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

import '../app/app_state.dart';
import '../services/api.dart';
import '../services/auth_storage.dart';

/// A dialog that handles phone number + OTP sign-in inline.
/// Returns true if sign-in was successful, false if cancelled.
class SignInDialog extends StatefulWidget {
  const SignInDialog({super.key});

  /// Shows the sign-in dialog and returns true if authenticated successfully
  static Future<bool> show(BuildContext context) async {
    final result = await showDialog<bool>(
      context: context,
      barrierDismissible: false,
      builder: (context) => const SignInDialog(),
    );
    return result ?? false;
  }

  @override
  State<SignInDialog> createState() => _SignInDialogState();
}

enum _SignInStep { phone, otp }

class _SignInDialogState extends State<SignInDialog> {
  _SignInStep _currentStep = _SignInStep.phone;

  final _phoneController = TextEditingController();
  final _otpController = TextEditingController();
  final _phoneFocus = FocusNode();
  final _otpFocus = FocusNode();

  String _uuid = '';
  String _phone = '';

  bool _isLoading = false;
  String? _errorMessage;

  @override
  void initState() {
    super.initState();
    // Auto-focus the phone field when dialog opens
    WidgetsBinding.instance.addPostFrameCallback((_) {
      _phoneFocus.requestFocus();
    });
  }

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

  String _formatPhoneDisplay(String phone) {
    if (phone.length == 10) {
      return '(${phone.substring(0, 3)}) ${phone.substring(3, 6)}-${phone.substring(6)}';
    }
    return phone;
  }

  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 = _SignInStep.otp;
        _isLoading = false;
      });

      // Auto-focus the OTP field
      WidgetsBinding.instance.addPostFrameCallback((_) {
        _otpFocus.requestFocus();
      });
    } 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,
      );

      // Update app state
      final appState = context.read<AppState>();
      appState.setUserId(response.userId);

      // Close dialog with success
      Navigator.of(context).pop(true);

      // Show welcome message
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(
          content: Text(
            'Welcome${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),
        ),
      );
    } catch (e) {
      if (!mounted) return;
      setState(() {
        _errorMessage = e.toString().replaceFirst('StateError: ', '');
        _isLoading = false;
      });
    }
  }

  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(
        const SnackBar(
          content: Text('New code sent!', style: TextStyle(color: Colors.black)),
          backgroundColor: Color(0xFF90EE90),
          behavior: SnackBarBehavior.floating,
        ),
      );
    } catch (e) {
      if (!mounted) return;
      setState(() {
        _errorMessage = e.toString().replaceFirst('StateError: ', '');
        _isLoading = false;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Dialog(
      shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(20)),
      child: Padding(
        padding: const EdgeInsets.all(24),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            // Header
            Row(
              children: [
                Expanded(
                  child: Text(
                    _currentStep == _SignInStep.phone ? 'Sign In to Continue' : 'Enter Code',
                    style: Theme.of(context).textTheme.titleLarge?.copyWith(
                          fontWeight: FontWeight.bold,
                        ),
                  ),
                ),
                IconButton(
                  icon: const Icon(Icons.close),
                  onPressed: _isLoading ? null : () => Navigator.of(context).pop(false),
                  padding: EdgeInsets.zero,
                  constraints: const BoxConstraints(),
                ),
              ],
            ),
            const SizedBox(height: 8),
            Text(
              _currentStep == _SignInStep.phone
                  ? 'Enter your phone number to add items to your cart'
                  : 'We sent a code to ${_formatPhoneDisplay(_phone)}',
              style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                    color: Colors.grey.shade600,
                  ),
            ),
            const SizedBox(height: 24),

            // Form content
            if (_currentStep == _SignInStep.phone) _buildPhoneStep(),
            if (_currentStep == _SignInStep.otp) _buildOtpStep(),

            // Error message
            if (_errorMessage != null) ...[
              const SizedBox(height: 16),
              Container(
                padding: const EdgeInsets.all(12),
                decoration: BoxDecoration(
                  color: Colors.red.shade50,
                  borderRadius: BorderRadius.circular(8),
                  border: Border.all(color: Colors.red.shade200),
                ),
                child: Row(
                  children: [
                    Icon(Icons.error_outline, color: Colors.red.shade600, size: 20),
                    const SizedBox(width: 8),
                    Expanded(
                      child: Text(
                        _errorMessage!,
                        style: TextStyle(color: Colors.red.shade800, fontSize: 13),
                      ),
                    ),
                  ],
                ),
              ),
            ],
          ],
        ),
      ),
    );
  }

  Widget _buildPhoneStep() {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        TextFormField(
          controller: _phoneController,
          focusNode: _phoneFocus,
          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: 20),
        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 Code'),
        ),
      ],
    );
  }

  Widget _buildOtpStep() {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        TextFormField(
          controller: _otpController,
          focusNode: _otpFocus,
          decoration: InputDecoration(
            labelText: 'Verification 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: 20,
            letterSpacing: 6,
            fontWeight: FontWeight.bold,
          ),
          enabled: !_isLoading,
          onFieldSubmitted: (_) => _handleVerifyOtp(),
        ),
        const SizedBox(height: 20),
        FilledButton(
          onPressed: _isLoading ? null : _handleVerifyOtp,
          child: _isLoading
              ? const SizedBox(
                  height: 20,
                  width: 20,
                  child: CircularProgressIndicator(
                    strokeWidth: 2,
                    valueColor: AlwaysStoppedAnimation<Color>(Colors.white),
                  ),
                )
              : const Text('Verify & Continue'),
        ),
        const SizedBox(height: 12),
        Row(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            TextButton(
              onPressed: _isLoading ? null : _handleResendOtp,
              child: const Text('Resend Code'),
            ),
            const SizedBox(width: 8),
            TextButton(
              onPressed: _isLoading
                  ? null
                  : () {
                      setState(() {
                        _currentStep = _SignInStep.phone;
                        _otpController.clear();
                        _errorMessage = null;
                      });
                      WidgetsBinding.instance.addPostFrameCallback((_) {
                        _phoneFocus.requestFocus();
                      });
                    },
              child: const Text('Change Number'),
            ),
          ],
        ),
      ],
    );
  }
}