Edit history from formerRepresentations

Pleroma and Akkoma send a post's earlier versions with it. A post PrivaPub first meets after its edits now has its
history, and an edit that carries them brings the versions missed in between; each is read as the post itself is. The
Akkoma scenario checks a post fetched after two edits by an account no persona follows.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

PrivaPub/Federation/Objects/NoteParser.cs

@@ -52,6 +52,7 @@ namespace PrivaPub.Federation.Objects
 		public EventDetails Event { get; init; }
 		public PostPlace Place { get; init; }
 		public bool? CommentsEnabled { get; init; }//Lemmy, PieFed and Mbin: false once its moderators lock it; null when not said
+		public IReadOnlyList<PostRevision> FormerRepresentations { get; init; } = Array.Empty<PostRevision>();//its earlier versions, oldest first
 	}
 
 	public static class NoteParser
@@ -59,6 +60,7 @@ namespace PrivaPub.Federation.Objects
 		static readonly string[] NoteTypes = { "Note", "Article", "Page", "Question", "Event", "Video", "Audio", "Image", "ChatMessage", "PodcastEpisode" };
 		const int MaxAttachments = 16;
 		const int MaxTags = 64;
+		public const int MaxRevisions = 20;
 
 		public static NoteDocument Parse(JsonNode node)
 		{
@@ -75,8 +77,7 @@ namespace PrivaPub.Federation.Objects
 			var summary = Value(note, "summary");
 			var excerpt = ObjectShapes.Text(summary, 1000)
 				?? (note["preview"] is JsonObject preview && Value(preview, "type") == "Note" ? ObjectShapes.Text(Value(preview, "content"), 1000) : default);
-			var sensitive = note["sensitive"] is JsonValue flag && flag.TryGetValue<bool>(out var marked) && marked;
-			var summaryWarns = type is "Note" or "Question" || sensitive;
+			var (sensitive, summaryWarns) = Warns(note, type, summary);
 			return new NoteDocument
 			{
 				Id = id,
@@ -87,7 +88,7 @@ namespace PrivaPub.Federation.Objects
 				Title = ObjectShapes.Text(Value(note, "name"), 500),
 				SpoilerText = summaryWarns ? Plain(summary, 500) : default,
 				Excerpt = summaryWarns ? default : excerpt,
-				Sensitive = sensitive || summaryWarns && !string.IsNullOrWhiteSpace(summary),
+				Sensitive = sensitive,
 				Language = language,
 				Url = UrlOf(note["url"]) ?? id,
 				InReplyTo = Id(note["inReplyTo"]),
@@ -128,10 +129,45 @@ namespace PrivaPub.Federation.Objects
 				Audio = ObjectShapes.Audio(type == "PodcastEpisode" ? note["audio"] as JsonObject : note),
 				Event = ObjectShapes.Event(note),
 				Place = ObjectShapes.NotePlace(note),
-				CommentsEnabled = note["commentsEnabled"] is JsonValue comments && comments.TryGetValue<bool>(out var enabled) ? enabled : null
+				CommentsEnabled = note["commentsEnabled"] is JsonValue comments && comments.TryGetValue<bool>(out var enabled) ? enabled : null,
+				FormerRepresentations = Former(note, type)
 			};
 		}
 
+		// a summary is a content warning only on a Note or a Question, or a post marked sensitive; elsewhere it is an excerpt
+		static (bool Sensitive, bool SummaryWarns) Warns(JsonObject note, string type, string summary)
+		{
+			var marked = note["sensitive"] is JsonValue flag && flag.TryGetValue<bool>(out var value) && value;
+			var warns = type is "Note" or "Question" || marked;
+			return (marked || warns && !string.IsNullOrWhiteSpace(summary), warns);
+		}
+
+		// Pleroma's and Akkoma's earlier versions of an edited post (`formerRepresentations`, newest first there), each read as
+		// the post itself is: the newest twenty, oldest first, each dated when it was written
+		static List<PostRevision> Former(JsonObject note, string type)
+		{
+			if (note["formerRepresentations"] is not JsonObject former || former["orderedItems"] is not JsonArray items)
+				return [];
+			return items.OfType<JsonObject>().Take(MaxRevisions * 2)
+				.Select(version =>
+				{
+					var summary = Value(version, "summary");
+					var (sensitive, warns) = Warns(version, type, summary);
+					return new PostRevision
+					{
+						Title = ObjectShapes.Text(Value(version, "name"), 500),
+						SpoilerText = warns ? Plain(summary, 500) : default,
+						ContentHtml = ContentSanitizer.Html(Content(version).Html),
+						HasContentWarning = sensitive,
+						EditedAt = Time(Value(version, "updated")) ?? Time(Value(version, "published")) ?? default
+					};
+				})
+				.Reverse()
+				.OrderBy(r => r.EditedAt)
+				.TakeLast(MaxRevisions)
+				.ToList();
+		}
+
 		// Castopod's PodcastEpisode: its words in `description` (a Note of its own), its sound in `audio`, its title the
 		// sound's name; read as a post with those
 		static JsonObject Episode(JsonObject episode)