A social network for athlete enthusiasts.

const { onDocumentCreated } = require("firebase-functions/v2/firestore");
const admin = require("firebase-admin");
admin.initializeApp();

exports.fanoutActivity = onDocumentCreated("activities/{activityId}", async (event) => {
const activityData = event.data.data();
const authorId = activityData.userId;

// 1. Get all followers of the athlete
const followersSnapshot = await admin.firestore()
.collection(`users/${authorId}/followers`).get();

const batch = admin.firestore().batch();

// 2. Queue up the fanned-out write for each follower
followersSnapshot.forEach((doc) => {
const followerId = doc.id;
const feedRef = admin.firestore()
.doc(`users/${followerId}/feeds/${event.params.activityId}`);
batch.set(feedRef, activityData);
});

// 3. Commit the batch write in a single operation
return batch.commit();
});

The issue provides a Firebase Functions snippet using Firestore, but names no repository file, test, or entry point. First clarify whether this is a requested feature and define the expected social-network behavior, data model, and completion criteria before attempting implementation.

Written by the indexing model from the issue text.