Refactor: replace custom body parser with express.json built-in middleware

Author: zohrehKazemianpour

app-builtin.js

@@ -0,0 +1,54 @@
+const express = require('express'); 
+const app = express();
+app.use(express.json());
+
+//  Header Middleware
+const checkUsername = (req, res, next) => {
+  const usernameHeader = req.get("X-Username");
+  req.username = usernameHeader || null;
+  next();
+};
+
+
+// validates data
+const validateSubjects = (req, res, next) => {
+
+  const subjects = req.body;
+
+  if (
+    !Array.isArray(subjects) ||
+    !subjects.every((item) => typeof item === "string")
+  ) {
+    return res.status(400).send("Invalid input: expected an array of strings.");
+  }
+  next();
+};
+
+
+
+//  The Endpoint
+app.post("/subjects", checkUsername, validateSubjects, (req, res) => {
+  const { username, body: subjects } = req;
+
+  // Handle Authentication Message
+  const authPart = username
+    ? `You are authenticated as ${username}.`
+    : "You are not authenticated.";
+
+  // Handle subject vs subjects
+  const count = subjects.length;
+  const subjectText = count === 1 ? "subject" : "subjects";
+
+  // 3. Handle the list formatting
+  const listPart = count > 0 ? `: ${subjects.join(", ")}.` : ".";
+
+  res.send(
+    `${authPart}\n\nYou have requested information about ${count} ${subjectText}${listPart}`,
+  );
+});
+
+
+
+app.listen(3000, () => {
+  console.log('Server is running on port 3000');
+});