import 'dart:convert';
import 'dart:developer';
import 'dart:io';

import 'package:dio/dio.dart';
import 'package:uuid/uuid.dart';

/// Wrapper for YooKassa payment response
class YookassaPayment {
  final String id;
  final String status;
  final String? confirmationUrl;

  YookassaPayment({
    required this.id,
    required this.status,
    this.confirmationUrl,
  });
}

/// Handler for YooKassa payment integration
/// Implements YooKassa API v3 according to OpenAPI specification
/// https://yookassa.ru/developers/using-api/openapi-specification
/// Note: Registered via @module in modules.dart to provide environment variables
class YooMoneyHandler {
  final String _shopId;
  final String _secretKey;
  final String? _returnUrlBase;
  late final Dio? _dio;
  final _uuid = const Uuid();
  static const String _baseUrl = 'https://api.yookassa.ru/v3';

  YooMoneyHandler({required String shopId, required String secretKey})
    : _shopId = shopId,
      _secretKey = secretKey,
      _returnUrlBase = Platform.environment['YOOKASSA_RETURN_URL'] {
    // Validate credentials
    if (_shopId.isEmpty || _secretKey.isEmpty) {
      log(
        'YooKassa credentials not configured. Payments will not work.',
        name: 'YooMoneyHandler',
      );
      _dio = null;
    } else {
      // Initialize Dio with Basic Auth
      // According to spec: Basic Auth with shopId:secretKey
      _dio = Dio(
        BaseOptions(
          baseUrl: _baseUrl,
          headers: {'Content-Type': 'application/json'},
        ),
      );

      // Set up Basic Auth interceptor
      _dio!.interceptors.add(
        InterceptorsWrapper(
          onRequest: (options, handler) {
            // Basic Auth: base64(shopId:secretKey)
            final credentials = base64Encode(
              utf8.encode('$_shopId:$_secretKey'),
            );
            options.headers['Authorization'] = 'Basic $credentials';
            handler.next(options);
          },
        ),
      );
    }
  }

  /// Check if YooKassa is properly configured
  bool get isConfigured => _dio != null;

  /// Create a payment in YooKassa
  /// According to spec: POST /v3/payments
  /// Required: amount, description
  /// Optional: confirmation (redirect), receipt, metadata
  Future<YookassaPayment> createPayment({
    required String amount,
    required String description,
    required String userId,
  }) async {
    if (!isConfigured) {
      throw Exception(
        'YooKassa is not configured. Please set YOOKASSA_SHOP_ID and YOOKASSA_SECRET_KEY environment variables.',
      );
    }

    try {
      // Parse amount - remove non-digit characters and format as decimal
      final amountValue = amount.replaceAll(RegExp(r'\D'), '');
      if (amountValue.isEmpty) {
        throw Exception('Invalid amount: $amount');
      }

      // Format amount as decimal string (e.g., "1000.00")
      // According to spec: MonetaryAmount.value must be decimal string
      final formattedAmount = amountValue.length > 2
          ? '${amountValue.substring(0, amountValue.length - 2)}.${amountValue.substring(amountValue.length - 2)}'
          : '0.${amountValue.padLeft(2, '0')}';

      // Build return URL for payment confirmation
      // According to spec: ReturnUrl - URL where user returns after payment
      // Max 2048 characters per spec
      final returnUrl = _buildReturnUrl(userId);

      // Generate idempotence key for request
      // According to spec: Idempotence-Key header (required)
      final idempotenceKey = _uuid.v4();

      // Create payment request according to CreatePaymentRequest schema
      final requestBody = {
        'amount': {'value': formattedAmount, 'currency': 'RUB'},
        'description': description.length > 128
            ? description.substring(0, 128)
            : description, // Max 128 chars per spec
        'confirmation': {'type': 'redirect', 'return_url': returnUrl},
        'capture': true, // Auto-capture payment when succeeded
        'metadata': {
          'userId': userId,
          'createdAt': DateTime.now().toIso8601String(),
        },
      };

      log(
        'Creating YooKassa payment',
        name: 'YooMoneyHandler',
        error: {
          'amount': formattedAmount,
          'description': description,
          'userId': userId,
        },
      );

      // Create payment via YooKassa API
      // POST /v3/payments with Idempotence-Key header
      final response = await _dio!.post<Map<String, dynamic>>(
        '/payments',
        data: requestBody,
        options: Options(headers: {'Idempotence-Key': idempotenceKey}),
      );

      final paymentData = response.data;
      if (paymentData == null) {
        throw Exception('Empty response from YooKassa API');
      }

      // Extract payment ID and status
      final paymentId = paymentData['id'] as String?;
      if (paymentId == null) {
        throw Exception('Payment ID not found in response');
      }

      final paymentStatus = paymentData['status'] as String? ?? 'pending';

      // Extract confirmation URL from payment response
      // According to spec: confirmation.confirmation_url for redirect type
      String? confirmationUrl;
      final confirmation = paymentData['confirmation'] as Map<String, dynamic>?;
      if (confirmation != null) {
        final confirmationType = confirmation['type'] as String?;
        if (confirmationType == 'redirect') {
          confirmationUrl = confirmation['confirmation_url'] as String?;
        } else {
          print('Payment created with confirmation type: $confirmationType');
        }
      }

      if (confirmationUrl == null) {
        print('Warning: No confirmation URL in payment response');
      }

      print('YooKassa payment created successfully');

      return YookassaPayment(
        id: paymentId,
        status: paymentStatus,
        confirmationUrl: confirmationUrl,
      );
    } on DioException catch (e, stackTrace) {
      print('YooKassa API error when creating payment $e $stackTrace');
      if (e.response != null) {
        print('YooKassa error response: ${e.response?.data}');
      }
      throw Exception(
        'Failed to create YooKassa payment: ${e.message ?? 'Unknown error'}',
      );
    } on Exception catch (e, stackTrace) {
      print('Unexpected error when creating YooKassa payment $e $stackTrace');
      rethrow;
    }
  }

  /// Check payment status in YooKassa
  /// According to spec: GET /v3/payments/{payment_id}
  Future<YookassaPayment> checkPayment(String paymentId) async {
    if (!isConfigured) {
      throw Exception(
        'YooKassa is not configured. Please set YOOKASSA_SHOP_ID and YOOKASSA_SECRET_KEY environment variables.',
      );
    }

    try {
      print('Checking YooKassa payment status $paymentId');

      // Get payment info from YooKassa API
      // According to spec: GET /v3/payments/{payment_id}
      final response = await _dio!.get<Map<String, dynamic>>(
        '/payments/$paymentId',
      );

      final paymentData = response.data;
      if (paymentData == null) {
        throw Exception('Empty response from YooKassa API');
      }

      // Extract payment ID and status
      final id = paymentData['id'] as String? ?? paymentId;
      final paymentStatus = paymentData['status'] as String? ?? 'pending';
      final paid = paymentData['paid'] as bool? ?? false;

      // Extract confirmation URL if available
      String? confirmationUrl;
      final confirmation = paymentData['confirmation'] as Map<String, dynamic>?;
      if (confirmation != null) {
        final confirmationType = confirmation['type'] as String?;
        if (confirmationType == 'redirect') {
          confirmationUrl = confirmation['confirmation_url'] as String?;
        }
      }

      print('''YooKassa payment status retrieved
        ${{'paymentId': id, 'status': paymentStatus, 'paid': paid}}''');

      return YookassaPayment(
        id: id,
        status: paymentStatus,
        confirmationUrl: confirmationUrl,
      );
    } on DioException catch (e, stackTrace) {
      print('YooKassa API error when checking payment $e $stackTrace');
      if (e.response != null) {
        print('YooKassa error response: ${e.response?.data}');
      }
      throw Exception(
        'Failed to check YooKassa payment: ${e.message ?? 'Unknown error'}',
      );
    } on Exception catch (e, stackTrace) {
      print('Unexpected error when checking YooKassa payment $e $stackTrace');
      rethrow;
    }
  }

  /// Build return URL for payment confirmation
  /// Uses YOOKASSA_RETURN_URL env var if set, otherwise defaults to web app URL
  String _buildReturnUrl(String userId) {
    // Use configured return URL base if available
    final returnUrlBase = _returnUrlBase;
    if (returnUrlBase != null && returnUrlBase.isNotEmpty) {
      return '$returnUrlBase?userId=$userId';
    }

    // Default to web app URL
    // This should be configured via environment variable in production
    return 'https://mnemo-cards.online/payment/return?userId=$userId';
  }
}