SocialPub/PrivaPub/Federation/Inbox/RemotePosts.cs

using MongoDB.Driver;
using MongoDB.Entities;

using PrivaPub.Federation.Actors;
using PrivaPub.Federation.Moderation;
using PrivaPub.Federation.Objects;
using PrivaPub.Infrastructure.Ids;
using PrivaPub.Infrastructure.Jobs;
using PrivaPub.Models.Federation;
using PrivaPub.Models.Jobs;
using PrivaPub.Models.Post;
using PrivaPub.Models.User;
using PrivaPub.StaticServices;

using System.Text.Json;
using System.Text.Json.Nodes;

using PostEntity = PrivaPub.Models.Post.Post;

namespace PrivaPub.Federation.Inbox
{
	public sealed record AncestorsPayload(string PostId, int Depth);

	public interface IRemotePosts
	{
		Task<PostEntity> Build(NoteDocument note, ForeignAvatar author, PostVisibility visibility, IReadOnlyList<string> to, IReadOnlyList<string> cc,
			PostEntity parent, CancellationToken token);
		Task<PostEntity> Parent(string inReplyTo, int depth, CancellationToken token);
		Task<PostEntity> StoreContext(string objectUri, int depth, CancellationToken token);
	}

	public class RemotePosts : IRemotePosts
	{
		public const int MaxDepth = 10;

		readonly DbEntities _dbEntities;
		readonly ILocalActorService _localActors;
		readonly IRemoteActorService _remoteActors;
		readonly IDomainBlocks _domainBlocks;
		readonly IJobQueue _queue;
		readonly IObjectRecords _records;

		public RemotePosts(DbEntities dbEntities, ILocalActorService localActors, IRemoteActorService remoteActors, IDomainBlocks domainBlocks,
			IJobQueue queue, IObjectRecords records)
		{
			_records = records;
			_dbEntities = dbEntities;
			_localActors = localActors;
			_remoteActors = remoteActors;
			_domainBlocks = domainBlocks;
			_queue = queue;
		}

		public async Task<PostEntity> Build(NoteDocument note, ForeignAvatar author, PostVisibility visibility, IReadOnlyList<string> to,
			IReadOnlyList<string> cc, PostEntity parent, CancellationToken token)
		{
			var mentions = new List<PostMention>();
			foreach (var mention in note.Mentions)
			{
				var local = await _localActors.FindByUri(mention.ActorURI, token);
				mentions.Add(new PostMention { ActorURI = mention.ActorURI, Handle = mention.Handle, IsLocal = local != default, AccountId = local?.Id });
			}

			return new PostEntity
			{
				ID = PrivacyIds.Arrived(note.Published),
				ObjectURI = note.Id,
				ActorURI = author.ActorURI,
				AuthorAccountId = author.ID,
				Visibility = visibility,
				To = to.ToList(),
				Cc = cc.ToList(),
				Url = note.Url,
				ContextURI = note.Context,
				QuoteURI = note.QuoteUri,
				ObjectType = note.Type,
				Title = note.Title,
				SpoilerText = note.SpoilerText,
				Excerpt = note.Excerpt,
				HasContentWarning = note.Sensitive,
				Text = note.ContentHtml,
				ContentHtml = note.ContentHtml,
				ContentFormat = ContentFormat.Html,
				Language = note.Language,
				Mentions = mentions,
				Tags = note.Tags.ToList(),
				Media = _domainBlocks.Find(new Uri(author.ActorURI).Host)?.RejectMedia == true ? new() : note.Attachments.ToList(),
				InReplyToURI = note.InReplyTo,
				AnsweringToPostId = parent?.ID,
				InReplyToAccountId = parent?.AuthorAccountId ?? parent?.GroupUserId,
				IsFederatedCopy = true,
				CreationDate = note.Published,
				UpdateDate = note.Updated ?? note.Published,
				EditedAt = note.Updated
			};
		}

		public async Task<PostEntity> Parent(string inReplyTo, int depth, CancellationToken token)
		{
			if (string.IsNullOrEmpty(inReplyTo))
				return default;
			var known = await _dbEntities.Posts.Match(p => p.ObjectURI == inReplyTo && !p.DeletedAt.HasValue).ExecuteFirstAsync(token);
			if (known != default || inReplyTo.StartsWith(_localActors.BaseAddress + "/", StringComparison.OrdinalIgnoreCase))
				return known;
			return await StoreContext(inReplyTo, depth, token);
		}

		public async Task<PostEntity> StoreContext(string objectUri, int depth, CancellationToken token)
		{
			var existing = await _dbEntities.Posts.Match(p => p.ObjectURI == objectUri).ExecuteFirstAsync(token);
			if (existing != default || depth > MaxDepth)
				return existing;

			using var fetched = await _remoteActors.FetchObject(objectUri, token);
			var note = fetched == default ? default : NoteParser.Parse(JsonNode.Parse(fetched.Root.GetRawText()));
			if (note == default || !Origin.Same(note.Id, note.AttributedTo))
				return default;
			var visibility = Addressing.Classify(note.To, note.Cc, default);
			if (visibility is not (PostVisibility.Public or PostVisibility.Unlisted))
				return default;
			var author = await _remoteActors.GetActor(note.AttributedTo, refresh: false, token);
			if (author == default)
				return default;

			var grandparent = string.IsNullOrEmpty(note.InReplyTo)
				? default
				: await _dbEntities.Posts.Match(p => p.ObjectURI == note.InReplyTo && !p.DeletedAt.HasValue).ExecuteFirstAsync(token);
			var post = await Build(note, author, visibility, note.To, note.Cc, grandparent, token);
			try
			{
				await DB.Default.SaveAsync(post, token);
			}
			catch (MongoWriteException ex) when (ex.WriteError?.Category == ServerErrorCategory.DuplicateKey)
			{
				return await _dbEntities.Posts.Match(p => p.ObjectURI == objectUri).ExecuteFirstAsync(token);
			}
			await _records.Record(note, post, ObjectPath.Fetched, refetched: false, token);

			if (grandparent == default && !string.IsNullOrEmpty(note.InReplyTo) && depth < MaxDepth)
				await _queue.Enqueue(JobKind.FetchAncestors, JsonSerializer.Serialize(new AncestorsPayload(post.ID, depth + 1)), new Uri(note.InReplyTo).Host,
					"ancestors|" + post.ID, token);
			return post;
		}
	}

	public class AncestorsJobHandler : IJobHandler
	{
		readonly DbEntities _dbEntities;
		readonly IRemotePosts _remotePosts;

		public AncestorsJobHandler(DbEntities dbEntities, IRemotePosts remotePosts)
		{
			_dbEntities = dbEntities;
			_remotePosts = remotePosts;
		}

		public JobKind Kind => JobKind.FetchAncestors;
		public int Concurrency => 1;
		public int MaxAttempts => 3;
		public int PerHostLimit => 1;

		public async Task<JobOutcome> Handle(Job job, CancellationToken token)
		{
			var payload = JsonSerializer.Deserialize<AncestorsPayload>(job.Payload);
			var child = await _dbEntities.Posts.MatchID(payload.PostId).ExecuteFirstAsync(token);
			if (child == default || string.IsNullOrEmpty(child.InReplyToURI) || !string.IsNullOrEmpty(child.AnsweringToPostId))
				return JobOutcome.Done;

			var parent = await _remotePosts.Parent(child.InReplyToURI, payload.Depth, token);
			if (parent == default)
				return JobOutcome.Done;
			await DB.Default.Update<PostEntity>().MatchID(child.ID)
				.Modify(p => p.AnsweringToPostId, parent.ID)
				.Modify(p => p.InReplyToAccountId, parent.AuthorAccountId ?? parent.GroupUserId)
				.ExecuteAsync(token);
			return JobOutcome.Done;
		}
	}
}