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

namespace ErsatzTV.Application.ProgramSchedules;

public class CreateProgramScheduleHandler :
    IRequestHandler<CreateProgramSchedule, Either<BaseError, CreateProgramScheduleResult>>
{
    private readonly IDbContextFactory<TvContext> _dbContextFactory;

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

    public async Task<Either<BaseError, CreateProgramScheduleResult>> Handle(
        CreateProgramSchedule request,
        CancellationToken cancellationToken)
    {
        await using TvContext dbContext = await _dbContextFactory.CreateDbContextAsync(cancellationToken);

        Validation<BaseError, ProgramSchedule> validation = await Validate(dbContext, request);
        return await validation.Apply(ps => PersistProgramSchedule(dbContext, ps));
    }

    private static async Task<CreateProgramScheduleResult> PersistProgramSchedule(
        TvContext dbContext,
        ProgramSchedule programSchedule)
    {
        await dbContext.ProgramSchedules.AddAsync(programSchedule);
        await dbContext.SaveChangesAsync();
        return new CreateProgramScheduleResult(programSchedule.Id);
    }

    private static Task<Validation<BaseError, ProgramSchedule>> Validate(
        TvContext dbContext,
        CreateProgramSchedule request) =>
        ValidateName(dbContext, request).MapT(
            name =>
            {
                bool keepMultiPartEpisodesTogether = request.KeepMultiPartEpisodesTogether;
                return new ProgramSchedule
                {
                    Name = name,
                    KeepMultiPartEpisodesTogether = keepMultiPartEpisodesTogether,
                    TreatCollectionsAsShows = keepMultiPartEpisodesTogether && request.TreatCollectionsAsShows,
                    ShuffleScheduleItems = request.ShuffleScheduleItems,
                    RandomStartPoint = request.RandomStartPoint
                };
            });

    private static async Task<Validation<BaseError, string>> ValidateName(
        TvContext dbContext,
        CreateProgramSchedule createProgramSchedule)
    {
        Validation<BaseError, string> result1 = createProgramSchedule.NotEmpty(c => c.Name)
            .Bind(_ => createProgramSchedule.NotLongerThan(50)(c => c.Name));

        int duplicateNameCount = await dbContext.ProgramSchedules
            .CountAsync(ps => ps.Name == createProgramSchedule.Name);

        var result2 = Optional(duplicateNameCount)
            .Where(count => count == 0)
            .ToValidation<BaseError>("Schedule name must be unique");

        return (result1, result2).Apply((_, _) => createProgramSchedule.Name);
    }
}