Ads: move isExpired to tested utils function

app/soapbox/queries/ads.ts

@@ -2,6 +2,7 @@ import { useQuery } from '@tanstack/react-query';
 
 import { Ad, getProvider } from 'soapbox/features/ads/providers';
 import { useAppDispatch } from 'soapbox/hooks';
+import { isExpired } from 'soapbox/utils/ads';
 
 export default function useAds() {
   const dispatch = useAppDispatch();
@@ -22,11 +23,7 @@ export default function useAds() {
   });
 
   // Filter out expired ads.
-  const data = result.data?.filter(ad => {
-    const now = new Date();
-    const isExpired = ad.expires && (now.getTime() > ad.expires.getTime());
-    return !isExpired;
-  });
+  const data = result.data?.filter(isExpired);
 
   return {
     ...result,

app/soapbox/utils/__tests__/ads.test.ts

@@ -0,0 +1,22 @@
+import { normalizeCard } from 'soapbox/normalizers';
+
+import { isExpired } from '../ads';
+
+/** 3 minutes in milliseconds. */
+const threeMins = 3 * 60 * 1000;
+
+/** 5 minutes in milliseconds. */
+const fiveMins = 5 * 60 * 1000;
+
+test('isExpired()', () => {
+  const now = new Date();
+  const card = normalizeCard({});
+
+  // Sanity tests.
+  expect(isExpired({ expires: now, card })).toBe(true);
+  expect(isExpired({ expires: new Date(now.getTime() + 999999), card })).toBe(false);
+
+  // Testing the 5-minute mark.
+  expect(isExpired({ expires: new Date(now.getTime() + threeMins), card }, fiveMins)).toBe(true);
+  expect(isExpired({ expires: new Date(now.getTime() + fiveMins + 1000), card }, fiveMins)).toBe(false);
+});

app/soapbox/utils/ads.ts

@@ -0,0 +1,16 @@
+import type { Ad } from 'soapbox/features/ads/providers';
+
+/** Time (ms) window to not display an ad if it's about to expire. */
+const AD_EXPIRY_THRESHOLD = 5 * 60 * 1000;
+
+/** Whether the ad is expired or about to expire. */
+const isExpired = (ad: Ad, threshold = AD_EXPIRY_THRESHOLD): boolean => {
+  if (ad.expires) {
+    const now = new Date();
+    return now.getTime() > (ad.expires.getTime() - threshold);
+  } else {
+    return false;
+  }
+};
+
+export { isExpired };