import 'dart:async';

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

import '../../core/theme/app_colors.dart';
import '../../core/widgets/app_icon.dart';
import '../../data/models/bluetooth_device_info.dart';
import '../../data/models/bluetooth_power_state.dart';
import '../home/obd_controller.dart';

/// Settings card for the optional Bluetooth Classic ELM327 adapter only.
class ObdSettingsCard extends StatefulWidget {
  const ObdSettingsCard({super.key});

  @override
  State<ObdSettingsCard> createState() => _ObdSettingsCardState();
}

class _ObdSettingsCardState extends State<ObdSettingsCard>
    with WidgetsBindingObserver {
  bool _showAllDevices = false;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!mounted) return;
      unawaited(
        context.read<ObdController>().refreshDevices(
          requestPermission: false,
          force: true,
        ),
      );
    });
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state != AppLifecycleState.resumed || !mounted) return;
    // The controller performs a cheap power-state check. It only lists bonded
    // devices again when the cached list is missing, so returning from Android
    // Settings does not hit the Bluetooth stack with a bond query every time.
    unawaited(context.read<ObdController>().refreshDevices(dueToResume: true));
  }

  @override
  Widget build(BuildContext context) {
    final colors = context.colors;
    final theme = Theme.of(context);
    final obd = context.watch<ObdController>();

    final selected = obd.selectedAddress;
    final options = <BluetoothDeviceInfo>[
      ...obd.obdDevices,
      if (_showAllDevices) ...obd.otherDevices,
    ];
    if (selected != null && !options.any((d) => d.address == selected)) {
      options.add(
        BluetoothDeviceInfo(name: 'Saved adapter', address: selected),
      );
    }
    final selectedInOptions = options.any((d) => d.address == selected);
    final dropdownValue = selectedInOptions ? selected : null;

    final statusColor = obd.connected
        ? colors.accent
        : obd.error != null || obd.bluetoothState == BluetoothPowerState.unknown
        ? colors.danger
        : colors.inkFaint;

    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Row(
          children: [
            Container(
              width: 42,
              height: 42,
              decoration: BoxDecoration(
                color: colors.accentSoft,
                borderRadius: BorderRadius.circular(14),
              ),
              alignment: Alignment.center,
              child: AppIcon(
                'assets/icons/car.svg',
                size: 20,
                color: colors.accent,
              ),
            ),
            const SizedBox(width: 14),
            Expanded(
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text('OBD-II adapter', style: theme.textTheme.titleMedium),
                  const SizedBox(height: 2),
                  Row(
                    children: [
                      Container(
                        width: 7,
                        height: 7,
                        decoration: BoxDecoration(
                          color: statusColor,
                          shape: BoxShape.circle,
                        ),
                      ),
                      const SizedBox(width: 7),
                      Expanded(
                        child: Text(
                          obd.statusLabel,
                          maxLines: 1,
                          overflow: TextOverflow.ellipsis,
                          style: theme.textTheme.bodySmall?.copyWith(
                            color: colors.inkMuted,
                          ),
                        ),
                      ),
                    ],
                  ),
                ],
              ),
            ),
            TextButton.icon(
              onPressed: obd.loadingDevices
                  ? null
                  : () async {
                      final ok = await obd.refreshDevices(
                        requestPermission: true,
                        force: true,
                      );
                      if (!ok && context.mounted) {
                        _message(
                          context,
                          obd.devicesError ??
                              'Could not read paired Bluetooth devices.',
                        );
                      }
                    },
              icon: AppIcon(
                'assets/icons/search.svg',
                size: 16,
                color: colors.accent,
              ),
              label: Text(obd.needsBluetoothPermission ? 'Allow' : 'Find'),
              style: TextButton.styleFrom(foregroundColor: colors.accent),
            ),
          ],
        ),
        const SizedBox(height: 12),
        DropdownButtonFormField<String?>(
          key: ValueKey('${dropdownValue ?? 'none'}-$_showAllDevices'),
          initialValue: dropdownValue,
          isExpanded: true,
          dropdownColor: colors.surface,
          style: theme.textTheme.bodyLarge?.copyWith(color: colors.ink),
          decoration: const InputDecoration(
            labelText: 'Bluetooth device',
            isDense: true,
          ),
          items: [
            const DropdownMenuItem<String?>(value: null, child: Text('None')),
            for (final device in options)
              DropdownMenuItem<String?>(
                value: device.address,
                child: Text(
                  device.label,
                  maxLines: 1,
                  overflow: TextOverflow.ellipsis,
                ),
              ),
          ],
          onChanged: obd.loadingDevices
              ? null
              : (value) async {
                  await obd.selectAdapter(value);
                  if (!context.mounted) return;
                  if (obd.error != null) {
                    _message(context, obd.error!);
                  }
                },
        ),
        if (obd.otherDevices.isNotEmpty) ...[
          const SizedBox(height: 2),
          TextButton(
            onPressed: () {
              setState(() => _showAllDevices = !_showAllDevices);
            },
            style: TextButton.styleFrom(
              foregroundColor: colors.accent,
              padding: EdgeInsets.zero,
              alignment: Alignment.centerLeft,
            ),
            child: Text(
              _showAllDevices
                  ? 'Show only OBD-II adapters'
                  : 'Show all paired devices',
            ),
          ),
          if (_showAllDevices)
            Text(
              'Phones, headsets and other devices usually cannot act as an '
              'OBD-II adapter.',
              style: theme.textTheme.bodySmall?.copyWith(
                color: colors.inkMuted,
              ),
            ),
        ],
        if (obd.canRetry) ...[
          const SizedBox(height: 2),
          TextButton(
            onPressed: () async {
              await obd.retryConnection();
              if (!context.mounted) return;
              if (obd.error != null) {
                _message(context, obd.error!);
              }
            },
            style: TextButton.styleFrom(
              foregroundColor: colors.accent,
              padding: EdgeInsets.zero,
              alignment: Alignment.centerLeft,
            ),
            child: const Text('Retry connection'),
          ),
        ],
        if (obd.devicesError != null &&
            !obd.needsBluetoothPermission &&
            (obd.bluetoothState.isOn ||
                obd.bluetoothState == BluetoothPowerState.unavailable)) ...[
          const SizedBox(height: 6),
          Text(
            obd.devicesError!,
            style: theme.textTheme.bodySmall?.copyWith(color: colors.danger),
          ),
        ],
        if (obd.bluetoothOff) ...[
          const SizedBox(height: 2),
          TextButton.icon(
            onPressed: () async {
              final opened = await obd.openBluetoothSettings();
              if (!opened && context.mounted) {
                _message(context, 'Could not open Bluetooth settings.');
              }
            },
            icon: AppIcon(
              'assets/icons/settings.svg',
              size: 16,
              color: colors.accent,
            ),
            label: const Text('Open Bluetooth settings'),
            style: TextButton.styleFrom(
              foregroundColor: colors.accent,
              padding: EdgeInsets.zero,
              alignment: Alignment.centerLeft,
            ),
          ),
        ],
        const SizedBox(height: 8),
        Text(
          'Only Bluetooth Classic OBD-II adapters are listed. Pair the ELM327 '
          'in Android Bluetooth settings first. CarDash only reads standard '
          'OBD-II PIDs; it never writes.',
          style: theme.textTheme.bodySmall?.copyWith(color: colors.inkMuted),
        ),
      ],
    );
  }

  void _message(BuildContext context, String message) {
    final messenger = ScaffoldMessenger.of(context);
    messenger.hideCurrentSnackBar();
    messenger.showSnackBar(SnackBar(content: Text(message)));
  }
}