import 'dart:async';
import 'dart:io';
import '../models/server_profile.dart';

class ProbeResult {
  final List<String> addresses;
  final int tcpMs;
  // DNS lookup time and the address the TCP connection was made to.
  final int? dnsMs;
  final InternetAddress? connected;
  ProbeResult(this.addresses, this.tcpMs, {this.dnsMs, this.connected});
}

/// A probe that failed in a known stage, so the UI can say which test failed.
class ProbeFailure implements Exception {
  final String stage; // 'dns' or 'tcp'
  final Object cause;
  final List<String> addresses;
  final int? dnsMs;
  const ProbeFailure(
    this.stage,
    this.cause, {
    this.addresses = const [],
    this.dnsMs,
  });
  @override
  String toString() => 'ProbeFailure($stage, $cause)';
}

class Diagnostics {
  Future<ProbeResult> probe(
    String host,
    int port, {
    InternetAddressType type = InternetAddressType.any,
  }) async {
    normalizeHost(host);
    final dnsWatch = Stopwatch()..start();
    final List<InternetAddress> addresses;
    try {
      addresses = await InternetAddress.lookup(
        host,
        type: type,
      ).timeout(const Duration(seconds: 10));
    } catch (e) {
      throw ProbeFailure('dns', e);
    }
    final dnsMs = dnsWatch.elapsedMilliseconds;
    final names = addresses.map((a) => a.address).toList();
    final deadline = DateTime.now().add(const Duration(seconds: 10));
    Object lastError = const SocketException('No address for requested family');
    for (final address in addresses) {
      final remaining = deadline.difference(DateTime.now());
      if (remaining <= Duration.zero) {
        throw ProbeFailure(
          'tcp',
          TimeoutException('TCP'),
          addresses: names,
          dnsMs: dnsMs,
        );
      }
      final watch = Stopwatch()..start();
      try {
        final socket = await Socket.connect(address, port, timeout: remaining);
        socket.destroy();
        return ProbeResult(
          names,
          watch.elapsedMilliseconds,
          dnsMs: dnsMs,
          connected: address,
        );
      } catch (e) {
        lastError = e;
      }
    }
    throw ProbeFailure('tcp', lastError, addresses: names, dnsMs: dnsMs);
  }
}