feat(favicon): swap tab favicon for SFW vs NSFW boards

src/lib/update-favicon.ts

@@ -0,0 +1,54 @@
+const DEFAULT_FAVICON = '/favicon.ico';
+const SFW_FAVICON = '/favicon2.ico';
+
+let currentHref: string | null = null;
+
+/**
+ * Swap the tab favicon between the default (NSFW/home) and SFW variants.
+ * Uses remove-and-recreate to bypass aggressive browser favicon caching.
+ */
+export const updateFavicon = (isSfw: boolean): void => {
+  const href = isSfw ? SFW_FAVICON : DEFAULT_FAVICON;
+  if (href === currentHref) return;
+  currentHref = href;
+
+  const existing = document.querySelector<HTMLLinkElement>('link[rel="icon"]');
+  if (existing) existing.remove();
+
+  const link = document.createElement('link');
+  link.rel = 'icon';
+  link.href = href;
+  document.head.appendChild(link);
+};
+
+/**
+ * Determine whether the current navigation context is a SFW board.
+ *
+ * Pure function — no hooks, no side-effects, fully testable.
+ */
+export const isSfwBoard = ({
+  pathname,
+  isSpecialTheme,
+  isInAllView,
+  isInSubscriptionsView,
+  isInModView,
+  subplebbitAddress,
+  directories,
+}: {
+  pathname: string;
+  isSpecialTheme: boolean;
+  isInAllView: boolean;
+  isInSubscriptionsView: boolean;
+  isInModView: boolean;
+  subplebbitAddress: string | undefined;
+  directories: { address: string; nsfw?: boolean }[];
+}): boolean => {
+  if (pathname === '/' || pathname.startsWith('/rules')) return false;
+  if (isSpecialTheme) return false;
+  if (isInAllView || isInSubscriptionsView || isInModView) return false;
+
+  if (!subplebbitAddress) return false;
+
+  const entry = directories.find((d) => d.address === subplebbitAddress);
+  return !entry?.nsfw;
+};