SocialPub/PrivaPub.Tests/Federation/ServiceReportTests.cs

using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.Logging.Abstractions;

using MongoDB.Entities;

using PrivaPub.Federation.Actors;
using PrivaPub.Federation.Outbox;
using PrivaPub.Federation.Signing;
using PrivaPub.Infrastructure.Http;
using PrivaPub.Infrastructure.Jobs;
using PrivaPub.Models.Federation;
using PrivaPub.Models.Jobs;
using PrivaPub.Models.Post;
using PrivaPub.Models.User;
using PrivaPub.Tests.Support;

using System.Security.Cryptography;
using System.Text;
using System.Text.Json;
using System.Text.Json.Nodes;

namespace PrivaPub.Tests.Federation
{
	// Lemmy takes a report only from a person or a service, about one post or comment, addressed to its community (owner
	// decision 2026-10-06): a report about a post in a community on a Lemmy leaves from the server's reporter, one per post.
	// Alone in its collection: the server rows it writes for the peer's hosts decide for whoever reports there.
	[Trait("Category", "Integration")]
	[Xunit.Collection(nameof(Exclusive))]
	public sealed class ServiceReportTests : IAsyncLifetime
	{
		static readonly string[] PeerHosts = { "localhost", "127.0.0.1" };

		Harness _harness;

		public async ValueTask InitializeAsync()
		{
			Assert.SkipUnless(MongoFixture.Enabled, MongoFixture.Skip);
			_harness = await Harness.Start();
			await DB.Default.DeleteAsync<RemoteInstance>(i => PeerHosts.Contains(i.Host));
		}

		public async ValueTask DisposeAsync()
		{
			if (_harness == default)
				return;
			await DB.Default.DeleteAsync<RemoteInstance>(i => PeerHosts.Contains(i.Host));
			await _harness.DisposeAsync();
		}

		static CancellationToken Token => TestContext.Current.CancellationToken;

		static string Origin(RemoteActor actor) => new Uri(actor.Id).GetLeftPart(UriPartial.Authority);

		// what NodeInfo said the server at that host runs
		static async Task Runs(string host, string software)
		{
			await DB.Default.DeleteAsync<RemoteInstance>(i => i.Host == host);
			await DB.Default.SaveAsync(new RemoteInstance { Host = host, Software = software, SoftwareVersion = "1.0.0" }, Token);
		}

		async Task<ForeignAvatar> Known(RemoteActor actor) => await _harness.Remote.GetActor(actor.Id, refresh: false, Token);

		static async Task<Post> Held(RemoteActor author, string community = default, Post parent = default)
		{
			var post = new Post
			{
				ObjectURI = $"{Origin(author)}/post/{Guid.NewGuid():N}",
				ActorURI = author.Id,
				AudienceURI = community,
				AnsweringToPostId = parent?.ID,
				ContentHtml = "<p>reported</p>"
			};
			await DB.Default.SaveAsync(post, Token);
			return post;
		}

		async Task<List<(DeliveryPayload Payload, JsonObject Body)>> Queued() =>
			(await DB.Default.Find<Job>().Match(j => j.Kind == JobKind.Deliver && j.CreatedAt >= DateTime.UtcNow.AddMinutes(-5)).ExecuteAsync(Token))
				.Select(j => JsonSerializer.Deserialize<DeliveryPayload>(j.Payload))
				.Select(p => (p, JsonNode.Parse(p.Body)!.AsObject()))
				.ToList();

		// a community on a Lemmy (the peer as localhost), and one of its posters there
		async Task<(RemoteActor Community, RemoteActor Poster)> OnLemmy()
		{
			var community = new RemoteActor(_harness.Peer, "cats", _harness.Peer.B, type: "Group", sharedInbox: true);
			var poster = new RemoteActor(_harness.Peer, "poster", _harness.Peer.B);
			await Known(community);
			await Known(poster);
			await Runs("localhost", "lemmy");
			return (community, poster);
		}

		[Fact]
		public async Task A_post_in_a_lemmy_community_is_reported_to_its_community_by_the_reporter_and_nowhere_else()
		{
			var (_, alice) = await _harness.Persona("alice");
			var (community, poster) = await OnLemmy();
			var post = await Held(poster, community.Id);
			var reporter = await _harness.Local.GetReporterActor(Token);

			var report = await _harness.Reports.File(alice, (await Known(poster)).ID, new[] { post.ID }, "  a slur in the title ", "violation", forward: true, Token);

			Assert.True(report.Forwarded);
			var flag = Assert.Single(await _harness.Outgoing(community.SharedInbox));
			Assert.Equal("Flag", flag["type"]!.GetValue<string>());
			Assert.Equal(reporter.Uri, flag["actor"]!.GetValue<string>());
			Assert.EndsWith("/peasants/privapub_reports", reporter.Uri);
			Assert.StartsWith(reporter.Uri + "/", flag["id"]!.GetValue<string>());
			Assert.Equal(new[] { community.Id }, flag["to"]!.AsArray().Select(t => t!.GetValue<string>()));
			Assert.Equal(community.Id, flag["audience"]!.GetValue<string>());
			Assert.Equal(post.ObjectURI, flag["object"]!.GetValue<string>());
			Assert.Equal("a slur in the title", flag["summary"]!.GetValue<string>());
			Assert.Equal("a slur in the title", flag["content"]!.GetValue<string>());
			Assert.Empty(await _harness.Outgoing(poster.Id + "/inbox"));
			Assert.DoesNotContain(await Queued(), q => q.Payload.Inbox != community.SharedInbox && q.Body.ToJsonString().Contains(post.ObjectURI));
			Assert.DoesNotContain(alice.UserName, flag.ToJsonString());
			Assert.DoesNotContain(alice.Id, flag.ToJsonString());
			var queued = Assert.Single(await Queued(), q => q.Body["actor"]!.GetValue<string>() == reporter.Uri && q.Body["object"]!.GetValue<string>() == post.ObjectURI);
			Assert.Equal(LocalActorKind.Reporter, queued.Payload.SignerKind);
		}

		[Fact]
		public async Task The_reporter_signs_its_flag_with_its_own_key()
		{
			var (_, alice) = await _harness.Persona("alice");
			var (community, poster) = await OnLemmy();
			var post = await Held(poster, community.Id);
			var reporter = await _harness.Local.GetReporterActor(Token);
			var instance = await _harness.Local.GetInstanceActor(Token);
			_harness.Peer.Answer("/inbox", 202);
			await _harness.Reports.File(alice, (await Known(poster)).ID, new[] { post.ID }, default, "spam", forward: true, Token);
			var job = await DB.Default.Find<Job>()
				.Match(j => j.Kind == JobKind.Deliver && j.DedupeKey.StartsWith(reporter.ActivityUri($"flag-")))
				.Sort(j => j.CreatedAt, Order.Descending).ExecuteFirstAsync(Token);

			var handler = new DeliveryJobHandler(_harness.Local, Peer.Http(), new HostCircuitBreaker(new MemoryCache(new MemoryCacheOptions())),
				NullLogger<DeliveryJobHandler>.Instance);
			var outcome = await handler.Handle(job, Token);

			Assert.Equal(JobResult.Done, outcome.Result);
			var received = Assert.Single(_harness.Peer.Requests, r => r.Path == "/inbox" && r.Method == "POST");
			// no words: Lemmy takes no report without a reason, so the category is it
			Assert.Equal("spam", JsonNode.Parse(received.Body)!["summary"]!.GetValue<string>());
			var signature = HttpSignatures.Parse(received.Signature);
			Assert.Equal(reporter.KeyId, signature.KeyId);
			Assert.NotEqual(instance.PublicKeyPem, reporter.PublicKeyPem);
			var signingString = $"(request-target): post /inbox\nhost: {received.Headers["Host"]}\ndate: {received.Headers["Date"]}\ndigest: {received.Headers["Digest"]}";
			using var key = RSA.Create();
			key.ImportFromPem(reporter.PublicKeyPem);
			Assert.True(key.VerifyData(Encoding.UTF8.GetBytes(signingString), signature.Signature, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1));
		}

		[Fact]
		public async Task A_comment_finds_its_community_through_its_thread_and_two_posts_are_two_flags()
		{
			var (_, alice) = await _harness.Persona("alice");
			var (community, poster) = await OnLemmy();
			var thread = await Held(poster, community.Id);
			var comment = await Held(poster, parent: thread);
			var answer = await Held(poster, parent: comment);

			var report = await _harness.Reports.File(alice, (await Known(poster)).ID, new[] { comment.ID, answer.ID }, "harassment", "other", forward: true, Token);

			Assert.True(report.Forwarded);
			var flags = await _harness.Outgoing(community.SharedInbox);
			Assert.Equal(2, flags.Count);
			Assert.Equal(new[] { comment.ObjectURI, answer.ObjectURI }.Order(), flags.Select(f => f["object"]!.GetValue<string>()).Order());
			Assert.All(flags, f => Assert.Equal(community.Id, f["to"]![0]!.GetValue<string>()));
			Assert.Equal(2, flags.Select(f => f["id"]!.GetValue<string>()).Distinct().Count());
		}

		[Fact]
		public async Task An_account_alone_on_a_lemmy_is_reported_to_nobody()
		{
			var (_, alice) = await _harness.Persona("alice");
			var (community, poster) = await OnLemmy();

			var report = await _harness.Reports.File(alice, (await Known(poster)).ID, Array.Empty<string>(), "a spammer", "spam", forward: true, Token);

			Assert.False(report.Forwarded);
			Assert.False((await DB.Default.Find<PrivaPub.Models.Social.Report>().OneAsync(report.ID, Token)).Forwarded);
			Assert.Empty(await _harness.Outgoing(community.SharedInbox));
			Assert.Empty(await _harness.Outgoing(poster.Id + "/inbox"));
		}

		[Fact]
		public async Task Any_other_server_still_gets_the_instance_flag_and_a_lemmy_community_its_own()
		{
			var (_, alice) = await _harness.Persona("alice");
			var (community, _) = await OnLemmy();
			// an account on a Mastodon (the peer as 127.0.0.1) that wrote in the community on the Lemmy, and elsewhere
			var mastodonian = new RemoteActor(_harness.Peer, "masto");
			await Runs("127.0.0.1", "mastodon");
			var inCommunity = await Held(mastodonian, community.Id);
			var elsewhere = await Held(mastodonian);
			var instance = await _harness.Local.GetInstanceActor(Token);

			var report = await _harness.Reports.File(alice, (await Known(mastodonian)).ID, new[] { inCommunity.ID, elsewhere.ID }, "spam", "spam", forward: true, Token);

			Assert.True(report.Forwarded);
			var toCommunity = Assert.Single(await _harness.Outgoing(community.SharedInbox));
			Assert.Equal(inCommunity.ObjectURI, toCommunity["object"]!.GetValue<string>());
			var toAuthor = Assert.Single(await _harness.Outgoing(mastodonian.Id + "/inbox"));
			Assert.Equal(instance.Uri, toAuthor["actor"]!.GetValue<string>());
			Assert.Equal(new[] { mastodonian.Id, inCommunity.ObjectURI, elsewhere.ObjectURI }.Order(),
				toAuthor["object"]!.AsArray().Select(o => o!.GetValue<string>()).Order());
			Assert.Null(toAuthor["to"]);
		}

		[Fact]
		public async Task A_community_on_a_server_that_takes_no_service_reports_gets_nothing_new()
		{
			var (_, alice) = await _harness.Persona("alice");
			var community = new RemoteActor(_harness.Peer, "forum", _harness.Peer.B, type: "Group", sharedInbox: true);
			var poster = new RemoteActor(_harness.Peer, "poster", _harness.Peer.B);
			await Known(community);
			var foreign = await Known(poster);
			await Runs("localhost", "friendica");
			var post = await Held(poster, community.Id);

			var report = await _harness.Reports.File(alice, foreign.ID, new[] { post.ID }, "spam", "spam", forward: true, Token);

			Assert.True(report.Forwarded);
			Assert.Empty(await _harness.Outgoing(community.SharedInbox));
			var flag = Assert.Single(await _harness.Outgoing(poster.Id + "/inbox"));
			Assert.EndsWith("/peasants/privapub", flag["actor"]!.GetValue<string>());
		}

		[Fact]
		public async Task Nobody_follows_the_reporter()
		{
			var follower = new RemoteActor(_harness.Peer, "follower");
			var reporter = await _harness.Local.GetReporterActor(Token);

			var result = await _harness.Deliver(follower, "/human-centipede", new JsonObject
			{
				["id"] = $"{Origin(follower)}/follow/{Guid.NewGuid():N}", ["type"] = "Follow", ["actor"] = follower.Id, ["object"] = reporter.Uri
			});

			Assert.Equal(404, result.StatusCode);
			Assert.False(await DB.Default.Find<Follower>().Match(f => f.ActorURI == follower.Id).ExecuteAnyAsync(Token));
		}
	}
}