import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_usb_serial/flutter_usb_serial.dart';

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

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

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  List<UsbSerialDevice> _devices = const [];
  String _status = 'Tap refresh to scan for attached USB serial devices.';
  bool _isLoading = false;

  @override
  void initState() {
    super.initState();
    unawaited(_refreshDevices());
  }

  Future<void> _refreshDevices() async {
    setState(() {
      _isLoading = true;
    });

    try {
      final devices = await FlutterUsbSerial.listDevices();
      if (!mounted) return;
      setState(() {
        _devices = devices;
        _status = devices.isEmpty
            ? 'No USB serial devices detected.'
            : 'Found ${devices.length} USB serial device(s).';
      });
    } on MissingPluginException {
      if (!mounted) return;
      setState(() {
        _devices = const [];
        _status = 'USB serial support is only available on Android.';
      });
    } on PlatformException catch (error) {
      if (!mounted) return;
      setState(() {
        _devices = const [];
        _status = error.message ?? 'Failed to list USB serial devices.';
      });
    } finally {
      if (mounted) {
        setState(() {
          _isLoading = false;
        });
      }
    }
  }

  Future<void> _requestPermission(UsbSerialDevice device) async {
    String status;
    try {
      final granted = await FlutterUsbSerial.requestPermission(device);
      status = granted
          ? 'Permission granted for device ${device.deviceId}.'
          : 'Permission denied for device ${device.deviceId}.';
    } on MissingPluginException {
      status = 'USB serial support is only available on Android.';
    } on PlatformException catch (error) {
      status = error.message ?? 'Failed to request USB permission.';
    }

    if (!mounted) return;
    setState(() {
      _status = status;
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('USB Serial Example'),
        ),
        body: SafeArea(
          child: Column(
            children: [
              Padding(
                padding: const EdgeInsets.all(16),
                child: Row(
                  children: [
                    Expanded(
                      child: Text(
                        _status,
                        key: const Key('status_text'),
                      ),
                    ),
                    const SizedBox(width: 12),
                    FilledButton.icon(
                      onPressed: _isLoading ? null : _refreshDevices,
                      icon: const Icon(Icons.refresh),
                      label: const Text('Refresh devices'),
                    ),
                  ],
                ),
              ),
              Expanded(
                child: _isLoading
                    ? const Center(child: CircularProgressIndicator())
                    : _devices.isEmpty
                        ? const Center(
                            child: Text('Connect an Android USB serial device to see it here.'),
                          )
                        : ListView.separated(
                            itemCount: _devices.length,
                            separatorBuilder: (_, __) => const Divider(height: 1),
                            itemBuilder: (context, index) {
                              final device = _devices[index];
                              return ListTile(
                                leading: const Icon(Icons.usb),
                                title: Text(
                                  device.deviceName.isEmpty
                                      ? 'USB device ${device.deviceId}'
                                      : device.deviceName,
                                ),
                                subtitle: Text(
                                  'VID 0x${device.vendorId.toRadixString(16).padLeft(4, '0')} '
                                  'PID 0x${device.productId.toRadixString(16).padLeft(4, '0')}\n'
                                  'Manufacturer: ${device.manufacturerName.isEmpty ? 'Unknown' : device.manufacturerName}',
                                ),
                                isThreeLine: true,
                                trailing: OutlinedButton(
                                  onPressed: () => _requestPermission(device),
                                  child: const Text('Request permission'),
                                ),
                              );
                            },
                          ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}