nestjs-custom-cache.interceptor.ts

gistfile1.txt

import {
  Injectable,
  NestInterceptor,
  ExecutionContext,
  CallHandler,
} from "@nestjs/common";
import { CACHE_MANAGER, Inject } from "@nestjs/common";
import { Cache } from "cache-manager";
import {
  from,
  map,
  Observable,
  of,
  mergeMap,
  switchMap,
  firstValueFrom,
  forkJoin,
} from "rxjs";

@Injectable()
export class CustomCacheInterceptor implements NestInterceptor {
  constructor(@Inject(CACHE_MANAGER) private cacheService: Cache) {}
  intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
    // check if data is in cache:
    const url = context.switchToHttp().getRequest().url;
    const CACHE_KEY = `URL__${url}`;
    // console.log(
    //   "your context",
    //   context.switchToHttp().getRequest().url,
    //   CACHE_KEY
    // );
    const cacheResult$ = from(this.cacheService.get<any>(CACHE_KEY));
    const cacheExpire$ = from(this.cacheService.get<any>(CACHE_KEY + '_expire'));
    return forkJoin([cacheResult$, cacheExpire$]).pipe(
        switchMap(([cacheResult, cacheExpire]) => {
          if (cacheResult && cacheExpire && Date.now() < +cacheExpire) {
            return this.checkCache({cacheResult, CACHE_KEY, shouldRender: true}, next, context);
          } else {
            return this.checkCache({cacheResult, CACHE_KEY, shouldRender: false}, next, context);
          }
        })
        )
      }
      
    checkCache({cacheResult, CACHE_KEY, shouldRender}, next, context) {
    // console.log('should render or not?', shouldRender, cacheResult )
    if (shouldRender) {
      // console.log("nice, we have cache now, response the cache instead");
      context.switchToHttp().getResponse().send(cacheResult);
      return of(cacheResult);
    } else {
      
      // if (cacheResult) {
      //   console.log("cache here but invalid, render and save cache");
      // } else {
      //   console.log("we dont have cache, render and save cache");
      // }

      return next.handle().pipe(
        map((resData) => {
          this.cacheService.set(CACHE_KEY, resData, { ttl: 0 });
          this.cacheService.set(CACHE_KEY + '_expire', new Date().getTime() + 10 * 1000, { ttl: 0 });
          console.log("cached res data:", resData);
          return resData;
        })
      );
    }
  }
}