write logic to get eta for shuttle and stop id

src/repositories/ApiBasedRepository.ts

@@ -40,6 +40,20 @@ export class ApiBasedRepository implements GetterRepository {
   }
 
   public async getEtaForShuttleAndStopId(shuttleId: string, stopId: string): Promise<IEta | null> {
+    const shuttle = await this.getShuttleById(shuttleId);
+    const systemId = shuttle?.systemId;
+    if (!systemId) {
+      return null;
+    }
+
+    if (this.initialCache?.etasForStopId !== undefined) {
+      const etas = this.initialCache.etasForStopId[systemId];
+      const foundEta = etas.find((eta) => eta.stopId === stopId);
+      if (foundEta) {
+        return foundEta;
+      }
+    }
+
     return null;
   }
 
@@ -76,7 +90,7 @@ export class ApiBasedRepository implements GetterRepository {
     return Promise.resolve([]);
   }
 
-  public async getShuttleById(shuttleId: string): Promise<| null> {
+  public async getShuttleById(shuttleId: string): Promise<IShuttle | null> {
     return Promise.resolve(null);
   }