Handle SYNC intent with user credentials

index.js

// Connect to Cloud Firestore
const admin = require('firebase-admin');
admin.initializeApp();

const db = admin.firestore();
db.settings({timestampsInSnapshots: true});

app.onSync(async (body, headers) => {
  const userEmail = await getEmail(headers);
  const userDoc = await db.collection('users').doc(userEmail).get();

  if (!userDoc.exists) {
    // User account does not exist in database.
    // TODO Create user

    // Return an empty device array
    return {
      requestId: body.requestId,
      payload: {
        agentUserId: userEmail,
        devices: []
      }
    }
  }

  const userDevices = await db.collection('users')
      .doc(userEmail)
      .collection('devices')
      .get();
  const devices = [];
  userDevices.forEach(deviceDoc => {
    const data = deviceDoc.data();
    const device = {
      id: doc.id,
      type: data.type,
      traits: data.traits,
      name: {
        defaultNames: data.defaultNames,
        name: data.name,
        nicknames: data.nicknames
      },
      deviceInfo: {
        manufacturer: data.manufacturer,
        model: data.model,
        hwVersion: data.hwVersion,
        swVersion: data.swVersion
      },
      willReportState: false,
      attributes: {}
    };
    devices.push(device);
  });

  return {
    requestId: body.requestId,
    payload: {
      agentUserId: userEmail,
      devices
    }
  }
});