perf(tracks): bound playback rendering work

vehicle-data-platform/apps/web/src/v2/domain/track.ts

@@ -16,6 +16,30 @@ export function sampledEventIndex(event: TrackPlaybackEvent, sampledCount: numbe
   return Math.max(0, Math.min(sampledCount - 1, Math.round(event.index * (sampledCount - 1) / (originalCount - 1))));
 }
 
+export function trackPlaybackInterval(speed: number) {
+  return Math.max(55, 300 / Math.max(0.5, speed));
+}
+
+export function buildTrackRailSelection(track?: TrackPlaybackResponse) {
+  const pointCount = track?.points.length ?? 0;
+  const stopIndexesByPoint: Array<number[] | undefined> = new Array(pointCount);
+  const eventIndexesByPoint: Array<number[] | undefined> = new Array(pointCount);
+  if (!track || pointCount === 0) return { stopIndexesByPoint, eventIndexesByPoint };
+
+  track.stops.forEach((stop, stopIndex) => {
+    for (let offset = -1; offset <= 1; offset += 1) {
+      const pointIndex = stop.sampledIndex + offset;
+      if (pointIndex < 0 || pointIndex >= pointCount) continue;
+      (stopIndexesByPoint[pointIndex] ??= []).push(stopIndex);
+    }
+  });
+  track.events.forEach((event, eventIndex) => {
+    const pointIndex = sampledEventIndex(event, pointCount, track.summary.pointCount);
+    (eventIndexesByPoint[pointIndex] ??= []).push(eventIndex);
+  });
+  return { stopIndexesByPoint, eventIndexesByPoint };
+}
+
 function csvCell(value: unknown) {
   const text = String(value ?? '');
   return /[",\n]/.test(text) ? `"${text.replace(/"/g, '""')}"` : text;