// src/Webshop.Application/Services/Admin/AdminPaymentMethodService.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json; // Wichtig für JsonSerializer
using System.Threading.Tasks;
using Webshop.Application.DTOs.Payments; // AdminPaymentMethodDto und die neuen Configuration-DTOs
using Webshop.Domain.Entities; // PaymentMethod
using Webshop.Domain.Enums; // PaymentGatewayType
using Webshop.Domain.Interfaces; // IPaymentMethodRepository

namespace Webshop.Application.Services.Admin
{
    public class AdminPaymentMethodService : IAdminPaymentMethodService
    {
        private readonly IPaymentMethodRepository _paymentMethodRepository;

        public AdminPaymentMethodService(IPaymentMethodRepository paymentMethodRepository)
        {
            _paymentMethodRepository = paymentMethodRepository;
        }

        public async Task<IEnumerable<AdminPaymentMethodDto>> GetAllAsync()
        {
            var paymentMethods = await _paymentMethodRepository.GetAllAsync();

            return paymentMethods.Select(pm => new AdminPaymentMethodDto
            {
                Id = pm.Id,
                Name = pm.Name,
                Description = pm.Description,
                IsActive = pm.IsActive,
                PaymentGatewayType = pm.PaymentGatewayType,
                // Deserialisiere den JSON-String aus der DB in ein Objekt für die Admin-Ansicht
                Configuration = pm.Configuration != null ? JsonSerializer.Deserialize<object>(pm.Configuration) : null,
                ProcessingFee = pm.ProcessingFee
            }).ToList();
        }

        public async Task<AdminPaymentMethodDto?> GetByIdAsync(Guid id)
        {
            var paymentMethod = await _paymentMethodRepository.GetByIdAsync(id);
            if (paymentMethod == null) return null;

            return new AdminPaymentMethodDto
            {
                Id = paymentMethod.Id,
                Name = paymentMethod.Name,
                Description = paymentMethod.Description,
                IsActive = paymentMethod.IsActive,
                PaymentGatewayType = paymentMethod.PaymentGatewayType,
                // Deserialisiere den JSON-String aus der DB in ein Objekt
                Configuration = paymentMethod.Configuration != null ? JsonSerializer.Deserialize<object>(paymentMethod.Configuration) : null,
                ProcessingFee = paymentMethod.ProcessingFee
            };
        }

        public async Task<AdminPaymentMethodDto> CreateAsync(AdminPaymentMethodDto paymentMethodDto)
        {
            var (isValid, configJson, errorMessage) = ValidateAndSerializeConfiguration(paymentMethodDto.PaymentGatewayType, paymentMethodDto.Configuration);
            if (!isValid)
            {
                // In einer echten Anwendung würden Sie hier eine benutzerdefinierte Validierungs-Exception werfen,
                // damit der Controller einen 400 Bad Request zurückgeben kann.
                throw new ArgumentException(errorMessage);
            }

            var newPaymentMethod = new PaymentMethod
            {
                Id = Guid.NewGuid(),
                Name = paymentMethodDto.Name,
                Description = paymentMethodDto.Description,
                IsActive = paymentMethodDto.IsActive,
                PaymentGatewayType = paymentMethodDto.PaymentGatewayType,
                Configuration = configJson, // Speichere den validierten JSON-String
                ProcessingFee = paymentMethodDto.ProcessingFee
            };

            await _paymentMethodRepository.AddAsync(newPaymentMethod);

            paymentMethodDto.Id = newPaymentMethod.Id;
            return paymentMethodDto;
        }

        public async Task<bool> UpdateAsync(AdminPaymentMethodDto paymentMethodDto)
        {
            var existingPaymentMethod = await _paymentMethodRepository.GetByIdAsync(paymentMethodDto.Id);
            if (existingPaymentMethod == null) return false;

            var (isValid, configJson, errorMessage) = ValidateAndSerializeConfiguration(paymentMethodDto.PaymentGatewayType, paymentMethodDto.Configuration);
            if (!isValid)
            {
                throw new ArgumentException(errorMessage);
            }

            existingPaymentMethod.Name = paymentMethodDto.Name;
            existingPaymentMethod.Description = paymentMethodDto.Description;
            existingPaymentMethod.IsActive = paymentMethodDto.IsActive;
            existingPaymentMethod.PaymentGatewayType = paymentMethodDto.PaymentGatewayType;
            existingPaymentMethod.Configuration = configJson;
            existingPaymentMethod.ProcessingFee = paymentMethodDto.ProcessingFee;

            await _paymentMethodRepository.UpdateAsync(existingPaymentMethod);
            return true;
        }

        public async Task<bool> DeleteAsync(Guid id)
        {
            var paymentMethod = await _paymentMethodRepository.GetByIdAsync(id);
            if (paymentMethod == null) return false;

            await _paymentMethodRepository.DeleteAsync(id);
            return true;
        }

        private (bool IsValid, string? ConfigJson, string? ErrorMessage) ValidateAndSerializeConfiguration(PaymentGatewayType type, object? configObject)
        {
            if (configObject == null) return (true, null, null);

            var configElement = (JsonElement)configObject;

            try
            {
                switch (type)
                {
                    case PaymentGatewayType.BankTransfer:
                        var bankConfig = configElement.Deserialize<BankTransferConfigurationDto>();
                        if (bankConfig == null || string.IsNullOrEmpty(bankConfig.IBAN) || string.IsNullOrEmpty(bankConfig.BIC))
                        {
                            return (false, null, "Für Banküberweisung müssen IBAN und BIC angegeben werden.");
                        }
                        return (true, JsonSerializer.Serialize(bankConfig), null);

                    case PaymentGatewayType.Stripe:
                        var stripeConfig = configElement.Deserialize<StripeConfigurationDto>();
                        if (stripeConfig == null || string.IsNullOrEmpty(stripeConfig.PublicKey) || string.IsNullOrEmpty(stripeConfig.SecretKey))
                        {
                            return (false, null, "Für Stripe müssen PublicKey und SecretKey angegeben werden.");
                        }
                        return (true, JsonSerializer.Serialize(stripeConfig), null);

                    case PaymentGatewayType.PayPal:
                        var payPalConfig = configElement.Deserialize<PayPalConfigurationDto>();
                        if (payPalConfig == null || string.IsNullOrEmpty(payPalConfig.ClientId) || string.IsNullOrEmpty(payPalConfig.ClientSecret))
                        {
                            return (false, null, "Für PayPal müssen ClientId und ClientSecret angegeben werden.");
                        }
                        return (true, JsonSerializer.Serialize(payPalConfig), null);

                    default:
                        // Für Typen wie Invoice oder CashOnDelivery, die keine spezielle Konfiguration brauchen,
                        // ist ein leeres JSON-Objekt '{}' ein gültiger Wert.
                        return (true, JsonSerializer.Serialize(new object()), null);
                }
            }
            catch (JsonException ex)
            {
                return (false, null, $"Ungültiges JSON-Format für die Konfiguration: {ex.Message}");
            }
        }
    }
}