fix: improvements to firebase rtdb module

Author: patrickmichalina

src/modules/firebase/server.firebase.module.ts

@@ -6,9 +6,7 @@ import {
   SkipSelf
 } from '@angular/core'
 import { ServerUniversalRtDbService } from './server.firebase.rtdb.service'
-import { HttpClient } from '@angular/common/http'
 import { UniversalRtDbService } from './browser.firebase.rtdb.service'
-import { AngularFireDatabase } from 'angularfire2/database'
 
 export interface LruCache {
   readonly get: <T>(key: string) => T
@@ -31,13 +29,7 @@ export class FirebaseServerModule {
       providers: [
         {
           provide: UniversalRtDbService,
-          useClass: ServerUniversalRtDbService,
-          deps: [
-            HttpClient,
-            AngularFireDatabase,
-            FIREBASE_USER_AUTH_TOKEN,
-            LRU_CACHE
-          ]
+          useClass: ServerUniversalRtDbService
         }
       ]
     }

src/modules/firebase/server.firebase.rtdb.service.ts

@@ -37,12 +37,16 @@ function mapUndefined(err: any) {
   return of(undefined)
 }
 
-function attempToCacheInLru(key: string, lru?: LruCache) {
+function attemptToCacheInLru(key: string, lru?: LruCache) {
   return function(response?: any) {
     lru && lru.set(sha256(key), response)
   }
 }
 
+function attemptToGetCachedValue<T>(key: string, lru?: LruCache) {
+  return lru && lru.get<T>(key)
+}
+
 // tslint:disable:no-this
 // tslint:disable-next-line:no-class
 @Injectable()
@@ -62,15 +66,18 @@ export class ServerUniversalRtDbService implements IUniversalRtdbService {
     const url = constructFbUrl(this.afdb, path)
     const params = getParams({ auth: this.authToken })
     const cacheKey = getFullUrl(url, params)
+    const cachedValue = attemptToGetCachedValue<T>(cacheKey)
 
     const baseObs = this.authToken
       ? this.http.get<T>(url, { params })
       : this.http.get<T>(url)
 
-    return baseObs.pipe(
-      take(1),
-      tap(attempToCacheInLru(cacheKey, this.lru)),
-      catchError(mapUndefined)
-    )
+    return cachedValue
+      ? of(cachedValue)
+      : baseObs.pipe(
+          take(1),
+          tap(attemptToCacheInLru(cacheKey, this.lru)),
+          catchError(mapUndefined)
+        )
   }
 }

src/modules/index.ts

@@ -14,3 +14,4 @@ export {
   ServerUniversalRtDbService
 } from './firebase/server.firebase.rtdb.service'
 export { UniversalRtDbService } from './firebase/browser.firebase.rtdb.service'
+export { LRU_CACHE } from './firebase/server.firebase.module'