components/LiteCharms.Features/ShoppingCarts/Commands/Handlers/AddItemToShoppingCartCommandHandler.cs

using LiteCharms.Infrastructure.Database;

namespace LiteCharms.Features.ShoppingCarts.Commands.Handlers;

public class AddItemToShoppingCartCommandHandler(IDbContextFactory<ShopDbContext> contextFactory) : IRequestHandler<AddItemToShoppingCartCommand, Result>
{
    public async ValueTask<Result> Handle(AddItemToShoppingCartCommand request, CancellationToken cancellationToken)
    {
        try
        {
            using var context = await contextFactory.CreateDbContextAsync(cancellationToken);

            if (!await context.ProductPrices.AnyAsync(c => c.Id == request.ProductPriceId, cancellationToken))
                return Result.Fail($"Product item could not be found with id {request.ProductPriceId}");

            var cart = await context.ShoppingCarts.FirstOrDefaultAsync(c => c.Id == request.ShoppingCartId, cancellationToken);

            if (cart is null)
                return Result.Fail($"Shopping cart could not be found with id {request.ShoppingCartId}");

            if (cart.ShoppingCartItems?.Any(i => i.ProductPriceId == request.ProductPriceId) == true)
                return Result.Fail($"Item already in shopping cart with id {request.ShoppingCartId}");

            context.ShoppingCartItems.Add(new Entities.ShoppingCartItem
            {
                ShoppingCartId = request.ShoppingCartId,
                ProductPriceId = request.ProductPriceId,
                Quantity = request.Quantity
            });

            return await context.SaveChangesAsync(cancellationToken) > 0
                ? Result.Ok()
                : Result.Fail($"Failed to add cart item with id {request.ProductPriceId}");
        }
        catch (Exception ex)
        {
            return Result.Fail(new Error(ex.Message).CausedBy(ex));
        }
    }
}