using LiteCqrs;
using Microsoft.EntityFrameworkCore;
using TeleWave.Application.Common.Interfaces;
using TeleWave.Application.Common.Models;

namespace TeleWave.Application.Programming.Templates.Junctions;

public sealed class DeleteJunctionCommandHandler(IAppDbContext dbContext)
    : ICommandHandler<DeleteJunctionCommand, Result>
{
    public async Task<Result> Handle(
        DeleteJunctionCommand command,
        CancellationToken cancellationToken
    )
    {
        var junction = await JunctionLoader.LoadAsync(
            dbContext,
            command.JunctionId,
            cancellationToken
        );
        if (junction is null)
            return Result.Failure(TemplateErrors.JunctionNotFound);

        // Стык общий: слот чужого канала, ссылающийся на удалённый стык, молча остался бы без врезок.
        var usedBySlot = await dbContext.Slots.AnyAsync(
            s => s.JunctionBetweenId == junction.Id || s.JunctionAfterId == junction.Id,
            cancellationToken
        );
        var usedByDefault = await dbContext.ScheduleTemplates.AnyAsync(
            t => t.DefaultJunctionId == junction.Id,
            cancellationToken
        );
        if (usedBySlot || usedByDefault)
            return Result.Failure(TemplateErrors.JunctionInUse);

        dbContext.JunctionTemplates.Remove(junction);
        return Result.Success();
    }
}