fetch item prices - throttle end points with promise queue

app/services/storage.service.ts

@@ -1,4 +1,7 @@
 import Store from 'electron-store';
+import { DateTime } from 'luxon';
+import { IItemPrice } from '../model';
+import { IItem } from '../model/item';
 const store = new Store();
 
 const storeUsername = (username: string) => {
@@ -17,9 +20,30 @@ const getUsername = (): string | undefined => {
   return store.get('user') || undefined;
 };
 
+const getItemCache = (id: string): IItem | undefined => {
+  const storedVal = store.get(id);
+  if (!storedVal) {
+    return undefined;
+  }
+  const val = JSON.parse(storedVal);
+  if (DateTime.fromISO(val.timestamp) < DateTime.local().plus({ minutes: 10 })) {
+    return val.item;
+  }
+  store.delete(id);
+  return undefined;
+};
+
+const storeItemCache = (id: string, item: IItemPrice) => {
+  const timestamp = DateTime.local();
+  const val = JSON.stringify({ timestamp, item });
+  store.set(id, val);
+};
+
 export const StorageService = {
+  getItemCache,
   getUsername,
   getSessionID,
+  storeItemCache,
   storeUsername,
   storeSessionID,
 };