import "package:flutter/material.dart";
import "package:flutter/services.dart";
import "package:provider/provider.dart";

import "../app/app_router.dart";
import "../app/app_state.dart";
import "../models/cart.dart";
import "../services/api.dart";
import "../services/auth_storage.dart";

enum LoginStep { phone, otp }

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

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

class _LoginScreenState extends State<LoginScreen> {
  LoginStep _currentStep = LoginStep.phone;

  final _phoneController = TextEditingController();
  final _otpController = TextEditingController();

  String _uuid = "";
  String _phone = "";

  bool _isLoading = false;
  String? _errorMessage;

  @override
  void dispose() {
    _phoneController.dispose();
    _otpController.dispose();
    super.dispose();
  }

  String _formatPhoneNumber(String input) {
    final digits = input.replaceAll(RegExp(r'[^\d]'), '');
    if (digits.length == 11 && digits.startsWith('1')) {
      return digits.substring(1);
    }
    return digits;
  }

  Future<void> _handleSendOtp() async {
    final phone = _formatPhoneNumber(_phoneController.text);

    if (phone.length != 10) {
      setState(() {
        _errorMessage = "Please enter a valid 10-digit phone number";
      });
      return;
    }

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

    try {
      final response = await Api.sendLoginOtp(phone: phone);

      if (!mounted) return;

      if (response.uuid.isEmpty) {
        setState(() {
          _errorMessage = "Server error - please try again";
          _isLoading = false;
        });
        return;
      }

      setState(() {
        _uuid = response.uuid;
        _phone = phone;
        _currentStep = LoginStep.otp;
        _isLoading = false;
      });
    } catch (e) {
      if (!mounted) return;
      setState(() {
        _errorMessage = e.toString().replaceFirst("StateError: ", "");
        _isLoading = false;
      });
    }
  }

  Future<void> _handleVerifyOtp() async {
    if (_uuid.isEmpty) {
      setState(() {
        _errorMessage = "Session expired. Please go back and try again.";
      });
      return;
    }

    final otp = _otpController.text.trim();

    if (otp.length != 6) {
      setState(() {
        _errorMessage = "Please enter the 6-digit code";
      });
      return;
    }

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

    try {
      final response = await Api.verifyLoginOtp(uuid: _uuid, otp: otp);

      if (!mounted) return;

      // Save credentials for persistent login
      await AuthStorage.saveAuth(
        userId: response.userId,
        token: response.token,
      );

      final appState = context.read<AppState>();
      appState.setUserId(response.userId);

      // Show success
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(
          content: Text(
            "Welcome back${response.userFirstName.isNotEmpty ? ', ${response.userFirstName}' : ''}!",
            style: const TextStyle(color: Colors.black),
          ),
          backgroundColor: const Color(0xFF90EE90),
          behavior: SnackBarBehavior.floating,
          margin: const EdgeInsets.only(bottom: 80, left: 16, right: 16),
        ),
      );

      // Check for existing cart
      ActiveCartInfo? existingCart;
      try {
        existingCart = await Api.getActiveCart(userId: response.userId);
        if (existingCart != null && !existingCart.hasItems) {
          existingCart = null;
        }
      } catch (e) {
        // Ignore - treat as no cart
      }

      if (!mounted) return;

      if (existingCart != null) {
        // Show continue or start fresh dialog
        _showExistingCartDialog(existingCart);
      } else {
        // No existing cart - just pop back
        if (Navigator.of(context).canPop()) {
          Navigator.of(context).pop();
        } else {
          Navigator.of(context).pushReplacementNamed(AppRoutes.restaurantSelect);
        }
      }
    } catch (e) {
      if (!mounted) return;
      setState(() {
        _errorMessage = e.toString().replaceFirst("StateError: ", "");
        _isLoading = false;
      });
    }
  }

  void _showExistingCartDialog(ActiveCartInfo cart) {
    showDialog(
      context: context,
      barrierDismissible: false,
      builder: (context) => AlertDialog(
        title: const Text("Existing Order Found"),
        content: Text(
          "You have ${cart.itemCount} item${cart.itemCount == 1 ? '' : 's'} in your cart at ${cart.businessName}.\n\nWould you like to continue that order or start fresh?",
        ),
        actions: [
          TextButton(
            onPressed: () {
              Navigator.of(context).pop();
              // Start fresh - go to restaurant select
              Navigator.of(this.context).pushReplacementNamed(AppRoutes.restaurantSelect);
            },
            child: const Text("Start Fresh"),
          ),
          ElevatedButton(
            onPressed: () async {
              Navigator.of(context).pop();
              // Continue existing order - load cart and go to menu
              final appState = this.context.read<AppState>();
              appState.setBusinessAndServicePoint(
                cart.businessId,
                cart.servicePointId,
                businessName: cart.businessName,
                servicePointName: cart.servicePointName,
              );
              appState.setCartOrder(
                orderId: cart.orderId,
                orderUuid: cart.orderUuid,
                itemCount: cart.itemCount,
              );
              Navigator.of(this.context).pushReplacementNamed(AppRoutes.menuBrowse);
            },
            child: const Text("Continue Order"),
          ),
        ],
      ),
    );
  }

  Future<void> _handleResendOtp() async {
    setState(() {
      _isLoading = true;
      _errorMessage = null;
    });

    try {
      final response = await Api.sendLoginOtp(phone: _phone);

      if (!mounted) return;

      setState(() {
        _uuid = response.uuid;
        _isLoading = false;
      });

      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(
          content: const Text("New code sent!", style: TextStyle(color: Colors.black)),
          backgroundColor: const Color(0xFF90EE90),
          behavior: SnackBarBehavior.floating,
          margin: const EdgeInsets.only(bottom: 80, left: 16, right: 16),
        ),
      );
    } catch (e) {
      if (!mounted) return;
      setState(() {
        _errorMessage = e.toString().replaceFirst("StateError: ", "");
        _isLoading = false;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(_currentStep == LoginStep.phone ? "Login" : "Verify Phone"),
      ),
      body: Center(
        child: SingleChildScrollView(
          padding: const EdgeInsets.all(24),
          child: ConstrainedBox(
            constraints: const BoxConstraints(maxWidth: 400),
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: [
                if (_currentStep == LoginStep.phone) _buildPhoneStep(),
                if (_currentStep == LoginStep.otp) _buildOtpStep(),

                // Error message
                if (_errorMessage != null) ...[
                  const SizedBox(height: 16),
                  _buildErrorMessage(),
                ],
              ],
            ),
          ),
        ),
      ),
    );
  }

  Widget _buildPhoneStep() {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        const Text(
          "PAYFRIT",
          textAlign: TextAlign.center,
          style: TextStyle(
            fontSize: 32,
            fontWeight: FontWeight.bold,
            letterSpacing: 2,
          ),
        ),
        const SizedBox(height: 8),
        const Text(
          "Enter your phone number to login",
          textAlign: TextAlign.center,
          style: TextStyle(
            fontSize: 16,
            color: Colors.grey,
          ),
        ),
        const SizedBox(height: 32),
        TextFormField(
          controller: _phoneController,
          decoration: InputDecoration(
            labelText: "Phone Number",
            hintText: "(555) 123-4567",
            hintStyle: TextStyle(color: Colors.grey.shade400),
            border: const OutlineInputBorder(),
            prefixIcon: const Icon(Icons.phone),
            prefixText: "+1 ",
          ),
          keyboardType: TextInputType.phone,
          inputFormatters: [
            FilteringTextInputFormatter.digitsOnly,
            LengthLimitingTextInputFormatter(10),
          ],
          enabled: !_isLoading,
          onFieldSubmitted: (_) => _handleSendOtp(),
        ),
        const SizedBox(height: 24),
        FilledButton(
          onPressed: _isLoading ? null : _handleSendOtp,
          child: _isLoading
              ? const SizedBox(
                  height: 20,
                  width: 20,
                  child: CircularProgressIndicator(
                    strokeWidth: 2,
                    valueColor: AlwaysStoppedAnimation<Color>(Colors.white),
                  ),
                )
              : const Text("Send Login Code"),
        ),
        const SizedBox(height: 16),
        TextButton(
          onPressed: _isLoading
              ? null
              : () {
                  Navigator.of(context).pushReplacementNamed(AppRoutes.signup);
                },
          child: const Text("Don't have an account? Sign Up"),
        ),
      ],
    );
  }

  Widget _buildOtpStep() {
    final formattedPhone = _phone.length == 10
        ? "(${_phone.substring(0, 3)}) ${_phone.substring(3, 6)}-${_phone.substring(6)}"
        : _phone;

    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        Icon(
          Icons.sms,
          size: 64,
          color: Theme.of(context).colorScheme.primary,
        ),
        const SizedBox(height: 16),
        Text(
          "We sent a code to",
          textAlign: TextAlign.center,
          style: Theme.of(context).textTheme.titleMedium,
        ),
        const SizedBox(height: 4),
        Text(
          formattedPhone,
          textAlign: TextAlign.center,
          style: Theme.of(context).textTheme.titleLarge?.copyWith(
                fontWeight: FontWeight.bold,
              ),
        ),
        const SizedBox(height: 24),
        TextFormField(
          controller: _otpController,
          decoration: InputDecoration(
            labelText: "Login Code",
            hintText: "123456",
            hintStyle: TextStyle(color: Colors.grey.shade400),
            border: const OutlineInputBorder(),
            prefixIcon: const Icon(Icons.lock),
          ),
          keyboardType: TextInputType.number,
          inputFormatters: [
            FilteringTextInputFormatter.digitsOnly,
            LengthLimitingTextInputFormatter(6),
          ],
          textAlign: TextAlign.center,
          style: const TextStyle(
            fontSize: 24,
            letterSpacing: 8,
            fontWeight: FontWeight.bold,
          ),
          enabled: !_isLoading,
          onFieldSubmitted: (_) => _handleVerifyOtp(),
        ),
        const SizedBox(height: 24),
        FilledButton(
          onPressed: _isLoading ? null : _handleVerifyOtp,
          child: _isLoading
              ? const SizedBox(
                  height: 20,
                  width: 20,
                  child: CircularProgressIndicator(
                    strokeWidth: 2,
                    valueColor: AlwaysStoppedAnimation<Color>(Colors.white),
                  ),
                )
              : const Text("Login"),
        ),
        const SizedBox(height: 16),
        Row(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            TextButton(
              onPressed: _isLoading ? null : _handleResendOtp,
              child: const Text("Resend Code"),
            ),
            const SizedBox(width: 16),
            TextButton(
              onPressed: _isLoading
                  ? null
                  : () {
                      setState(() {
                        _currentStep = LoginStep.phone;
                        _otpController.clear();
                        _errorMessage = null;
                      });
                    },
              child: const Text("Change Number"),
            ),
          ],
        ),
      ],
    );
  }

  Widget _buildErrorMessage() {
    return Container(
      padding: const EdgeInsets.all(12),
      decoration: BoxDecoration(
        color: Colors.red.shade50,
        borderRadius: BorderRadius.circular(8),
        border: Border.all(color: Colors.red.shade300),
      ),
      child: Row(
        children: [
          Icon(Icons.error_outline, color: Colors.red.shade700),
          const SizedBox(width: 12),
          Expanded(
            child: Text(
              _errorMessage!,
              style: TextStyle(color: Colors.red.shade900),
            ),
          ),
        ],
      ),
    );
  }
}