docs(examples): 3rd part of the "private messaging" example

See also: https://socket.io/get-started/private-messaging-part-3/

examples/private-messaging/server/index.js

@@ -11,6 +11,9 @@ const randomId = () => crypto.randomBytes(8).toString("hex");
 const { InMemorySessionStore } = require("./sessionStore");
 const sessionStore = new InMemorySessionStore();
 
+const { InMemoryMessageStore } = require("./messageStore");
+const messageStore = new InMemoryMessageStore();
+
 io.use((socket, next) => {
   const sessionID = socket.handshake.auth.sessionID;
   if (sessionID) {
@@ -51,11 +54,22 @@ io.on("connection", (socket) => {
 
   // fetch existing users
   const users = [];
+  const messagesPerUser = new Map();
+  messageStore.findMessagesForUser(socket.userID).forEach((message) => {
+    const { from, to } = message;
+    const otherUser = socket.userID === from ? to : from;
+    if (messagesPerUser.has(otherUser)) {
+      messagesPerUser.get(otherUser).push(message);
+    } else {
+      messagesPerUser.set(otherUser, [message]);
+    }
+  });
   sessionStore.findAllSessions().forEach((session) => {
     users.push({
       userID: session.userID,
       username: session.username,
       connected: session.connected,
+      messages: messagesPerUser.get(session.userID) || [],
     });
   });
   socket.emit("users", users);
@@ -65,15 +79,18 @@ io.on("connection", (socket) => {
     userID: socket.userID,
     username: socket.username,
     connected: true,
+    messages: [],
   });
 
   // forward the private message to the right recipient (and to other tabs of the sender)
   socket.on("private message", ({ content, to }) => {
-    socket.to(to).to(socket.userID).emit("private message", {
+    const message = {
       content,
       from: socket.userID,
       to,
-    });
+    };
+    socket.to(to).to(socket.userID).emit("private message", message);
+    messageStore.saveMessage(message);
   });
 
   // notify users upon disconnection

examples/private-messaging/server/messageStore.js

@@ -0,0 +1,25 @@
+/* abstract */ class MessageStore {
+  saveMessage(message) {}
+  findMessagesForUser(userID) {}
+}
+
+class InMemoryMessageStore extends MessageStore {
+  constructor() {
+    super();
+    this.messages = [];
+  }
+
+  saveMessage(message) {
+    this.messages.push(message);
+  }
+
+  findMessagesForUser(userID) {
+    return this.messages.filter(
+      ({ from, to }) => from === userID || to === userID
+    );
+  }
+}
+
+module.exports = {
+  InMemoryMessageStore,
+};

examples/private-messaging/src/components/Chat.vue

@@ -68,16 +68,19 @@ export default {
     });
 
     const initReactiveProperties = (user) => {
-      user.messages = [];
       user.hasNewMessages = false;
     };
 
     socket.on("users", (users) => {
       users.forEach((user) => {
+        user.messages.forEach((message) => {
+          message.fromSelf = message.from === socket.userID;
+        });
         for (let i = 0; i < this.users.length; i++) {
           const existingUser = this.users[i];
           if (existingUser.userID === user.userID) {
             existingUser.connected = user.connected;
+            existingUser.messages = user.messages;
             return;
           }
         }