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

using MongoDB.Driver;
using MongoDB.Entities;

using PrivaPub.Domain.Social;
using PrivaPub.Models.Post;
using PrivaPub.Models.Social;
using PrivaPub.Models.User;
using PrivaPub.StaticServices;

using System.Text.Json.Nodes;

using static PrivaPub.Federation.Objects.ActivityJson;

using PostEntity = PrivaPub.Models.Post.Post;

namespace PrivaPub.Federation.Inbox.Handlers
{
	public class LikeHandler : IActivityHandler
	{
		readonly DbEntities _dbEntities;

		public LikeHandler(DbEntities dbEntities)
		{
			_dbEntities = dbEntities;
		}

		public string Type => "Like";

		public async Task Handle(JsonNode activity, ForeignAvatar actor, CancellationToken token)
		{
			var objectUri = Id(activity["object"]);
			var post = objectUri == default
				? default
				: await _dbEntities.Posts.Match(p => p.ObjectURI == objectUri && !p.DeletedAt.HasValue && p.ReblogOfPostId == null).ExecuteFirstAsync(token);
			if (post == default || !MaySee(post, actor))
				return;

			try
			{
				await DB.Default.SaveAsync(new Favourite { AccountId = actor.ID, ActorURI = actor.ActorURI, PostId = post.ID, ActivityURI = Id(activity) }, token);
			}
			catch (MongoWriteException ex) when (ex.WriteError?.Category == ServerErrorCategory.DuplicateKey)
			{
				return;
			}
			await DB.Default.Update<PostEntity>().MatchID(post.ID).Modify(b => b.Inc(p => p.FavouritesCount, 1)).ExecuteAsync(token);
			if (!post.IsFederatedCopy)
				await Notifications.Add(post.GroupUserId, NotificationType.Favourite, actor.ID, actor.ActorURI, post.ID, token);
		}

		public static bool MaySee(PostEntity post, ForeignAvatar actor) =>
			post.Visibility is PostVisibility.Public or PostVisibility.Unlisted
			|| post.Visibility is PostVisibility.FollowersOnly or PostVisibility.Direct
				&& (post.To.Contains(actor.ActorURI) || post.Cc.Contains(actor.ActorURI) || post.Mentions.Any(m => m.ActorURI == actor.ActorURI));
	}
}