add opentok code examples

firebase/JavaScript/functions/index.js

@@ -3,6 +3,7 @@ const admin = require('firebase-admin');
 admin.initializeApp();
 
 exports.messaging = require('./messaging');
+exports.opentok = require('./opentok');
 exports.sms = require('./sms');
 exports.voice = require('./voice');
 exports.verify = require('./verify');

firebase/JavaScript/functions/opentok/index.js

@@ -0,0 +1 @@
+exports.session = require('./session');

firebase/JavaScript/functions/opentok/session.js

@@ -0,0 +1,27 @@
+const functions = require('firebase-functions');
+const admin = require('firebase-admin');
+const OpenTok = require('opentok');
+
+const {
+  api_key,
+  api_secret,
+} = functions.config().opentok;
+
+const opentok = new OpenTok(api_key, api_secret);
+
+let db = admin.firestore();
+
+function createSession(opts = {}) {
+  return new Promise((resolve, reject) => {
+    opentok.createSession(opts, (err, res) => {
+      if (err) reject(err);
+      resolve(res);
+    });
+  });
+}
+
+exports.method = functions.https.create(async (req, res) => {
+  let session = await createSession();
+  let ref = await db.collection('opentok-sessions').add(session);
+  res.send(200).send({sessionRef: ref.id});
+});