move index finding to separate method

src/repositories/UnoptimizedInMemoryRepository.ts

@@ -1,13 +1,5 @@
 import { GetterSetterRepository } from "./GetterSetterRepository";
-import {
+import { IEntityWithId, IEta, IOrderedStop, IRoute, IShuttle, IStop, ISystem } from "../entities/entities";
-  IEntityWithId,
-  IEta,
-  IOrderedStop,
-  IRoute,
-  IShuttle,
-  IStop,
-  ISystem
-} from "../entities/entities";
 
 /**
  * An unoptimized in memory repository.
@@ -94,6 +86,10 @@ export class UnoptimizedInMemoryRepository implements GetterSetterRepository {
     return entity;
   }
 
+  private findEntityIndexById<T extends IEntityWithId>(entityId: string, arrayToSearchIn: T[]) {
+    return arrayToSearchIn.findIndex((value) => value.id === entityId);
+  }
+
   public async addOrUpdateSystem(system: ISystem): Promise<void> {
     const index = this.systems.findIndex((s) => s.id === system.id);
     if (index !== -1) {
@@ -149,7 +145,7 @@ export class UnoptimizedInMemoryRepository implements GetterSetterRepository {
   }
 
   public async removeSystemIfExists(systemId: string): Promise<ISystem | null> {
-    const index = this.systems.findIndex((s) => s.id === systemId);
+    const index = this.findEntityIndexById(systemId, this.systems);
     if (index > -1) {
       const systemToReturn = this.systems[index];
       this.systems.splice(index, 1);