From 4b37f3a12100d949cbb4f43552816ba53f359f88 Mon Sep 17 00:00:00 2001
From: Brendan Chen <me@bchen.dev>
Date: Tue, 11 Nov 2025 19:34:05 -0800
Subject: [PATCH] Add a helper method for setting the "reference time" of the
 self-updating repo

---
 .../eta/InMemorySelfUpdatingETARepository.ts  |  3 ++
 .../eta/RedisSelfUpdatingETARepository.ts     | 53 +++++++++++++++++--
 .../shuttle/eta/SelfUpdatingETARepository.ts  |  7 +++
 3 files changed, 58 insertions(+), 5 deletions(-)

diff --git a/src/repositories/shuttle/eta/InMemorySelfUpdatingETARepository.ts b/src/repositories/shuttle/eta/InMemorySelfUpdatingETARepository.ts
index de42361..a94955d 100644
--- a/src/repositories/shuttle/eta/InMemorySelfUpdatingETARepository.ts
+++ b/src/repositories/shuttle/eta/InMemorySelfUpdatingETARepository.ts
@@ -8,6 +8,9 @@ export class InMemorySelfUpdatingETARepository extends BaseInMemoryETARepository
   ) {
     super();
   }
+  setReferenceTime(referenceTime: Date): void {
+    throw new Error("Method not implemented.");
+  }
 
   getAverageTravelTimeSeconds(identifier: ShuttleTravelTimeDataIdentifier, dateFilter: ShuttleTravelTimeDateFilterArguments): Promise<number | undefined> {
     throw new Error("Method not implemented.");
diff --git a/src/repositories/shuttle/eta/RedisSelfUpdatingETARepository.ts b/src/repositories/shuttle/eta/RedisSelfUpdatingETARepository.ts
index 5899cfd..971c21e 100644
--- a/src/repositories/shuttle/eta/RedisSelfUpdatingETARepository.ts
+++ b/src/repositories/shuttle/eta/RedisSelfUpdatingETARepository.ts
@@ -16,30 +16,73 @@ export class RedisSelfUpdatingETARepository extends BaseRedisETARepository imple
         reconnectStrategy: REDIS_RECONNECT_INTERVAL,
       },
     }),
+    private referenceTime: Date | null = null,
   ) {
     super(redisClient);
   }
 
+  setReferenceTime(referenceTime: Date) {
+    this.referenceTime = referenceTime;
+  }
+
   getAverageTravelTimeSeconds(identifier: ShuttleTravelTimeDataIdentifier, dateFilter: ShuttleTravelTimeDateFilterArguments): Promise<number | undefined> {
     throw new Error("Method not implemented.");
   }
 
   startListeningForUpdates() {
     this.shuttleRepository.addListener(ShuttleRepositoryEvent.SHUTTLE_UPDATED, this.handleShuttleUpdate);
-    this.shuttleRepository.addListener(ShuttleRepositoryEvent.SHUTTLE_WILL_ARRIVE_AT_STOP, this.handleShuttleArriveAtStop)
+    this.shuttleRepository.addListener(ShuttleRepositoryEvent.SHUTTLE_WILL_ARRIVE_AT_STOP, this.handleShuttleWillArriveAtStop)
   }
 
   stopListeningForUpdates() {
     this.shuttleRepository.removeListener(ShuttleRepositoryEvent.SHUTTLE_UPDATED, this.handleShuttleUpdate);
-    this.shuttleRepository.removeListener(ShuttleRepositoryEvent.SHUTTLE_WILL_ARRIVE_AT_STOP, this.handleShuttleArriveAtStop);
+    this.shuttleRepository.removeListener(ShuttleRepositoryEvent.SHUTTLE_WILL_ARRIVE_AT_STOP, this.handleShuttleWillArriveAtStop);
   }
 
   private handleShuttleUpdate(shuttle: IShuttle) {
     // TODO: handle shuttle update
   }
 
-  private handleShuttleArriveAtStop(shuttleArrival: ShuttleStopArrival) {
-    // TODO: handle shuttle arrive at stop
-    
+  private async handleShuttleWillArriveAtStop(
+    shuttleArrival: ShuttleStopArrival,
+
+  ) {
+    const lastStop = await this.shuttleRepository.getShuttleLastStopArrival(shuttleArrival.shuttleId);
+    if (lastStop == undefined) return;
+
+    const shuttle = await this.shuttleRepository.getShuttleById(shuttleArrival.shuttleId);
+    if (shuttle == null) return;
+
+    let referenceCurrentTime = new Date();
+    if (this.referenceTime != null) {
+      referenceCurrentTime = this.referenceTime;
+    }
+
+    const oneWeekAgo = new Date(referenceCurrentTime.getTime() - (60 * 60 * 24 * 7 * 1000));
+
+    const lastOrderedStop = await this.shuttleRepository.getOrderedStopByRouteAndStopId(shuttle.routeId, lastStop.stopId);
+    const nextStop = lastOrderedStop?.nextStop;
+    if (nextStop == null) return;
+
+    const travelTimeSeconds = await this.getAverageTravelTimeSeconds({
+      routeId: shuttle.routeId,
+      fromStopId: lastStop.stopId,
+      toStopId: nextStop.stopId,
+    }, {
+      from: oneWeekAgo,
+      to: new Date(oneWeekAgo.getTime() + (60 * 60 * 1000))
+    });
+    if (travelTimeSeconds == undefined) return;
+
+    const elapsedTimeMs = referenceCurrentTime.getTime() - lastStop.timestamp.getTime();
+    const predictedTimeSeconds = travelTimeSeconds - (elapsedTimeMs / 1000);
+
+    await this.addOrUpdateEta({
+      secondsRemaining: predictedTimeSeconds,
+      shuttleId: shuttle.id,
+      stopId: nextStop.stopId,
+      systemId: nextStop.systemId,
+      updatedTime: new Date(),
+    });
   }
 }
diff --git a/src/repositories/shuttle/eta/SelfUpdatingETARepository.ts b/src/repositories/shuttle/eta/SelfUpdatingETARepository.ts
index 331e1cc..4dae81a 100644
--- a/src/repositories/shuttle/eta/SelfUpdatingETARepository.ts
+++ b/src/repositories/shuttle/eta/SelfUpdatingETARepository.ts
@@ -18,4 +18,11 @@ export interface SelfUpdatingETARepository extends ETAGetterRepository {
     identifier: ShuttleTravelTimeDataIdentifier,
     dateFilter: ShuttleTravelTimeDateFilterArguments
   ): Promise<number | undefined>;
+
+  /**
+   * Set the "current time" as the class knows it, in order to calculate
+   * ETAs based on past data.
+   * @param referenceTime
+   */
+  setReferenceTime(referenceTime: Date): void;
 }