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

/// Screen 1: Login & Registrierung (E-Mail / Passwort) über Firebase Auth.
class AuthScreen extends StatefulWidget {
  const AuthScreen({super.key});

  @override
  State<AuthScreen> createState() => _AuthScreenState();
}

class _AuthScreenState extends State<AuthScreen>
    with SingleTickerProviderStateMixin {
  late final TabController _tabController;

  final _loginEmail = TextEditingController();
  final _loginPassword = TextEditingController();

  final _regName = TextEditingController();
  final _regEmail = TextEditingController();
  final _regPassword = TextEditingController();

  bool _loading = false;

  @override
  void initState() {
    super.initState();
    _tabController = TabController(length: 2, vsync: this);
  }

  @override
  void dispose() {
    _tabController.dispose();
    _loginEmail.dispose();
    _loginPassword.dispose();
    _regName.dispose();
    _regEmail.dispose();
    _regPassword.dispose();
    super.dispose();
  }

  void _snack(String text) {
    if (!mounted) return;
    ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text(text)));
  }

  String _authMessage(FirebaseAuthException e) {
    switch (e.code) {
      case 'user-not-found':
      case 'wrong-password':
      case 'invalid-credential':
        return 'E-Mail oder Passwort ist falsch.';
      case 'email-already-in-use':
        return 'Diese E-Mail ist bereits registriert.';
      case 'weak-password':
        return 'Passwort ist zu schwach (mindestens 6 Zeichen).';
      case 'invalid-email':
        return 'Ungültige E-Mail-Adresse.';
      case 'network-request-failed':
        return 'Netzwerkfehler. Internet prüfen.';
      default:
        return e.message ?? 'Fehler: ${e.code}';
    }
  }

  Future<void> _login() async {
    final email = _loginEmail.text.trim();
    final password = _loginPassword.text;
    if (email.isEmpty || password.isEmpty) {
      _snack('E-Mail und Passwort eingeben.');
      return;
    }
    setState(() => _loading = true);
    try {
      await FirebaseAuth.instance.signInWithEmailAndPassword(
        email: email,
        password: password,
      );
    } on FirebaseAuthException catch (e) {
      _snack(_authMessage(e));
    } catch (e) {
      _snack('Unerwarteter Fehler: $e');
    } finally {
      if (mounted) setState(() => _loading = false);
    }
  }

  Future<void> _register() async {
    final email = _regEmail.text.trim();
    final password = _regPassword.text;
    final name = _regName.text.trim();
    if (email.isEmpty || password.isEmpty) {
      _snack('E-Mail und Passwort eingeben.');
      return;
    }
    if (password.length < 6) {
      _snack('Passwort mindestens 6 Zeichen (Firebase).');
      return;
    }
    setState(() => _loading = true);
    try {
      final cred = await FirebaseAuth.instance.createUserWithEmailAndPassword(
        email: email,
        password: password,
      );
      if (name.isNotEmpty && cred.user != null) {
        await cred.user!.updateDisplayName(name);
      }
    } on FirebaseAuthException catch (e) {
      _snack(_authMessage(e));
    } catch (e) {
      _snack('Unerwarteter Fehler: $e');
    } finally {
      if (mounted) setState(() => _loading = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    final scheme = Theme.of(context).colorScheme;

    return Scaffold(
      body: SafeArea(
        child: ListView(
          padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 16),
          children: [
            const SizedBox(height: 24),
            Icon(Icons.construction, size: 48, color: scheme.primary),
            const SizedBox(height: 16),
            Text(
              'Handwerksapp',
              textAlign: TextAlign.center,
              style: Theme.of(context).textTheme.headlineMedium?.copyWith(
                    fontWeight: FontWeight.bold,
                  ),
            ),
            const SizedBox(height: 8),
            Text(
              'Nach dem Login: Aufträge anlegen, Fotos, Kunden-Unterschrift, PDF teilen.\n'
              'Zuerst: Konto anlegen oder anmelden.',
              textAlign: TextAlign.center,
              style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                    color: scheme.onSurfaceVariant,
                  ),
            ),
            const SizedBox(height: 32),
            TabBar(
              controller: _tabController,
              tabs: const [
                Tab(text: 'Anmelden'),
                Tab(text: 'Registrieren'),
              ],
            ),
            const SizedBox(height: 16),
            SizedBox(
              height: 320,
              child: TabBarView(
                controller: _tabController,
                children: [
                  _LoginForm(
                    email: _loginEmail,
                    password: _loginPassword,
                    loading: _loading,
                    onSubmit: _login,
                  ),
                  _RegisterForm(
                    name: _regName,
                    email: _regEmail,
                    password: _regPassword,
                    loading: _loading,
                    onSubmit: _register,
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class _LoginForm extends StatelessWidget {
  const _LoginForm({
    required this.email,
    required this.password,
    required this.loading,
    required this.onSubmit,
  });

  final TextEditingController email;
  final TextEditingController password;
  final bool loading;
  final VoidCallback onSubmit;

  @override
  Widget build(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        TextField(
          controller: email,
          keyboardType: TextInputType.emailAddress,
          autocorrect: false,
          autofillHints: const [AutofillHints.email],
          decoration: const InputDecoration(labelText: 'E-Mail'),
        ),
        const SizedBox(height: 12),
        TextField(
          controller: password,
          obscureText: true,
          autofillHints: const [AutofillHints.password],
          decoration: const InputDecoration(labelText: 'Passwort'),
          onSubmitted: (_) => onSubmit(),
        ),
        const Spacer(),
        FilledButton(
          onPressed: loading ? null : onSubmit,
          child: loading
              ? const SizedBox(
                  height: 22,
                  width: 22,
                  child: CircularProgressIndicator(strokeWidth: 2),
                )
              : const Text('Anmelden'),
        ),
      ],
    );
  }
}

class _RegisterForm extends StatelessWidget {
  const _RegisterForm({
    required this.name,
    required this.email,
    required this.password,
    required this.loading,
    required this.onSubmit,
  });

  final TextEditingController name;
  final TextEditingController email;
  final TextEditingController password;
  final bool loading;
  final VoidCallback onSubmit;

  @override
  Widget build(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        TextField(
          controller: name,
          textCapitalization: TextCapitalization.words,
          decoration: const InputDecoration(
            labelText: 'Firmen- oder Anzeigename',
          ),
        ),
        const SizedBox(height: 12),
        TextField(
          controller: email,
          keyboardType: TextInputType.emailAddress,
          autocorrect: false,
          autofillHints: const [AutofillHints.email],
          decoration: const InputDecoration(labelText: 'E-Mail'),
        ),
        const SizedBox(height: 12),
        TextField(
          controller: password,
          obscureText: true,
          autofillHints: const [AutofillHints.newPassword],
          decoration: const InputDecoration(labelText: 'Passwort (min. 6 Zeichen)'),
        ),
        const Spacer(),
        FilledButton(
          onPressed: loading ? null : onSubmit,
          child: loading
              ? const SizedBox(
                  height: 22,
                  width: 22,
                  child: CircularProgressIndicator(strokeWidth: 2),
                )
              : const Text('Konto erstellen'),
        ),
      ],
    );
  }
}