import 'dart:convert';

import 'package:dartssh2/dartssh2.dart';
import 'package:flutter/material.dart';

// for ed2219 key generation
import 'package:cryptography/cryptography.dart';
import 'package:flutter/services.dart';

// secret storage
import 'package:flutter_secure_storage/flutter_secure_storage.dart';

void main() {
  runApp(const MyApp());
}

Future<OpenSSHEd25519KeyPair> generateKeyPair() async {
  final algorithm = Ed25519();

  // Generate a key pair
  final cryptographyKeyPair = await algorithm.newKeyPair();

  final privateKey = await cryptographyKeyPair.extractPrivateKeyBytes();
  final publicKey = (await cryptographyKeyPair.extractPublicKey()).bytes;

  final dartsshKeyPair = OpenSSHEd25519KeyPair(
    Uint8List.fromList(publicKey),
    Uint8List.fromList(privateKey + publicKey),
    "",
  );

  return dartsshKeyPair;
}

String encodePublicKey(OpenSSHEd25519KeyPair keyPair, {String comment = ''}) {
  final publicKeyBytes = keyPair.toPublicKey().encode();
  return "ssh-ed25519 ${base64.encode(publicKeyBytes)} $comment";
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
      ),
      home: const MyHomePage(title: 'LeineLab e.V. Key App'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int navIndex = 0;
  OpenSSHEd25519KeyPair? keyPair;
  String _output = '';
  String key = '';
  Future<void> doSSH() async {
    SSHSocket? socket;

    try {
      socket = await SSHSocket.connect(
        '192.168.2.123',
        22,
        timeout: const Duration(seconds: 0, milliseconds: 500),
      );

      final client = SSHClient(
        socket,
        username: 'test',
        identities: List.of(keyPair != null ? [keyPair!] : []),
      );

      final uptime = await client.run('uptime');
      setState(() {
        _output = utf8.decode(uptime);
      });
    } catch (e) {
      setState(() {
        _output = "Error: $e";
      });
      return;
    }
  }

  Future<void> obtainKeyPair({bool regenerate = false}) async {
    // Generate a key pair

    final storage = const FlutterSecureStorage();
    final storedKey = await storage.read(key: 'ssh_key_pair');

    // Restore the key if we have one stored and regeneration is not requested
    if (storedKey != null && !regenerate) {
      // If we have a stored key, use it
      final keyPairsFromStorage = SSHKeyPair.fromPem(storedKey);
      assert(keyPairsFromStorage.length == 1);
      assert(keyPairsFromStorage[0] is OpenSSHEd25519KeyPair);

      final keyPairFromStorage =
          keyPairsFromStorage[0] as OpenSSHEd25519KeyPair;

      setState(() {
        keyPair = keyPairFromStorage;
        key = encodePublicKey(keyPairFromStorage, comment: "leinelab-app-key");
      });
      return;
    }

    final generatedKeyPair =
        await generateKeyPair(); // local variable avoids downcast to ? ptr

    await storage.write(key: 'ssh_key_pair', value: generatedKeyPair.toPem());

    setState(() {
      keyPair = generatedKeyPair;
      key = encodePublicKey(generatedKeyPair, comment: "leinelab-app-key");
    });

    await SystemChannels.platform.invokeMethod<void>(
      'Clipboard.setData',
      <String, dynamic>{'text': key},
    );
  }

  @override
  void initState() {
    super.initState();

    // we do not await generateKey() here, as this is the intended way
    obtainKeyPair();
  }

  @override
  Widget build(BuildContext context) {
    final String outputText = _output.isNotEmpty
        ? 'Output: $_output'
        : 'Press the button to run a command.';

    final bodyComponentMain = Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Text('Current output:'),
          Text(outputText, style: Theme.of(context).textTheme.headlineMedium),
        ],
      ),
    );

    final bodyComponentInfo = Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[Center(child: Text('Info\n\n$key'))],
      ),
    );

    final actionButtonMain = FloatingActionButton(
      onPressed: doSSH,
      tooltip: 'Do SSH',
      child: const Icon(Icons.computer),
    );

    final actionButtonInfo = FloatingActionButton(
      onPressed: () => obtainKeyPair(regenerate: true),
      tooltip: 'Regenerate Key',
      child: const Icon(Icons.refresh),
    );

    var bodyComponent = bodyComponentMain;
    var actionButton = actionButtonMain;

    if (navIndex == 0) {
      // Main page
      bodyComponent = bodyComponentMain;
      actionButton = actionButtonMain;
    } else if (navIndex == 1) {
      // Info page
      bodyComponent = bodyComponentInfo;
      actionButton = actionButtonInfo;
    } else {
      throw Exception('Unknown navIndex: $navIndex');
    }

    return Scaffold(
      appBar: AppBar(backgroundColor: Colors.amber, title: Text(widget.title)),
      body: bodyComponent,
      floatingActionButton: actionButton,
      drawer: Drawer(
        child: ListView(
          padding: EdgeInsets.zero,
          children: <Widget>[
            DrawerHeader(
              decoration: BoxDecoration(color: Colors.amber),
              child: Text(
                widget.title,
                style: TextStyle(color: Colors.black, fontSize: 24),
              ),
            ),
            ListTile(
              title: const Text('Main Page'),
              onTap: () {
                setState(() {
                  navIndex = 0;
                });
                Navigator.pop(context);
              },
            ),
            ListTile(
              title: const Text('Info Page'),
              onTap: () {
                setState(() {
                  navIndex = 1;
                });
                Navigator.pop(context);
              },
            ),
          ],
        ),
      ),
    );
  }
}