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

namespace ErsatzTV.Application.Playouts;

public class UpdatePlayoutHandler : IRequestHandler<UpdatePlayout, Either<BaseError, PlayoutNameViewModel>>
{
    private readonly IDbContextFactory<TvContext> _dbContextFactory;

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

    public async Task<Either<BaseError, PlayoutNameViewModel>> Handle(
        UpdatePlayout request,
        CancellationToken cancellationToken)
    {
        await using TvContext dbContext = await _dbContextFactory.CreateDbContextAsync(cancellationToken);
        Validation<BaseError, Playout> validation = await Validate(dbContext, request, cancellationToken);
        return await validation.Apply(playout => ApplyUpdateRequest(dbContext, request, playout, cancellationToken));
    }

    private static async Task<PlayoutNameViewModel> ApplyUpdateRequest(
        TvContext dbContext,
        UpdatePlayout request,
        Playout playout,
        CancellationToken cancellationToken)
    {
        playout.DailyRebuildTime = null;

        foreach (TimeSpan dailyRebuildTime in request.DailyRebuildTime)
        {
            playout.DailyRebuildTime = dailyRebuildTime;
        }

        // Rotate the playout ETag only when the daily-rebuild-time actually changed — a no-op re-submit
        // must not bump (#269). When it changed, force-write past a concurrent Version bump from a
        // replace-all editor (this settings writer takes no If-Match, so a benign race must not 500) —
        // #253/#269 §7a.
        if (dbContext.ChangeTracker.HasChanges())
        {
            playout.Version++;
            await dbContext.SaveChangesForcingVersion(cancellationToken);
        }

        return new PlayoutNameViewModel(
            playout.Id,
            playout.ScheduleKind,
            playout.Channel.Name,
            playout.Channel.Number,
            playout.Channel.Id,
            playout.Channel.PlayoutMode,
            playout.ProgramSchedule?.Name ?? string.Empty,
            playout.ScheduleFile,
            playout.DailyRebuildTime,
            playout.BuildStatus,
            playout.DecoId,
            playout.Deco?.Name,
            playout.Version,
            playout.Seed);
    }

    private static Task<Validation<BaseError, Playout>> Validate(
        TvContext dbContext,
        UpdatePlayout request,
        CancellationToken cancellationToken) =>
        PlayoutMustExist(dbContext, request, cancellationToken);

    private static Task<Validation<BaseError, Playout>> PlayoutMustExist(
        TvContext dbContext,
        UpdatePlayout updatePlayout,
        CancellationToken cancellationToken) =>
        dbContext.Playouts
            .Include(p => p.Channel)
            .Include(p => p.ProgramSchedule)
            .SelectOneAsync(p => p.Id, p => p.Id == updatePlayout.PlayoutId, cancellationToken)
            .Map(o => o.ToValidation<BaseError>("Playout does not exist."));
}
