From bdc7669ff933ce04ec32258e18e2009a4256785d Mon Sep 17 00:00:00 2001
From: Maneesh Tewani <mtewani@google.com>
Date: Mon, 29 Aug 2022 14:18:02 -0700
Subject: [PATCH 1/6] Fixed onDisconnect logic to use deviceId

---
 presence-firestore/README.md          |  2 +-
 presence-firestore/firebase.json      | 24 +++++++++++-
 presence-firestore/functions/index.js | 26 ++++++++++---
 presence-firestore/public/index.js    | 53 ++++++++++++++++-----------
 4 files changed, 75 insertions(+), 30 deletions(-)

diff --git a/presence-firestore/README.md b/presence-firestore/README.md
index 803fc1ce6..cf2de43bc 100644
--- a/presence-firestore/README.md
+++ b/presence-firestore/README.md
@@ -38,7 +38,7 @@ To deploy the sample to your Firebase app,
 1. Run `npm install` to install dependencies for the server-side [functions](functions/) as detailed above.
 2. From this top-level sample directory, deploy the `Realtime Database` trigger defined in [functions](functions/) to `Firebase Functions` and the [public](public/) directory app to `Firebase Hosting`.
 
-Assumimg you've created a Firebase application called `firebase-example-123` (make sure it's upgraded to the Spark plan and that `Anonymous Authentication` are enabled).
+Assumimg you've created a Firebase application called `firebase-example-123` (make sure it's upgraded to the Blaze plan and that `Anonymous Authentication` are enabled).
 
 ```sh
 firebase use --add firebase-example-123
diff --git a/presence-firestore/firebase.json b/presence-firestore/firebase.json
index 8759d50d8..b78b3f009 100644
--- a/presence-firestore/firebase.json
+++ b/presence-firestore/firebase.json
@@ -1,3 +1,25 @@
 {
-  "hosting": {"public": "public"}
+  "hosting": {
+    "public": "public"
+  },
+  "functions": {
+    "source": "functions"
+  },
+  "emulators": {
+    "functions": {
+      "port": 5001
+    },
+    "hosting": {
+      "port": 5000
+    },
+    "ui": {
+      "enabled": true
+    },
+    "firestore": {
+      "port": 8080
+    },
+    "database": {
+      "port": 9000
+    }
+  }
 }
diff --git a/presence-firestore/functions/index.js b/presence-firestore/functions/index.js
index 7cc4633ab..f34f83346 100644
--- a/presence-firestore/functions/index.js
+++ b/presence-firestore/functions/index.js
@@ -18,6 +18,7 @@
 const functions = require('firebase-functions');
 const admin = require('firebase-admin');
 admin.initializeApp();
+functions.logger.log(process.env);
 
 // Since this code will be running in the Cloud Functions environment
 // we call initialize Firestore without any arguments because it
@@ -26,14 +27,18 @@ const firestore = admin.firestore();
 
 // Create a new function which is triggered on changes to /status/{uid}
 // Note: This is a Realtime Database trigger, *not* Firestore.
-exports.onUserStatusChanged = functions.database.ref('/status/{uid}').onUpdate(
+exports.onUserStatusChanged = functions.database.ref('/status/{uid}/devices/{deviceId}').onUpdate(
     async (change, context) => {
       // Get the data written to Realtime Database
       const eventStatus = change.after.val();
 
+      const deviceKey = context.params.deviceId;
+
       // Then use other event data to create a reference to the
       // corresponding Firestore document.
-      const userStatusFirestoreRef = firestore.doc(`status/${context.params.uid}`);
+      const userFirestoreRef = firestore.doc(`status/${context.params.uid}`);
+      const userDeviceCollectionRef = userFirestoreRef.collection(`devices`);
+      const userStatusFirestoreRef = userDeviceCollectionRef.doc(deviceKey);
 
       // It is likely that the Realtime Database change that triggered
       // this event has already been overwritten by a fast change in
@@ -41,17 +46,26 @@ exports.onUserStatusChanged = functions.database.ref('/status/{uid}').onUpdate(
       // and compare the timestamps.
       const statusSnapshot = await change.after.ref.once('value');
       const status = statusSnapshot.val();
-      functions.logger.log(status, eventStatus);
+      // functions.logger.log(status, eventStatus);
       // If the current timestamp for this data is newer than
       // the data that triggered this event, we exit this function.
       if (status.last_changed > eventStatus.last_changed) {
         return null;
       }
-
       // Otherwise, we convert the last_changed field to a Date
       eventStatus.last_changed = new Date(eventStatus.last_changed);
 
-      // ... and write it to Firestore.
-      return userStatusFirestoreRef.set(eventStatus);
+      if(status.state === 'offline') {
+        // ... and write it to Firestore.
+        await userStatusFirestoreRef.delete();
+
+        if ((await userDeviceCollectionRef.get()).empty) {
+          return userFirestoreRef.delete();
+        }
+      } else {
+        await userFirestoreRef.set({ uid: context.params.uid });
+        return userStatusFirestoreRef.set(status.devices[deviceKey]);
+      }
+      return null;
     });
 // [END presence_sync_function]
diff --git a/presence-firestore/public/index.js b/presence-firestore/public/index.js
index 76094eeb6..ad9ce9403 100644
--- a/presence-firestore/public/index.js
+++ b/presence-firestore/public/index.js
@@ -21,7 +21,8 @@ function rtdb_presence() {
 
     // Create a reference to this user's specific status node.
     // This is where we will store data about being online/offline.
-    var userStatusDatabaseRef = firebase.database().ref('/status/' + uid);
+    // `push()` will add a new key to the user's path, acting as a deviceId
+    var deviceStatusDatabaseRef = firebase.database().ref('/status/' + uid + '/devices').push();
 
     // We'll create two constants which we will write to 
     // the Realtime database when this device is offline
@@ -49,7 +50,7 @@ function rtdb_presence() {
         // method to add a set which will only trigger once this 
         // client has disconnected by closing the app, 
         // losing internet, or any other means.
-        userStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
+        deviceStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
             // The promise returned from .onDisconnect().set() will
             // resolve as soon as the server acknowledges the onDisconnect() 
             // request, NOT once we've actually disconnected:
@@ -57,17 +58,18 @@ function rtdb_presence() {
 
             // We can now safely set ourselves as 'online' knowing that the
             // server will mark us as offline once we lose connection.
-            userStatusDatabaseRef.set(isOnlineForDatabase);
+            deviceStatusDatabaseRef.set(isOnlineForDatabase);
         });
     });
     // [END rtdb_presence]
 }
 
-function rtdb_and_local_fs_presence() {
+async function rtdb_and_local_fs_presence() {
     // [START rtdb_and_local_fs_presence]
     // [START_EXCLUDE]
     var uid = firebase.auth().currentUser.uid;
-    var userStatusDatabaseRef = firebase.database().ref('/status/' + uid);
+    var deviceStatusDatabaseRef = await firebase.database().ref('/status/' + uid + '/devices').push();
+    var deviceId = deviceStatusDatabaseRef.key;
 
     var isOfflineForDatabase = {
         state: 'offline',
@@ -80,34 +82,39 @@ function rtdb_and_local_fs_presence() {
     };
 
     // [END_EXCLUDE]
-    var userStatusFirestoreRef = firebase.firestore().doc('/status/' + uid);
+    var userFirestoreRef = firebase.firestore().collection('status').doc(uid);
+    await userFirestoreRef.set({ uid }); // In case the user's id document doesn't already exist.
+    
+    var devicesCollectionRef = userFirestoreRef.collection('devices');
+    var deviceStatusFirestoreRef = devicesCollectionRef.doc(deviceId);
+
 
     // Firestore uses a different server timestamp value, so we'll 
     // create two more constants for Firestore state.
-    var isOfflineForFirestore = {
-        state: 'offline',
-        last_changed: firebase.firestore.FieldValue.serverTimestamp(),
-    };
-
     var isOnlineForFirestore = {
         state: 'online',
         last_changed: firebase.firestore.FieldValue.serverTimestamp(),
     };
 
-    firebase.database().ref('.info/connected').on('value', function(snapshot) {
-        if (snapshot.val() == false) {
-            // Instead of simply returning, we'll also set Firestore's state
-            // to 'offline'. This ensures that our Firestore cache is aware
-            // of the switch to 'offline.'
-            userStatusFirestoreRef.set(isOfflineForFirestore);
+    firebase.database().ref('.info/connected').on('value', async function(snapshot) {
+        if (snapshot.val() === false) {
+            // Instead of simply returning, we'll also remove the device id from the user, 
+            // and if no devices are left, we should delete the user as well.
+            // This ensures that our Firestore cache is aware that the device and/or user has been deleted
+            deviceStatusFirestoreRef.delete();
+            const deviceCollection = await devicesCollectionRef.get();
+            if(deviceCollection.empty) {
+                userFirestoreRef.delete();
+            }
             return;
         };
 
-        userStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
-            userStatusDatabaseRef.set(isOnlineForDatabase);
+        deviceStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
+            deviceStatusDatabaseRef.set(isOnlineForDatabase);
 
             // We'll also add Firestore set here for when we come online.
-            userStatusFirestoreRef.set(isOnlineForFirestore);
+            userFirestoreRef.set({ uid });
+            deviceStatusFirestoreRef.set(isOnlineForFirestore);
         });
     });
     // [END rtdb_and_local_fs_presence]
@@ -116,7 +123,7 @@ function rtdb_and_local_fs_presence() {
 function fs_listen() {
     // [START fs_onsnapshot]
     userStatusFirestoreRef.onSnapshot(function(doc) {
-        var isOnline = doc.data().state == 'online';
+        var isOnline = !doc.empty;
         // ... use isOnline
     });
     // [END fs_onsnapshot]
@@ -126,9 +133,9 @@ function fs_listen_online() {
     var history = document.querySelector('#history');
     // [START fs_onsnapshot_online]
     firebase.firestore().collection('status')
-        .where('state', '==', 'online')
         .onSnapshot(function(snapshot) {
             snapshot.docChanges().forEach(function(change) {
+                console.log(change);
                 if (change.type === 'added') {
                     var msg = 'User ' + change.doc.id + ' is online.';
                     console.log(msg);
@@ -147,6 +154,8 @@ function fs_listen_online() {
         });
     // [END fs_onsnapshot_online]
 }
+firebase.database().useEmulator("localhost", 9000);
+firebase.firestore().useEmulator("localhost", 8080);
 
 firebase.auth().signInAnonymously().then(function() {
     rtdb_and_local_fs_presence();

From 0e8fccc3163a13978e29ff043409e20f39a93a78 Mon Sep 17 00:00:00 2001
From: Maneesh Tewani <mtewani@google.com>
Date: Mon, 29 Aug 2022 15:42:32 -0700
Subject: [PATCH 2/6] Removed unnecessary changes

---
 presence-firestore/firebase.json      | 24 +-----------------------
 presence-firestore/functions/index.js |  3 +--
 presence-firestore/public/index.js    |  3 ---
 3 files changed, 2 insertions(+), 28 deletions(-)

diff --git a/presence-firestore/firebase.json b/presence-firestore/firebase.json
index b78b3f009..8759d50d8 100644
--- a/presence-firestore/firebase.json
+++ b/presence-firestore/firebase.json
@@ -1,25 +1,3 @@
 {
-  "hosting": {
-    "public": "public"
-  },
-  "functions": {
-    "source": "functions"
-  },
-  "emulators": {
-    "functions": {
-      "port": 5001
-    },
-    "hosting": {
-      "port": 5000
-    },
-    "ui": {
-      "enabled": true
-    },
-    "firestore": {
-      "port": 8080
-    },
-    "database": {
-      "port": 9000
-    }
-  }
+  "hosting": {"public": "public"}
 }
diff --git a/presence-firestore/functions/index.js b/presence-firestore/functions/index.js
index f34f83346..c0d070773 100644
--- a/presence-firestore/functions/index.js
+++ b/presence-firestore/functions/index.js
@@ -18,7 +18,6 @@
 const functions = require('firebase-functions');
 const admin = require('firebase-admin');
 admin.initializeApp();
-functions.logger.log(process.env);
 
 // Since this code will be running in the Cloud Functions environment
 // we call initialize Firestore without any arguments because it
@@ -46,7 +45,7 @@ exports.onUserStatusChanged = functions.database.ref('/status/{uid}/devices/{dev
       // and compare the timestamps.
       const statusSnapshot = await change.after.ref.once('value');
       const status = statusSnapshot.val();
-      // functions.logger.log(status, eventStatus);
+      functions.logger.log(status, eventStatus);
       // If the current timestamp for this data is newer than
       // the data that triggered this event, we exit this function.
       if (status.last_changed > eventStatus.last_changed) {
diff --git a/presence-firestore/public/index.js b/presence-firestore/public/index.js
index ad9ce9403..a168a7b82 100644
--- a/presence-firestore/public/index.js
+++ b/presence-firestore/public/index.js
@@ -135,7 +135,6 @@ function fs_listen_online() {
     firebase.firestore().collection('status')
         .onSnapshot(function(snapshot) {
             snapshot.docChanges().forEach(function(change) {
-                console.log(change);
                 if (change.type === 'added') {
                     var msg = 'User ' + change.doc.id + ' is online.';
                     console.log(msg);
@@ -154,8 +153,6 @@ function fs_listen_online() {
         });
     // [END fs_onsnapshot_online]
 }
-firebase.database().useEmulator("localhost", 9000);
-firebase.firestore().useEmulator("localhost", 8080);
 
 firebase.auth().signInAnonymously().then(function() {
     rtdb_and_local_fs_presence();

From 2cdfa44104bd045b6794e2dec3ed43b9607e8d0b Mon Sep 17 00:00:00 2001
From: Maneesh Tewani <mtewani@google.com>
Date: Tue, 30 Aug 2022 16:01:37 -0700
Subject: [PATCH 3/6] Renamed some variables

---
 presence-firestore/functions/index.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/presence-firestore/functions/index.js b/presence-firestore/functions/index.js
index c0d070773..15209d4c5 100644
--- a/presence-firestore/functions/index.js
+++ b/presence-firestore/functions/index.js
@@ -37,7 +37,7 @@ exports.onUserStatusChanged = functions.database.ref('/status/{uid}/devices/{dev
       // corresponding Firestore document.
       const userFirestoreRef = firestore.doc(`status/${context.params.uid}`);
       const userDeviceCollectionRef = userFirestoreRef.collection(`devices`);
-      const userStatusFirestoreRef = userDeviceCollectionRef.doc(deviceKey);
+      const userDeviceStatusFirestoreRef = userDeviceCollectionRef.doc(deviceKey);
 
       // It is likely that the Realtime Database change that triggered
       // this event has already been overwritten by a fast change in
@@ -56,14 +56,14 @@ exports.onUserStatusChanged = functions.database.ref('/status/{uid}/devices/{dev
 
       if(status.state === 'offline') {
         // ... and write it to Firestore.
-        await userStatusFirestoreRef.delete();
+        await userDeviceStatusFirestoreRef.delete();
 
         if ((await userDeviceCollectionRef.get()).empty) {
           return userFirestoreRef.delete();
         }
       } else {
         await userFirestoreRef.set({ uid: context.params.uid });
-        return userStatusFirestoreRef.set(status.devices[deviceKey]);
+        return userDeviceStatusFirestoreRef.set(status.devices[deviceKey]);
       }
       return null;
     });

From b0ddd63cd56fd8fc0916b69d7f9f4e68e55338d1 Mon Sep 17 00:00:00 2001
From: Maneesh Tewani <mtewani@google.com>
Date: Wed, 31 Aug 2022 09:17:00 -0700
Subject: [PATCH 4/6] Addressed comment

---
 presence-firestore/functions/index.js | 16 ++++++------
 presence-firestore/public/index.js    | 36 +++++++++++++--------------
 2 files changed, 26 insertions(+), 26 deletions(-)

diff --git a/presence-firestore/functions/index.js b/presence-firestore/functions/index.js
index 15209d4c5..6a3cf7282 100644
--- a/presence-firestore/functions/index.js
+++ b/presence-firestore/functions/index.js
@@ -24,20 +24,20 @@ admin.initializeApp();
 // detects authentication from the environment.
 const firestore = admin.firestore();
 
-// Create a new function which is triggered on changes to /status/{uid}
+// Create a new function which is triggered on changes to /status/{uid}/sessions/{sessionId}
 // Note: This is a Realtime Database trigger, *not* Firestore.
-exports.onUserStatusChanged = functions.database.ref('/status/{uid}/devices/{deviceId}').onUpdate(
+exports.onUserStatusChanged = functions.database.ref('/status/{uid}/sessions/{sessionId}').onUpdate(
     async (change, context) => {
       // Get the data written to Realtime Database
       const eventStatus = change.after.val();
 
-      const deviceKey = context.params.deviceId;
+      const sessionId = context.params.sessionId;
 
       // Then use other event data to create a reference to the
       // corresponding Firestore document.
       const userFirestoreRef = firestore.doc(`status/${context.params.uid}`);
-      const userDeviceCollectionRef = userFirestoreRef.collection(`devices`);
-      const userDeviceStatusFirestoreRef = userDeviceCollectionRef.doc(deviceKey);
+      const userSessionCollectionRef = userFirestoreRef.collection('sessions');
+      const sessionStatusFirestoreRef = userSessionCollectionRef.doc(sessionId);
 
       // It is likely that the Realtime Database change that triggered
       // this event has already been overwritten by a fast change in
@@ -56,14 +56,14 @@ exports.onUserStatusChanged = functions.database.ref('/status/{uid}/devices/{dev
 
       if(status.state === 'offline') {
         // ... and write it to Firestore.
-        await userDeviceStatusFirestoreRef.delete();
+        await sessionStatusFirestoreRef.delete();
 
-        if ((await userDeviceCollectionRef.get()).empty) {
+        if ((await userSessionCollectionRef.get()).empty) {
           return userFirestoreRef.delete();
         }
       } else {
         await userFirestoreRef.set({ uid: context.params.uid });
-        return userDeviceStatusFirestoreRef.set(status.devices[deviceKey]);
+        return sessionStatusFirestoreRef.set(status.sessions[sessionId]);
       }
       return null;
     });
diff --git a/presence-firestore/public/index.js b/presence-firestore/public/index.js
index a168a7b82..2b23c3d7d 100644
--- a/presence-firestore/public/index.js
+++ b/presence-firestore/public/index.js
@@ -21,11 +21,11 @@ function rtdb_presence() {
 
     // Create a reference to this user's specific status node.
     // This is where we will store data about being online/offline.
-    // `push()` will add a new key to the user's path, acting as a deviceId
-    var deviceStatusDatabaseRef = firebase.database().ref('/status/' + uid + '/devices').push();
+    // `push()` will add a new key to the user's path, acting as a sessionId
+    var sessionStatusDatabaseRef = firebase.database().ref('/status/' + uid + '/sessions').push();
 
     // We'll create two constants which we will write to 
-    // the Realtime database when this device is offline
+    // the Realtime database when this session is offline
     // or online.
     var isOfflineForDatabase = {
         state: 'offline',
@@ -50,7 +50,7 @@ function rtdb_presence() {
         // method to add a set which will only trigger once this 
         // client has disconnected by closing the app, 
         // losing internet, or any other means.
-        deviceStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
+        sessionStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
             // The promise returned from .onDisconnect().set() will
             // resolve as soon as the server acknowledges the onDisconnect() 
             // request, NOT once we've actually disconnected:
@@ -58,7 +58,7 @@ function rtdb_presence() {
 
             // We can now safely set ourselves as 'online' knowing that the
             // server will mark us as offline once we lose connection.
-            deviceStatusDatabaseRef.set(isOnlineForDatabase);
+            sessionStatusDatabaseRef.set(isOnlineForDatabase);
         });
     });
     // [END rtdb_presence]
@@ -68,8 +68,8 @@ async function rtdb_and_local_fs_presence() {
     // [START rtdb_and_local_fs_presence]
     // [START_EXCLUDE]
     var uid = firebase.auth().currentUser.uid;
-    var deviceStatusDatabaseRef = await firebase.database().ref('/status/' + uid + '/devices').push();
-    var deviceId = deviceStatusDatabaseRef.key;
+    var sessionStatusDatabaseRef = await firebase.database().ref('/status/' + uid + '/sessions').push();
+    var sessionId = sessionStatusDatabaseRef.key;
 
     var isOfflineForDatabase = {
         state: 'offline',
@@ -85,8 +85,8 @@ async function rtdb_and_local_fs_presence() {
     var userFirestoreRef = firebase.firestore().collection('status').doc(uid);
     await userFirestoreRef.set({ uid }); // In case the user's id document doesn't already exist.
     
-    var devicesCollectionRef = userFirestoreRef.collection('devices');
-    var deviceStatusFirestoreRef = devicesCollectionRef.doc(deviceId);
+    var sessionsCollectionRef = userFirestoreRef.collection('sessions');
+    var sessionStatusFirestoreRef = sessionsCollectionRef.doc(sessionId);
 
 
     // Firestore uses a different server timestamp value, so we'll 
@@ -98,23 +98,23 @@ async function rtdb_and_local_fs_presence() {
 
     firebase.database().ref('.info/connected').on('value', async function(snapshot) {
         if (snapshot.val() === false) {
-            // Instead of simply returning, we'll also remove the device id from the user, 
-            // and if no devices are left, we should delete the user as well.
-            // This ensures that our Firestore cache is aware that the device and/or user has been deleted
-            deviceStatusFirestoreRef.delete();
-            const deviceCollection = await devicesCollectionRef.get();
-            if(deviceCollection.empty) {
+            // Instead of simply returning, we'll also remove the session id from the user, 
+            // and if no sessions are left, we should delete the user as well.
+            // This ensures that our Firestore cache is aware that the session and/or user has been deleted
+            sessionStatusFirestoreRef.delete();
+            const sessionCollection = await sessionsCollectionRef.get();
+            if(sessionCollection.empty) {
                 userFirestoreRef.delete();
             }
             return;
         };
 
-        deviceStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
-            deviceStatusDatabaseRef.set(isOnlineForDatabase);
+        sessionStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
+            sessionStatusDatabaseRef.set(isOnlineForDatabase);
 
             // We'll also add Firestore set here for when we come online.
             userFirestoreRef.set({ uid });
-            deviceStatusFirestoreRef.set(isOnlineForFirestore);
+            sessionStatusFirestoreRef.set(isOnlineForFirestore);
         });
     });
     // [END rtdb_and_local_fs_presence]

From 60e0d0568eada68c26ac32e45be30eb8cfeac9e3 Mon Sep 17 00:00:00 2001
From: Maneesh Tewani <mtewani@google.com>
Date: Wed, 31 Aug 2022 10:18:43 -0700
Subject: [PATCH 5/6] Fixed offline mode bug

---
 presence-firestore/functions/index.js |  4 ++--
 presence-firestore/public/index.js    | 16 ++++++++++++++--
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/presence-firestore/functions/index.js b/presence-firestore/functions/index.js
index 6a3cf7282..952b84739 100644
--- a/presence-firestore/functions/index.js
+++ b/presence-firestore/functions/index.js
@@ -61,9 +61,9 @@ exports.onUserStatusChanged = functions.database.ref('/status/{uid}/sessions/{se
         if ((await userSessionCollectionRef.get()).empty) {
           return userFirestoreRef.delete();
         }
-      } else {
+      } else { // TODO(mtewani): Do we really need to handle this?
         await userFirestoreRef.set({ uid: context.params.uid });
-        return sessionStatusFirestoreRef.set(status.sessions[sessionId]);
+        return sessionStatusFirestoreRef.set(status);
       }
       return null;
     });
diff --git a/presence-firestore/public/index.js b/presence-firestore/public/index.js
index 2b23c3d7d..3fef3ec5b 100644
--- a/presence-firestore/public/index.js
+++ b/presence-firestore/public/index.js
@@ -70,6 +70,7 @@ async function rtdb_and_local_fs_presence() {
     var uid = firebase.auth().currentUser.uid;
     var sessionStatusDatabaseRef = await firebase.database().ref('/status/' + uid + '/sessions').push();
     var sessionId = sessionStatusDatabaseRef.key;
+    console.log('my ID', sessionId);
 
     var isOfflineForDatabase = {
         state: 'offline',
@@ -96,18 +97,24 @@ async function rtdb_and_local_fs_presence() {
         last_changed: firebase.firestore.FieldValue.serverTimestamp(),
     };
 
+    // When a user goes offline, it reads from the cache to know how many sessions are left.
+    // This listener is to ensure that the full session cache is populated and can be read from when offline.
+    sessionsCollectionRef.onSnapshot(() => {});
+
     firebase.database().ref('.info/connected').on('value', async function(snapshot) {
         if (snapshot.val() === false) {
             // Instead of simply returning, we'll also remove the session id from the user, 
             // and if no sessions are left, we should delete the user as well.
             // This ensures that our Firestore cache is aware that the session and/or user has been deleted
-            sessionStatusFirestoreRef.delete();
+            sessionStatusFirestoreRef.delete().then(() => console.log('session deletion completed'));
             const sessionCollection = await sessionsCollectionRef.get();
             if(sessionCollection.empty) {
-                userFirestoreRef.delete();
+                userFirestoreRef.delete().then(() => console.log('user deletion completed'));
             }
             return;
         };
+        const sessionCollection = await sessionsCollectionRef.get();
+        console.log(sessionCollection);
 
         sessionStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
             sessionStatusDatabaseRef.set(isOnlineForDatabase);
@@ -153,6 +160,11 @@ function fs_listen_online() {
         });
     // [END fs_onsnapshot_online]
 }
+const db = firebase.database();
+const firestore = firebase.firestore();
+db.useEmulator("localhost", 9000);
+firestore.useEmulator("localhost", 8080);
+
 
 firebase.auth().signInAnonymously().then(function() {
     rtdb_and_local_fs_presence();

From 066cbe2708aa46f009791f394f8a06a506fcf865 Mon Sep 17 00:00:00 2001
From: Maneesh Tewani <mtewani@google.com>
Date: Wed, 31 Aug 2022 10:20:44 -0700
Subject: [PATCH 6/6] Removed unnecessary code

---
 presence-firestore/public/index.js | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/presence-firestore/public/index.js b/presence-firestore/public/index.js
index 3fef3ec5b..26ef00fcd 100644
--- a/presence-firestore/public/index.js
+++ b/presence-firestore/public/index.js
@@ -70,7 +70,6 @@ async function rtdb_and_local_fs_presence() {
     var uid = firebase.auth().currentUser.uid;
     var sessionStatusDatabaseRef = await firebase.database().ref('/status/' + uid + '/sessions').push();
     var sessionId = sessionStatusDatabaseRef.key;
-    console.log('my ID', sessionId);
 
     var isOfflineForDatabase = {
         state: 'offline',
@@ -106,15 +105,13 @@ async function rtdb_and_local_fs_presence() {
             // Instead of simply returning, we'll also remove the session id from the user, 
             // and if no sessions are left, we should delete the user as well.
             // This ensures that our Firestore cache is aware that the session and/or user has been deleted
-            sessionStatusFirestoreRef.delete().then(() => console.log('session deletion completed'));
+            sessionStatusFirestoreRef.delete();
             const sessionCollection = await sessionsCollectionRef.get();
             if(sessionCollection.empty) {
-                userFirestoreRef.delete().then(() => console.log('user deletion completed'));
+                userFirestoreRef.delete();
             }
             return;
         };
-        const sessionCollection = await sessionsCollectionRef.get();
-        console.log(sessionCollection);
 
         sessionStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
             sessionStatusDatabaseRef.set(isOnlineForDatabase);
@@ -160,11 +157,6 @@ function fs_listen_online() {
         });
     // [END fs_onsnapshot_online]
 }
-const db = firebase.database();
-const firestore = firebase.firestore();
-db.useEmulator("localhost", 9000);
-firestore.useEmulator("localhost", 8080);
-
 
 firebase.auth().signInAnonymously().then(function() {
     rtdb_and_local_fs_presence();