London |26-JUL - SDC | Ping Wang |Sprint 3| middleware exercises CYF -1165

.gitignore

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+</> gitignore
+node_modules/
+

Sprint 3- middlewares/custom-written middlewares/custom.js

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+const express = require("express");
+
+const app = express();
+const PORT = 3000;
+
+// Middleware 1: get username from X-Username header
+function usernameMiddleware(req, res, next) {
+    const username = req.get("X-Username");
+
+    if (username) {
+        req.username = username;
+    } else {
+        req.username = null;
+    }
+
+    next();
+}
+
+// Middleware 2: parse and validate JSON array
+function bodyMiddleware(req, res, next) {
+    let body = "";
+
+    req.on("data", (chunk) => {
+        body += chunk;
+    });
+
+    req.on("end", () => {
+        try {
+            const parsedBody = JSON.parse(body);
+
+            // Must be an array
+            if (!Array.isArray(parsedBody)) {
+                return res.status(400).send("Request body must be a JSON array.");
+            }
+
+            // Every item must be a string
+            if (!parsedBody.every((item) => typeof item === "string")) {
+                return res.status(400).send("Array must contain only strings.");
+            }
+
+            req.body = parsedBody;
+            next();
+        } catch (error) {
+            res.status(400).send("Request body must be valid JSON.");
+        }
+    });
+}
+
+// Use our two middlewares
+app.use(usernameMiddleware);
+app.use(bodyMiddleware);
+
+// POST endpoint
+app.post("/", (req, res) => {
+    const subjects = req.body;
+
+    if (req.username) {
+        res.send(
+            `You are authenticated as ${req.username}.\n\n` +
+            `You have requested information about ${subjects.length} ` +
+            `${subjects.length === 1 ? "subject" : "subjects"}` +
+            `${subjects.length > 0 ? ": " + subjects.join(", ") : ""}.`
+        );
+    } else {
+        res.send(
+            `You are not authenticated.\n\n` +
+            `You have requested information about ${subjects.length} ` +
+            `${subjects.length === 1 ? "subject" : "subjects"}` +
+            `${subjects.length > 0 ? ": " + subjects.join(", ") : ""}.`
+        );
+    }
+});
+
+app.listen(PORT, () => {
+    console.log(`Server running on http://localhost:${PORT}`);
+});

Sprint 3- middlewares/off-shelf middleware/off shelf.js

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+const express = require("express");
+
+const app = express();
+const PORT = 3000;
+
+// Built-in Express JSON middleware
+app.use(express.json());
+
+// Custom username middleware
+function usernameMiddleware(req, res, next) {
+    const username = req.get("X-Username");
+
+    if (username) {
+        req.username = username;
+    } else {
+        req.username = null;
+    }
+
+    next();
+}
+
+app.use(usernameMiddleware);
+
+// POST endpoint
+app.post("/", (req, res) => {
+    const subjects = req.body;
+
+    if (!Array.isArray(subjects) ||
+        !subjects.every((subject) => typeof subject === "string")) {
+        return res.status(400).send("Invalid request body.");
+    }
+
+    if (req.username) {
+        res.send(
+            `You are authenticated as ${req.username}.\n\n` +
+            `You have requested information about ${subjects.length} ` +
+            `${subjects.length === 1 ? "subject" : "subjects"}` +
+            `${subjects.length > 0 ? ": " + subjects.join(", ") : ""}.`
+        );
+    } else {
+        res.send(
+            `You are not authenticated.\n\n` +
+            `You have requested information about ${subjects.length} ` +
+            `${subjects.length === 1 ? "subject" : "subjects"}` +
+            `${subjects.length > 0 ? ": " + subjects.join(", ") : ""}.`
+        );
+    }
+});
+
+app.listen(PORT, () => {
+    console.log(`Server running on http://localhost:${PORT}`);
+});