generation logic using pointycastle
    final keyParams = crypto.RSAKeyGeneratorParameters(
      BigInt.parse('65537'),
      2048,
      64,
    );

    final secureRandom = crypto.FortunaRandom();

    // Seed the random number generator
    final random = Random.secure();
    final seeds = List<int>.generate(32, (_) => random.nextInt(256));
    secureRandom.seed(crypto.KeyParameter(Uint8List.fromList(seeds)));

    final rngParams = crypto.ParametersWithRandom(keyParams, secureRandom);
    final keyGenerator = crypto.RSAKeyGenerator();
    keyGenerator.init(rngParams);

    final pair = keyGenerator.generateKeyPair();
    final publicKey = pair.publicKey as crypto.RSAPublicKey;
    final privateKey = pair.privateKey as crypto.RSAPrivateKey;

    // Convert keys to PEM format
    final publicKeyPem = _encodePublicKeyToPemPKCS1(publicKey);
    final privateKeyPem = _encodePrivateKeyToPemPKCS1(privateKey);

    // Save keys securely (not implemented here)

    return {'publicKey': publicKeyPem, 'privateKey': privateKeyPem};
  }

  String _encodePublicKeyToPemPKCS1(crypto.RSAPublicKey publicKey) {
    final bytes = _encodePublicKeyToDer(publicKey);
    return _formatPem(bytes, 'RSA PUBLIC KEY');
  }

  String _encodePrivateKeyToPemPKCS1(crypto.RSAPrivateKey privateKey) {
    final bytes = _encodePrivateKeyToDer(privateKey);
    return _formatPem(bytes, 'RSA PRIVATE KEY');
  }

  Uint8List _encodePublicKeyToDer(crypto.RSAPublicKey publicKey) {
    final algorithmSeq = ASN1Sequence();
    algorithmSeq.add(ASN1ObjectIdentifier.fromName('rsaEncryption'));
    algorithmSeq.add(ASN1Null());

    final publicKeySeq = ASN1Sequence();
    publicKeySeq.add(ASN1Integer(publicKey.modulus!));
    publicKeySeq.add(ASN1Integer(publicKey.exponent!));

    final publicKeyBitString = ASN1BitString(Uint8List.fromList(publicKeySeq.encodedBytes));

    final topLevelSeq = ASN1Sequence();
    topLevelSeq.add(algorithmSeq);
    topLevelSeq.add(publicKeyBitString);

    return Uint8List.fromList(topLevelSeq.encodedBytes);
  }

  Uint8List _encodePrivateKeyToDer(crypto.RSAPrivateKey privateKey) {
    final privateKeySeq = ASN1Sequence();
    privateKeySeq.add(ASN1Integer(BigInt.from(0))); // Version
    privateKeySeq.add(ASN1Integer(privateKey.n!));
    privateKeySeq.add(ASN1Integer(privateKey.exponent!));
    privateKeySeq.add(ASN1Integer(privateKey.d!));
    privateKeySeq.add(ASN1Integer(privateKey.p!));
    privateKeySeq.add(ASN1Integer(privateKey.q!));
    privateKeySeq.add(ASN1Integer(privateKey.d! % (privateKey.p! - BigInt.one)));
    privateKeySeq.add(ASN1Integer(privateKey.d! % (privateKey.q! - BigInt.one)));
    privateKeySeq.add(ASN1Integer(privateKey.q!.modInverse(privateKey.p!)));

    return Uint8List.fromList(privateKeySeq.encodedBytes);
  }

  String _formatPem(Uint8List bytes, String label) {
    final base64 = base64Encode(bytes);
    final chunks = RegExp('.{1,64}').allMatches(base64).map((m) => m.group(0)!);
    return '-----BEGIN $label-----\n${chunks.join('\n')}\n-----END $label-----';
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.black,
      appBar: AppBar(
        title: const Text('Génération d\'une Nouvelle Paire de Clés'),
      ),
      body: Center(
        child: ElevatedButton(
          onPressed: () async {
            final keys = await _generateKeyPair();
            // Display a confirmation dialog or message
            showDialog(
              context: context,
              builder: (context) => AlertDialog(
                title: const Text('Clés Générées'),
                content: const Text('La nouvelle paire de clés a été générée avec succès.'),
                actions: [
                  TextButton(
                    onPressed: () => Navigator.pop(context),
                    child: const Text('OK'),
                  ),
                ],
              ),
            );
          },
          child: const Text('Générer une Nouvelle Paire de Clés'),
        ),
      ),
    );
  }
}