Add 'apps/mobile/' from commit '5fa30f365f21531094cd4d2045042bb4f1370ac3'

git-subtree-dir: apps/mobile
git-subtree-mainline: 86f8987dff
git-subtree-split: 5fa30f365f

apps/mobile/lib/use-running-elapsed.ts

@@ -0,0 +1,29 @@
+import { useEffect, useState } from "react";
+
+/** Live elapsed seconds since `startedAt`, ticking every second. */
+export function useRunningElapsed(startedAt?: string | Date | null) {
+  const [elapsed, setElapsed] = useState(0);
+
+  useEffect(() => {
+    if (!startedAt) {
+      setElapsed(0);
+      return;
+    }
+
+    const startMs = new Date(startedAt).getTime();
+    if (Number.isNaN(startMs)) {
+      setElapsed(0);
+      return;
+    }
+
+    const tick = () => {
+      setElapsed(Math.max(0, Math.floor((Date.now() - startMs) / 1000)));
+    };
+
+    tick();
+    const id = setInterval(tick, 1000);
+    return () => clearInterval(id);
+  }, [startedAt]);
+
+  return elapsed;
+}