feat: incorporate tag preferences into blacklist filter stage

- Implements `hasDisinterestedTag` helper in `js/feedEngine/utils.js` to check for disinterested tags in both raw Nostr tags and NIP-71 metadata.
- Updates `createBlacklistFilterStage` in `js/feedEngine/stages.js` to filter out videos matching `context.runtime.tagPreferences` disinterests.
- Ensures existing blacklist logic remains undisturbed.
- Verified with new unit test `tests/feed-engine-tag-pref.test.mjs` and existing feed engine tests.

js/feedEngine/stages.js

@@ -10,7 +10,7 @@ import nostrService from "../services/nostrService.js";
 import moderationService from "../services/moderationService.js";
 import logger from "../utils/logger.js";
 import { dedupeToNewestByRoot } from "../utils/videoDeduper.js";
-import { isPlainObject, toSet } from "./utils.js";
+import { isPlainObject, toSet, hasDisinterestedTag } from "./utils.js";
 
 const FEED_HIDE_BYPASS_NAMES = new Set(["home", "recent"]);
 
@@ -276,9 +276,9 @@ export function createBlacklistFilterStage({
 
     const options = { blacklistedEventIds: blacklist, isAuthorBlocked };
 
-    // TODO(tag-preferences): incorporate context.runtime.tagPreferences once the
-    // filtering helpers are in place so this stage can drop disinterested tags
-    // without disturbing existing blacklist logic.
+    const tagPreferences = context?.runtime?.tagPreferences;
+    const disinterests = toSet(tagPreferences?.disinterests);
+    const hasTagPreferences = disinterests.size > 0;
 
     const results = [];
 
@@ -289,6 +289,17 @@ export function createBlacklistFilterStage({
         continue;
       }
 
+      if (hasTagPreferences && hasDisinterestedTag(video, disinterests)) {
+        context?.addWhy?.({
+          stage: stageName,
+          type: "filter",
+          reason: "disinterested-tag",
+          videoId: typeof video.id === "string" ? video.id : null,
+          pubkey: typeof video.pubkey === "string" ? video.pubkey : null,
+        });
+        continue;
+      }
+
       let include = false;
       try {
         include = includeFn(video, options) !== false;

js/feedEngine/utils.js

@@ -27,3 +27,31 @@ export function toArray(value) {
   }
   return [value];
 }
+
+export function hasDisinterestedTag(video, disinterestsSet) {
+  if (!video || !disinterestsSet || !(disinterestsSet instanceof Set) || disinterestsSet.size === 0) {
+    return false;
+  }
+
+  // Check raw tags
+  if (Array.isArray(video.tags)) {
+    for (const tag of video.tags) {
+      if (Array.isArray(tag) && tag[0] === "t" && typeof tag[1] === "string") {
+        if (disinterestsSet.has(tag[1].toLowerCase())) {
+          return true;
+        }
+      }
+    }
+  }
+
+  // Check NIP-71 metadata hashtags if available
+  if (video.nip71 && Array.isArray(video.nip71.hashtags)) {
+    for (const tag of video.nip71.hashtags) {
+      if (typeof tag === "string" && disinterestsSet.has(tag.toLowerCase())) {
+        return true;
+      }
+    }
+  }
+
+  return false;
+}