P6: emoji reactions in and out

- Incoming reactions in all three shapes: Misskey and Sharkey Likes carrying an emoji (`content` or
  `_misskey_reaction`), Pleroma, Akkoma and Iceshrimp.NET EmojiReacts, and their Undo. Unicode reactions are one
  grapheme; custom ones need their Emoji tag and keep its image; `:name@host:` is read as `name`. A Like whose
  content is a heart stays a favourite.
- Reactions are kept per account and emoji on our posts and on remote ones we hold, and the author of a local post
  gets a `pleroma:emoji_reaction` notification with the emoji.
- Personas react through Pleroma's API (PUT/DELETE /api/v1/pleroma/statuses/:id/reactions/:emoji, GET for the list),
  which sends an EmojiReact (or its Undo) to the post's author.
- Statuses carry `emoji_reactions` (read by Phanpy) and `pleroma.emoji_reactions`, with counts and whether the viewer
  reacted.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

PrivaPub/Api/Mastodon/Controllers/ReactionsController.cs

@@ -0,0 +1,76 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+using MongoDB.Entities;
+
+using PrivaPub.Api.Mastodon.Infrastructure;
+using PrivaPub.Api.Mastodon.Mappers;
+using PrivaPub.Domain.Privacy;
+using PrivaPub.Domain.Social;
+using PrivaPub.Models.Post;
+using PrivaPub.Models.Social;
+using PrivaPub.StaticServices;
+
+using PostEntity = PrivaPub.Models.Post.Post;
+
+namespace PrivaPub.Api.Mastodon.Controllers
+{
+	public class ReactionsController : MastodonController
+	{
+		readonly DbEntities _dbEntities;
+		readonly MastodonMapper _mapper;
+		readonly IReactions _reactions;
+
+		public ReactionsController(DbEntities dbEntities, MastodonMapper mapper, IReactions reactions)
+		{
+			_dbEntities = dbEntities;
+			_mapper = mapper;
+			_reactions = reactions;
+		}
+
+		[HttpGet("/api/v1/pleroma/statuses/{id}/reactions"), Scope("read:statuses", requiresUser: false), AllowAnonymous]
+		public async Task<IActionResult> List(string id, CancellationToken token)
+		{
+			var post = await Visible(id, token);
+			if (post == default)
+				return NotFoundError();
+			var reactions = await DB.Default.Find<Reaction>().Match(r => r.PostId == post.ID).ExecuteAsync(token);
+			var accounts = await _mapper.Accounts(reactions.Select(r => r.AccountId), token);
+			return Json(reactions.GroupBy(r => r.Emoji).Select(group => new
+			{
+				name = group.Key,
+				count = group.Count(),
+				me = MyId != default && group.Any(r => r.AccountId == MyId),
+				url = _mapper.ProxiedUrl(group.First().EmojiURL),
+				accounts = group.Select(r => accounts.GetValueOrDefault(r.AccountId)).Where(a => a != default).ToList()
+			}).OrderByDescending(r => r.count).ToList());
+		}
+
+		[HttpPut("/api/v1/pleroma/statuses/{id}/reactions/{emoji}"), Scope("write:favourites")]
+		public async Task<IActionResult> React(string id, string emoji, CancellationToken token)
+		{
+			var post = await Visible(id, token);
+			if (post == default)
+				return NotFoundError();
+			if (!await _reactions.React(Me, post, Uri.UnescapeDataString(emoji), token))
+				return Error(StatusCodes.Status422UnprocessableEntity, "Validation failed: That emoji cannot be used here");
+			return Json(await _mapper.Status(post, MyId, token));
+		}
+
+		[HttpDelete("/api/v1/pleroma/statuses/{id}/reactions/{emoji}"), Scope("write:favourites")]
+		public async Task<IActionResult> Unreact(string id, string emoji, CancellationToken token)
+		{
+			var post = await Visible(id, token);
+			if (post == default)
+				return NotFoundError();
+			await _reactions.Unreact(Me, post, Uri.UnescapeDataString(emoji), token);
+			return Json(await _mapper.Status(post, MyId, token));
+		}
+
+		async Task<PostEntity> Visible(string id, CancellationToken token)
+		{
+			var post = await _dbEntities.Posts.Match(p => p.ID == id && !p.DeletedAt.HasValue && p.ReblogOfPostId == null).ExecuteFirstAsync(token);
+			return post != default && post.Visibility != PostVisibility.LocalGeo && await VisibilityPolicy.CanSee(post, MyId, token) ? post : default;
+		}
+	}
+}

PrivaPub/Api/Mastodon/Controllers/TimelinesController.cs

@@ -163,7 +163,8 @@ namespace PrivaPub.Api.Mastodon.Controllers
 			[NotificationType.Favourite] = "favourite",
 			[NotificationType.Reblog] = "reblog",
 			[NotificationType.Update] = "update",
-			[NotificationType.Poll] = "poll"
+			[NotificationType.Poll] = "poll",
+			[NotificationType.Reaction] = "pleroma:emoji_reaction"
 		};
 
 		readonly MastodonMapper _mapper;
@@ -234,7 +235,9 @@ namespace PrivaPub.Api.Mastodon.Controllers
 					CreatedAt = MastodonJson.Time(n.CreatedAt),
 					GroupKey = $"ungrouped-{n.ID}",
 					Account = accounts[n.FromAccountId],
-					Status = n.PostId == default ? default : statuses[n.PostId]
+					Status = n.PostId == default ? default : statuses[n.PostId],
+					Emoji = n.Emoji == default ? default : n.EmojiURL == default ? n.Emoji : $":{n.Emoji}:",
+					EmojiUrl = _mapper.ProxiedUrl(n.EmojiURL)
 				})
 				.ToList();
 		}

PrivaPub/Api/Mastodon/Entities/Entities.cs

@@ -161,6 +161,20 @@ namespace PrivaPub.Api.Mastodon.Entities
 		public int Down { get; set; }
 	}
 
+	public class EmojiReactionEntity
+	{
+		public string Name { get; set; }
+		public int Count { get; set; }
+		public bool Me { get; set; }
+		public string Url { get; set; }
+		public string StaticUrl { get; set; }
+	}
+
+	public class PleromaStatus
+	{
+		public List<EmojiReactionEntity> EmojiReactions { get; set; } = new();
+	}
+
 	public class PollEntity
 	{
 		public string Id { get; set; }
@@ -237,6 +251,8 @@ namespace PrivaPub.Api.Mastodon.Entities
 		public string Text { get; set; }
 		public List<object> Filtered { get; set; } = new();
 		public PrivaPubStatus Privapub { get; set; }
+		public List<EmojiReactionEntity> EmojiReactions { get; set; } = new();
+		public PleromaStatus Pleroma { get; set; }
 	}
 
 	public class MediaAttachment
@@ -305,6 +321,8 @@ namespace PrivaPub.Api.Mastodon.Entities
 		public string GroupKey { get; set; }
 		public Account Account { get; set; }
 		public Status Status { get; set; }
+		public string Emoji { get; set; }
+		public string EmojiUrl { get; set; }
 	}
 
 	public class Context

PrivaPub/Api/Mastodon/Mappers/MastodonMapper.cs

@@ -36,6 +36,8 @@ namespace PrivaPub.Api.Mastodon.Mappers
 
 		string Proxied(string url) => _proxy == default ? url : _proxy.Wrap(url);
 
+		public string ProxiedUrl(string url) => Proxied(url);
+
 		string MissingAvatar => $"{_localActors.BaseAddress}/media/missing-avatar.png";
 		string MissingHeader => $"{_localActors.BaseAddress}/media/missing-header.png";
 
@@ -166,6 +168,19 @@ namespace PrivaPub.Api.Mastodon.Mappers
 				? new HashSet<string>()
 				: (await DB.Default.Find<Bookmark>().Match(b => b.AvatarId == viewerId && ids.Contains(b.PostId)).ExecuteAsync(token)).Select(b => b.PostId).ToHashSet();
 			var pinned = (await DB.Default.Find<Pin>().Match(p => ids.Contains(p.PostId)).ExecuteAsync(token)).Select(p => p.PostId).ToHashSet();
+			var reactions = (await DB.Default.Find<Reaction>().Match(r => ids.Contains(r.PostId)).ExecuteAsync(token))
+				.GroupBy(r => r.PostId)
+				.ToDictionary(g => g.Key, g => g.GroupBy(r => r.Emoji)
+					.Select(e => new EmojiReactionEntity
+					{
+						Name = e.Key,
+						Count = e.Count(),
+						Me = viewerId != default && e.Any(r => r.AccountId == viewerId),
+						Url = Proxied(e.First().EmojiURL),
+						StaticUrl = Proxied(e.First().EmojiURL)
+					})
+					.OrderByDescending(e => e.Count)
+					.ToList());
 			var pollIds = all.Where(p => p.Poll != default).Select(p => p.ID).ToList();
 			var ownVotes = viewerId == default || pollIds.Count == 0
 				? new Dictionary<string, List<int>>()
@@ -210,6 +225,8 @@ namespace PrivaPub.Api.Mastodon.Mappers
 					Poll = Poll(post, viewerId, ownVotes.GetValueOrDefault(post.ID)),
 					Emojis = Emojis(post.Emojis),
 					Privapub = Extension(post),
+					EmojiReactions = reactions.GetValueOrDefault(post.ID) ?? new(),
+					Pleroma = new PleromaStatus { EmojiReactions = reactions.GetValueOrDefault(post.ID) ?? new() },
 					Mentions = post.Mentions.Select(m => Mention(m, mentionAccounts)).Where(m => m != default).ToList(),
 					Tags = post.Tags.Select(t => new StatusTag { Name = t, Url = ActivityPubRenderer.TagUrl(_localActors.BaseAddress, t) }).ToList()
 				};