SocialPub/PrivaPub/Federation/Inbox/Handlers/FeaturedHandler.cs

using PrivaPub.Federation.Actors;
using PrivaPub.Models.User;

using System.Text.Json.Nodes;

namespace PrivaPub.Federation.Inbox.Handlers
{
	// An account pins one of its posts (Add to its `featured` collection) or unpins it (Remove), as Mastodon and Akkoma
	// send it; inside a community's announce, the community features a post made in it. On its wall (Smithereen's, FEP-400e)
	// it tells of a post someone wrote there, or takes it off. Any other target (a community's moderators) is not ours to
	// keep.
	public class FeaturedHandler : IActivityHandler
	{
		readonly IFeaturedPosts _featured;
		readonly IWalls _walls;
		readonly IRemoteActorService _remoteActors;
		readonly bool _add;

		public FeaturedHandler(IFeaturedPosts featured, bool add, IWalls walls = default, IRemoteActorService remoteActors = default)
		{
			_featured = featured;
			_walls = walls;
			_remoteActors = remoteActors;
			_add = add;
		}

		public string Type => _add ? "Add" : "Remove";

		public async Task Handle(JsonNode activity, ForeignAvatar actor, CancellationToken token)
		{
			var target = Objects.ActivityJson.Id(activity["target"]);
			// a collection of its own we do not know of: its document read again, at most hourly, in case it was kept before
			// we read that collection (a wall)
			if (_remoteActors != default && target != default && target != actor.FeaturedURL && target != actor.WallURL
				&& Objects.Origin.Same(target, actor.ActorURI) && actor.UpdatedAt < DateTime.UtcNow.AddHours(-1))
				actor = await _remoteActors.GetActor(actor.ActorURI, refresh: true, token) ?? actor;
			if (_walls != default && !string.IsNullOrEmpty(actor.WallURL) && target == actor.WallURL)
				await _walls.Receive(activity, actor, _add, token);
			else
				await _featured.Receive(activity, actor, _add, token);
		}
	}
}