Add image-only spam detection and tracking

Add support for detecting and tracking image-only spam across channels. spamDetector.js: introduce image helpers (isImageAttachment, getImageAttachments), buildImageFingerprint, isImageOnlyMessage, and extend detectSpam to report image-only reasons and a duplicateImageAcrossChannels flag. rapidSpamTracker.js: refactor cross-channel tracking with trackCrossChannelPost, pruneExpiredPosts, dedupePriorMessages, and add trackImageOnlySpam which uses optional image fingerprints; export dedupePriorMessages. index.js: wire image-only tracking into message handling (build fingerprint, trackImageOnlySpam, pass duplicateImageAcrossChannels to detectSpam), merge and dedupe prior message lists, and include attachments in mod log previews. commands.js: update detection rules text to mention image spam. These changes enable identifying image-only spam (including fingerprinting) and avoid duplicate prior-message entries when creating moderation logs.

Anti-Spam/src/rapidSpamTracker.js

@@ -5,8 +5,18 @@ function normalizeKey(text) {
   return text.toLowerCase().replace(/\s+/g, " ").trim().slice(0, 200);
 }
 
-export function trackCrossChannelMessage(guildId, userId, channelId, messageId, text) {
-  const normalized = normalizeKey(text);
+function dedupePriorMessages(priorMessages) {
+  const seen = new Set();
+  return priorMessages.filter(({ channelId, messageId }) => {
+    const entry = `${channelId}:${messageId}`;
+    if (seen.has(entry)) return false;
+    seen.add(entry);
+    return true;
+  });
+}
+
+function trackCrossChannelPost(guildId, userId, channelId, messageId, keySuffix) {
+  const normalized = normalizeKey(keySuffix);
   if (!normalized) {
     return { duplicateAcrossChannels: false, priorMessages: [] };
   }
@@ -34,13 +44,40 @@ export function trackCrossChannelMessage(guildId, userId, channelId, messageId,
     firstSeen: now,
   });
 
-  if (recentPosts.size > 5000) {
-    for (const [entryKey, entry] of recentPosts) {
-      if (now - entry.firstSeen > WINDOW_MS) {
-        recentPosts.delete(entryKey);
-      }
-    }
-  }
+  pruneExpiredPosts(now);
 
   return { duplicateAcrossChannels: false, priorMessages: [] };
 }
+
+function pruneExpiredPosts(now) {
+  if (recentPosts.size <= 5000) return;
+
+  for (const [entryKey, entry] of recentPosts) {
+    if (now - entry.firstSeen > WINDOW_MS) {
+      recentPosts.delete(entryKey);
+    }
+  }
+}
+
+export function trackCrossChannelMessage(guildId, userId, channelId, messageId, text) {
+  return trackCrossChannelPost(guildId, userId, channelId, messageId, normalizeKey(text));
+}
+
+export function trackImageOnlySpam(guildId, userId, channelId, messageId, fingerprint) {
+  const trackers = [trackCrossChannelPost(guildId, userId, channelId, messageId, "imgonly")];
+
+  if (fingerprint) {
+    trackers.push(
+      trackCrossChannelPost(guildId, userId, channelId, messageId, `imgfp:${fingerprint}`)
+    );
+  }
+
+  const duplicateAcrossChannels = trackers.some((tracker) => tracker.duplicateAcrossChannels);
+  const priorMessages = duplicateAcrossChannels
+    ? dedupePriorMessages(trackers.flatMap((tracker) => tracker.priorMessages))
+    : [];
+
+  return { duplicateAcrossChannels, priorMessages };
+}
+
+export { dedupePriorMessages };