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

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

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

class _AuthScreenState extends State<AuthScreen> {
  final _controller = TextEditingController();
  final _formKey = GlobalKey<FormState>();
  bool _isLoading = false;
  String _error = '';
  
  // Secret key for accessing the web app
  static const String _secretKey = 'DocRec2025TestKey!@#';

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

  Future<void> _checkAuthStatus() async {
    final prefs = await SharedPreferences.getInstance();
    final isAuthenticated = prefs.getBool('is_authenticated') ?? false;
    
    if (isAuthenticated && mounted) {
      Navigator.of(context).pushReplacement(
        MaterialPageRoute(builder: (_) => const HomeScreen()),
      );
    }
  }

  Future<void> _authenticate() async {
    if (!_formKey.currentState!.validate()) return;

    setState(() {
      _isLoading = true;
      _error = '';
    });

    await Future.delayed(const Duration(milliseconds: 500)); // Simulate network delay

    if (_controller.text.trim() == _secretKey) {
      final prefs = await SharedPreferences.getInstance();
      await prefs.setBool('is_authenticated', true);
      
      if (mounted) {
        Navigator.of(context).pushReplacement(
          MaterialPageRoute(builder: (_) => const HomeScreen()),
        );
      }
    } else {
      setState(() {
        _error = '密钥错误，请检查后重试';
        _isLoading = false;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          constraints: const BoxConstraints(maxWidth: 400),
          padding: const EdgeInsets.all(24.0),
          child: Card(
            child: Padding(
              padding: const EdgeInsets.all(32.0),
              child: Form(
                key: _formKey,
                child: Column(
                  mainAxisSize: MainAxisSize.min,
                  crossAxisAlignment: CrossAxisAlignment.stretch,
                  children: [
                    Icon(
                      Icons.lock_outline,
                      size: 64,
                      color: Theme.of(context).primaryColor,
                    ),
                    const SizedBox(height: 24),
                    Text(
                      'DocRec 访问验证',
                      style: Theme.of(context).textTheme.headlineSmall,
                      textAlign: TextAlign.center,
                    ),
                    const SizedBox(height: 8),
                    Text(
                      '请输入访问密钥以继续',
                      style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                        color: Colors.grey[600],
                      ),
                      textAlign: TextAlign.center,
                    ),
                    const SizedBox(height: 32),
                    TextFormField(
                      controller: _controller,
                      obscureText: true,
                      decoration: const InputDecoration(
                        labelText: '访问密钥',
                        hintText: '请输入密钥',
                        prefixIcon: Icon(Icons.key),
                      ),
                      validator: (value) {
                        if (value == null || value.trim().isEmpty) {
                          return '请输入访问密钥';
                        }
                        return null;
                      },
                      onFieldSubmitted: (_) => _authenticate(),
                    ),
                    if (_error.isNotEmpty) ...[
                      const SizedBox(height: 16),
                      Text(
                        _error,
                        style: TextStyle(
                          color: Theme.of(context).colorScheme.error,
                          fontSize: 14,
                        ),
                        textAlign: TextAlign.center,
                      ),
                    ],
                    const SizedBox(height: 24),
                    ElevatedButton(
                      onPressed: _isLoading ? null : _authenticate,
                      child: _isLoading
                          ? const SizedBox(
                              height: 20,
                              width: 20,
                              child: CircularProgressIndicator(strokeWidth: 2),
                            )
                          : const Text('验证访问'),
                    ),
                  ],
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }
}