P7: FEP-268d searchableBy decides what search finds

A remote account's searchableBy, and a post's own, outrank indexable in status search: Public lets anyone find a
public post, the author's followers only those who follow it, anything else nobody but those it already reaches
(their own, named, favourited, bookmarked or boosted posts). Read on actors and posts, kept through edits; PrivaPub
does not emit it.

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

PrivaPub/Api/Mastodon/Controllers/SearchController.cs

@@ -105,15 +105,30 @@ namespace PrivaPub.Api.Mastodon.Controllers
 			mine.UnionWith((await _dbEntities.Posts.Match(p => p.AuthorAccountId == MyId && ids.Contains(p.ReblogOfPostId) && !p.DeletedAt.HasValue).ExecuteAsync(token))
 				.Select(p => p.ReblogOfPostId));
 			var authors = candidates.Select(p => p.AuthorAccountId ?? p.GroupUserId).Where(a => a != default).Distinct().ToList();
-			var indexable = (await _dbEntities.Avatars.Match(a => authors.Contains(a.ID) && a.Settings.IsIndexable).ExecuteAsync(token)).Select(a => a.ID)
-				.Concat((await _dbEntities.ForeignAvatars.Match(f => authors.Contains(f.ID) && f.IsIndexable).ExecuteAsync(token)).Select(f => f.ID))
-				.ToHashSet();
+			var indexable = (await _dbEntities.Avatars.Match(a => authors.Contains(a.ID) && a.Settings.IsIndexable).ExecuteAsync(token)).Select(a => a.ID).ToHashSet();
+			// a remote author's searchableBy (FEP-268d) outranks its indexable, and a post's own outranks both
+			var remoteAuthors = (await _dbEntities.ForeignAvatars.Match(f => authors.Contains(f.ID)).ExecuteAsync(token)).ToDictionary(f => f.ID);
+			var stating = remoteAuthors.Values.Where(f => f.SearchableBy != default).Select(f => f.ActorURI)
+				.Concat(candidates.Where(p => p.SearchableBy != default).Select(p => p.ActorURI))
+				.Where(uri => uri != default).Distinct().ToList();
+			var followed = stating.Count == 0
+				? new HashSet<string>()
+				: (await _dbEntities.Followings.Match(f => f.AvatarId == MyId && stating.Contains(f.TargetActorURI) && f.State == Models.Social.FollowState.Accepted)
+					.ExecuteAsync(token)).Select(f => f.TargetActorURI).ToHashSet();
+			bool Searchable(PostEntity post, string author)
+			{
+				var remote = remoteAuthors.GetValueOrDefault(author);
+				var rule = post.SearchableBy ?? remote?.SearchableBy;
+				if (rule != default)
+					return Federation.Objects.ObjectShapes.Searchable(rule, remote?.FollowersURL, followed.Contains(post.ActorURI ?? string.Empty));
+				return remote?.IsIndexable == true || indexable.Contains(author);
+			}
 			var found = new List<PostEntity>();
 			foreach (var post in candidates)
 			{
 				var author = post.AuthorAccountId ?? post.GroupUserId;
 				var reachable = author == MyId && !post.IsFederatedCopy || mine.Contains(post.ID) || post.Mentions.Any(m => m.AccountId == MyId)
-					|| post.Visibility == PostVisibility.Public && indexable.Contains(author);
+					|| post.Visibility == PostVisibility.Public && Searchable(post, author);
 				if (reachable && await VisibilityPolicy.CanSee(post, MyId, token))
 					found.Add(post);
 				if (found.Count >= offset + limit)