using CMSMicroservice.Application.Common.Interfaces;
using CMSMicroservice.Application.Common.Services;
using CMSMicroservice.Domain.Entities.DiscountShop;
using CMSMicroservice.Domain.Entities.Payment;
using CMSMicroservice.Domain.Enums;
using MediatR;
using Microsoft.EntityFrameworkCore;

namespace CMSMicroservice.Application.DiscountShopCQ.Commands.PlaceOrder;

public class PlaceOrderCommandHandler : IRequestHandler<PlaceOrderCommand, PlaceOrderResponseDto>
{
    private readonly IApplicationDbContext _context;
    private readonly IInventoryService _inventoryService;

    public PlaceOrderCommandHandler(
        IApplicationDbContext context,
        IInventoryService inventoryService)
    {
        _context = context;
        _inventoryService = inventoryService;
    }

    public async Task<PlaceOrderResponseDto> Handle(PlaceOrderCommand request, CancellationToken cancellationToken)
    {
        // Get user wallet
        var userWallet = await _context.UserWallets
            .FirstOrDefaultAsync(w => w.UserId == request.UserId, cancellationToken);

        if (userWallet == null)
        {
            return new PlaceOrderResponseDto
            {
                Success = false,
                Message = "کیف پول کاربر یافت نشد"
            };
        }

        // Get cart items with products
        var cartItems = await _context.DiscountShoppingCarts
            .Where(c => c.UserId == request.UserId)
            .Include(c => c.Product)
            .ToListAsync(cancellationToken);

        if (!cartItems.Any())
        {
            return new PlaceOrderResponseDto
            {
                Success = false,
                Message = "سبد خرید خالی است"
            };
        }

        // Validate stock and calculate totals
        long totalAmount = 0;
        long totalDiscountAmount = 0;
        var orderDetails = new List<DiscountOrderDetail>();

        foreach (var cartItem in cartItems)
        {
            var product = cartItem.Product;

            // Check stock
            if (product.RemainingCount < cartItem.Count)
            {
                return new PlaceOrderResponseDto
                {
                    Success = false,
                    Message = $"موجودی محصول '{product.Title}' کافی نیست"
                };
            }

            // Check if product is active
            if (!product.IsActive)
            {
                return new PlaceOrderResponseDto
                {
                    Success = false,
                    Message = $"محصول '{product.Title}' غیرفعال است"
                };
            }

            // Calculate discount for this product
            var itemTotal = product.Price * cartItem.Count;
            var maxDiscountForItem = (itemTotal * product.MaxDiscountPercent) / 100;

            totalAmount += itemTotal;
            totalDiscountAmount += maxDiscountForItem;

            orderDetails.Add(new DiscountOrderDetail
            {
                ProductId = product.Id,
                Count = cartItem.Count,
                UnitPrice = product.Price,
                DiscountPercentUsed = product.MaxDiscountPercent,
                DiscountAmount = maxDiscountForItem,
                FinalPrice = itemTotal - maxDiscountForItem
            });
        }

        // Validate discount balance usage
        var maxDiscountBalanceUsable = totalDiscountAmount;
        var actualDiscountBalanceUsed = Math.Min(request.DiscountBalanceToUse, maxDiscountBalanceUsable);
        actualDiscountBalanceUsed = Math.Min(actualDiscountBalanceUsed, userWallet.DiscountBalance);

        if (actualDiscountBalanceUsed < request.DiscountBalanceToUse)
        {
            return new PlaceOrderResponseDto
            {
                Success = false,
                Message = $"موجودی تخفیف کافی نیست. حداکثر قابل استفاده: {maxDiscountBalanceUsable:N0} تومان، موجودی شما: {userWallet.DiscountBalance:N0} تومان"
            };
        }

        var gatewayAmountRequired = totalAmount - actualDiscountBalanceUsed;

        // Calculate VAT using centralized calculator
        var vatBreakdown = VatCalculator.CalculateBreakdown(gatewayAmountRequired);
        var vatAmount = vatBreakdown.VatAmount;
        var finalGatewayAmount = vatBreakdown.GrossAmount;

        // Create transaction for gateway payment
        var transaction = new Transaction
        {
            Amount = finalGatewayAmount,
            Description = $"خرید از فروشگاه تخفیف - مبلغ کل: {totalAmount:N0}، اعتبار تخفیف: {actualDiscountBalanceUsed:N0}",
            PaymentStatus = PaymentStatus.Pending,
            Type = TransactionType.DiscountShopPurchase
        };

        _context.Transactions.Add(transaction);
        await _context.SaveChangesAsync(cancellationToken);

        // Create order
        var order = new DiscountOrder
        {
            UserId = request.UserId,
            TotalAmount = totalAmount,
            DiscountBalanceUsed = actualDiscountBalanceUsed,
            GatewayAmountPaid = finalGatewayAmount,
            VatAmount = vatAmount,
            PaymentStatus = PaymentStatus.Pending,
            TransactionId = transaction.Id,
            UserAddressId = request.UserAddressId,
            DeliveryStatus = DeliveryStatus.Pending
        };

        _context.DiscountOrders.Add(order);
        await _context.SaveChangesAsync(cancellationToken);

        // Add order details
        foreach (var detail in orderDetails)
        {
            detail.DiscountOrderId = order.Id;
        }

        _context.DiscountOrderDetails.AddRange(orderDetails);

        // رزرو موجودی برای سفارش pending
        foreach (var cartItem in cartItems)
        {
            await _inventoryService.ReserveStockAsync(
                cartItem.ProductId,
                ProductType.DiscountProduct,
                cartItem.Count,
                order.Id,
                cancellationToken);
        }

        // Clear cart
        _context.DiscountShoppingCarts.RemoveRange(cartItems);

        await _context.SaveChangesAsync(cancellationToken);

        return new PlaceOrderResponseDto
        {
            Success = true,
            Message = "سفارش ایجاد شد. لطفا پرداخت را تکمیل کنید",
            OrderId = order.Id,
            TransactionId = transaction.Id,
            TotalAmount = totalAmount,
            DiscountBalanceUsed = actualDiscountBalanceUsed,
            GatewayAmountRequired = finalGatewayAmount
        };
    }
}