// lib/screens/login.dart

import 'dart:async'; // Import for TimeoutException

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:connectivity_plus/connectivity_plus.dart'; // Keep for potential future use, though not strictly necessary for the new logic

import 'package:environment_monitoring_app/services/api_service.dart';
import 'package:environment_monitoring_app/auth_provider.dart';
import 'package:environment_monitoring_app/home_page.dart';

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

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

class _LoginScreenState extends State<LoginScreen> {
  final _formKey = GlobalKey<FormState>();
  final TextEditingController _emailController = TextEditingController();
  final TextEditingController _passwordController = TextEditingController();
  bool _isLoading = false;
  String _errorMessage = '';

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

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

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

    final auth = Provider.of<AuthProvider>(context, listen: false);
    final apiService = Provider.of<ApiService>(context, listen: false);
    final String email = _emailController.text.trim();
    final String password = _passwordController.text.trim();

    // --- START: MODIFIED Internet-First Strategy with Improved Fallback ---
    try {
      // --- Attempt 1: Online Login ---
      debugPrint("Login attempt: Trying online authentication...");
      final Map<String, dynamic> result = await apiService
          .login(email, password)
          .timeout(const Duration(seconds: 10));

      if (result['success'] == true) {
        // --- Online Success ---
        final String token = result['data']['token'];
        final Map<String, dynamic> profile = result['data']['profile'];
        await auth.login(token, profile, password);

        if (auth.isFirstLogin) {
          await auth.setIsFirstLogin(false);
        }

        if (!mounted) return;
        Navigator.of(context).pushReplacement(
          MaterialPageRoute(builder: (context) => const HomePage()),
        );
      } else {
        // --- Online Failure (API Error) ---
        setState(() {
          _errorMessage = result['message'] ?? 'Invalid email or password.';
        });
        _showSnackBar(_errorMessage, isError: true);
      }
    } on TimeoutException catch (_) {
      // --- Online Failure (Timeout) ---
      debugPrint("Login attempt: Online request timed out after 10 seconds. Triggering offline fallback.");
      _showSnackBar("Slow connection detected. Trying offline login...", isError: true);
      await _attemptOfflineLogin(auth, email, password);
    } catch (e) {
      // --- Online Failure (Other Network Error, e.g., SocketException) ---
      debugPrint("Login attempt: Network error ($e). Triggering offline fallback immediately.");
      _showSnackBar("Connection failed. Trying offline login...", isError: true);
      // FIX: Removed the unreliable connectivity check. Treat all exceptions here as a reason to try offline.
      await _attemptOfflineLogin(auth, email, password);
    } finally {
      if (mounted) {
        setState(() {
          _isLoading = false;
        });
      }
    }
    // --- END: MODIFIED Internet-First Strategy ---
  }

  /// Helper function to perform offline validation and update UI.
  Future<void> _attemptOfflineLogin(AuthProvider auth, String email, String password) async {
    final bool offlineSuccess = await auth.loginOffline(email, password);

    if (mounted) {
      if (offlineSuccess) {
        Navigator.of(context).pushReplacement(
          MaterialPageRoute(builder: (context) => const HomePage()),
        );
      } else {
        setState(() {
          _errorMessage = "Offline login failed. Check credentials or connect to internet to sync.";
        });
        _showSnackBar(_errorMessage, isError: true);
      }
    }
  }

  void _showSnackBar(String message, {bool isError = false}) {
    if (mounted) {
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(
          content: Text(message),
          backgroundColor: isError ? Theme.of(context).colorScheme.error : null,
        ),
      );
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Login'),
        centerTitle: true,
      ),
      body: Center(
        child: SingleChildScrollView(
          padding: const EdgeInsets.all(16.0),
          child: Form(
            key: _formKey,
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Text(
                  "PSTW MMS V4",
                  style: Theme.of(context).textTheme.headlineMedium?.copyWith(
                    fontWeight: FontWeight.bold,
                  ),
                ),
                const SizedBox(height: 32),
                Center(
                  child: Image.asset(
                    'assets/icon_3_512x512.png',
                    height: 120,
                    width: 120,
                  ),
                ),
                const SizedBox(height: 48),
                TextFormField(
                  controller: _emailController,
                  decoration: const InputDecoration(labelText: "Email"),
                  keyboardType: TextInputType.emailAddress,
                  validator: (val) => val == null || val.isEmpty ? "Enter your email" : null,
                ),
                const SizedBox(height: 16),
                TextFormField(
                  controller: _passwordController,
                  decoration: const InputDecoration(labelText: "Password"),
                  obscureText: true,
                  validator: (val) => val == null || val.length < 6 ? "Minimum 6 characters" : null,
                ),
                const SizedBox(height: 24),
                _isLoading
                    ? const CircularProgressIndicator()
                    : ElevatedButton(
                  onPressed: _login,
                  style: ElevatedButton.styleFrom(
                    minimumSize: const Size(double.infinity, 50),
                    shape: RoundedRectangleBorder(
                      borderRadius: BorderRadius.circular(10),
                    ),
                  ),
                  child: const Text(
                    'Login',
                    style: TextStyle(fontSize: 18),
                  ),
                ),
                if (_errorMessage.isNotEmpty)
                  Padding(
                    padding: const EdgeInsets.only(top: 12),
                    child: Text(
                      _errorMessage,
                      style: TextStyle(color: Theme.of(context).colorScheme.error),
                      textAlign: TextAlign.center,
                    ),
                  ),
                const SizedBox(height: 15),
                TextButton(
                  onPressed: () {
                    Navigator.pushNamed(context, '/forgot-password');
                  },
                  child: const Text('Forgot Password?'),
                ),
                TextButton(
                  onPressed: () {
                    Navigator.pushNamed(context, '/register');
                  },
                  child: const Text('Don\'t have an account? Register'),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}