SocialPub/PrivaPub/Domain/Timelines/Fanout.cs

using MongoDB.Driver;
using MongoDB.Entities;

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

using GroupEntity = PrivaPub.Models.Group.Group;

namespace PrivaPub.Domain.Timelines
{
	public interface IFanout
	{
		Task Distribute(Post post, CancellationToken token);
	}

	public class Fanout : IFanout
	{
		readonly DbEntities _dbEntities;

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

		public async Task Distribute(Post post, CancellationToken token)
		{
			var recipients = new HashSet<string>(StringComparer.Ordinal);
			if (!post.IsFederatedCopy && !string.IsNullOrEmpty(post.GroupUserId))
				recipients.Add(post.GroupUserId);

			switch (post.Visibility)
			{
				case PostVisibility.Public or PostVisibility.Unlisted or PostVisibility.FollowersOnly:
					var followers = post.IsFederatedCopy
						? await _dbEntities.Followings.Match(f => f.TargetActorURI == post.ActorURI && f.State == FollowState.Accepted).ExecuteAsync(token)
						: await _dbEntities.Followings.Match(f => f.TargetAccountId == post.GroupUserId && f.TargetIsLocal && f.State == FollowState.Accepted).ExecuteAsync(token);
					foreach (var following in followers)
						if (await Shows(following, post, token))
							recipients.Add(following.AvatarId);
					break;
				case PostVisibility.Direct when !string.IsNullOrEmpty(post.ConversationId):
					var conversation = await _dbEntities.DmGroups.MatchID(post.ConversationId).ExecuteFirstAsync(token);
					foreach (var member in conversation?.Members.Where(m => !m.IsForeign) ?? Enumerable.Empty<GroupMember>())
						recipients.Add(member.AvatarId);
					break;
				case PostVisibility.Circle when !string.IsNullOrEmpty(post.GroupId):
					var circle = await DB.Default.Find<GroupEntity>().MatchID(post.GroupId).ExecuteFirstAsync(token);
					foreach (var member in circle?.Members.Where(m => !m.IsForeign) ?? Enumerable.Empty<GroupMember>())
						recipients.Add(member.AvatarId);
					break;
			}

			foreach (var avatarId in recipients)
			{
				try
				{
					await DB.Default.SaveAsync(new TimelineEntry
					{
						AvatarId = avatarId,
						PostId = post.ID,
						AuthorAccountId = post.AuthorAccountId ?? post.GroupUserId,
						ReblogOfPostId = post.ReblogOfPostId
					}, token);
				}
				catch (MongoWriteException ex) when (ex.WriteError?.Category == ServerErrorCategory.DuplicateKey)
				{
				}
			}

			if (string.IsNullOrEmpty(post.ReblogOfPostId))
				foreach (var mention in post.Mentions.Where(m => m.IsLocal && !string.IsNullOrEmpty(m.AccountId)))
					await Notifications.Add(mention.AccountId, NotificationType.Mention, post.AuthorAccountId ?? post.GroupUserId, post.ActorURI, post.ID, token);
		}

		async Task<bool> Shows(Following following, Post post, CancellationToken token)
		{
			if (!string.IsNullOrEmpty(post.ReblogOfPostId))
				return following.ShowReblogs;
			var repliedTo = post.InReplyToAccountId;
			var author = post.AuthorAccountId ?? post.GroupUserId;
			if (string.IsNullOrEmpty(post.InReplyToURI) || repliedTo == author || repliedTo == following.AvatarId)
				return true;
			if (string.IsNullOrEmpty(repliedTo))
				return false;
			return await _dbEntities.Followings
				.Match(f => f.AvatarId == following.AvatarId && f.TargetAccountId == repliedTo && f.State == FollowState.Accepted)
				.ExecuteAnyAsync(token);
		}
	}
}