import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import '../../widgets/auth_button.dart';
import '../providers/auth_provider.dart';
import '../../../../core/errors/auth_exceptions.dart';
import '../../../../core/utils/password_validator.dart';
import '../../../../core/router/app_router.dart';

/// Password update page for handling password reset from email links
/// 
/// This page handles the password reset flow when users click on reset links
/// from their email. It validates the reset token and allows users to set
/// a new password.
class UpdatePasswordPage extends ConsumerStatefulWidget {
  const UpdatePasswordPage({super.key});

  @override
  ConsumerState<UpdatePasswordPage> createState() => _UpdatePasswordPageState();
}

class _UpdatePasswordPageState extends ConsumerState<UpdatePasswordPage> {
  final _formKey = GlobalKey<FormState>();
  final _newPasswordController = TextEditingController();
  final _confirmPasswordController = TextEditingController();
  
  bool _isLoading = false;
  bool _showPassword = false;
  bool _showConfirmPassword = false;
  String? _errorMessage;
  bool _passwordUpdated = false;

  String? _resetToken;
  String? _resetEmail;

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

  @override
  void dispose() {
    _newPasswordController.dispose();
    _confirmPasswordController.dispose();
    super.dispose();
  }

  /// Extract reset token and email from URL parameters for deep linking
  void _extractResetParameters() {
    final resetData = AppRouter.handlePasswordResetDeepLink(context);
    _resetToken = resetData['token'];
    _resetEmail = resetData['email'];
    
    if (_resetToken != null && _resetEmail != null) {
      print('Reset parameters extracted for email: $_resetEmail');
    }
  }

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

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

    try {
      final authProvider = ref.read(authProvider.notifier);
      
      // Use reset token and email if available (from deep linking)
      if (_resetToken != null && _resetEmail != null) {
        await authProvider.updatePasswordWithToken(
          _resetToken!,
          _resetEmail!,
          _newPasswordController.text.trim(),
        );
      } else {
        // Fallback to regular password update
        await authProvider.updatePasswordFromReset(
          _newPasswordController.text.trim(),
        );
      }
      
      if (mounted) {
        setState(() {
          _isLoading = false;
          _passwordUpdated = true;
        });
      }
    } catch (e) {
      if (mounted) {
        setState(() {
          _isLoading = false;
          _errorMessage = _mapErrorToMessage(e);
        });
      }
    }
  }

  String _mapErrorToMessage(Object error) {
    if (error is InvalidTokenException) {
      return 'This password reset link has expired or is invalid. Please request a new one.';
    } else if (error is WeakPasswordException) {
      return 'Password is too weak. Please choose a stronger password.';
    } else if (error is SessionExpiredException) {
      return 'Password reset session expired. Please request a new reset link.';
    } else if (error is NetworkException) {
      return 'Network error. Please check your connection and try again.';
    } else if (error is AuthException) {
      return error.message;
    } else {
      return 'An unexpected error occurred. Please try again.';
    }
  }

  void _navigateToLogin() {
    Navigator.of(context).pushReplacementNamed('/login');
  }

  bool _isPasswordValid() {
    final password = _newPasswordController.text;
    return password.length >= 8 &&
        password.contains(RegExp(r'[A-Z]')) &&
        password.contains(RegExp(r'[a-z]')) &&
        password.contains(RegExp(r'[0-9]'));
  }

  String? _validatePassword(String? value) {
    if (value == null || value.isEmpty) {
      return 'Please enter a new password';
    }
    
    if (value.length < 8) {
      return 'Password must be at least 8 characters';
    }
    
    if (!value.contains(RegExp(r'[A-Z]'))) {
      return 'Password must contain at least one uppercase letter';
    }
    
    if (!value.contains(RegExp(r'[a-z]'))) {
      return 'Password must contain at least one lowercase letter';
    }
    
    if (!value.contains(RegExp(r'[0-9]'))) {
      return 'Password must contain at least one number';
    }
    
    return null;
  }

  String? _validateConfirmPassword(String? value) {
    if (value == null || value.isEmpty) {
      return 'Please confirm your new password';
    }
    
    if (value != _newPasswordController.text) {
      return 'Passwords do not match';
    }
    
    return null;
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final colorScheme = theme.colorScheme;

    return Scaffold(
      appBar: AppBar(
        title: const Text('Update Password'),
        backgroundColor: Colors.transparent,
        elevation: 0,
        leading: IconButton(
          icon: const Icon(Icons.close),
          onPressed: _navigateToLogin,
          tooltip: 'Cancel',
        ),
      ),
      body: SafeArea(
        child: SingleChildScrollView(
          padding: const EdgeInsets.all(24.0),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: [
              const SizedBox(height: 32),
              if (!_passwordUpdated) ...[
                _buildHeader(),
                const SizedBox(height: 32),
                _buildInstructions(),
                const SizedBox(height: 32),
                _buildPasswordForm(),
                const SizedBox(height: 24),
                _buildSubmitButton(),
                if (_errorMessage != null) ...[
                  const SizedBox(height: 16),
                  _buildErrorMessage(),
                ],
              ] else ...[
                _buildSuccessMessage(),
                const SizedBox(height: 32),
                _buildLoginButton(),
              ],
            ],
          ),
        ),
      ),
    );
  }

  Widget _buildHeader() {
    return Column(
      children: [
        Icon(
          Icons.lock_outline,
          size: 64,
          color: Theme.of(context).colorScheme.primary,
        ),
        const SizedBox(height: 16),
        Text(
          'Set New Password',
          style: Theme.of(context).textTheme.headlineMedium?.copyWith(
            fontWeight: FontWeight.bold,
          ),
        ),
      ],
    );
  }

  Widget _buildInstructions() {
    return Container(
      padding: const EdgeInsets.all(16),
      decoration: BoxDecoration(
        color: Theme.of(context).colorScheme.surfaceVariant,
        borderRadius: BorderRadius.circular(12),
      ),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Row(
            children: [
              Icon(
                Icons.info_outline,
                size: 20,
                color: Theme.of(context).colorScheme.onSurfaceVariant,
              ),
              const SizedBox(width: 8),
              Expanded(
                child: Text(
                  'Create a strong password for your account security.',
                  style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                    color: Theme.of(context).colorScheme.onSurfaceVariant,
                  ),
                ),
              ),
            ],
          ),
        ],
      ),
    );
  }

  Widget _buildPasswordForm() {
    return Form(
      key: _formKey,
      child: Column(
        children: [
          TextFormField(
            controller: _newPasswordController,
            obscureText: !_showPassword,
            enabled: !_isLoading,
            decoration: InputDecoration(
              labelText: 'New Password',
              hintText: 'Enter your new password',
              prefixIcon: const Icon(Icons.lock_outline),
              suffixIcon: IconButton(
                icon: Icon(
                  _showPassword ? Icons.visibility : Icons.visibility_off,
                ),
                onPressed: () {
                  setState(() {
                    _showPassword = !_showPassword;
                  });
                },
              ),
            ),
            validator: _validatePassword,
            autovalidateMode: AutovalidateMode.onUserInteraction,
          ),
          const SizedBox(height: 16),
          TextFormField(
            controller: _confirmPasswordController,
            obscureText: !_showConfirmPassword,
            enabled: !_isLoading,
            decoration: InputDecoration(
              labelText: 'Confirm Password',
              hintText: 'Confirm your new password',
              prefixIcon: const Icon(Icons.lock_outline),
              suffixIcon: IconButton(
                icon: Icon(
                  _showConfirmPassword ? Icons.visibility : Icons.visibility_off,
                ),
                onPressed: () {
                  setState(() {
                    _showConfirmPassword = !_showConfirmPassword;
                  });
                },
              ),
            ),
            validator: _validateConfirmPassword,
            autovalidateMode: AutovalidateMode.onUserInteraction,
          ),
          const SizedBox(height: 16),
          _buildPasswordStrengthIndicator(),
        ],
      ),
    );
  }

  Widget _buildPasswordStrengthIndicator() {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Row(
          children: [
            Text(
              'Password Strength:',
              style: Theme.of(context).textTheme.bodySmall?.copyWith(
                fontWeight: FontWeight.w500,
              ),
            ),
            const SizedBox(width: 8),
            Text(
              _getPasswordStrengthText(),
              style: Theme.of(context).textTheme.bodySmall?.copyWith(
                color: _getPasswordStrengthColor(),
                fontWeight: FontWeight.bold,
              ),
            ),
          ],
        ),
        const SizedBox(height: 8),
        LinearProgressIndicator(
          value: _getPasswordStrength(),
          backgroundColor: Theme.of(context).colorScheme.surfaceVariant,
          valueColor: AlwaysStoppedAnimation<Color>(_getPasswordStrengthColor()),
        ),
        const SizedBox(height: 8),
        Text(
          'Password must contain:\n• At least 8 characters\n• Uppercase and lowercase letters\n• At least one number',
          style: Theme.of(context).textTheme.bodySmall?.copyWith(
            color: Theme.of(context).colorScheme.onSurfaceVariant,
          ),
        ),
      ],
    );
  }

  double _getPasswordStrength() {
    final password = _newPasswordController.text;
    double strength = 0.0;
    
    if (password.length >= 8) strength += 0.25;
    if (password.contains(RegExp(r'[A-Z]'))) strength += 0.25;
    if (password.contains(RegExp(r'[a-z]'))) strength += 0.25;
    if (password.contains(RegExp(r'[0-9]'))) strength += 0.25;
    
    return strength;
  }

  String _getPasswordStrengthText() {
    final strength = _getPasswordStrength();
    if (strength <= 0.25) return 'Weak';
    if (strength <= 0.5) return 'Fair';
    if (strength <= 0.75) return 'Good';
    return 'Strong';
  }

  Color _getPasswordStrengthColor() {
    final strength = _getPasswordStrength();
    if (strength <= 0.25) return Colors.red;
    if (strength <= 0.5) return Colors.orange;
    if (strength <= 0.75) return Colors.yellow.shade700;
    return Colors.green;
  }

  Widget _buildSubmitButton() {
    return AuthButton(
      text: 'Update Password',
      onPressed: _isPasswordValid() ? _handlePasswordUpdate : null,
      isLoading: _isLoading,
      icon: const Icon(Icons.lock_reset),
    );
  }

  Widget _buildErrorMessage() {
    return Container(
      padding: const EdgeInsets.all(12),
      decoration: BoxDecoration(
        color: Theme.of(context).colorScheme.errorContainer,
        borderRadius: BorderRadius.circular(8),
      ),
      child: Row(
        children: [
          Icon(
            Icons.error_outline,
            color: Theme.of(context).colorScheme.error,
            size: 20,
          ),
          const SizedBox(width: 8),
          Expanded(
            child: Text(
              _errorMessage!,
              style: Theme.of(context).textTheme.bodySmall?.copyWith(
                color: Theme.of(context).colorScheme.error,
              ),
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildSuccessMessage() {
    return Container(
      padding: const EdgeInsets.all(16),
      decoration: BoxDecoration(
        color: Theme.of(context).colorScheme.primaryContainer,
        borderRadius: BorderRadius.circular(12),
      ),
      child: Column(
        children: [
          Icon(
            Icons.check_circle_outline,
            size: 64,
            color: Theme.of(context).colorScheme.primary,
          ),
          const SizedBox(height: 16),
          Text(
            'Password Updated!',
            style: Theme.of(context).textTheme.titleLarge?.copyWith(
              fontWeight: FontWeight.bold,
              color: Theme.of(context).colorScheme.onPrimaryContainer,
            ),
          ),
          const SizedBox(height: 8),
          Text(
            'Your password has been successfully updated. You can now sign in with your new password.',
            style: Theme.of(context).textTheme.bodyMedium?.copyWith(
              color: Theme.of(context).colorScheme.onPrimaryContainer,
            ),
            textAlign: TextAlign.center,
          ),
        ],
      ),
    );
  }

  Widget _buildLoginButton() {
    return AuthButton(
      text: 'Sign In',
      onPressed: _navigateToLogin,
      variant: AuthButtonVariant.primary,
      icon: const Icon(Icons.login),
    );
  }
}