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

import '../../../l10n/generated/app_localizations.dart';
import '../data/auth_repository.dart';

class LoginScreen extends ConsumerStatefulWidget {
  const LoginScreen({super.key});

  @override
  ConsumerState<LoginScreen> createState() => _LoginScreenState();
}

class _LoginScreenState extends ConsumerState<LoginScreen> {
  final _formKey = GlobalKey<FormState>();
  final _emailController = TextEditingController();
  final _passwordController = TextEditingController();
  bool _isSignUp = false;
  bool _busy = false;
  String? _errorText;

  @override
  void dispose() {
    _emailController.dispose();
    _passwordController.dispose();
    super.dispose();
  }

  String _messageForCode(String code, AppLocalizations l10n) {
    return switch (code) {
      'invalid-credential' ||
      'user-not-found' ||
      'wrong-password' =>
        l10n.authErrorInvalidCredential,
      'email-already-in-use' => l10n.authErrorEmailInUse,
      'weak-password' => l10n.authErrorWeakPassword,
      'invalid-email' => l10n.authErrorInvalidEmail,
      _ => l10n.authErrorGeneric,
    };
  }

  Future<void> _submit() async {
    final l10n = AppLocalizations.of(context);
    if (!_formKey.currentState!.validate()) return;

    setState(() {
      _busy = true;
      _errorText = null;
    });
    try {
      final repo = ref.read(authRepositoryProvider);
      final email = _emailController.text.trim();
      final password = _passwordController.text;
      if (_isSignUp) {
        await repo.signUp(email: email, password: password);
      } else {
        await repo.signIn(email: email, password: password);
      }
      // Weiterleitung übernimmt der Router (redirect bei Auth-Änderung).
    } on FirebaseAuthException catch (e) {
      setState(() => _errorText = _messageForCode(e.code, l10n));
    } catch (_) {
      setState(() => _errorText = l10n.authErrorGeneric);
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    final theme = Theme.of(context);

    return Scaffold(
      body: SafeArea(
        child: Center(
          child: SingleChildScrollView(
            padding: const EdgeInsets.all(24),
            child: ConstrainedBox(
              constraints: const BoxConstraints(maxWidth: 420),
              child: Form(
                key: _formKey,
                child: Column(
                  mainAxisSize: MainAxisSize.min,
                  crossAxisAlignment: CrossAxisAlignment.stretch,
                  children: [
                    Icon(Icons.eco, size: 64, color: theme.colorScheme.primary),
                    const SizedBox(height: 12),
                    Text(
                      l10n.appTitle,
                      style: theme.textTheme.headlineMedium,
                      textAlign: TextAlign.center,
                    ),
                    const SizedBox(height: 4),
                    Text(
                      l10n.loginSubtitle,
                      style: theme.textTheme.bodyLarge,
                      textAlign: TextAlign.center,
                    ),
                    const SizedBox(height: 32),
                    TextFormField(
                      controller: _emailController,
                      decoration: InputDecoration(
                        labelText: l10n.emailLabel,
                        border: const OutlineInputBorder(),
                        prefixIcon: const Icon(Icons.mail_outline),
                      ),
                      keyboardType: TextInputType.emailAddress,
                      autocorrect: false,
                      textInputAction: TextInputAction.next,
                      validator: (value) =>
                          (value == null || value.trim().isEmpty)
                              ? l10n.requiredField
                              : null,
                    ),
                    const SizedBox(height: 16),
                    TextFormField(
                      controller: _passwordController,
                      decoration: InputDecoration(
                        labelText: l10n.passwordLabel,
                        border: const OutlineInputBorder(),
                        prefixIcon: const Icon(Icons.lock_outline),
                      ),
                      obscureText: true,
                      textInputAction: TextInputAction.done,
                      onFieldSubmitted: (_) => _submit(),
                      validator: (value) => (value == null || value.isEmpty)
                          ? l10n.requiredField
                          : null,
                    ),
                    if (_errorText != null) ...[
                      const SizedBox(height: 16),
                      Text(
                        _errorText!,
                        style: theme.textTheme.bodyMedium
                            ?.copyWith(color: theme.colorScheme.error),
                        textAlign: TextAlign.center,
                      ),
                    ],
                    const SizedBox(height: 24),
                    FilledButton(
                      onPressed: _busy ? null : _submit,
                      child: _busy
                          ? const SizedBox(
                              height: 22,
                              width: 22,
                              child: CircularProgressIndicator(strokeWidth: 2),
                            )
                          : Text(
                              _isSignUp ? l10n.signUpButton : l10n.signInButton),
                    ),
                    const SizedBox(height: 8),
                    TextButton(
                      onPressed: _busy
                          ? null
                          : () => setState(() {
                                _isSignUp = !_isSignUp;
                                _errorText = null;
                              }),
                      child: Text(_isSignUp
                          ? l10n.switchToSignIn
                          : l10n.switchToSignUp),
                    ),
                  ],
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}