Api/NetinaShop.Repository/Handlers/Discounts/CalculateDiscountCommandHandler.cs

namespace NetinaShop.Repository.Handlers.Discounts;

public class CalculateDiscountCommandHandler : IRequestHandler<CalculateDiscountCommand , double>
{
    private readonly IRepositoryWrapper _repositoryWrapper;

    public CalculateDiscountCommandHandler(IRepositoryWrapper repositoryWrapper)
    {
        _repositoryWrapper = repositoryWrapper;
    }
    public async Task<double> Handle(CalculateDiscountCommand request, CancellationToken cancellationToken)
    {
        if (request.Order == null)
            throw new AppException("Order is null", ApiResultStatusCode.BadRequest);
        var discount = await _repositoryWrapper.SetRepository<Discount>()
            .TableNoTracking
            .FirstOrDefaultAsync(d => d.Code == request.DiscountCode, cancellationToken);
        if (discount == null)
            throw new AppException("Discount not found", ApiResultStatusCode.NotFound);

        double discountPrice = 0;

        if (discount.Type == DiscountType.All)
        {
            var totalPrice = request.Order.OrderProducts.Sum(op => op.ProductCost);
            discountPrice = discount.AmountType == DiscountAmountType.Amount
                ? totalPrice - discount.DiscountAmount
                : totalPrice - ((totalPrice / 100) * discount.DiscountAmount);
        }
        else if (discount.Type == DiscountType.Category)
        {
            var categoryDiscount = await _repositoryWrapper.SetRepository<CategoryDiscount>()
                .TableNoTracking
                .FirstOrDefaultAsync(d => d.Code == request.DiscountCode, cancellationToken);

            var totalPrice = request.Order.OrderProducts.Where(op=>op.ProductCategoryId == categoryDiscount!.CategoryId).Sum(op => op.ProductCost);
            discountPrice = discount.AmountType == DiscountAmountType.Amount
                ? totalPrice - discount.DiscountAmount
                : totalPrice - ((totalPrice / 100) * discount.DiscountAmount);
        }
        else if (discount.Type == DiscountType.Product)
        {
            var productDiscount = await _repositoryWrapper.SetRepository<ProductDiscount>()
                .TableNoTracking
                .FirstOrDefaultAsync(d => d.Code == request.DiscountCode, cancellationToken);

            var totalPrice = request.Order.OrderProducts.Where(op => op.ProductId == productDiscount!.ProductId).Sum(op => op.ProductCost);
            discountPrice = discount.AmountType == DiscountAmountType.Amount
                ? totalPrice - discount.DiscountAmount
                : totalPrice - ((totalPrice / 100) * discount.DiscountAmount);
        }
        else if (discount.Type == DiscountType.Subscriber)
        {
            throw new NotImplementedException("Subscribe discount not implemented");
        }

        return discountPrice;
    }
}