import 'package:get/get.dart';
import 'package:flutter/services.dart';
import 'api_service.dart';

/// PhonePe Payment Gateway Integration Service
/// Handles PhonePe payments for chit fund installments
class PhonePeService extends GetxController {
  static PhonePeService get to => Get.find();
  
  final ApiService _apiService = ApiService();
  
  // Observable state
  final RxBool _isProcessing = false.obs;
  final RxString _error = ''.obs;
  final RxString _currentTransactionId = ''.obs;
  
  // Getters
  bool get isProcessing => _isProcessing.value;
  String get error => _error.value;
  String get currentTransactionId => _currentTransactionId.value;
  
  /// Initiate a payment for monthly installment
  Future<Map<String, dynamic>?> initiatePayment({
    required String groupId,
    required String userId,
    required int month,
    required int year,
    required double amount,
    required String userName,
    required String userMobile,
  }) async {
    try {
      _isProcessing.value = true;
      _error.value = '';
      
      // Generate unique transaction ID
      final transactionId = 'TXN_${DateTime.now().millisecondsSinceEpoch}';
      _currentTransactionId.value = transactionId;
      
      // Create payment request on backend
      final response = await _apiService.post(
        '/payments/phonepe/initiate',
        {
          'group_id': groupId,
          'user_id': userId,
          'month': month,
          'year': year,
          'amount': amount,
          'transaction_id': transactionId,
          'user_name': userName,
          'user_mobile': userMobile,
        },
      );
      
      if (response['success'] == true) {
        final paymentData = response['data'];
        
        // Launch PhonePe payment
        final result = await _launchPhonePePayment(paymentData);
        
        if (result != null && result['success'] == true) {
          // Verify payment on backend
          return await verifyPayment(transactionId);
        } else {
          _error.value = result?['message'] ?? 'Payment failed';
          return null;
        }
      } else {
        _error.value = response['message'] ?? 'Failed to initiate payment';
        return null;
      }
    } catch (e) {
      print('PhonePe payment error: $e');
      _error.value = 'Payment failed: $e';
      return null;
    } finally {
      _isProcessing.value = false;
    }
  }
  
  /// Launch PhonePe payment flow
  Future<Map<String, dynamic>?> _launchPhonePePayment(
    Map<String, dynamic> paymentData,
  ) async {
    try {
      // Use PhonePe SDK or deep link
      final String paymentUrl = paymentData['payment_url'];
      final String checksum = paymentData['checksum'];
      
      // Method 1: Using platform channel (if PhonePe SDK is integrated)
      try {
        final result = await _invokePhonePeSDK(
          paymentUrl: paymentUrl,
          checksum: checksum,
        );
        return result;
      } catch (e) {
        print('PhonePe SDK not available: $e');
        
        // Method 2: Using URL launcher as fallback
        return await _launchPhonePeUrl(paymentUrl);
      }
    } catch (e) {
      print('Error launching PhonePe: $e');
      return {
        'success': false,
        'message': 'Failed to launch PhonePe: $e',
      };
    }
  }
  
  /// Invoke PhonePe SDK via platform channel
  Future<Map<String, dynamic>> _invokePhonePeSDK({
    required String paymentUrl,
    required String checksum,
  }) async {
    const platform = MethodChannel('com.luckychit.phonepe');
    
    try {
      final result = await platform.invokeMethod('startPayment', {
        'paymentUrl': paymentUrl,
        'checksum': checksum,
        'callbackUrl': 'luckychit://payment/callback',
      });
      
      return {
        'success': true,
        'data': result,
      };
    } on PlatformException catch (e) {
      return {
        'success': false,
        'message': e.message ?? 'Payment failed',
      };
    }
  }
  
  /// Launch PhonePe using URL (fallback method)
  Future<Map<String, dynamic>> _launchPhonePeUrl(String paymentUrl) async {
    // This would use url_launcher in a real implementation
    // For now, return a simulated response
    return {
      'success': true,
      'message': 'Payment URL opened',
    };
  }
  
  /// Verify payment status on backend
  Future<Map<String, dynamic>?> verifyPayment(String transactionId) async {
    try {
      final response = await _apiService.post(
        '/payments/phonepe/verify',
        {'transaction_id': transactionId},
      );
      
      if (response['success'] == true) {
        return response['data'];
      } else {
        _error.value = response['message'] ?? 'Payment verification failed';
        return null;
      }
    } catch (e) {
      print('Payment verification error: $e');
      _error.value = 'Verification failed: $e';
      return null;
    }
  }
  
  /// Check payment status
  Future<String> getPaymentStatus(String transactionId) async {
    try {
      final response = await _apiService.get(
        '/payments/phonepe/status/$transactionId',
      );
      
      if (response['success'] == true) {
        return response['data']['status'] ?? 'pending';
      } else {
        return 'failed';
      }
    } catch (e) {
      print('Error checking payment status: $e');
      return 'error';
    }
  }
  
  /// Handle payment callback (for deep links)
  Future<void> handlePaymentCallback(Map<String, dynamic> callbackData) async {
    try {
      final transactionId = callbackData['transactionId'];
      final status = callbackData['status'];
      
      if (status == 'SUCCESS') {
        // Verify payment
        await verifyPayment(transactionId);
      } else {
        _error.value = 'Payment ${status.toLowerCase()}';
      }
    } catch (e) {
      print('Error handling callback: $e');
      _error.value = 'Failed to process payment callback';
    }
  }
  
  /// Initiate refund (for cancelled payments)
  Future<bool> initiateRefund({
    required String transactionId,
    required double amount,
    String? reason,
  }) async {
    try {
      final response = await _apiService.post(
        '/payments/phonepe/refund',
        {
          'transaction_id': transactionId,
          'amount': amount,
          'reason': reason,
        },
      );
      
      return response['success'] == true;
    } catch (e) {
      print('Refund error: $e');
      _error.value = 'Refund failed: $e';
      return false;
    }
  }
  
  /// Get transaction details
  Future<Map<String, dynamic>?> getTransactionDetails(
    String transactionId,
  ) async {
    try {
      final response = await _apiService.get(
        '/payments/phonepe/transaction/$transactionId',
      );
      
      if (response['success'] == true) {
        return response['data'];
      }
      return null;
    } catch (e) {
      print('Error fetching transaction: $e');
      return null;
    }
  }
  
  /// Clear error state
  void clearError() {
    _error.value = '';
  }
}