// login_screen.dart
// This file contains the LoginScreen widget, which handles user authentication (login and registration) and role selection.

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

/// The LoginScreen allows users to log in or register, and select their role (trainer or player).
class LoginScreen extends StatefulWidget {
  final void Function() onLoginSuccess;
  const LoginScreen({super.key, required this.onLoginSuccess});

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

/// State for the LoginScreen, manages form state, authentication, and error handling.
class _LoginScreenState extends State<LoginScreen> {
  final _formKey = GlobalKey<FormState>();
  final _emailController = TextEditingController();
  final _passwordController = TextEditingController();
  final _nameController = TextEditingController();
  String? _error;
  bool _loading = false;
  bool _isLogin = true;
  bool _isTrainer = false;

  /// Handles login or registration when the form is submitted.
  Future<void> _submit() async {
    setState(() { _loading = true; _error = null; });
    try {
      if (_isLogin) {
        // Login
        try {
          UserCredential cred = await FirebaseAuth.instance.signInWithEmailAndPassword(
            email: _emailController.text.trim(),
            password: _passwordController.text.trim(),
          );
          
          // Check if user profile exists in Firestore
          final uid = cred.user!.uid;
          final userDoc = await FirebaseFirestore.instance.collection('User').doc(uid).get();
          
          if (userDoc.exists) {
            widget.onLoginSuccess();
          } else {
            setState(() { _error = 'Kein Benutzerprofil in der Datenbank gefunden!'; });
            await FirebaseAuth.instance.signOut();
          }
        } catch (e) {
          rethrow;
        }
      } else {
        // Registration - Direct attempt to create user
        try {
          UserCredential cred = await FirebaseAuth.instance.createUserWithEmailAndPassword(
            email: _emailController.text.trim(),
            password: _passwordController.text.trim(),
          );
          
          // Create user document in Firestore
          final uid = cred.user!.uid;
          await FirebaseFirestore.instance.collection('User').doc(uid).set({
            'email': _emailController.text.trim(),
            'name': _nameController.text.trim(),
            'role': _isTrainer ? 'trainer' : 'player',
            'createdAt': FieldValue.serverTimestamp(),
            'favorites': [],
            'trainings': {},
            'cancelledTrainings': [],
            'trainingTimes': {},
            'trainingDurations': {},
          });
          
          widget.onLoginSuccess();
        } catch (e) {
          rethrow;
        }
      }
    } on FirebaseAuthException catch (e) {
      // Handle Firebase authentication errors
      String errorMessage;
      switch (e.code) {
        case 'user-not-found':
          errorMessage = 'Kein Benutzer mit dieser E-Mail-Adresse gefunden.';
          break;
        case 'wrong-password':
          errorMessage = 'Falsches Passwort.';
          break;
        case 'invalid-email':
          errorMessage = 'Ungültige E-Mail-Adresse.';
          break;
        case 'user-disabled':
          errorMessage = 'Dieses Konto wurde deaktiviert.';
          break;
        case 'email-already-in-use':
          errorMessage = 'Diese E-Mail-Adresse wird bereits verwendet. Bitte melde dich an oder verwende eine andere E-Mail-Adresse.';
          break;
        case 'weak-password':
          errorMessage = 'Das Passwort ist zu schwach.';
          break;
        case 'operation-not-allowed':
          errorMessage = 'Diese Aktion ist nicht erlaubt.';
          break;
        default:
          errorMessage = 'Ein Fehler ist aufgetreten: ${e.message}';
      }
      setState(() { _error = errorMessage; });
    } catch (e) {
      setState(() { _error = 'Ein unerwarteter Fehler ist aufgetreten. Bitte versuche es später erneut.'; });
    } finally {
      setState(() { _loading = false; });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: SingleChildScrollView(
          padding: const EdgeInsets.all(24),
          child: Form(
            key: _formKey,
            child: Column(
              mainAxisSize: MainAxisSize.min,
              children: [
                // Title
                Text(_isLogin ? 'Anmeldung' : 'Registrieren', style: Theme.of(context).textTheme.headlineMedium),
                const SizedBox(height: 32),
                if (!_isLogin) ...[
                  // Name field for registration
                  TextFormField(
                    controller: _nameController,
                    decoration: const InputDecoration(labelText: 'Name'),
                    validator: (v) => v != null && v.trim().isNotEmpty ? null : 'Bitte gib deinen Namen ein',
                  ),
                  const SizedBox(height: 16),
                  // Role selection
                  Row(
                    children: [
                      Checkbox(
                        value: _isTrainer,
                        onChanged: (v) {
                          setState(() { _isTrainer = v ?? false; });
                        },
                      ),
                      const Text('Ich bin Trainer'),
                      const SizedBox(width: 16),
                      Checkbox(
                        value: !_isTrainer,
                        onChanged: (v) {
                          setState(() { _isTrainer = !(v ?? false); });
                        },
                      ),
                      const Text('Ich bin Spieler'),
                    ],
                  ),
                  const SizedBox(height: 16),
                ],
                // Email field
                TextFormField(
                  controller: _emailController,
                  decoration: const InputDecoration(labelText: 'E-Mail'),
                  keyboardType: TextInputType.emailAddress,
                  validator: (v) => v != null && v.contains('@') ? null : 'Bitte gib eine gültige E-Mail ein',
                ),
                const SizedBox(height: 16),
                // Password field
                TextFormField(
                  controller: _passwordController,
                  decoration: const InputDecoration(labelText: 'Passwort'),
                  obscureText: true,
                  validator: (v) => v != null && v.length >= 6 ? null : 'Mindestens 6 Zeichen',
                ),
                const SizedBox(height: 24),
                if (_error != null) ...[
                  // Error message
                  Text(_error!, style: const TextStyle(color: Colors.red)),
                  const SizedBox(height: 12),
                ],
                // Submit button
                SizedBox(
                  width: double.infinity,
                  child: ElevatedButton(
                    onPressed: _loading
                        ? null
                        : () {
                            if (_formKey.currentState!.validate()) {
                              _submit();
                            }
                          },
                    child: _loading
                        ? const CircularProgressIndicator()
                        : Text(_isLogin ? 'Anmelden' : 'Registrieren'),
                  ),
                ),
                const SizedBox(height: 16),
                // Switch between login and registration
                TextButton(
                  onPressed: _loading
                      ? null
                      : () {
                          setState(() {
                            _isLogin = !_isLogin;
                            _error = null;
                          });
                        },
                  child: Text(_isLogin ? 'Noch kein Konto? Jetzt registrieren!' : 'Schon registriert? Jetzt anmelden!'),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}