using ErsatzTV.Core;
using ErsatzTV.Core.Domain;
using ErsatzTV.Core.Errors;
using ErsatzTV.Infrastructure.Data;
using ErsatzTV.Infrastructure.Extensions;
using Microsoft.EntityFrameworkCore;

namespace ErsatzTV.Application.ProgramSchedules;

public class DeleteProgramScheduleHandler : IRequestHandler<DeleteProgramSchedule, Either<BaseError, Unit>>
{
    private readonly IDbContextFactory<TvContext> _dbContextFactory;

    public DeleteProgramScheduleHandler(IDbContextFactory<TvContext> dbContextFactory) =>
        _dbContextFactory = dbContextFactory;

    public async Task<Either<BaseError, Unit>> Handle(
        DeleteProgramSchedule request,
        CancellationToken cancellationToken)
    {
        await using TvContext dbContext = await _dbContextFactory.CreateDbContextAsync(cancellationToken);
        Option<ProgramSchedule> maybeProgramSchedule = await ProgramScheduleMustExist(
            dbContext,
            request,
            cancellationToken);
        return await maybeProgramSchedule.Match(
            Some: programSchedule => DoDeletion(dbContext, programSchedule).Map(Right<BaseError, Unit>),
            None: () => Task.FromResult<Either<BaseError, Unit>>(
                new NotFoundError($"ProgramSchedule {request.ProgramScheduleId} does not exist.")));
    }

    private static Task<Unit> DoDeletion(TvContext dbContext, ProgramSchedule programSchedule)
    {
        dbContext.ProgramSchedules.Remove(programSchedule);
        return dbContext.SaveChangesAsync().ToUnit();
    }

    private static Task<Option<ProgramSchedule>> ProgramScheduleMustExist(
        TvContext dbContext,
        DeleteProgramSchedule request,
        CancellationToken cancellationToken) =>
        dbContext.ProgramSchedules
            .SelectOneAsync(ps => ps.Id, ps => ps.Id == request.ProgramScheduleId, cancellationToken)
            .Map(identity);
}