One visibility rule for every public read

VisibilityPolicy.IsPublic is the single expression for "anyone may see
this" (Public or Unlisted, not deleted); the outbox, the object and
activity endpoints, the HTML pages and NodeInfo all use it instead of
spelling it out. CanSee answers for a persona: the author, a mentioned
local persona, a conversation member for Direct, a circle member for
Circle; followers-only waits for P1.2's follows.

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

PrivaPub.Tests/Domain/VisibilityPolicyTests.cs

@@ -0,0 +1,42 @@
+using MongoDB.Entities;
+
+using PrivaPub.Domain.Privacy;
+using PrivaPub.Models.Group;
+using PrivaPub.Models.Post;
+using PrivaPub.Tests.Support;
+
+using GroupEntity = PrivaPub.Models.Group.Group;
+
+namespace PrivaPub.Tests.Domain
+{
+	[Trait("Category", "Integration")]
+	public class VisibilityPolicyTests
+	{
+		[Fact]
+		public async Task Who_sees_what()
+		{
+			Assert.SkipUnless(MongoFixture.Enabled, MongoFixture.Skip);
+			var token = TestContext.Current.CancellationToken;
+			var conversation = new DmGroup { Members = new() { new GroupMember { AvatarId = "alice" }, new GroupMember { AvatarId = "https://r.example/u/bob", IsForeign = true } } };
+			var circle = new GroupEntity { UserName = $"c{Guid.NewGuid():N}"[..20], Members = new() { new GroupMember { AvatarId = "carol" } } };
+			await DB.Default.SaveAsync(conversation, token);
+			await DB.Default.SaveAsync(circle, token);
+
+			var direct = new Post { Visibility = PostVisibility.Direct, ConversationId = conversation.ID, GroupUserId = "dave" };
+			var circlePost = new Post { Visibility = PostVisibility.Circle, GroupId = circle.ID };
+			var followersOnly = new Post { Visibility = PostVisibility.FollowersOnly, Mentions = new() { new PostMention { IsLocal = true, AccountId = "erin" } } };
+			var deleted = new Post { Visibility = PostVisibility.Public, DeletedAt = DateTime.UtcNow };
+
+			Assert.True(await VisibilityPolicy.CanSee(new Post(), default, token));
+			Assert.True(await VisibilityPolicy.CanSee(direct, "alice", token));
+			Assert.True(await VisibilityPolicy.CanSee(direct, "dave", token));
+			Assert.False(await VisibilityPolicy.CanSee(direct, "carol", token));
+			Assert.False(await VisibilityPolicy.CanSee(direct, default, token));
+			Assert.True(await VisibilityPolicy.CanSee(circlePost, "carol", token));
+			Assert.False(await VisibilityPolicy.CanSee(circlePost, "alice", token));
+			Assert.True(await VisibilityPolicy.CanSee(followersOnly, "erin", token));
+			Assert.False(await VisibilityPolicy.CanSee(followersOnly, "alice", token));
+			Assert.False(await VisibilityPolicy.CanSee(deleted, "alice", token));
+		}
+	}
+}

PrivaPub/Domain/Privacy/VisibilityPolicy.cs

@@ -0,0 +1,42 @@
+using MongoDB.Entities;
+
+using PrivaPub.Models.Group;
+using PrivaPub.Models.Post;
+
+using System.Linq.Expressions;
+
+using GroupEntity = PrivaPub.Models.Group.Group;
+
+namespace PrivaPub.Domain.Privacy
+{
+	public static class VisibilityPolicy
+	{
+		public static readonly Expression<Func<Post, bool>> IsPublic = p =>
+			!p.DeletedAt.HasValue && (p.Visibility == PostVisibility.Public || p.Visibility == PostVisibility.Unlisted);
+
+		static readonly Func<Post, bool> IsPublicCompiled = IsPublic.Compile();
+
+		public static async Task<bool> CanSee(Post post, string viewerAvatarId, CancellationToken token)
+		{
+			if (post == default || post.DeletedAt.HasValue)
+				return false;
+			if (IsPublicCompiled(post))
+				return true;
+			if (string.IsNullOrEmpty(viewerAvatarId))
+				return false;
+			if (post.GroupUserId == viewerAvatarId || post.Mentions.Any(m => m.IsLocal && m.AccountId == viewerAvatarId))
+				return true;
+
+			return post.Visibility switch
+			{
+				PostVisibility.Direct => !string.IsNullOrEmpty(post.ConversationId) && await DB.Default.Find<DmGroup>()
+					.Match(g => g.ID == post.ConversationId && g.Members.Any(m => !m.IsForeign && m.AvatarId == viewerAvatarId))
+					.ExecuteAnyAsync(token),
+				PostVisibility.Circle => !string.IsNullOrEmpty(post.GroupId) && await DB.Default.Find<GroupEntity>()
+					.Match(g => g.ID == post.GroupId && g.Members.Any(m => !m.IsForeign && m.AvatarId == viewerAvatarId))
+					.ExecuteAnyAsync(token),
+				_ => false
+			};
+		}
+	}
+}

PrivaPub/Federation/Controllers/PeasantsController.cs

@@ -10,6 +10,7 @@ using PrivaPub.StaticServices;
 using System.Text.Json.Nodes;
 
 using PostEntity = PrivaPub.Models.Post.Post;
+using PrivaPub.Domain.Privacy;
 using PrivaPub.Federation.Actors;
 using PrivaPub.Federation.Rendering;
 using PrivaPub.Federation.Inbox;
@@ -59,18 +60,14 @@ namespace PrivaPub.Federation.Controllers
 			if (!page)
 			{
 				var total = local.Kind == LocalActorKind.Group
-					? await DB.Default.CountAsync<PostEntity>(p => p.GroupId == local.Id && !p.DeletedAt.HasValue
+					? await DB.Default.CountAsync<PostEntity>(f => f.Where(p => p.GroupId == local.Id) & f.Where(VisibilityPolicy.IsPublic), token)
-						&& (p.Visibility == PostVisibility.Public || p.Visibility == PostVisibility.Unlisted), token)
+					: await DB.Default.CountAsync<PostEntity>(f => f.Where(p => p.GroupUserId == local.Id && !p.IsFederatedCopy) & f.Where(VisibilityPolicy.IsPublic), token);
-					: await DB.Default.CountAsync<PostEntity>(p => p.GroupUserId == local.Id && !p.IsFederatedCopy && !p.DeletedAt.HasValue
-						&& (p.Visibility == PostVisibility.Public || p.Visibility == PostVisibility.Unlisted), token);
 				return Activity(ActivityPubRenderer.OrderedCollection(local.Outbox, (int)total, default, $"{local.Outbox}?page=true"));
 			}
 
 			var query = local.Kind == LocalActorKind.Group
-				? _dbEntities.Posts.Match(p => p.GroupId == local.Id && !p.DeletedAt.HasValue
+				? _dbEntities.Posts.Match(p => p.GroupId == local.Id).Match(VisibilityPolicy.IsPublic)
-					&& (p.Visibility == PostVisibility.Public || p.Visibility == PostVisibility.Unlisted))
+				: _dbEntities.Posts.Match(p => p.GroupUserId == local.Id && !p.IsFederatedCopy).Match(VisibilityPolicy.IsPublic);
-				: _dbEntities.Posts.Match(p => p.GroupUserId == local.Id && !p.IsFederatedCopy && !p.DeletedAt.HasValue
-					&& (p.Visibility == PostVisibility.Public || p.Visibility == PostVisibility.Unlisted));
 			if (!string.IsNullOrEmpty(maxId))
 				query.Match(f => f.Lt(p => p.ID, maxId));
 			var latest = await query.Sort(p => p.ID, Order.Descending).Limit(OutboxSize).ExecuteAsync(token);
@@ -156,8 +153,8 @@ namespace PrivaPub.Federation.Controllers
 			if (local is not { IsFederated: true, Kind: LocalActorKind.Person })
 				return default;
 			var post = await _dbEntities.Posts
-				.Match(p => p.ID == postId && p.GroupUserId == local.Id && !p.IsFederatedCopy && !p.DeletedAt.HasValue
+				.Match(p => p.ID == postId && p.GroupUserId == local.Id && !p.IsFederatedCopy)
-					&& (p.Visibility == PostVisibility.Public || p.Visibility == PostVisibility.Unlisted))
+				.Match(VisibilityPolicy.IsPublic)
 				.ExecuteFirstAsync(token);
 			return (local, post);
 		}

PrivaPub/Federation/Controllers/WellKnownController.cs

@@ -10,6 +10,7 @@ using PrivaPub.StaticServices;
 using System.Text.Json.Nodes;
 
 using PostEntity = PrivaPub.Models.Post.Post;
+using PrivaPub.Domain.Privacy;
 using PrivaPub.Federation.Actors;
 
 namespace PrivaPub.Federation.Controllers
@@ -84,8 +85,7 @@ namespace PrivaPub.Federation.Controllers
 		public async Task<IActionResult> NodeInfo(string version, CancellationToken token)
 		{
 			var users = await DB.Default.CountAsync<Avatar>(a => !a.DeletionAt.HasValue, token);
-			var posts = await DB.Default.CountAsync<PostEntity>(p => !p.IsFederatedCopy && !p.DeletedAt.HasValue
+			var posts = await DB.Default.CountAsync<PostEntity>(f => f.Where(p => !p.IsFederatedCopy) & f.Where(VisibilityPolicy.IsPublic), token);
-				&& (p.Visibility == PostVisibility.Public || p.Visibility == PostVisibility.Unlisted), token);
 			var software = new JsonObject { ["name"] = "privapub", ["version"] = BuildInfo.Ref };
 			if (version == "2.1")
 			{

PrivaPub/Web/Pages/Pages.cs

@@ -3,6 +3,7 @@ using Microsoft.AspNetCore.Mvc.RazorPages;
 
 using MongoDB.Entities;
 
+using PrivaPub.Domain.Privacy;
 using PrivaPub.Federation.Actors;
 using PrivaPub.Federation.Rendering;
 using PrivaPub.Models.Federation;
@@ -70,7 +71,7 @@ namespace PrivaPub.Web.Pages
 			var posts = await (Actor.Kind == LocalActorKind.Group
 					? _dbEntities.Posts.Match(p => p.GroupId == Actor.Id)
 					: _dbEntities.Posts.Match(p => p.GroupUserId == Actor.Id && !p.IsFederatedCopy))
-				.Match(p => !p.DeletedAt.HasValue && (p.Visibility == PostVisibility.Public || p.Visibility == PostVisibility.Unlisted))
+				.Match(VisibilityPolicy.IsPublic)
 				.Sort(p => p.ID, Order.Descending)
 				.Limit(PageSize)
 				.ExecuteAsync(token);
@@ -111,8 +112,8 @@ namespace PrivaPub.Web.Pages
 			if (Actor is not { IsFederated: true, Kind: LocalActorKind.Person })
 				return NotFound();
 			var post = await _dbEntities.Posts
-				.Match(p => p.ID == id && p.GroupUserId == Actor.Id && !p.IsFederatedCopy && !p.DeletedAt.HasValue
+				.Match(p => p.ID == id && p.GroupUserId == Actor.Id && !p.IsFederatedCopy)
-					&& (p.Visibility == PostVisibility.Public || p.Visibility == PostVisibility.Unlisted))
+				.Match(VisibilityPolicy.IsPublic)
 				.ExecuteFirstAsync(token);
 			if (post == default)
 				return NotFound();