LONDON | 25-SDC-Nov | Zohreh Kazemianpour | Sprint 3 | Middleware

.gitignore

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+node_modules/
+.env

app-builtin.js

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+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');
+});

app.js

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+const express = require('express'); 
+const app = express();
+
+// 1. Header Middleware
+const checkUsername = (req, res, next) => {
+  const usernameHeader = req.get("X-Username");
+  req.username = usernameHeader || null;
+  next();
+};
+
+// 2. Body Parser Middleware
+const ensureJsonStringArray = (req, res, next) => {
+  let rawBody = "";
+
+  req.on("data", (chunk) => {
+    rawBody += chunk;
+  });
+
+  req.on("end", () => {
+    let parsed;
+
+    try {
+      parsed = JSON.parse(rawBody);
+    } catch {
+      return res.status(400).send("Request body must be valid JSON");
+    }
+
+    if (!Array.isArray(parsed)) {
+      return res.status(400).send("Request body must be a JSON array");
+    }
+
+    if (!parsed.every((item) => typeof item === "string")) {
+      return res.status(400).send("Array must contain only strings");
+    }
+
+    req.body = parsed;
+    next();
+  });
+};
+
+
+
+// 3. The Endpoint
+app.post("/subjects", checkUsername, ensureJsonStringArray, (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');
+});