update to use cachedRequest

frontend/src/app/lightning/lightning-api.service.ts

@@ -1,6 +1,6 @@
 import { Injectable } from '@angular/core';
 import { HttpClient, HttpParams } from '@angular/common/http';
-import { Observable } from 'rxjs';
+import { BehaviorSubject, Observable, catchError, filter, of, shareReplay, take, tap } from 'rxjs';
 import { StateService } from '../services/state.service';
 import { IChannel, INodesRanking, IOldestNodes, ITopNodesPerCapacity, ITopNodesPerChannels } from '../interfaces/node-api.interface';
 
@@ -10,6 +10,8 @@ import { IChannel, INodesRanking, IOldestNodes, ITopNodesPerCapacity, ITopNodesP
 export class LightningApiService {
   private apiBasePath = ''; // network path is /testnet, etc. or '' for mainnet
   
+  private requestCache = new Map<string, { subject: BehaviorSubject<any>, expiry: number }>;
+
   constructor(
     private httpClient: HttpClient,
     private stateService: StateService,
@@ -23,6 +25,46 @@ export class LightningApiService {
     });
   }
 
+  private generateCacheKey(functionName: string, params: any[]): string {
+    return functionName + JSON.stringify(params);
+  }
+
+  // delete expired cache entries
+  private cleanExpiredCache(): void {
+    this.requestCache.forEach((value, key) => {
+      if (value.expiry < Date.now()) {
+        this.requestCache.delete(key);
+      }
+    });
+  }
+
+  cachedRequest<T, F extends (...args: any[]) => Observable<T>>(
+    apiFunction: F,
+    expireAfter: number, // in ms
+    ...params: Parameters<F>
+  ): Observable<T> {
+    this.cleanExpiredCache();
+
+    const cacheKey = this.generateCacheKey(apiFunction.name, params);
+    if (!this.requestCache.has(cacheKey)) {
+      const subject = new BehaviorSubject<T | null>(null);
+      this.requestCache.set(cacheKey, { subject, expiry: Date.now() + expireAfter });
+
+      apiFunction.bind(this)(...params).pipe(
+        tap(data => {
+          subject.next(data as T);
+        }),
+        catchError((error) => {
+          subject.error(error);
+          return of(null);
+        }),
+        shareReplay(1),
+      ).subscribe();
+    }
+
+    return this.requestCache.get(cacheKey).subject.asObservable().pipe(filter(val => val !== null), take(1));
+  }
+
   getNode$(publicKey: string): Observable<any> {
     return this.httpClient.get<any>(this.apiBasePath + '/api/v1/lightning/nodes/' + publicKey);
   }

frontend/src/app/lightning/nodes-networks-chart/nodes-networks-chart.component.ts

@@ -82,9 +82,9 @@ export class NodesNetworksChartComponent implements OnInit {
           firstRun = false;
           this.miningWindowPreference = timespan;
           this.isLoading = true;
-          return this.lightningApiService.listStatistics$(timespan)
+          return this.lightningApiService.cachedRequest(this.lightningApiService.listStatistics$, 250, timespan)
             .pipe(
-              tap((response) => {
+              tap((response:any) => {
                 const data = response.body;
                 const chartData = {
                   tor_nodes: data.map(val => [val.added * 1000, val.tor_nodes]),

frontend/src/app/lightning/statistics-chart/lightning-statistics-chart.component.ts

@@ -81,9 +81,9 @@ export class LightningStatisticsChartComponent implements OnInit {
           firstRun = false;
           this.miningWindowPreference = timespan;
           this.isLoading = true;
-          return this.lightningApiService.listStatistics$(timespan)
+          return this.lightningApiService.cachedRequest(this.lightningApiService.listStatistics$, 250, timespan)
             .pipe(
-              tap((response) => {
+              tap((response:any) => {
                 const data = response.body;
                 this.prepareChartOptions({
                   channel_count: data.map(val => [val.added * 1000, val.channel_count]),