SocialPub/PrivaPub.Tests/Http/MastodonFeedTests.cs

using MongoDB.Entities;

using PrivaPub.Federation.Actors;
using PrivaPub.Models.Federation;
using PrivaPub.Models.Jobs;
using PrivaPub.Models.Post;
using PrivaPub.Models.Social;
using PrivaPub.Tests.Support;
using PrivaPub.Tests.Support.Host;

using System.Net;
using System.Text.Json.Nodes;

namespace PrivaPub.Tests.Http
{
	// Lemmy 1.0's multi-communities and PieFed's feeds are `Feed` actors whose `following` is their communities
	[Trait("Category", "Integration")]
	public sealed class MastodonFeedTests : IAsyncLifetime
	{
		PrivaPubHost _host;
		Peer _peer;

		public async ValueTask InitializeAsync()
		{
			Assert.SkipUnless(MongoFixture.Enabled, MongoFixture.Skip);
			_host = await PrivaPubHost.Shared();
			_peer = await Peer.Start();
		}

		public async ValueTask DisposeAsync()
		{
			if (_peer != default)
				await _peer.DisposeAsync();
		}

		[Fact]
		public async Task A_feed_shows_as_an_account_whose_following_is_its_communities()
		{
			var token = TestContext.Current.CancellationToken;
			var reader = await _host.Mastodon("feeder");
			var cats = new RemoteActor(_peer, "cats", type: "Group");
			var dogs = new RemoteActor(_peer, "dogs", type: "Group");
			var name = $"feed{Guid.NewGuid():N}"[..12];
			var feed = $"{_peer.A}/m/{name}";
			// as Lemmy serves one: the instance's inbox and key, its text in `description`
			_peer.Serve($"/m/{name}", new JsonObject
			{
				["@context"] = new JsonArray("https://join-lemmy.org/context.json", "https://www.w3.org/ns/activitystreams"),
				["type"] = "Feed", ["id"] = feed, ["inbox"] = $"{_peer.A}/inbox",
				["publicKey"] = new JsonObject { ["id"] = $"{_peer.A}/#main-key", ["owner"] = $"{_peer.A}/", ["publicKeyPem"] = "-----BEGIN PUBLIC KEY-----\n-----END PUBLIC KEY-----\n" },
				["following"] = $"{feed}/following", ["preferredUsername"] = name, ["name"] = "Pets", ["description"] = "every pet",
				["attributedTo"] = $"{_peer.A}/users/owner"
			}.ToJsonString());
			_peer.Serve($"/m/{name}/following", new JsonObject
			{
				["type"] = "Collection", ["id"] = $"{feed}/following", ["totalItems"] = 2, ["items"] = new JsonArray(cats.Id, dogs.Id)
			}.ToJsonString());

			var account = await _host.Get<IRemoteActorService>().GetActor(feed, refresh: true, token);
			Assert.NotNull(account);
			await _host.Run(j => j.Kind == JobKind.CountAccount && j.Payload == feed, token);

			var shown = (await reader.Client.Get($"/api/v1/accounts/{account.ID}")).Ok().Body;
			Assert.Equal(("Pets", 2), (shown.Text("display_name"), shown.Number("following_count")));
			Assert.Contains("every pet", shown.Text("note"));
			var communities = (await reader.Client.Get($"/api/v1/accounts/{account.ID}/following")).Ok().Array;
			Assert.Equal(new[] { cats.Id, dogs.Id }, communities.Select(c => c.Text("uri")));
			Assert.All(communities, c => Assert.True(c!["group"]!.GetValue<bool>()));
		}

		// owner decision 2026-10-07: a feed is read through the server, whose reader follows its communities; the persona
		// follows nothing, and reads the feed in a timeline of its own
		[Fact]
		public async Task A_feed_is_followed_by_the_servers_reader_and_read_in_its_own_timeline()
		{
			var token = TestContext.Current.CancellationToken;
			var since = DateTime.UtcNow.AddSeconds(-1);
			var persona = await _host.Mastodon("feedreader");
			var cats = new RemoteActor(_peer, "cats", type: "Group");
			var dogs = new RemoteActor(_peer, "dogs", type: "Group");
			var poster = new RemoteActor(_peer, "poster");
			var name = $"feed{Guid.NewGuid():N}"[..12];
			var feed = $"{_peer.A}/m/{name}";
			_peer.Serve($"/m/{name}", new JsonObject
			{
				["type"] = "Feed", ["id"] = feed, ["inbox"] = $"{_peer.A}/inbox", ["following"] = $"{feed}/following", ["preferredUsername"] = name, ["name"] = "Pets"
			}.ToJsonString());
			_peer.Serve($"/m/{name}/following", new JsonObject
			{
				["type"] = "Collection", ["id"] = $"{feed}/following", ["totalItems"] = 2, ["items"] = new JsonArray(cats.Id, dogs.Id)
			}.ToJsonString());
			var account = await _host.Get<IRemoteActorService>().GetActor(feed, refresh: true, token);
			await _host.Run(j => j.Kind == JobKind.CountAccount && j.Payload == feed, token);

			var followed = (await persona.Client.Post($"/api/v1/accounts/{account.ID}/follow")).Ok().Body;
			Assert.True(followed.Flag("following"));
			Assert.Equal(new[] { account.ID }, (await persona.Client.Get("/api/v1/feeds")).Ok().Ids);
			await _host.Run(j => j.Kind == JobKind.SyncFeeds, token);

			var readerActor = await _host.Get<ILocalActorService>().GetReaderActor(token);
			var follows = await DB.Default.Find<Following>().Match(f => f.AvatarId == readerActor.Id).ExecuteAsync(token);
			Assert.Equal(new[] { cats.Id, dogs.Id }.Order(), follows.Select(f => f.TargetActorURI).Order());
			Assert.All(follows, f => Assert.Equal(LocalActorKind.Reader, f.FollowerKind));
			Assert.False(await DB.Default.Find<Following>().Match(f => f.AvatarId == persona.Id).ExecuteAnyAsync(token));
			var asked = Assert.Single(await cats.Delivered(since), d => d.Type() == "Follow");
			Assert.Equal(readerActor.Uri, asked.Text("actor"));
			var document = (await _host.Client().Fetch(new Uri(readerActor.Uri).AbsolutePath)).Json;
			Assert.Equal(("Service", LocalActorService.ReaderUserName), (document.Text("type"), document.Text("preferredUsername")));

			await _host.Deliver(cats, "/human-centipede", new JsonObject
			{
				["id"] = $"{cats.Id}/accepts/{Guid.NewGuid():N}", ["type"] = "Accept", ["actor"] = cats.Id, ["object"] = asked.Text("id")
			});
			var create = poster.Create("<p>a thread among cats</p>", new[] { "https://www.w3.org/ns/activitystreams#Public", cats.Id }, shape: note =>
			{
				note["type"] = "Page";
				note["name"] = "Cats";
				note["audience"] = cats.Id;
			});
			_peer.Serve(new Uri(create["object"]!.Text("id")).AbsolutePath, create["object"]!.ToJsonString());
			await _host.Deliver(cats, "/human-centipede", new JsonObject
			{
				["id"] = $"{cats.Id}/announces/{Guid.NewGuid():N}", ["type"] = "Announce", ["actor"] = cats.Id, ["object"] = create,
				["to"] = new JsonArray("https://www.w3.org/ns/activitystreams#Public")
			});
			var thread = await DB.Default.Find<Post>().Match(p => p.ObjectURI == create["object"]!.Text("id")).ExecuteSingleAsync(token);

			Assert.Equal(new[] { thread.ID }, (await persona.Client.Get($"/api/v1/timelines/feed/{account.ID}")).Ok().Ids);
			Assert.DoesNotContain(thread.ID, (await persona.Client.Get("/api/v1/timelines/home")).Ok().Ids);
			Assert.False(await DB.Default.Find<TimelineEntry>().Match(e => e.PostId == thread.ID).ExecuteAnyAsync(token));
			var stranger = await _host.Mastodon("notreading");
			Assert.Equal(HttpStatusCode.NotFound, (await stranger.Client.Get($"/api/v1/timelines/feed/{account.ID}")).Status);

			Assert.False((await persona.Client.Post($"/api/v1/accounts/{account.ID}/unfollow")).Ok().Body.Flag("following"));
			await _host.Run(j => j.Kind == JobKind.SyncFeeds, token);
			Assert.False(await DB.Default.Find<Following>().Match(f => f.AvatarId == readerActor.Id).ExecuteAnyAsync(token));
			Assert.Contains(await cats.Delivered(since), d => d.Type() == "Undo" && d["object"].Text("type") == "Follow");
		}
	}
}