From 7c0e6dfea1d2d06faade6847368bb3ca187d5fc4 Mon Sep 17 00:00:00 2001
From: Laura Hausmann <laura@hausmann.dev>
Date: Sun, 10 Mar 2024 23:46:23 +0100
Subject: [PATCH] [backend/federation] Use dotNetRdf ForceArray option instead
 of patching the AS context (ISH-153)

---
 .../ActivityStreams/Contexts/as.json          |  3 +-
 .../Federation/ActivityStreams/LDHelpers.cs   |  6 +++-
 .../Federation/ActivityStreams/Types/ASTag.cs | 35 ++-----------------
 3 files changed, 9 insertions(+), 35 deletions(-)

diff --git a/Iceshrimp.Backend/Core/Federation/ActivityStreams/Contexts/as.json b/Iceshrimp.Backend/Core/Federation/ActivityStreams/Contexts/as.json
index 66b6d064..bd703726 100644
--- a/Iceshrimp.Backend/Core/Federation/ActivityStreams/Contexts/as.json
+++ b/Iceshrimp.Backend/Core/Federation/ActivityStreams/Contexts/as.json
@@ -200,8 +200,7 @@
     },
     "tag": {
       "@id": "as:tag",
-      "@type": "@id",
-      "@container": "@list"
+      "@type": "@id"
     },
     "target": {
       "@id": "as:target",
diff --git a/Iceshrimp.Backend/Core/Federation/ActivityStreams/LDHelpers.cs b/Iceshrimp.Backend/Core/Federation/ActivityStreams/LDHelpers.cs
index 128d928b..669a41c9 100644
--- a/Iceshrimp.Backend/Core/Federation/ActivityStreams/LDHelpers.cs
+++ b/Iceshrimp.Backend/Core/Federation/ActivityStreams/LDHelpers.cs
@@ -1,3 +1,4 @@
+using Iceshrimp.Backend.Core.Configuration;
 using Iceshrimp.Backend.Core.Database.Tables;
 using Iceshrimp.Backend.Core.Federation.ActivityStreams.Types;
 using Iceshrimp.Backend.Core.Federation.Cryptography;
@@ -60,12 +61,15 @@ public static class LdHelpers
 		JToken.Parse(File.ReadAllText(Path.Combine("Core", "Federation", "ActivityStreams", "Contexts",
 		                                           "as-extensions.json")));
 
+	private static IEnumerable<string> ASForceArray => ["tag", "to", "cc", "bcc", "bto"];
+
 	private static readonly JsonLdProcessorOptions Options = new()
 	{
 		DocumentLoader = CustomLoader,
 		ExpandContext  = ASExtensions,
 		ProcessingMode = JsonLdProcessingMode.JsonLd11,
-		KeepIRIs       = ["https://www.w3.org/ns/activitystreams#Public"]
+		KeepIRIs       = [$"{Constants.ActivityStreamsNs}#Public"],
+		ForceArray     = ASForceArray.Select(p => $"{Constants.ActivityStreamsNs}#{p}").ToList()
 	};
 
 	public static readonly JsonSerializerSettings JsonSerializerSettings = new()
diff --git a/Iceshrimp.Backend/Core/Federation/ActivityStreams/Types/ASTag.cs b/Iceshrimp.Backend/Core/Federation/ActivityStreams/Types/ASTag.cs
index 50e08b24..35aaf7e1 100644
--- a/Iceshrimp.Backend/Core/Federation/ActivityStreams/Types/ASTag.cs
+++ b/Iceshrimp.Backend/Core/Federation/ActivityStreams/Types/ASTag.cs
@@ -54,7 +54,7 @@ public class ASEmoji : ASTag
 
 public sealed class ASTagConverter : JsonConverter
 {
-	public override bool CanWrite => true;
+	public override bool CanWrite => false;
 
 	public override bool CanConvert(Type objectType)
 	{
@@ -74,27 +74,7 @@ public sealed class ASTagConverter : JsonConverter
 
 		if (reader.TokenType == JsonToken.StartArray)
 		{
-			// We have to use @list here because otherwise Akkoma will refuse to process activities with only one Tag.
-			// To solve this, we've patched the AS2 context to render & parse the tag type as @list, forcing it to be an array.
-			// Ref: https://akkoma.dev/AkkomaGang/akkoma/issues/720
-			var array = JArray.Load(reader);
-			if (array.Count > 0)
-			{
-				try
-				{
-					return array.SelectToken("$.[*].@list")
-					            ?.Children()
-					            .OfType<JObject>()
-					            .Select(HandleObject)
-					            .OfType<ASTag>()
-					            .ToList();
-				}
-				catch
-				{
-					//ignored
-				}
-			}
-
+			var array  = JArray.Load(reader);
 			var result = new List<ASTag>();
 			foreach (var token in array)
 			{
@@ -125,15 +105,6 @@ public sealed class ASTagConverter : JsonConverter
 
 	public override void WriteJson(JsonWriter writer, object? value, JsonSerializer serializer)
 	{
-		if (value == null)
-		{
-			writer.WriteNull();
-			return;
-		}
-
-		writer.WriteStartObject();
-		writer.WritePropertyName("@list");
-		serializer.Serialize(writer, value);
-		writer.WriteEndObject();
+		throw new NotImplementedException();
 	}
 }
\ No newline at end of file