fix(desktop): fold kind 40003 edit content into forum posts and comments

desktop/src-tauri/src/commands/messages/forum.rs

@@ -154,6 +154,56 @@ pub(super) fn apply_link_preview_suppression(
     }
 }
 
+/// Fold the latest kind:40003 edit content into an original event.
+///
+/// A 40003 edit is valid when its signer is the original's author or the
+/// author's verified agent owner. Among valid edits targeting the same
+/// original, the one with the highest `created_at` wins. The edit's content
+/// replaces the original's content; the edit's tags (excluding the routing
+/// `e` tag and any `link-preview` marker, which are already handled
+/// separately) are not folded — only the text changes.
+///
+/// Returns the edited content when a valid edit exists, or `None` when the
+/// original should be used as-is.
+pub(super) fn fold_edit_content(
+    original: &nostr::Event,
+    edits: &[nostr::Event],
+    owner_pubkeys: &std::collections::HashMap<String, String>,
+) -> Option<String> {
+    let original_author = original.pubkey.to_hex();
+    let original_id = original.id.to_hex();
+
+    let mut best: Option<&nostr::Event> = None;
+    for edit in edits {
+        if edit.kind.as_u16() != 40003 {
+            continue;
+        }
+        // Find the target event id from the e tag.
+        let target_id = edit.tags.iter().find_map(|tag| {
+            let values = tag.as_slice();
+            (values.first().map(String::as_str) == Some("e"))
+                .then(|| values.get(1).map(String::as_str))
+                .flatten()
+        });
+        if target_id != Some(original_id.as_str()) {
+            continue;
+        }
+        // Authorization: signer must be the original author or the
+        // author's verified agent owner.
+        let signer = edit.pubkey.to_hex();
+        let authorized = signer == original_author
+            || owner_pubkeys.get(&original_author) == Some(&signer);
+        if !authorized {
+            continue;
+        }
+        // Latest edit wins.
+        if best.is_none_or(|b| edit.created_at > b.created_at) {
+            best = Some(edit);
+        }
+    }
+    best.map(|e| e.content.clone())
+}
+
 #[tauri::command]
 pub async fn get_forum_posts(
     channel_id: String,
@@ -191,6 +241,9 @@ pub async fn get_forum_posts(
         .iter()
         .map(|ev| {
             let mut message = forum_message_from_event(ev, &channel_id);
+            if let Some(edited_content) = fold_edit_content(ev, &edits, &owner_pubkeys) {
+                message.content = edited_content;
+            }
             apply_link_preview_suppression(&mut message.tags, &message.event_id, &suppressed);
             message
         })
@@ -248,10 +301,16 @@ pub async fn get_forum_thread(
     for ev in &events {
         if ev.id.to_hex() == event_id {
             let mut message = forum_message_from_event(ev, &channel_id);
+            if let Some(edited_content) = fold_edit_content(ev, &edits, &owner_pubkeys) {
+                message.content = edited_content;
+            }
             apply_link_preview_suppression(&mut message.tags, &message.event_id, &suppressed);
             root = Some(message);
         } else if ev.kind.as_u16() as u32 != 40003 {
             let mut reply = forum_reply_from_event(ev, &channel_id, &event_id);
+            if let Some(edited_content) = fold_edit_content(ev, &edits, &owner_pubkeys) {
+                reply.content = edited_content;
+            }
             apply_link_preview_suppression(&mut reply.tags, &reply.event_id, &suppressed);
             replies.push(reply);
         }
@@ -315,4 +374,92 @@ mod tests {
         )
         .is_empty());
     }
+
+    fn edit_event(
+        keys: &Keys,
+        content: &str,
+        target_id: &str,
+        created_at: nostr::Timestamp,
+    ) -> nostr::Event {
+        let tags = vec![nostr::Tag::parse(["e", target_id]).unwrap()];
+        EventBuilder::new(Kind::Custom(40003), content)
+            .tags(tags)
+            .custom_created_at(created_at)
+            .sign_with_keys(keys)
+            .expect("edit signs")
+    }
+
+    #[test]
+    fn fold_edit_content_applies_author_edit() {
+        let author = Keys::generate();
+        let original = signed_event(&author, 45001, Vec::new());
+        let edit = edit_event(&author, "edited body", &original.id.to_hex(), nostr::Timestamp::now());
+        let owners = std::collections::HashMap::new();
+        let result = fold_edit_content(&original, std::slice::from_ref(&edit), &owners);
+        assert_eq!(result.as_deref(), Some("edited body"));
+    }
+
+    #[test]
+    fn fold_edit_content_applies_owner_edit() {
+        let author = Keys::generate();
+        let owner = Keys::generate();
+        let original = signed_event(&author, 45001, Vec::new());
+        let edit = edit_event(&owner, "owner-edited", &original.id.to_hex(), nostr::Timestamp::now());
+        let owners = std::collections::HashMap::from([(
+            author.public_key().to_hex(),
+            owner.public_key().to_hex(),
+        )]);
+        let result = fold_edit_content(&original, std::slice::from_ref(&edit), &owners);
+        assert_eq!(result.as_deref(), Some("owner-edited"));
+    }
+
+    #[test]
+    fn fold_edit_content_rejects_unauthorized_signer() {
+        let author = Keys::generate();
+        let attacker = Keys::generate();
+        let original = signed_event(&author, 45001, Vec::new());
+        let edit = edit_event(&attacker, "hacked", &original.id.to_hex(), nostr::Timestamp::now());
+        let owners = std::collections::HashMap::new();
+        let result = fold_edit_content(&original, std::slice::from_ref(&edit), &owners);
+        assert!(result.is_none(), "unauthorized edit must not apply");
+    }
+
+    #[test]
+    fn fold_edit_content_latest_edit_wins() {
+        let author = Keys::generate();
+        let original = signed_event(&author, 45001, Vec::new());
+        let older = edit_event(&author, "first", &original.id.to_hex(), nostr::Timestamp::from_secs(100));
+        let newer = edit_event(&author, "second", &original.id.to_hex(), nostr::Timestamp::from_secs(200));
+        let owners = std::collections::HashMap::new();
+        let edits = [older, newer];
+        let result = fold_edit_content(&original, &edits, &owners);
+        assert_eq!(result.as_deref(), Some("second"));
+    }
+
+    #[test]
+    fn fold_edit_content_ignores_edit_targeting_different_event() {
+        let author = Keys::generate();
+        let original = signed_event(&author, 45001, Vec::new());
+        // Distinct created_at so `other` has a different event id from `original`.
+        // Without this, both events share the same author, kind, content, and
+        // timestamp, producing the same event id — the edit targeting `other`
+        // would then match `original`, defeating the test's purpose.
+        let other = EventBuilder::new(Kind::Custom(45001), "body")
+            .custom_created_at(nostr::Timestamp::from_secs(1))
+            .sign_with_keys(&author)
+            .expect("event signs");
+        let edit = edit_event(&author, "wrong target", &other.id.to_hex(), nostr::Timestamp::now());
+        let owners = std::collections::HashMap::new();
+        let result = fold_edit_content(&original, std::slice::from_ref(&edit), &owners);
+        assert!(result.is_none(), "edit targeting a different event must not apply");
+    }
+
+    #[test]
+    fn fold_edit_content_no_edits_returns_none() {
+        let author = Keys::generate();
+        let original = signed_event(&author, 45001, Vec::new());
+        let owners = std::collections::HashMap::new();
+        let result = fold_edit_content(&original, &[], &owners);
+        assert!(result.is_none());
+    }
 }