added files

Author: TzeMingHo

chat-app/backend/app.js

@@ -0,0 +1,81 @@
+import express from "express";
+import cors from "cors";
+
+const app = express();
+app.use(cors({
+  origin: "https://tzemingho-chatapp-server-frontend.hosting.codeyourfuture.io"
+}));
+app.use(express.json());
+const port = 4000;
+
+const waitingRoom = [];
+
+const chatHistory = [
+  {
+    message: "Welcome to the channel.",
+    user: "System",
+    timestamp: new Date().getTime(),
+  },
+];
+
+app.get("/", (req, res) => {
+  res.json(chatHistory);
+});
+
+app.get("/messages", (req, res) => {
+  const since = parseInt(req.query.since);
+
+  if (isNaN(since)) {
+    return res.json(chatHistory);
+  }
+  const newMessages = chatHistory.filter(({timestamp}) => timestamp > since);
+
+  if (newMessages.length > 0) {
+    return res.json(newMessages);
+  }
+
+  const callback = (message) => res.json([message])
+  waitingRoom.push(callback);
+
+  const seconds = 25;
+  const miliseconds = 1000;
+
+  const timeout = setTimeout(() => {
+    const index = waitingRoom.indexOf(callback);
+    if (index !== -1) {
+      waitingRoom.splice(index, 1)
+      res.send([])
+    }
+  }, seconds * miliseconds)
+})
+
+app.post("/", (req, res) => {
+  try {
+    let { message, user, timestamp } = req.body;
+    if (!message?.trim() || !user?.trim()) {
+      res.status(406).json({ error: "Empty message or user are not allowed." });
+      return;
+    } else {
+      const newMessage = {
+        message: message,
+        user: user,
+        timestamp: timestamp
+      }
+      chatHistory.push(newMessage);
+
+      while(waitingRoom.length > 0) {
+        const callback = waitingRoom.pop();
+        callback(newMessage);
+      }      
+      res.status(201).send("sent");
+    }
+  } catch (error) {
+    console.error(`Failed to parse body as JSON: ${error}`);
+    res.status(400).json({ error: "Expected body to be JSON." });
+    return;
+  }
+});
+
+app.listen(port, () => {
+  console.log(`chatApp server is listening on port: ${port}`);
+});