SocialPub/PrivaPub/Federation/Outbox/OutboxPublisher.cs

using PrivaPub.Federation.Actors;
using PrivaPub.Federation.Rendering;
using PrivaPub.Models.Federation;
using PrivaPub.Models.Post;
using PrivaPub.StaticServices;

using System.Text.Json.Nodes;

using PostEntity = PrivaPub.Models.Post.Post;

namespace PrivaPub.Federation.Outbox
{
	public interface IOutboxPublisher
	{
		Task<IReadOnlyList<string>> Audience(LocalActor author, PostEntity post, CancellationToken token);
		Task Publish(LocalActor author, PostEntity post, JsonObject activity, CancellationToken token);
		Task PublishUpdate(LocalActor author, PostEntity post, string reason, CancellationToken token);
		Task PublishProfile(LocalActor actor, CancellationToken token);
	}

	public class OutboxPublisher : IOutboxPublisher
	{
		readonly DbEntities _dbEntities;
		readonly ILocalActorService _localActors;
		readonly IDeliveryService _delivery;

		public OutboxPublisher(DbEntities dbEntities, ILocalActorService localActors, IDeliveryService delivery)
		{
			_dbEntities = dbEntities;
			_localActors = localActors;
			_delivery = delivery;
		}

		public async Task<IReadOnlyList<string>> Audience(LocalActor author, PostEntity post, CancellationToken token)
		{
			if (post.Visibility == PostVisibility.LocalGeo || post.IsLocalOnly)
				return Array.Empty<string>();
			if (post.Visibility == PostVisibility.Circle)
				return await CircleMembers(post.GroupId, token);

			var inboxes = new List<string>();
			if (post.Visibility is PostVisibility.Public or PostVisibility.Unlisted or PostVisibility.FollowersOnly)
				inboxes.AddRange(await _delivery.FollowerInboxes(author, token));

			var addressed = post.Mentions.Where(m => !m.IsLocal).Select(m => m.ActorURI)
				.Concat(post.Visibility == PostVisibility.Direct ? post.To.Concat(post.Cc) : Enumerable.Empty<string>())
				.Where(uri => !uri.StartsWith(author.BaseAddress + "/", StringComparison.OrdinalIgnoreCase))
				.Distinct(StringComparer.Ordinal)
				.ToList();
			foreach (var uri in addressed)
			{
				var actor = await _dbEntities.ForeignAvatars.Match(a => a.ActorURI == uri).ExecuteFirstAsync(token);
				if (actor != default && !string.IsNullOrEmpty(actor.InboxURL))
					inboxes.Add(actor.InboxURL);
			}

			if (post.Visibility != PostVisibility.Direct && !string.IsNullOrEmpty(post.InReplyToAccountId))
			{
				var parentAuthor = await _dbEntities.ForeignAvatars.MatchID(post.InReplyToAccountId).ExecuteFirstAsync(token);
				if (parentAuthor != default && !string.IsNullOrEmpty(parentAuthor.InboxURL))
					inboxes.Add(parentAuthor.InboxURL);
			}

			if (post.Visibility is PostVisibility.Public or PostVisibility.Unlisted && !string.IsNullOrEmpty(post.QuotedPostId))
			{
				var quoted = await _dbEntities.Posts.MatchID(post.QuotedPostId).ExecuteFirstAsync(token);
				var quotedAuthor = quoted is { IsFederatedCopy: true }
					? await _dbEntities.ForeignAvatars.Match(a => a.ActorURI == quoted.ActorURI).ExecuteFirstAsync(token)
					: default;
				if (!string.IsNullOrEmpty(quotedAuthor?.InboxURL))
					inboxes.Add(quotedAuthor.InboxURL);
			}

			return inboxes.Where(i => !string.IsNullOrEmpty(i)).Distinct(StringComparer.Ordinal).ToList();
		}

		async Task<IReadOnlyList<string>> CircleMembers(string groupId, CancellationToken token) =>
			(await CircleRecipients(groupId, token)).Select(r => r.Inbox).Distinct(StringComparer.Ordinal).ToList();

		async Task<IReadOnlyList<(string Member, string Inbox)>> CircleRecipients(string groupId, CancellationToken token)
		{
			var circle = string.IsNullOrEmpty(groupId) ? default : await _dbEntities.Groups.MatchID(groupId).ExecuteFirstAsync(token);
			if (circle == default)
				return Array.Empty<(string, string)>();
			var remote = circle.Members.Where(m => m.IsForeign).Select(m => m.AvatarId).ToList();
			if (remote.Count == 0)
				return Array.Empty<(string, string)>();
			return (await _dbEntities.ForeignAvatars.Match(a => remote.Contains(a.ActorURI)).ExecuteAsync(token))
				.Where(a => !string.IsNullOrEmpty(a.InboxURL))
				.Select(a => (a.ActorURI, a.InboxURL))
				.ToList();
		}

		public async Task Publish(LocalActor author, PostEntity post, JsonObject activity, CancellationToken token)
		{
			if (post.Visibility == PostVisibility.Circle)
			{
				foreach (var (member, inbox) in await CircleRecipients(post.GroupId, token))
					await _delivery.Enqueue(author, new[] { inbox }, Naming(activity, new[] { member }), token);
				return;
			}
			var inboxes = await Audience(author, post, token);
			if (inboxes.Count > 0)
				await _delivery.Enqueue(author, inboxes, activity, token);
		}

		public async Task PublishUpdate(LocalActor author, PostEntity post, string reason, CancellationToken token)
		{
			var group = string.IsNullOrEmpty(post.GroupId) ? default : await _localActors.FindById(LocalActorKind.Group, post.GroupId, token);
			await Publish(author, post, ActivityPubRenderer.UpdateOf(post, author, group, reason), token);
		}

		// Mastodon and GoToSocial keep a post only when it names one of their own accounts, and a circle post names only the
		// circle. So each member's copy, or a member's refetch, also names that member in cc (owner decision 2026-10-04):
		// it tells each member nothing but that they are in the circle.
		public static JsonObject Naming(JsonObject activityOrObject, IEnumerable<string> members)
		{
			var copy = (JsonObject)activityOrObject.DeepClone();
			Name(copy, members);
			if (copy["object"] is JsonObject inner && inner.ContainsKey("to"))
				Name(inner, members);
			return copy;
		}

		static void Name(JsonObject node, IEnumerable<string> members)
		{
			var cc = node["cc"] as JsonArray ?? new JsonArray();
			foreach (var member in members)
				if (!cc.Any(c => c?.GetValue<string>() == member))
					cc.Add(member);
			node["cc"] = cc;
		}

		public async Task PublishProfile(LocalActor actor, CancellationToken token)
		{
			var document = ActivityPubRenderer.Actor(actor);
			document.Remove("@context");
			var update = new JsonObject
			{
				["@context"] = ActivityPubRenderer.Context(),
				["id"] = actor.ActivityUri($"update-profile-{DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()}"),
				["type"] = "Update",
				["actor"] = actor.Uri,
				["to"] = new JsonArray(ActivityPubRenderer.Public),
				["cc"] = new JsonArray(actor.Followers),
				["object"] = document
			};
			await _delivery.EnqueueToFollowers(actor, update, token);
		}
	}
}