Hotfix: add hacker count to Admin Dashboard

apps/site/src/app/admin/dashboard/AdminDashboard.tsx

@@ -10,6 +10,7 @@ import { isApplicationManager } from "@/lib/admin/authorization";
 import UserContext from "@/lib/admin/UserContext";
 
 import ApplicantSummary from "./components/ApplicantSummary";
+import HackerCount from "./components/HackerCount";
 
 function AdminDashboard() {
 	const { role } = useContext(UserContext);
@@ -19,6 +20,7 @@ function AdminDashboard() {
 			<SpaceBetween size="l">
 				<Container>Admin Dashboard</Container>
 				{isApplicationManager(role) && <ApplicantSummary />}
+				<HackerCount />
 			</SpaceBetween>
 		</ContentLayout>
 	);

apps/site/src/app/admin/dashboard/components/HackerCount.tsx

@@ -0,0 +1,33 @@
+import Container from "@cloudscape-design/components/container";
+import dayjs from "dayjs";
+import timezone from "dayjs/plugin/timezone";
+import utc from "dayjs/plugin/utc";
+
+import useParticipants, { Role } from "@/lib/admin/useParticipants";
+
+dayjs.extend(utc);
+dayjs.extend(timezone);
+
+const EVENT_TIMEZONE = "America/Los_Angeles";
+
+const FRIDAY = dayjs(new Date("2024-01-26T12:00:00")).tz(EVENT_TIMEZONE);
+
+function HackerCount() {
+	const { participants, loading } = useParticipants();
+
+	const checkedIn = participants
+		.filter((participant) => participant.role === Role.Applicant)
+		.filter((participant) =>
+			participant.checkins.some(([datetime]) =>
+				FRIDAY.isSame(dayjs(datetime).tz(EVENT_TIMEZONE), "date"),
+			),
+		);
+
+	if (loading) {
+		return <Container>-</Container>;
+	}
+
+	return <Container>HackerCount {checkedIn.length}</Container>;
+}
+
+export default HackerCount;