Located posts: local only, rounded, matched against their own radius

A post given a latitude and longitude becomes LocalGeo: its position is
rounded to two decimals (about a kilometre) and stored as a 2dsphere
point, its radius clamped to 1-50 km, and it is local only - no Create,
no delivery, no outbox, never in the Mastodon API or on a profile page.
/clientapi/post/nearby takes the viewer's position for the query only
(it is neither stored nor logged), runs $geoNear and keeps posts within
each post's own radius, minus authors the viewer blocks or mutes. A
located post cannot be direct or in a group.

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

PrivaPub.ClientModels/Post/InsertPostForm.cs

@@ -24,6 +24,15 @@ namespace PrivaPub.ClientModels.Post
 		public string SpoilerText { get; set; }
 
 		public string Visibility { get; set; }//public (default), unlisted, followersonly
+
+		[Range(-90, 90, ErrorMessageResourceName = "Range", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public double? Latitude { get; set; }
+
+		[Range(-180, 180, ErrorMessageResourceName = "Range", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public double? Longitude { get; set; }
+
+		[Range(1, 50, ErrorMessageResourceName = "Range", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public double? RangeKm { get; set; }
 	}
 
 	public class UpdatePostForm

PrivaPub.ClientModels/Post/ViewPost.cs

@@ -17,6 +17,8 @@ namespace PrivaPub.ClientModels.Post
 		public bool IsFederatedCopy { get; set; }
 		public DateTime CreationDate { get; set; }
 		public ViewPost ReblogOf { get; set; }
+		public double? RangeKm { get; set; }
+		public double? DistanceKm { get; set; }
 	}
 
 	public class ViewDmGroup

PrivaPub.Tests/Domain/NearbyTests.cs

@@ -0,0 +1,77 @@
+using MongoDB.Entities;
+
+using PrivaPub.ClientModels.Post;
+using PrivaPub.Domain.Privacy;
+using PrivaPub.Federation.Outbox;
+using PrivaPub.Models.Jobs;
+using PrivaPub.Models.Post;
+using PrivaPub.Tests.Support;
+
+using System.Text.Json;
+
+namespace PrivaPub.Tests.Domain
+{
+	[Trait("Category", "Integration")]
+	public sealed class NearbyTests : IAsyncLifetime
+	{
+		Harness _harness;
+
+		public async ValueTask InitializeAsync()
+		{
+			Assert.SkipUnless(MongoFixture.Enabled, MongoFixture.Skip);
+			_harness = await Harness.Start();
+		}
+
+		public async ValueTask DisposeAsync()
+		{
+			if (_harness != default)
+				await _harness.DisposeAsync();
+		}
+
+		[Fact]
+		public async Task A_located_post_reaches_only_those_within_its_radius_and_never_leaves_the_server()
+		{
+			var token = TestContext.Current.CancellationToken;
+			var latitude = 10 + Random.Shared.NextDouble() * 50;
+			var longitude = 10 + Random.Shared.NextDouble() * 50;
+			var (aliceRoot, alice) = await _harness.Persona("alice");
+			var (bobRoot, bob) = await _harness.Persona("bob");
+			var (carolRoot, carol) = await _harness.Persona("carol");
+			var follower = new RemoteActor(_harness.Peer, "follower");
+			await _harness.FollowedBy(alice, follower);
+
+			var created = await _harness.Posts.InsertPost(aliceRoot, new InsertPostForm
+			{
+				AvatarId = alice.Id, Text = "free bread at the bakery", Latitude = latitude, Longitude = longitude, RangeKm = 5
+			}, token);
+			var post = await DB.Default.Find<Post>().OneAsync(((ViewPost)created.Data).Id, token);
+
+			var three = (List<ViewPost>)(await _harness.Posts.Nearby(bobRoot, bob.Id, latitude + 0.027, longitude, token)).Data;
+			var eight = (List<ViewPost>)(await _harness.Posts.Nearby(carolRoot, carol.Id, latitude + 0.072, longitude, token)).Data;
+
+			Assert.Equal(PostVisibility.LocalGeo, post.Visibility);
+			Assert.Equal(Math.Round(latitude, 2), post.Geo.Coordinates[1]);
+			Assert.Contains(three, p => p.Id == post.ID);
+			Assert.InRange(three.First(p => p.Id == post.ID).DistanceKm.Value, 2.0, 4.0);
+			Assert.DoesNotContain(eight, p => p.Id == post.ID);
+			Assert.False(await VisibilityPolicy.CanSee(post, bob.Id, token));
+			var outgoing = (await DB.Default.Find<Job>().Match(j => j.Kind == JobKind.Deliver).ExecuteAsync(token))
+				.Select(j => JsonSerializer.Deserialize<DeliveryPayload>(j.Payload))
+				.Where(p => p.Body.Contains(post.ID));
+			Assert.Empty(outgoing);
+		}
+
+		[Fact]
+		public async Task A_located_post_cannot_be_direct_or_in_a_group()
+		{
+			var (root, alice) = await _harness.Persona("alice");
+
+			var result = await _harness.Statuses.Publish(alice, new PrivaPub.Domain.Statuses.StatusDraft
+			{
+				Text = "x", Latitude = 45, Longitude = 7, Visibility = PostVisibility.Direct
+			}, TestContext.Current.CancellationToken);
+
+			Assert.False(result.Ok);
+		}
+	}
+}

PrivaPub/Controllers/ClientToServer/PostController.cs

@@ -32,6 +32,10 @@ namespace PrivaPub.Controllers.ClientToServer
 		public async Task<IActionResult> Insert(InsertPostForm form, CancellationToken token) =>
 			!ModelState.IsValid ? Invalid() : Answer(await _postsService.InsertPost(User.GetUserId(), form, token));
 
+		[HttpGet, Route("/clientapi/post/nearby")]
+		public async Task<IActionResult> Nearby([FromQuery] string avatarId, [FromQuery] double latitude, [FromQuery] double longitude, CancellationToken token) =>
+			Answer(await _postsService.Nearby(User.GetUserId(), avatarId, latitude, longitude, token));
+
 		[HttpPost, Route("/clientapi/post/update")]
 		public async Task<IActionResult> Update(UpdatePostForm form, CancellationToken token) =>
 			!ModelState.IsValid ? Invalid() : Answer(await _postsService.UpdatePost(User.GetUserId(), form, token));

PrivaPub/Domain/Statuses/StatusService.cs

@@ -36,6 +36,9 @@ namespace PrivaPub.Domain.Statuses
 		public string ConversationId { get; init; }
 		public IReadOnlyList<string> Recipients { get; init; } = Array.Empty<string>();
 		public IReadOnlyList<string> MediaIds { get; init; }
+		public double? Latitude { get; init; }
+		public double? Longitude { get; init; }
+		public double? RangeKm { get; init; }
 	}
 
 	public sealed record StatusOutcome(PostEntity Post, int Status = StatusCodes.Status200OK, string Error = default)
@@ -102,9 +105,16 @@ namespace PrivaPub.Domain.Statuses
 			if (parent != default && !await VisibilityPolicy.CanSee(parent, author.Id, token))
 				return StatusOutcome.Fail(StatusCodes.Status404NotFound, "Record not found");
 
+			var located = draft.Latitude.HasValue || draft.Longitude.HasValue;
+			if (located && (draft.Latitude is not (>= -90 and <= 90) || draft.Longitude is not (>= -180 and <= 180) || group != default
+				|| draft.Visibility == PostVisibility.Direct))
+				return StatusOutcome.Fail(StatusCodes.Status422UnprocessableEntity, "Validation failed: A located post needs a valid position and no group or recipients");
+
 			var rendered = draft.PlainText ? await _content.PlainText(draft.Text ?? string.Empty, token) : await _content.Markdown(draft.Text ?? string.Empty, token);
-			var isLocalOnly = group is { IsFederated: false };
+			var isLocalOnly = group is { IsFederated: false } || located;
-			var visibility = isLocalOnly ? PostVisibility.Circle : draft.Visibility is PostVisibility.Circle or PostVisibility.LocalGeo ? PostVisibility.Public : draft.Visibility;
+			var visibility = located ? PostVisibility.LocalGeo
+				: isLocalOnly ? PostVisibility.Circle
+				: draft.Visibility is PostVisibility.Circle or PostVisibility.LocalGeo ? PostVisibility.Public : draft.Visibility;
 			var post = new PostEntity
 			{
 				GroupUserId = author.Id,
@@ -130,6 +140,11 @@ namespace PrivaPub.Domain.Statuses
 			post.ID = (string)post.GenerateNewID();
 			post.ObjectURI = author.PostUri(post.ID);
 			post.Url = author.PostHtmlUrl(post.ID);
+			if (located)
+			{
+				post.Geo = new Coordinates2D(Math.Round(draft.Longitude.Value, 2), Math.Round(draft.Latitude.Value, 2));
+				post.RangeKm = (float)Math.Clamp(draft.RangeKm ?? 5, 1, 50);
+			}
 
 			JsonObject create = default;
 			if (visibility == PostVisibility.Direct)

PrivaPub/Infrastructure/Data/Indexes.cs

@@ -21,6 +21,7 @@ namespace PrivaPub.Infrastructure.Data
 			await Plain<Post>(token, p => p.ActorURI);
 			await Plain<Post>(token, p => p.ConversationId, p => p.ID);
 			await Plain<Post>(token, p => p.InReplyToURI);
+			await DB.Default.Index<Post>().Key(p => p.Geo, KeyType.Geo2DSphere).CreateAsync(token);
 
 			await Unique<DmPost>(p => p.ObjectURI, Builders<DmPost>.Filter.Type(p => p.ObjectURI, BsonType.String), token);
 			await Plain<DmPost>(token, p => p.GroupId, p => p.ID);

PrivaPub/Models/Post/Post.cs

@@ -1,3 +1,4 @@
+using MongoDB.Bson.Serialization.Attributes;
 using MongoDB.Entities;
 
 namespace PrivaPub.Models.Post
@@ -24,6 +25,10 @@ namespace PrivaPub.Models.Post
 		public List<PostMedia> Media { get; set; } = new();
 		public List<float> Location { get; set; } = new();
 		public float RangeKm { get; set; } = 5.0f;
+		[BsonIgnoreIfNull]
+		public Coordinates2D Geo { get; set; }
+		[BsonIgnoreIfNull]
+		public double? Distance { get; set; }
 		public bool HasContentWarning { get; set; } = false;
 		public bool IsLocalOnly { get; set; }
 

PrivaPub/Services/PostsService.cs

@@ -1,5 +1,6 @@
 using Microsoft.Extensions.Localization;
 
+using MongoDB.Driver;
 using MongoDB.Entities;
 
 using PrivaPub.ClientModels;
@@ -27,6 +28,7 @@ namespace PrivaPub.Services
 		Task<WebResult> InsertPost(string rootUserId, InsertPostForm form, CancellationToken token);
 		Task<WebResult> DeletePost(string rootUserId, DeletePostForm form, CancellationToken token);
 		Task<WebResult> UpdatePost(string rootUserId, UpdatePostForm form, CancellationToken token);
+		Task<WebResult> Nearby(string rootUserId, string avatarId, double latitude, double longitude, CancellationToken token);
 		Task<WebResult> GetPosts(string rootUserId, string avatarId, string groupId, CancellationToken token);
 		Task<WebResult> InsertDm(string rootUserId, InsertDmForm form, CancellationToken token);
 		Task<WebResult> GetDms(string rootUserId, string avatarId, string dmGroupId, CancellationToken token);
@@ -68,7 +70,10 @@ namespace PrivaPub.Services
 				Sensitive = form.HasContentWarning,
 				Visibility = LocalVisibility(form.Visibility),
 				InReplyTo = form.AnsweringToPostId,
-				GroupId = form.GroupId
+				GroupId = form.GroupId,
+				Latitude = form.Latitude,
+				Longitude = form.Longitude,
+				RangeKm = form.RangeKm
 			}, token), nameof(InsertPost));
 		}
 
@@ -193,6 +198,35 @@ namespace PrivaPub.Services
 
 
 
+		public async Task<WebResult> Nearby(string rootUserId, string avatarId, double latitude, double longitude, CancellationToken token)
+		{
+			var result = new WebResult();
+			var viewer = await OwnedAvatar(rootUserId, avatarId, token);
+			if (viewer == default)
+				return result.Invalidate(_localizer["Avatar not found."], StatusCodes.Status404NotFound);
+			if (latitude is < -90 or > 90 || longitude is < -180 or > 180)
+				return result.Invalidate(_localizer["Invalid model."]);
+
+			var query = new MongoDB.Bson.BsonDocument
+			{
+				["Visibility"] = (int)PostVisibility.LocalGeo,
+				["DeletedAt"] = MongoDB.Bson.BsonNull.Value
+			};
+			var candidates = await DB.Default.GeoNear<PostEntity>(new Coordinates2D(longitude, latitude), p => p.Distance, true, 50_000, default, default, query)
+				.Limit(200)
+				.ToListAsync(token);
+			var near = candidates.Where(p => p.Distance <= p.RangeKm * 1000).ToList();
+			var hidden = await Domain.Relationships.Hidden.AuthorsHiddenFrom(viewer.Id, near.Select(p => p.ActorURI), forNotifications: false, token);
+			result.Data = near.Where(p => !hidden.Contains(p.ActorURI)).Select(p =>
+			{
+				var view = ToView(p);
+				view.RangeKm = p.RangeKm;
+				view.DistanceKm = Math.Round(p.Distance.Value / 1000, 1);
+				return view;
+			}).ToList();
+			return result;
+		}
+
 		async Task<WebResult> Answer(Func<Task<StatusOutcome>> action, string operation)
 		{
 			var result = new WebResult();