count-feed.ts

import * as functions from 'firebase-functions';
import { app } from '../../../utils/admin';
import { ERRORS } from '../../../consts/errors';
​
const getCountCommentsByPost = async (post: FirebaseFirestore.QueryDocumentSnapshot): Promise<number> => {
  const comments = await post.ref.collection('comments').get();
  const postComments = comments.size;
  const subCommentsPromises = comments.docs.map(comment => comment.ref.collection('subcomments').get());
  const subComments = await Promise.all(subCommentsPromises);
  const totalSubcomments = subComments.map(subComment => subComment.size).reduce((prev, curr) => prev + curr, 0);
  return postComments + totalSubcomments; 
};
​
const getLikesByPost = async (post: FirebaseFirestore.QueryDocumentSnapshot): Promise<number> => {
  const likes = await post.ref.collection('likes').get();
  const postLikes = likes.size;
  const commentsLikes = await post.ref.collection('comments').get();
  const likesCommentsPromises = commentsLikes.docs.map(comment => comment.ref.collection('likes').get());  
  const likesComments = await Promise.all(likesCommentsPromises);
  const countLikes = likesComments.map(like => like.size).reduce((prev, curr) => prev + curr , 0);
  return countLikes + postLikes;
};
​
module.exports = functions.https.onCall(async (data, context) => {
  if (!data.slug) {
    throw new functions.https.HttpsError('not-found', ERRORS.INVALID_EDITION);
  }
​
  const db = app.firestore();
  const snap = await db.collection(`editions/${data.slug}/posts`)
    .orderBy('createdAt', 'desc')
    .get();
​
  try {
    const promises = [];
    const totalPosts = snap.size;
    const totalCommentsPromises = snap.docs.map(post => {
      return getCountCommentsByPost(post);
    });
    const postComments = await Promise.all(totalCommentsPromises);
    const totalComments = postComments.reduce((prev, curr) => prev + curr, 0);
​
    const totalLikesPromises = snap.docs.map(post => {
      return getLikesByPost(post);
    })
    const likes = await Promise.all(totalLikesPromises);
    likes.reduce((prev, curr) => prev + curr, 0);
​
    return { totalPosts, totalComments, likes };
  } catch (e) {
    throw e;
  }
​
});