import 'dart:convert';
import 'dart:io';

import 'package:sqlite3/sqlite3.dart';

const seedLinks = [
  'vless://adbb9513-991a-4d64-9b30-1bf2283e7ed8@93.77.185.114:444?security=reality&encryption=none&pbk=M_VX89rLtCxGh45cRzXITGBgV3HTxW5c2zOEvqHFbSs&headerType=none&fp=random&spx=%2F&type=tcp&sni=www.apple.com&sid=f33f#6uuknvqv',
  'vless://833a8f71-2b99-4e69-b39a-6d242c82fabb@147.45.145.102:444?security=reality&encryption=none&pbk=jQ7nhZoFKsFAwl8lhR4g5rBl_PT_-BA_lQmt1kG3EAs&headerType=&fp=random&spx=%2F&type=tcp&sni=ya.ru&sid=5a#vless_1-zxdrfypi4',
];

Future<void> main() async {
  final db = _initDatabase();

  ProcessSignal.sigint.watch().listen((_) {
    db.dispose();
    exit(0);
  });

  final server = await HttpServer.bind(InternetAddress.anyIPv4, 8080);
  print('Server started on http://${server.address.address}:${server.port}');

  await for (final request in server) {
    final isConnectionsRoute = request.uri.path == '/connections';

    if (!isConnectionsRoute) {
      request.response
        ..statusCode = HttpStatus.notFound
        ..write('Not Found');
      await request.response.close();
      continue;
    }

    if (request.method == 'GET') {
      final result = db.select('SELECT url FROM connections ORDER BY id ASC');
      final links = result.map((row) => row['url'] as String).toList();

      request.response
        ..statusCode = HttpStatus.ok
        ..headers.contentType = ContentType.json
        ..write(jsonEncode({'links': links}));
      await request.response.close();
      continue;
    }

    if (request.method == 'POST') {
      await _handleCreateConnection(request, db);
      continue;
    }

    if (request.method == 'DELETE') {
      await _handleDeleteConnection(request, db);
      continue;
    }

    request.response
      ..statusCode = HttpStatus.methodNotAllowed
      ..headers.set(HttpHeaders.allowHeader, 'GET, POST, DELETE')
      ..headers.contentType = ContentType.json
      ..write(jsonEncode({'error': 'Method Not Allowed'}));
    await request.response.close();
  }
}

Database _initDatabase() {
  final dataDir = Directory('data');
  if (!dataDir.existsSync()) {
    dataDir.createSync(recursive: true);
  }

  final db = sqlite3.open('data/vpn_links.db');
  db.execute('''
    CREATE TABLE IF NOT EXISTS connections (
      id INTEGER PRIMARY KEY AUTOINCREMENT,
      url TEXT NOT NULL UNIQUE,
      created_at TEXT NOT NULL
    )
  ''');

  final insert = db.prepare(
    'INSERT OR IGNORE INTO connections(url, created_at) VALUES (?, ?)',
  );
  final createdAt = DateTime.now().toUtc().toIso8601String();
  for (final link in seedLinks) {
    insert.execute([link, createdAt]);
  }
  insert.dispose();

  return db;
}

Future<void> _handleCreateConnection(HttpRequest request, Database db) async {
  final body = await utf8.decoder.bind(request).join();
  final url = _extractUrl(body);

  if (url == null) {
    request.response
      ..statusCode = HttpStatus.badRequest
      ..headers.contentType = ContentType.json
      ..write(jsonEncode({'error': 'Body must be JSON: {"url": "..."}'}));
    await request.response.close();
    return;
  }

  try {
    db.execute(
      'INSERT INTO connections(url, created_at) VALUES (?, ?)',
      [url, DateTime.now().toUtc().toIso8601String()],
    );

    request.response
      ..statusCode = HttpStatus.created
      ..headers.contentType = ContentType.json
      ..write(jsonEncode({'message': 'Link added'}));
    await request.response.close();
  } on SqliteException catch (e) {
    if (e.extendedResultCode == 2067) {
      request.response
        ..statusCode = HttpStatus.conflict
        ..headers.contentType = ContentType.json
        ..write(jsonEncode({'error': 'Link already exists'}));
      await request.response.close();
      return;
    }

    request.response
      ..statusCode = HttpStatus.internalServerError
      ..headers.contentType = ContentType.json
      ..write(jsonEncode({'error': 'Database error'}));
    await request.response.close();
  }
}

Future<void> _handleDeleteConnection(HttpRequest request, Database db) async {
  final body = await utf8.decoder.bind(request).join();
  final url = _extractUrl(body);

  if (url == null) {
    request.response
      ..statusCode = HttpStatus.badRequest
      ..headers.contentType = ContentType.json
      ..write(jsonEncode({'error': 'Body must be JSON: {"url": "..."}'}));
    await request.response.close();
    return;
  }

  final delete = db.prepare('DELETE FROM connections WHERE url = ?');
  delete.execute([url]);
  final changes = db.updatedRows;
  delete.dispose();

  if (changes == 0) {
    request.response
      ..statusCode = HttpStatus.notFound
      ..headers.contentType = ContentType.json
      ..write(jsonEncode({'error': 'Link not found'}));
    await request.response.close();
    return;
  }

  request.response
    ..statusCode = HttpStatus.ok
    ..headers.contentType = ContentType.json
    ..write(jsonEncode({'message': 'Link deleted'}));
  await request.response.close();
}

String? _extractUrl(String body) {
  try {
    final json = jsonDecode(body);
    if (json is! Map<String, dynamic>) {
      return null;
    }

    final url = json['url'];
    if (url is! String || url.trim().isEmpty) {
      return null;
    }

    return url.trim();
  } catch (_) {
    return null;
  }
}