// =============================================================================
//  screens/settings/port_settings_screen.dart — COM port configuration
// =============================================================================
//
//  Lets the operator choose which COM port is the concentrador RX-OUT
//  (the one the display reads from) and which is the TX-IN
//  (the one the display writes commands to).
//
//  Ports are persisted in SharedPreferences and auto-applied at startup.
//
//  Layout:
//    • Two dropdowns — RX port, TX port — populated from available COM ports
//    • [Conectar] button — tries to open both ports; shows error if it fails
//    • [Desconectar] button — drops to demo mode
//    • Status row — green ● CONECTADO / grey ● DEMO
// =============================================================================

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

import '../../data/autopilot_state.dart';
import '../../theme/autopilot_theme.dart';
import '../../theme/theme_provider.dart';

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

  static const String routeName = '/settings/ports';

  @override
  State<PortSettingsScreen> createState() => _PortSettingsScreenState();
}

class _PortSettingsScreenState extends State<PortSettingsScreen> {
  static const _kRxKey = 'port.rx';
  static const _kTxKey = 'port.tx';

  List<String> _ports = [];
  String? _rxPort;
  String? _txPort;
  bool _connecting = false;
  String? _errorMsg;

  @override
  void initState() {
    super.initState();
    _loadPorts();
  }

  Future<void> _loadPorts() async {
    final available = AutopilotState.availablePorts();
    final prefs = await SharedPreferences.getInstance();
    setState(() {
      _ports = available;
      _rxPort = prefs.getString(_kRxKey);
      _txPort = prefs.getString(_kTxKey);
      // If saved port no longer exists, clear it.
      if (_rxPort != null && !_ports.contains(_rxPort)) _rxPort = null;
      if (_txPort != null && !_ports.contains(_txPort)) _txPort = null;
    });
  }

  Future<void> _connect() async {
    if (_rxPort == null || _txPort == null) return;
    setState(() {
      _connecting = true;
      _errorMsg = null;
    });

    try {
      final ap = context.read<AutopilotState>();
      await ap.connectToSerial(rxPort: _rxPort!, txPort: _txPort!);

      // Persist the working configuration
      final prefs = await SharedPreferences.getInstance();
      await prefs.setString(_kRxKey, _rxPort!);
      await prefs.setString(_kTxKey, _txPort!);

      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(
            content: Text('Conectado — RX: $_rxPort  TX: $_txPort'),
            backgroundColor: Colors.green.shade700,
            duration: const Duration(seconds: 3),
          ),
        );
        Navigator.pop(context);
      }
    } catch (e) {
      setState(() => _errorMsg = 'Error al abrir puertos: $e');
    } finally {
      if (mounted) setState(() => _connecting = false);
    }
  }

  Future<void> _disconnect() async {
    final ap = context.read<AutopilotState>();
    await ap.disconnectSerial();
    if (mounted) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(
          content: Text('Desconectado — modo demo activo'),
          duration: Duration(seconds: 2),
        ),
      );
      Navigator.pop(context);
    }
  }

  @override
  Widget build(BuildContext context) {
    final theme = context.watch<AutopilotThemeProvider>().current;
    final ap    = context.watch<AutopilotState>();

    return Scaffold(
      backgroundColor: theme.background,
      appBar: AppBar(
        backgroundColor: theme.backgroundMid,
        foregroundColor: theme.textMain,
        elevation: 0,
        title: Text(
          'Conexión al Concentrador',
          style: TextStyle(color: theme.textMain, fontWeight: FontWeight.w600),
        ),
      ),
      body: AnimatedContainer(
        duration: const Duration(milliseconds: 400),
        decoration: theme.backgroundDecoration,
        child: ListView(
          padding: const EdgeInsets.all(20),
          children: [
            // ── Status ────────────────────────────────────────────────────────
            _StatusRow(theme: theme, connected: ap.isConnected),
            const SizedBox(height: 24),

            // ── Port selection ────────────────────────────────────────────────
            _SectionLabel(label: 'Puerto RX (leer datos del concentrador)', theme: theme),
            const SizedBox(height: 8),
            _PortDropdown(
              theme: theme,
              value: _rxPort,
              ports: _ports,
              onChanged: (v) => setState(() => _rxPort = v),
            ),
            const SizedBox(height: 16),

            _SectionLabel(label: 'Puerto TX (enviar comandos al concentrador)', theme: theme),
            const SizedBox(height: 8),
            _PortDropdown(
              theme: theme,
              value: _txPort,
              ports: _ports,
              onChanged: (v) => setState(() => _txPort = v),
            ),
            const SizedBox(height: 8),

            // Note
            Text(
              'Conectar el cable USB-OUT del concentrador al puerto RX,\n'
              'y el USB-IN al puerto TX. Ambos a 115 200 baud, 8N1.',
              style: TextStyle(color: theme.textMuted, fontSize: 11),
            ),
            const SizedBox(height: 24),

            // ── Error message ─────────────────────────────────────────────────
            if (_errorMsg != null) ...[
              Container(
                padding: const EdgeInsets.all(12),
                decoration: BoxDecoration(
                  color: theme.disengageBackground.colors.first.withValues(alpha: 0.15),
                  borderRadius: BorderRadius.circular(6),
                  border: Border.all(color: theme.disengageBorder.withValues(alpha: 0.4)),
                ),
                child: Text(
                  _errorMsg!,
                  style: TextStyle(color: theme.disengageText, fontSize: 12),
                ),
              ),
              const SizedBox(height: 16),
            ],

            // ── Buttons ───────────────────────────────────────────────────────
            Row(
              children: [
                Expanded(
                  child: _ActionButton(
                    theme: theme,
                    label: _connecting ? 'Conectando…' : 'Conectar',
                    enabled: !_connecting && _rxPort != null && _txPort != null,
                    primary: true,
                    onPressed: _connect,
                  ),
                ),
                const SizedBox(width: 12),
                Expanded(
                  child: _ActionButton(
                    theme: theme,
                    label: 'Desconectar',
                    enabled: ap.isConnected && !_connecting,
                    primary: false,
                    onPressed: _disconnect,
                  ),
                ),
              ],
            ),
            const SizedBox(height: 16),

            // ── Refresh ports ─────────────────────────────────────────────────
            TextButton(
              onPressed: _loadPorts,
              child: Text(
                'Actualizar lista de puertos',
                style: TextStyle(color: theme.textMuted, fontSize: 12),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

// ── Private widgets ───────────────────────────────────────────────────────────

class _StatusRow extends StatelessWidget {
  const _StatusRow({required this.theme, required this.connected});
  final AutopilotTheme theme;
  final bool connected;

  @override
  Widget build(BuildContext context) {
    final color = connected ? theme.okColor : theme.textMuted;
    final label = connected ? 'CONECTADO AL CONCENTRADOR' : 'MODO DEMO (sin conexión)';
    return Row(
      children: [
        Container(
          width: 10,
          height: 10,
          decoration: BoxDecoration(
            shape: BoxShape.circle,
            color: color,
            boxShadow: connected
                ? [BoxShadow(color: color.withValues(alpha: 0.5), blurRadius: 8)]
                : null,
          ),
        ),
        const SizedBox(width: 10),
        Text(
          label,
          style: TextStyle(
            color: color,
            fontSize: 12,
            fontWeight: FontWeight.w600,
            letterSpacing: 0.8,
          ),
        ),
      ],
    );
  }
}

class _SectionLabel extends StatelessWidget {
  const _SectionLabel({required this.label, required this.theme});
  final String label;
  final AutopilotTheme theme;

  @override
  Widget build(BuildContext context) => Text(
        label.toUpperCase(),
        style: TextStyle(
          color: theme.textMuted,
          fontSize: 10,
          letterSpacing: 1.2,
          fontWeight: FontWeight.w600,
        ),
      );
}

class _PortDropdown extends StatelessWidget {
  const _PortDropdown({
    required this.theme,
    required this.value,
    required this.ports,
    required this.onChanged,
  });
  final AutopilotTheme theme;
  final String? value;
  final List<String> ports;
  final ValueChanged<String?> onChanged;

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: const EdgeInsets.symmetric(horizontal: 14),
      decoration: BoxDecoration(
        gradient: theme.panelBackground,
        borderRadius: BorderRadius.circular(6),
        border: Border.all(color: theme.panelBorder),
      ),
      child: DropdownButtonHideUnderline(
        child: DropdownButton<String>(
          value: ports.contains(value) ? value : null,
          hint: Text(
            ports.isEmpty ? 'Sin puertos disponibles' : 'Seleccionar puerto…',
            style: TextStyle(color: theme.textMuted, fontSize: 13),
          ),
          dropdownColor: theme.backgroundMid,
          style: TextStyle(color: theme.textMain, fontSize: 13),
          icon: Icon(Icons.expand_more, color: theme.textMuted),
          isExpanded: true,
          items: ports
              .map((p) => DropdownMenuItem(value: p, child: Text(p)))
              .toList(),
          onChanged: onChanged,
        ),
      ),
    );
  }
}

class _ActionButton extends StatelessWidget {
  const _ActionButton({
    required this.theme,
    required this.label,
    required this.enabled,
    required this.primary,
    required this.onPressed,
  });
  final AutopilotTheme theme;
  final String label;
  final bool enabled;
  final bool primary;
  final VoidCallback onPressed;

  @override
  Widget build(BuildContext context) {
    final color = primary ? theme.okColor : theme.accentMid;
    return GestureDetector(
      onTap: enabled ? onPressed : null,
      child: AnimatedContainer(
        duration: const Duration(milliseconds: 150),
        padding: const EdgeInsets.symmetric(vertical: 14),
        alignment: Alignment.center,
        decoration: BoxDecoration(
          color: enabled
              ? color.withValues(alpha: 0.15)
              : theme.backgroundDeep,
          borderRadius: BorderRadius.circular(7),
          border: Border.all(
            color: enabled ? color : theme.panelBorder,
            width: 1.5,
          ),
        ),
        child: Text(
          label,
          style: TextStyle(
            color: enabled ? color : theme.textDisabled,
            fontSize: 13,
            fontWeight: FontWeight.w700,
            letterSpacing: 1,
          ),
        ),
      ),
    );
  }
}