tools/lib/services/scanner.dart

import 'dart:async';
import 'dart:io';

import 'package:tools/models/device.dart';

int _ipToInt(String ip) {
  final parts = ip.split('.').map(int.parse).toList();
  return (parts[0] << 24) | (parts[1] << 16) | (parts[2] << 8) | parts[3];
}

String _intToIp(int value) {
  return '${(value >> 24) & 0xFF}.'
      '${(value >> 16) & 0xFF}.'
      '${(value >> 8) & 0xFF}.'
      '${value & 0xFF}';
}

Future<bool> _isHostAlive(
  String ip, {
  int port = 80,
  int timeoutMs = 300,
}) async {
  try {
    final socket = await Socket.connect(
      ip,
      port,
      timeout: Duration(milliseconds: timeoutMs),
    );
    await socket.close();
    return true;
  } catch (_) {
    return false;
  }
}

Future<bool> isHostAlive(String ip, {int port = 22, int timeoutMs = 500}) {
  return _isHostAlive(ip, port: port, timeoutMs: timeoutMs);
}

Future<Map<String, bool>> scanSelectedDevicesOnline(
  List<Device> devices, {
  int port = 22,
  int timeoutMs = 500,
}) async {
  final futures = <Future<MapEntry<String, bool>>>[];
  for (final device in devices) {
    futures.add(
      isHostAlive(
        device.address,
        port: port,
        timeoutMs: timeoutMs,
      ).then((isOnline) => MapEntry(device.address, isOnline)),
    );
  }

  final entries = await Future.wait(futures);
  return Map<String, bool>.fromEntries(entries);
}

String? _extractMac(String source) {
  final lladdrMatch = RegExp(
    r'lladdr\s+([0-9a-fA-F]{2}(?::[0-9a-fA-F]{2}){5})',
    caseSensitive: false,
  ).firstMatch(source);
  if (lladdrMatch != null) {
    return lladdrMatch.group(1)?.toLowerCase();
  }

  final genericMatch = RegExp(
    r'([0-9a-fA-F]{2}(?::[0-9a-fA-F]{2}){5})',
    caseSensitive: false,
  ).firstMatch(source);
  return genericMatch?.group(1)?.toLowerCase();
}

Future<String?> _resolveMacAddress(String ip) async {
  try {
    final ipResult = await Process.run('ip', ['neigh', 'show', ip]);
    final ipOutput = '${ipResult.stdout}\n${ipResult.stderr}';
    final ipMac = _extractMac(ipOutput);
    if (ipMac != null) {
      return ipMac;
    }
  } catch (_) {
    // ignore and fallback
  }

  try {
    final arpResult = await Process.run('arp', ['-n', ip]);
    final arpOutput = '${arpResult.stdout}\n${arpResult.stderr}';
    return _extractMac(arpOutput);
  } catch (_) {
    return null;
  }
}

Future<Device?> _scanHost(
  String host, {
  required bool Function() isCancelled,
}) async {
  if (isCancelled()) {
    return null;
  }

  final isAlive = await _isHostAlive(host, port: 80);
  if (!isAlive || isCancelled()) {
    return null;
  }

  final mac = await _resolveMacAddress(host);

  return Device(address: host, mac: mac ?? '');
}

Future<void> scanSubnet(
  String net,
  String mask,
  StreamController<Device> controller, {
  bool Function()? isCancelled,
  int maxConcurrent = 64,
}) async {
  final shouldCancel = isCancelled ?? () => false;
  final ipInt = _ipToInt(net);
  final maskInt = _ipToInt(mask);

  final network = ipInt & maskInt;
  final broadcast = network | (~maskInt & 0xFFFFFFFF);

  if (maxConcurrent < 1) {
    maxConcurrent = 1;
  }

  for (int start = network + 1; start < broadcast; start += maxConcurrent) {
    if (shouldCancel()) {
      return;
    }

    final end = (start + maxConcurrent) < broadcast
        ? (start + maxConcurrent)
        : broadcast;

    final futures = <Future<Device?>>[];
    for (int addr = start; addr < end; addr++) {
      futures.add(_scanHost(_intToIp(addr), isCancelled: shouldCancel));
    }

    final foundDevices = await Future.wait(futures);
    for (final device in foundDevices) {
      if (device == null || shouldCancel() || controller.isClosed) {
        continue;
      }
      controller.add(device);
    }
  }
}