implement backend server with socket.io for real-time messaging

Author: joseph-ayitey

chat-app/backend/server.js

@@ -0,0 +1,168 @@
+const express = require("express");
+const http = require("http");
+const cors = require("cors");
+const { Server } = require("socket.io");
+
+const app = express();
+
+app.use(cors());
+app.use(express.json());
+
+const server = http.createServer(app);
+
+const io = new Server(server, {
+  cors: {
+    origin: "*",
+  },
+});
+
+// Store messages in memory
+let messages = [];
+
+// Track online users
+let onlineUsers = [];
+
+io.on("connection", (socket) => {
+
+  // delete messages
+  socket.on("delete_message", (id) => {
+
+  // remove message from array
+  messages = messages.filter(
+    (msg) => msg.id !== id
+  );
+
+  // notify all clients
+  io.emit("message_deleted", id);
+});
+
+  console.log("User connected");
+
+  // Send old messages
+  socket.emit("load_messages", messages);
+
+
+  // USER JOIN
+
+  socket.on("join", (username) => {
+     socket.username = username;
+
+    if (
+      username && !onlineUsers.includes(username)
+    ) {
+      onlineUsers.push(username);
+    }
+
+    io.emit("online_users", onlineUsers);
+  });
+
+
+  // TYPING INDICATOR
+
+  socket.on("typing", (username) => {
+     socket.broadcast.emit(
+      "typing",
+      username
+    );
+  });
+
+
+  // SEND MESSAGE
+
+  socket.on("send_message", (message) => {
+    const newMessage = {
+      id: Date.now(),
+
+      text: message.text,
+      user: message.user,
+      color: message.color,
+
+      likes: 0,
+      dislikes: 0,
+
+      replyTo: message.replyTo || null,
+
+      createdAt: new Date(),
+    };
+
+
+    // SCHEDULED MESSAGE
+
+    if (message.scheduledFor) {
+
+      const delay = new Date(message.scheduledFor) - new Date();
+      
+      setTimeout(() => {
+        messages.push(newMessage);
+         io.emit(
+          "receive_message",
+          newMessage
+        );
+
+      }, delay);
+
+    } else {
+
+      messages.push(newMessage);
+
+      io.emit(
+        "receive_message",
+        newMessage
+      );
+    }
+  });
+
+
+  // LIKE MESSAGE
+
+  socket.on("like_message", (id) => {
+     const msg = messages.find( (m) => m.id === id
+    );
+     if (msg){
+         msg.likes++; io.emit(
+        "update_message",
+        msg
+      );
+    }
+  });
+
+
+  // DISLIKE MESSAGE
+
+  socket.on("dislike_message", (id) => {
+
+    const msg = messages.find(
+      (m) => m.id === id
+    );
+
+    if (msg) {
+
+      msg.dislikes++;
+
+      io.emit(
+        "update_message",
+        msg
+      );
+    }
+  });
+
+
+  // DISCONNECT
+
+  socket.on("disconnect", () => {
+    onlineUsers =
+      onlineUsers.filter((user) =>user !== socket.username
+      );
+
+    io.emit( "online_users", onlineUsers
+    );
+
+    console.log("User disconnected");
+  });
+});
+
+server.listen(5000, () => {
+  console.log(
+    "Server running on port 5000"
+  );
+});