SocialPub/PrivaPub/Domain/Statuses/ScheduledStatuses.cs

using MongoDB.Entities;

using PrivaPub.Federation.Actors;
using PrivaPub.Infrastructure.Jobs;
using PrivaPub.Models.Federation;
using PrivaPub.Models.Jobs;
using PrivaPub.Models.Media;
using PrivaPub.Models.Post;
using PrivaPub.Models.Social;
using PrivaPub.Models.User;
using PrivaPub.Domain.Media;

namespace PrivaPub.Domain.Statuses
{
	// Scheduled posts (Mastodon's scheduled_statuses): kept as asked, their media kept from the janitor, and published at
	// their time by a PublishScheduled job as if the persona posted then. Mastodon's limits hold: at least five minutes
	// ahead, 300 waiting, 25 on one day.
	public static class ScheduledStatuses
	{
		public static readonly TimeSpan Lead = TimeSpan.FromMinutes(5);
		public const int MaxWaiting = 300;
		public const int MaxPerDay = 25;

		public static StatusDraft Draft(ScheduledParams p, string scheduledId = default) => new()
		{
			ScheduledStatusId = scheduledId,
			Text = p.Text,
			PlainText = true,
			SpoilerText = p.SpoilerText,
			Sensitive = p.Sensitive,
			Visibility = Visibility(p.Visibility),
			InReplyTo = p.InReplyToId,
			Language = p.Language,
			MediaIds = p.MediaIds,
			QuotedStatusId = p.QuotedStatusId,
			QuotePolicy = p.QuotePolicy,
			Poll = p.Poll == default ? default : new PollDraft(p.Poll.Options, p.Poll.ExpiresIn, p.Poll.Multiple, p.Poll.HideTotals)
		};

		public static PostVisibility Visibility(string value) => value?.ToLowerInvariant() switch
		{
			"unlisted" => PostVisibility.Unlisted,
			"private" => PostVisibility.FollowersOnly,
			"direct" => PostVisibility.Direct,
			_ => PostVisibility.Public
		};

		// why the persona cannot schedule at this time, or default
		public static async Task<string> Refusal(string avatarId, DateTime at, string except, CancellationToken token)
		{
			if (at < DateTime.UtcNow + Lead)
				return "Scheduled at The scheduled date must be at least 5 minutes in the future";
			if (await DB.Default.CountAsync<ScheduledStatus>(s => s.AvatarId == avatarId && s.ID != except, token) >= MaxWaiting)
				return $"Scheduled at You have exceeded the limit of {MaxWaiting} scheduled statuses";
			var day = at.Date;
			var next = day.AddDays(1);
			if (await DB.Default.CountAsync<ScheduledStatus>(s => s.AvatarId == avatarId && s.ID != except && s.ScheduledAt >= day && s.ScheduledAt < next, token) >= MaxPerDay)
				return $"Scheduled at You have exceeded the limit of {MaxPerDay} scheduled statuses on that day";
			return default;
		}

		// a job per scheduled time: a rescheduled post has a job for its new time, and the old one finds it not due
		public static Job JobFor(ScheduledStatus scheduled, string host) => new()
		{
			Kind = JobKind.PublishScheduled,
			Payload = scheduled.ID,
			Host = host,
			DedupeKey = $"scheduled|{scheduled.ID}|{scheduled.ScheduledAt.Ticks}",
			RunAt = scheduled.ScheduledAt
		};

		// whether a persona may still publish: neither deleted nor its root deleted or banned
		public static async Task<bool> MayPublish(string avatarId, CancellationToken token)
		{
			if (!await DB.Default.Find<Avatar>().Match(a => a.ID == avatarId && !a.DeletionAt.HasValue).ExecuteAnyAsync(token))
				return false;
			var rootIds = (await DB.Default.Find<RootToAvatar>().Match(r => r.AvatarId == avatarId).ExecuteAsync(token)).Select(r => r.RootId).ToList();
			return await DB.Default.Find<RootUser>().Match(u => rootIds.Contains(u.ID) && u.DeletedAt == null && !u.IsBanned).ExecuteAnyAsync(token);
		}

		// the post's media go back to being plain uploads (the janitor's after a day), or are attached to the post by now
		public static Task Release(string scheduledId, CancellationToken token) =>
			DB.Default.Update<MediaAttachment>().Match(m => m.ScheduledStatusId == scheduledId).Modify(m => m.ScheduledStatusId, null).ExecuteAsync(token);
	}

	public class PublishScheduledJob : IJobHandler
	{
		readonly IServiceScopeFactory _scopes;
		readonly ILogger<PublishScheduledJob> _logger;

		public PublishScheduledJob(IServiceScopeFactory scopes, ILogger<PublishScheduledJob> logger)
		{
			_scopes = scopes;
			_logger = logger;
		}

		public JobKind Kind => JobKind.PublishScheduled;
		public int Concurrency => 2;
		public int MaxAttempts => 3;
		public int PerHostLimit => 2;

		public async Task<JobOutcome> Handle(Job job, CancellationToken token)
		{
			var scheduled = await DB.Default.Find<ScheduledStatus>().MatchID(job.Payload).ExecuteFirstAsync(token);
			if (scheduled == default || scheduled.ScheduledAt > DateTime.UtcNow.AddSeconds(30))
				return JobOutcome.Done;//dropped, or moved to a later time that has its own job
			using var scope = _scopes.CreateScope();
			// a persona deleted or banned since it was scheduled publishes nothing, and what it held is trashed
			if (!await ScheduledStatuses.MayPublish(scheduled.AvatarId, token))
			{
				await scope.ServiceProvider.GetRequiredService<IMediaService>().Trash(m => m.ScheduledStatusId == scheduled.ID, "its author is gone", token);
				await DB.Default.DeleteAsync<ScheduledStatus>(scheduled.ID);
				return JobOutcome.Done;
			}
			var author = await scope.ServiceProvider.GetRequiredService<ILocalActorService>().FindById(LocalActorKind.Person, scheduled.AvatarId, token);
			if (author != default)
			{
				var outcome = await scope.ServiceProvider.GetRequiredService<IStatusService>().Publish(author, ScheduledStatuses.Draft(scheduled.Params, scheduled.ID), token);
				if (!outcome.Ok)
					_logger.LogWarning("Scheduled status {Id} of {Avatar} could not be published: {Error}", scheduled.ID, scheduled.AvatarId, outcome.Error);
			}
			await ScheduledStatuses.Release(scheduled.ID, token);
			await DB.Default.DeleteAsync<ScheduledStatus>(scheduled.ID);
			return JobOutcome.Done;
		}
	}
}