refactor: replace res.json delete interception with syndicator delete() hook

Remove the fragile middleware in contentNegotiationRoutes that wrapped
res.json to detect successful Micropub delete responses. Replace it with
clean delete() and update() lifecycle methods on ActivityPubEndpoint that
are called directly by post-content.js via callSyndicatorHook.

Also adds broadcastPostUpdate() to send Update activities for edited posts,
mirroring the broadcastDelete() batch-delivery pattern.

index.js

@@ -387,38 +387,6 @@ export default class ActivityPubEndpoint {
     const router = express.Router(); // eslint-disable-line new-cap
     const self = this;
 
-    // Intercept Micropub delete actions to broadcast Delete to fediverse.
-    // Wraps res.json to detect successful delete responses, then fires
-    // broadcastDelete asynchronously so remote servers remove the post.
-    router.use((req, res, next) => {
-      if (req.method !== "POST") return next();
-      if (!req.path.endsWith("/micropub")) return next();
-
-      const action = req.query?.action || req.body?.action;
-      if (action !== "delete") return next();
-
-      const postUrl = req.query?.url || req.body?.url;
-      if (!postUrl) return next();
-
-      const originalJson = res.json.bind(res);
-      res.json = function (body) {
-        // Fire broadcastDelete after successful delete (status 200)
-        if (res.statusCode === 200 && body?.success === "delete") {
-          console.info(
-            `[ActivityPub] Micropub delete detected for ${postUrl}, broadcasting Delete to followers`,
-          );
-          self.broadcastDelete(postUrl).catch((error) => {
-            console.warn(
-              `[ActivityPub] broadcastDelete after Micropub delete failed: ${error.message}`,
-            );
-          });
-        }
-        return originalJson(body);
-      };
-
-      return next();
-    });
-
     // Let Fedify handle NodeInfo data (/nodeinfo/2.1)
     // Only pass GET/HEAD requests — POST/PUT/DELETE must not go through
     // Fedify here, because fromExpressRequest() consumes the body stream,
@@ -1181,6 +1149,125 @@ export default class ActivityPubEndpoint {
     }
   }
 
+  /**
+   * Called by post-content.js when a Micropub delete succeeds.
+   * Broadcasts an ActivityPub Delete activity to all followers.
+   * @param {string} url - Full URL of the deleted post
+   */
+  async delete(url) {
+    await this.broadcastDelete(url).catch((err) =>
+      console.warn(`[ActivityPub] broadcastDelete failed for ${url}: ${err.message}`)
+    );
+  }
+
+  /**
+   * Called by post-content.js when a Micropub update succeeds.
+   * Broadcasts an ActivityPub Update activity for the post to all followers.
+   * @param {object} properties - JF2 post properties (must include url)
+   */
+  async update(properties) {
+    await this.broadcastPostUpdate(properties).catch((err) =>
+      console.warn(`[ActivityPub] broadcastPostUpdate failed for ${properties?.url}: ${err.message}`)
+    );
+  }
+
+  /**
+   * Send an Update activity to all followers for a modified post.
+   * Mirrors broadcastDelete() pattern: batch delivery with shared inbox dedup.
+   * @param {object} properties - JF2 post properties
+   */
+  async broadcastPostUpdate(properties) {
+    if (!this._federation) return;
+
+    try {
+      const actorUrl = this._getActorUrl();
+      const activity = jf2ToAS2Activity(
+        properties,
+        actorUrl,
+        this._publicationUrl,
+        { visibility: this.options.defaultVisibility },
+      );
+
+      if (!activity) {
+        console.warn(`[ActivityPub] broadcastPostUpdate: could not convert post to AS2 for ${properties?.url}`);
+        return;
+      }
+
+      const handle = this.options.actor.handle;
+      const ctx = this._federation.createContext(
+        new URL(this._publicationUrl),
+        { handle, publicationUrl: this._publicationUrl },
+      );
+
+      const followers = await this._collections.ap_followers
+        .find({})
+        .project({ actorUrl: 1, inbox: 1, sharedInbox: 1 })
+        .toArray();
+
+      const inboxMap = new Map();
+      for (const f of followers) {
+        const key = f.sharedInbox || f.inbox;
+        if (key && !inboxMap.has(key)) {
+          inboxMap.set(key, f);
+        }
+      }
+
+      const uniqueRecipients = [...inboxMap.values()];
+      const BATCH_SIZE = 25;
+      const BATCH_DELAY_MS = 5000;
+      let delivered = 0;
+      let failed = 0;
+
+      console.info(
+        `[ActivityPub] Broadcasting Update for ${properties.url} to ${uniqueRecipients.length} unique inboxes`,
+      );
+
+      for (let i = 0; i < uniqueRecipients.length; i += BATCH_SIZE) {
+        const batch = uniqueRecipients.slice(i, i + BATCH_SIZE);
+        const recipients = batch.map((f) => ({
+          id: new URL(f.actorUrl),
+          inboxId: new URL(f.inbox || f.sharedInbox),
+          endpoints: f.sharedInbox
+            ? { sharedInbox: new URL(f.sharedInbox) }
+            : undefined,
+        }));
+
+        try {
+          await ctx.sendActivity(
+            { identifier: handle },
+            recipients,
+            activity,
+            { preferSharedInbox: true },
+          );
+          delivered += batch.length;
+        } catch (error) {
+          failed += batch.length;
+          console.warn(
+            `[ActivityPub] Update batch ${Math.floor(i / BATCH_SIZE) + 1} failed: ${error.message}`,
+          );
+        }
+
+        if (i + BATCH_SIZE < uniqueRecipients.length) {
+          await new Promise((resolve) => setTimeout(resolve, BATCH_DELAY_MS));
+        }
+      }
+
+      console.info(
+        `[ActivityPub] Update broadcast complete for ${properties.url}: ${delivered} delivered, ${failed} failed`,
+      );
+
+      await logActivity(this._collections.ap_activities, {
+        direction: "outbound",
+        type: "Update",
+        actorUrl: this._publicationUrl,
+        objectUrl: properties.url,
+        summary: `Sent Update for ${properties.url} to ${delivered} inboxes`,
+      }).catch(() => {});
+    } catch (error) {
+      console.warn("[ActivityPub] broadcastPostUpdate failed:", error.message);
+    }
+  }
+
   /**
    * Build the full actor URL from config.
    * @returns {string}