London | 26-SDC-July | Raihan Sharif | Sprint 3 | Middleware exercises

.gitignore

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+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+lerna-debug.log*
+
+# Diagnostic reports (https://nodejs.org/api/report.html)
+report.[0-9]*.[0-9]*.[0-9]*.[0-9]*.json
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+*.lcov
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (https://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (https://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# Snowpack dependency directory (https://snowpack.dev/)
+web_modules/
+
+# TypeScript cache
+*.tsbuildinfo
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional stylelint cache
+.stylelintcache
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variable files
+.env
+.env.*
+!.env.example
+
+# parcel-bundler cache (https://parceljs.org/)
+.cache
+.parcel-cache
+
+# Next.js build output
+.next
+out
+
+# Nuxt.js build / generate output
+.nuxt
+dist
+.output
+
+# Gatsby files
+.cache/
+# Comment in the public line in if your project uses Gatsby and not Next.js
+# https://nextjs.org/blog/next-9-1#public-directory-support
+# public
+
+# vuepress build output
+.vuepress/dist
+
+# vuepress v2.x temp directory
+.temp
+
+# Sveltekit cache directory
+.svelte-kit/
+
+# vitepress build output
+**/.vitepress/dist
+
+# vitepress cache directory
+**/.vitepress/cache
+
+# Docusaurus cache and generated files
+.docusaurus
+
+# Serverless directories
+.serverless/
+
+# FuseBox cache
+.fusebox/
+
+# DynamoDB Local files
+.dynamodb/
+
+# Firebase cache directory
+.firebase/
+
+# TernJS port file
+.tern-port
+
+# Stores Visual Studio Code versions used for testing Visual Studio Code extensions
+.vscode-test
+
+# pnpm
+.pnpm-store
+
+# yarn v3
+.pnp.*
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/sdks
+!.yarn/versions
+
+# Vite files
+vite.config.js.timestamp-*
+vite.config.ts.timestamp-*
+.vite/
+
+CORS_ORIGINS
+
+.vscode

built-in-middleware/app.js

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+import express from "express";
+
+const app = express();
+app.use(express.json());
+app.use(express.urlencoded({ extended: true }));
+
+function usernameMiddleware(req, res, next) {
+    const username = req.get("X-username");
+    req.username = username;
+    next();
+}
+
+app.use(usernameMiddleware);
+
+app.post("/", (req, res) => {
+    let responseStr = "";
+    if (req.username) {
+        responseStr = `You are authenticated as ${req.username}.\n`;
+    } else {
+        responseStr = `You are not authenticated.\n`;
+    }
+
+    if (req.body) {
+        responseStr = responseStr.concat(
+            `You have requested information about ${req.body.length} subjects: ${req.body.join(", ")}\n`,
+        );
+    }
+    res.send(responseStr);
+});
+
+/*
+previous CURL does not work because curl --data sends 'content-type: application/x-www-form-urlencoded', is not parsed by expres.json()
+but by urlencoded(), which tries to create a key:value pair set rather than an array. 
+
+By setting the content type explicitly, this can force the app to use the desired middleware:
+
+curl -X POST http://localhost:3000/ \
+  -H "Content-Type: application/json" \
+  -H "X-Username: Ahmed" \
+  --data '["Bees", "birds", "lizards"]'
+*/
+
+app.listen(3000, () => {
+    console.log(`Listening on port: 3000`);
+});

custom-middleware/app.js

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+import express from "express";
+
+const app = express();
+
+function usernameMiddleware(req, res, next) {
+    const username = req.get("X-username");
+    req.username = username;
+    next();
+}
+
+function parseBodyAsJSONArray(req, res, next) {
+    const chunks = [];
+
+    req.on("data", (chunk) => {
+        chunks.push(chunk);
+    });
+
+    req.on("end", () => {
+        const raw = Buffer.concat(chunks).toString("utf8");
+
+        try {
+            const parsed = JSON.parse(raw);
+
+            if (!Array.isArray(parsed)) {
+                return res.status(400).send("Body must be a JSON array");
+            }
+
+            if (parsed.some((elem) => typeof elem !== "string")) {
+                return res
+                    .status(400)
+                    .send("All elements in array must be strings");
+            }
+
+            req.body = parsed;
+            next();
+        } catch (e) {
+            return res.status(400).send("Invalid JSON string");
+        }
+    });
+
+    req.on("error", (err) => {
+        next(err);
+    });
+}
+
+app.use([usernameMiddleware, parseBodyAsJSONArray]);
+app.post("/", (req, res) => {
+    let responseStr = "";
+    if (req.username) {
+        responseStr = `You are authenticated as ${req.username}.\n`;
+    } else {
+        responseStr = `You are not authenticated.\n`;
+    }
+
+    if (req.body) {
+        responseStr = responseStr.concat(
+            `You have requested information about ${req.body.length} subjects: ${req.body.join(", ")}\n`,
+        );
+    }
+
+    res.send(responseStr);
+});
+
+app.listen(3000, () => {
+    console.log(`Listening on port: 3000`);
+});