Add apiService cachedRequest function, apply to outspends requests

frontend/src/app/components/transactions-list/transactions-list.component.ts

@@ -6,7 +6,7 @@ import { Outspend, Transaction, Vin, Vout } from '../../interfaces/electrs.inter
 import { ElectrsApiService } from '../../services/electrs-api.service';
 import { environment } from '../../../environments/environment';
 import { AssetsService } from '../../services/assets.service';
-import { filter, map, tap, switchMap, shareReplay } from 'rxjs/operators';
+import { filter, map, tap, switchMap, shareReplay, catchError } from 'rxjs/operators';
 import { BlockExtended } from '../../interfaces/node-api.interface';
 import { ApiService } from '../../services/api.service';
 import { PriceService } from '../../services/price.service';
@@ -53,6 +53,7 @@ export class TransactionsListComponent implements OnInit, OnChanges {
     private assetsService: AssetsService,
     private ref: ChangeDetectorRef,
     private priceService: PriceService,
+    private cd: ChangeDetectorRef,
   ) { }
 
   ngOnInit(): void {
@@ -75,7 +76,7 @@ export class TransactionsListComponent implements OnInit, OnChanges {
               for (let i = 0; i < txIds.length; i += 50) {
                 batches.push(txIds.slice(i, i + 50));
               }
-              return forkJoin(batches.map(batch => this.apiService.getOutspendsBatched$(batch)));
+              return forkJoin(batches.map(batch => { return this.apiService.cachedRequest(this.apiService.getOutspendsBatched$, 5000, batch); }));
             } else {
               return of([]);
             }
@@ -90,6 +91,7 @@ export class TransactionsListComponent implements OnInit, OnChanges {
             outspends.forEach((outspend, i) => {
               transactions[i]._outspends = outspend;
             });
+            this.cd.markForCheck();
           }),
         ),
       this.stateService.utxoSpent$
@@ -108,6 +110,10 @@ export class TransactionsListComponent implements OnInit, OnChanges {
           .pipe(
             filter(() => this.stateService.env.LIGHTNING),
             switchMap((txIds) => this.apiService.getChannelByTxIds$(txIds)),
+            catchError((error) => {
+              // handle 404
+              return of([]);
+            }),
             tap((channels) => {
               if (!this.transactions) {
                 return;

frontend/src/app/components/tx-bowtie-graph/tx-bowtie-graph.component.ts

@@ -123,7 +123,7 @@ export class TxBowtieGraphComponent implements OnInit, OnChanges {
         .pipe(
           switchMap((txid) => {
             if (!this.cached) {
-              return this.apiService.getOutspendsBatched$([txid]);
+              return this.apiService.cachedRequest(this.apiService.getOutspendsBatched$, 5000, [txid]);
             } else {
               return of(null);
             }

frontend/src/app/services/api.service.ts

@@ -2,7 +2,7 @@ import { Injectable } from '@angular/core';
 import { HttpClient, HttpParams, HttpResponse } from '@angular/common/http';
 import { CpfpInfo, OptimizedMempoolStats, AddressInformation, LiquidPegs, ITranslators,
   PoolStat, BlockExtended, TransactionStripped, RewardStats, AuditScore, BlockSizesAndWeights, RbfTree, BlockAudit } from '../interfaces/node-api.interface';
-import { Observable, of } from 'rxjs';
+import { BehaviorSubject, Observable, catchError, filter, of, shareReplay, take, tap } from 'rxjs';
 import { StateService } from './state.service';
 import { IBackendInfo, WebsocketResponse } from '../interfaces/websocket.interface';
 import { Outspend, Transaction } from '../interfaces/electrs.interface';
@@ -20,6 +20,8 @@ export class ApiService {
   private apiBaseUrl: string; // base URL is protocol, hostname, and port
   private apiBasePath: string; // 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,
@@ -44,6 +46,46 @@ export class ApiService {
     }
   }
 
+  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));
+  }
+
   list2HStatistics$(): Observable<OptimizedMempoolStats[]> {
     return this.httpClient.get<OptimizedMempoolStats[]>(this.apiBaseUrl + this.apiBasePath + '/api/v1/statistics/2h');
   }