notes.ts

import * as functions from 'firebase-functions';
import * as admin from 'firebase-admin';
import { INote, IUser } from 'firebasenoteapptypes';

export const NoteCreated = functions.firestore
  .document('Notes/{NoteId}')
  .onCreate((snapshot, context) => {
    const note = snapshot.data() as INote;

    const userRef = admin
      .firestore()
      .collection('Users')
      .doc(note.Author);

    return admin
      .firestore()
      .runTransaction(t =>
        t.get(userRef).then(doc => {
          const user = doc.data() as IUser;
          return t.update(userRef, {
            NumNotes: user.NumNotes + 1
          });
        })
      )
      .catch(e => console.log('TRANSACTION ERROR: ', e));
  });

export const NoteDeleted = functions.firestore
  .document('Notes/{NoteId}')
  .onDelete((snapshot, context) => {
    const note = snapshot.data() as INote;

    const userRef = admin.firestore().doc(`Users/${note.Author}`);

    return admin
      .firestore()
      .runTransaction(t =>
        t.get(userRef).then(doc => {
          const user = doc.data() as IUser;
          return t.update(userRef, {
            NumNotes: user.NumNotes - 1
          });
        })
      )
      .catch(e => console.log('TRANSACTION ERROR: ', e));
  });