// src/Webshop.Application/Services/Customers/OrderService.cs
using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Webshop.Application.DTOs.Customers;
using Webshop.Application.DTOs.Orders;
using Webshop.Domain.Entities;
using Webshop.Domain.Enums;
using Webshop.Domain.Interfaces;
using Webshop.Infrastructure.Data;

namespace Webshop.Application.Services.Customers
{
    public class OrderService : IOrderService
    {
        private readonly ApplicationDbContext _context;
        private readonly IOrderRepository _orderRepository;
        private readonly IProductRepository _productRepository;
        private readonly IShippingMethodRepository _shippingMethodRepository;
        private readonly ICustomerRepository _customerRepository;

        public OrderService(
            ApplicationDbContext context,
            IOrderRepository orderRepository,
            IProductRepository productRepository,
            IShippingMethodRepository shippingMethodRepository,
            ICustomerRepository customerRepository)
        {
            _context = context;
            _orderRepository = orderRepository;
            _productRepository = productRepository;
            _shippingMethodRepository = shippingMethodRepository;
            _customerRepository = customerRepository;
        }

        public async Task<(bool Success, OrderDetailDto? CreatedOrder, string? ErrorMessage)> CreateOrderAsync(CreateOrderDto orderDto, string userId)
        {
            await using var transaction = await _context.Database.BeginTransactionAsync();

            try
            {
                var customer = await _customerRepository.GetByUserIdAsync(userId);
                if (customer == null)
                {
                    return (false, null, "Kundenprofil nicht gefunden.");
                }

                var shippingMethod = await _shippingMethodRepository.GetByIdAsync(orderDto.ShippingMethodId);
                if (shippingMethod == null || !shippingMethod.IsActive) return (false, null, "Ungültige Versandmethode.");

                var paymentMethod = await _context.PaymentMethods.FindAsync(orderDto.PaymentMethodId);
                if (paymentMethod == null || !paymentMethod.IsActive) return (false, null, "Ungültige Zahlungsmethode.");

                if (!await _context.Addresses.AnyAsync(a => a.Id == orderDto.ShippingAddressId && a.Customer.AspNetUserId == userId) ||
                    !await _context.Addresses.AnyAsync(a => a.Id == orderDto.BillingAddressId && a.Customer.AspNetUserId == userId))
                {
                    return (false, null, "Ungültige oder nicht zugehörige Liefer- oder Rechnungsadresse.");
                }

                var orderItems = new List<OrderItem>();
                decimal itemsTotal = 0;

                foreach (var itemDto in orderDto.Items)
                {
                    var product = await _productRepository.GetProductByIdAsync(itemDto.ProductId);
                    if (product == null || !product.IsActive)
                    {
                        await transaction.RollbackAsync();
                        return (false, null, $"Produkt mit ID {itemDto.ProductId} ist nicht verfügbar.");
                    }

                    if (product.StockQuantity < itemDto.Quantity)
                    {
                        await transaction.RollbackAsync();
                        return (false, null, $"Nicht genügend Lagerbestand für {product.Name}. Verfügbar: {product.StockQuantity}.");
                    }

                    var orderItem = new OrderItem
                    {
                        Id = Guid.NewGuid(),
                        ProductId = product.Id,
                        ProductVariantId = itemDto.ProductVariantId,
                        ProductName = product.Name,
                        ProductSKU = product.SKU,
                        Quantity = itemDto.Quantity,
                        UnitPrice = product.Price,
                        TotalPrice = product.Price * itemDto.Quantity
                    };

                    orderItems.Add(orderItem);
                    itemsTotal += orderItem.TotalPrice;

                    product.StockQuantity -= itemDto.Quantity;
                    _context.Products.Update(product);
                }

                decimal shippingCost = shippingMethod.BaseCost;
                decimal taxAmount = (itemsTotal + shippingCost) * 0.19m; // Annahme: 19% MwSt.
                decimal orderTotal = itemsTotal + shippingCost + taxAmount;

                var newOrder = new Order
                {
                    Id = Guid.NewGuid(),
                    OrderNumber = $"WS-{DateTime.UtcNow:yyyyMMdd}-{new Random().Next(1000, 9999)}",
                    CustomerId = customer.Id, // Verwende die interne Customer-ID
                    OrderDate = DateTimeOffset.UtcNow,
                    OrderStatus = OrderStatus.Pending.ToString(),
                    PaymentStatus = PaymentStatus.Pending.ToString(),
                    OrderTotal = orderTotal,
                    ShippingCost = shippingCost,
                    TaxAmount = taxAmount,
                    DiscountAmount = 0,
                    PaymentMethod = paymentMethod.Name,
                    PaymentMethodId = paymentMethod.Id,
                    ShippingMethodId = shippingMethod.Id,
                    BillingAddressId = orderDto.BillingAddressId,
                    ShippingAddressId = orderDto.ShippingAddressId,
                    OrderItems = orderItems
                };

                await _orderRepository.AddAsync(newOrder);

                await transaction.CommitAsync();

                var createdOrderDto = new OrderDetailDto { Id = newOrder.Id, OrderNumber = newOrder.OrderNumber /* ... weitere Felder mappen ... */ };
                return (true, createdOrderDto, null);
            }
            catch (Exception ex)
            {
                await transaction.RollbackAsync();
                return (false, null, $"Ein unerwarteter Fehler ist aufgetreten: {ex.Message}");
            }
        }

        public async Task<IEnumerable<OrderSummaryDto>> GetMyOrdersAsync(string userId)
        {
            var customer = await _customerRepository.GetByUserIdAsync(userId);
            if (customer == null)
            {
                return new List<OrderSummaryDto>();
            }

            var orders = await _context.Orders
                .Where(o => o.CustomerId == customer.Id)
                .OrderByDescending(o => o.OrderDate)
                .ToListAsync();

            return orders.Select(o => new OrderSummaryDto
            {
                Id = o.Id,
                OrderNumber = o.OrderNumber,
                OrderDate = o.OrderDate,
                CustomerName = $"{customer.FirstName} {customer.LastName}",
                TotalAmount = o.OrderTotal,
                Status = Enum.TryParse<OrderStatus>(o.OrderStatus, true, out var orderStatus) ? orderStatus : OrderStatus.Pending,
                PaymentStatus = Enum.TryParse<PaymentStatus>(o.PaymentStatus, true, out var paymentStatus) ? paymentStatus : PaymentStatus.Pending
            }).ToList();
        }

        public async Task<OrderDetailDto?> GetMyOrderByIdAsync(Guid orderId, string userId)
        {
            var customer = await _customerRepository.GetByUserIdAsync(userId);
            if (customer == null)
            {
                return null;
            }

            var order = await _context.Orders
                .Include(o => o.BillingAddress) // Lade die Address-Entität
                .Include(o => o.ShippingAddress) // Lade die Address-Entität
                .Include(o => o.PaymentMethodInfo)
                .Include(o => o.OrderItems)
                    .ThenInclude(oi => oi.Product)
                .FirstOrDefaultAsync(o => o.Id == orderId && o.CustomerId == customer.Id);

            if (order == null)
            {
                return null;
            }

            // << KORREKTUR: Manuelles Mapping von Address-Entität zu AddressDto >>
            return new OrderDetailDto
            {
                Id = order.Id,
                OrderNumber = order.OrderNumber,
                OrderDate = order.OrderDate,
                CustomerId = order.CustomerId,
                Status = Enum.TryParse<OrderStatus>(order.OrderStatus, true, out var orderStatus) ? orderStatus : OrderStatus.Pending,
                TotalAmount = order.OrderTotal,
                ShippingAddress = new AddressDto
                {
                    Id = order.ShippingAddress.Id,
                    Street = order.ShippingAddress.Street,
                    HouseNumber = order.ShippingAddress.HouseNumber,
                    City = order.ShippingAddress.City,
                    PostalCode = order.ShippingAddress.PostalCode,
                    Country = order.ShippingAddress.Country,
                    Type = order.ShippingAddress.Type
                },
                BillingAddress = new AddressDto
                {
                    Id = order.BillingAddress.Id,
                    Street = order.BillingAddress.Street,
                    HouseNumber = order.BillingAddress.HouseNumber,
                    City = order.BillingAddress.City,
                    PostalCode = order.BillingAddress.PostalCode,
                    Country = order.BillingAddress.Country,
                    Type = order.BillingAddress.Type
                },
                PaymentMethod = order.PaymentMethod,
                PaymentStatus = Enum.TryParse<PaymentStatus>(order.PaymentStatus, true, out var paymentStatus) ? paymentStatus : PaymentStatus.Pending,
                ShippingTrackingNumber = order.ShippingTrackingNumber,
                ShippedDate = order.ShippedDate,
                DeliveredDate = order.DeliveredDate,
                OrderItems = order.OrderItems.Select(oi => new OrderItemDto
                {
                    Id = oi.Id,
                    ProductId = oi.ProductId,
                    ProductVariantId = oi.ProductVariantId,
                    ProductName = oi.ProductName,
                    ProductSKU = oi.ProductSKU,
                    Quantity = oi.Quantity,
                    UnitPrice = oi.UnitPrice,
                    TotalPrice = oi.TotalPrice
                }).ToList()
            };
        }
    }
}