Preserve selected schedule day when navigating away

client/src/components/Schedule/Schedule.jsx

@@ -1,4 +1,4 @@
-import { useState } from "react";
+import { useSearchParams } from "react-router-dom";
 import { Box, Grid, Tab, Tabs } from "@mui/material";
 import ScheduleCard from "./ScheduleCard";
 import { groupBy, uniq, orderBy } from "../../lib/utils";
@@ -10,6 +10,21 @@
 import { eventRoundForActivityCode } from "../../lib/competition";
 import { parseActivityCode } from "../../lib/activity-code";
 
+const SCHEDULE_DATE_KEY = "scheduleDate";
+
+function getStoredScheduleDate(competitionId, dates) {
+  try {
+    const stored = JSON.parse(sessionStorage.getItem(SCHEDULE_DATE_KEY));
+    if (
+      stored?.competitionId === competitionId &&
+      dates.includes(stored?.date)
+    ) {
+      return stored.date;
+    }
+  } catch {}
+  return null;
+}
+
 function Schedule({ venues, competitionEvents, competitionId }) {
   const activities = venues
     .flatMap((venue) => venue.rooms)
@@ -33,7 +48,26 @@
     sortedActivities.map((activity) => toLocalDateString(activity.startTime)),
   );
 
-  const [selectedDate, setSelectedDate] = useState(closestDateString(dates));
+  // We keep the selected date in the URL, so that it's preserved
+  // when the user navigates to a round and goes back.
+  const [searchParams, setSearchParams] = useSearchParams();
+
+  const dateParam = searchParams.get("date");
+  const selectedDate = dates.includes(dateParam)
+    ? dateParam
+    : (getStoredScheduleDate(competitionId, dates) ?? closestDateString(dates));
+
+  function setSelectedDate(date) {
+    sessionStorage.setItem(
+      SCHEDULE_DATE_KEY,
+      JSON.stringify({ competitionId, date }),
+    );
+    const newSearchParams = new URLSearchParams(searchParams);
+    newSearchParams.set("date", date);
+    // Replace the current history entry, so that switching between days
+    // doesn't require going back once per switch.
+    setSearchParams(newSearchParams, { replace: true });
+  }
 
   const selectedDateActivities = sortedActivities.filter(
     (activity) => toLocalDateString(activity.startTime) === selectedDate,