utils.ts

import * as firebase from 'firebase/app';
import { Subscription } from 'rxjs/Subscription';
import { Scheduler } from 'rxjs/Scheduler';
import { queue } from 'rxjs/scheduler/queue';
import { PathReference, DatabaseReference, FirebaseOperation, FirebaseOperationCases } from './interfaces';
import { FirebaseApp } from 'angularfire2';

export function isString(value: any): boolean {
  return typeof value === 'string';
}

export function isFirebaseDataSnapshot(value: any): boolean {
  return typeof value.exportVal === 'function';
}

export function isNil(obj: any): boolean {
  return obj === undefined || obj === null;
}

export function isFirebaseRef(value: any): boolean {
  return typeof value.set === 'function';
}

/**
 * Returns a database reference given a Firebase App and an
 * absolute or relative path.
 * @param app - Firebase App
 * @param path - Database path, relative or absolute
 */
export function getRef(app: FirebaseApp, pathRef: PathReference): DatabaseReference {
  // if a db ref was passed in, just return it
  return isFirebaseRef(pathRef) ? pathRef as DatabaseReference 
    : app.database().ref(pathRef as string);
}

export function checkOperationCases(item: FirebaseOperation, cases: FirebaseOperationCases) : Promise<void | any> {
  if (isString(item)) {
    return cases.stringCase();
  } else if (isFirebaseRef(item)) {
    return cases.firebaseCase!();
  } else if (isFirebaseDataSnapshot(item)) {
    return cases.snapshotCase!();
  }
  throw new Error(`Expects a string, snapshot, or reference. Got: ${typeof item}`);
}