app and middlewares

Author: ZabihollahNamazi

middleware-costum/app.js

@@ -1,4 +1,31 @@
 import express from "express";
+import usernameMiddleware from "./middleware/usernameMiddleware";
+import jsonArrayMiddleware from "./middleware/jsonArrayMiddleware";
 
 const app = express();
 
+app.post("/", usernameMiddleware, jsonArrayMiddleware, (req, res) => {
+  const subjects = req.body;
+
+  const auth =
+    req.username
+      ? `You are authenticated as ${req.username}.`
+      : "You are not authenticated.";
+
+  let message = "";
+
+  if (subjects.length === 0) {
+    message = "You have requested information about 0 subjects.";
+  } else if (subjects.length === 1) {
+    message = `You have requested information about 1 subject: ${subjects[0]}.`;
+  } else {
+    message = `You have requested information about ${subjects.length} subjects: ${subjects.join(", ")}.`;
+  }
+
+  res.send(`${auth}\n\n${message}`);
+});
+
+
+app.listen(3000, () => {
+  console.log("Server running on 3000");
+});

middleware-costum/middleware/jsonArrayMiddleware.js

@@ -0,0 +1,31 @@
+export default function jsonArrayMiddleware(req, res, next) {
+  const chunks = [];
+
+  req.on("data", (chunk) => {
+    chunks.push(chunk);
+  });
+
+  req.on("end", () => {
+    const bodyString = Buffer.concat(chunks).toString();
+
+    let data;
+
+    try {
+      data = JSON.parse(bodyString);
+    } catch {
+      return res.status(400).send("Invalid JSON");
+    }
+
+    if (!Array.isArray(data)) {
+      return res.status(400).send("Body must be an array");
+    }
+
+    if (!data.every(item => typeof item === "string")) {
+      return res.status(400).send("Array must contain only strings");
+    }
+
+    req.body = data;
+
+    next();
+  });
+}

middleware-costum/middleware/usernameMiddleware.js

@@ -1,4 +1,4 @@
-function usernameMiddleware(req, res, next) {
+export default function usernameMiddleware(req, res, next) {
   const username = req.header("X-Username");
 
   req.username = username || null;