feat(api): decouple api from curriculum (#40703)

api-server/server/utils/rx.js

@@ -1,60 +0,0 @@
-import Rx, { AsyncSubject, Observable } from 'rx';
-import moment from 'moment';
-import debugFactory from 'debug';
-
-const debug = debugFactory('fcc:rxUtils');
-
-export function saveInstance(instance) {
-  return new Rx.Observable.create(function(observer) {
-    if (!instance || typeof instance.save !== 'function') {
-      debug('no instance or save method');
-      observer.onNext();
-      return observer.onCompleted();
-    }
-    return instance.save(function(err, savedInstance) {
-      if (err) {
-        return observer.onError(err);
-      }
-      debug('instance saved');
-      observer.onNext(savedInstance);
-      return observer.onCompleted();
-    });
-  });
-}
-
-// alias saveInstance
-export const saveUser = saveInstance;
-
-// observeQuery(Model: Object, methodName: String, query: Any) => Observable
-export function observeQuery(Model, methodName, query) {
-  return Rx.Observable.fromNodeCallback(Model[methodName], Model)(query);
-}
-
-// observeMethod(
-//   context: Object, methodName: String
-// ) => (query: Any) => Observable
-export function observeMethod(context, methodName) {
-  return Rx.Observable.fromNodeCallback(context[methodName], context);
-}
-
-// must be bound to an observable instance
-// timeCache(amount: Number, unit: String) => Observable
-export function timeCache(time, unit) {
-  const source = this;
-  let cache;
-  let expireCacheAt;
-  return Observable.create(observable => {
-    // if there is no expire time set
-    // or if expireCacheAt is smaller than now,
-    // set new expire time in MS and create new subscription to source
-    if (!expireCacheAt || expireCacheAt < Date.now()) {
-      // set expire in ms;
-      expireCacheAt = moment()
-        .add(time, unit)
-        .valueOf();
-      cache = new AsyncSubject();
-      source.subscribe(cache);
-    }
-    return cache.subscribe(observable);
-  });
-}