MireaBackend/Application/Cqrs/Day/Commands/CreateDay/CreateDayCommandHandler.cs

using MediatR;
using Microsoft.EntityFrameworkCore;
using Mirea.Api.DataAccess.Application.Common.Exceptions;
using Mirea.Api.DataAccess.Application.Interfaces.DbContexts.Schedule;
using System.Threading;
using System.Threading.Tasks;

namespace Mirea.Api.DataAccess.Application.Cqrs.Day.Commands.CreateDay;

public class CreateDayCommandHandler(IDayDbContext dbContext) : IRequestHandler<CreateDayCommand, int>
{
    public async Task<int> Handle(CreateDayCommand request, CancellationToken cancellationToken)
    {
        var entity = await dbContext.Days
            .FirstOrDefaultAsync(d =>
                d.LessonId == request.LessonId
                && d.PairNumber == request.PairNumber
                && d.GroupId == request.GroupId
                && d.Index == request.Index,
                cancellationToken: cancellationToken);

        if (entity != null)
            throw new RecordExistException(typeof(Domain.Schedule.Day), entity.Id);

        var day = new Domain.Schedule.Day()
        {
            Index = request.Index,
            PairNumber = request.PairNumber,
            GroupId = request.GroupId,
            LessonId = request.LessonId
        };

        var result = await dbContext.Days.AddAsync(day, cancellationToken);
        await dbContext.SaveChangesAsync(cancellationToken);

        return result.Entity.Id;
    }
}