add solution

src/createServer.js

@@ -1,8 +1,78 @@
 'use strict';
 
+const http = require('http');
+const path = require('path');
+const fs = require('fs');
+
 function createServer() {
   /* Write your code here */
   // Return instance of http.Server class
+  return http.createServer((req, res) => {
+    const { url } = req;
+    const publicPathPrefix = '/file';
+    const pathname = url;
+
+    let relativeFilePath;
+
+    if (pathname === publicPathPrefix || pathname === `${publicPathPrefix}/`) {
+      res.statusCode = 200;
+      res.setHeader('Content-Type', 'text/plain');
+      relativeFilePath = 'index.html';
+    } else if (pathname.startsWith(`${publicPathPrefix}/`)) {
+      relativeFilePath = pathname.substring(publicPathPrefix.length + 1);
+    } else {
+      res.statusCode = 400;
+      res.setHeader('Content-Type', 'text/plain');
+
+      res.end(
+        'Invalid file request. Files must be requested via /file/path/to/file.',
+      );
+
+      return;
+    }
+
+    const publicDir = path.resolve(__dirname, '..', 'public');
+    let filePath = relativeFilePath;
+
+    if (filePath === '' || filePath === '/') {
+      filePath = 'index.html';
+    }
+
+    if (filePath.includes('..')) {
+      res.writeHead(400, { 'Content-Type': 'text/plain' });
+      res.end('Bad Request');
+
+      return;
+    }
+
+    if (filePath.includes('//')) {
+      res.writeHead(404, { 'Content-Type': 'text/plain' });
+      res.end('Bad Request');
+
+      return;
+    }
+
+    const fullPath = path.join(publicDir, filePath);
+
+    if (!fullPath.startsWith(publicDir)) {
+      res.writeHead(400, { 'Content-Type': 'text/plain' });
+      res.end('Bad Request');
+
+      return;
+    }
+
+    fs.readFile(fullPath, (err, data) => {
+      if (err) {
+        res.writeHead(404, { 'Content-Type': 'text/plain' });
+        res.end('File not found');
+
+        return;
+      }
+
+      res.writeHead(200);
+      res.end(data);
+    });
+  });
 }
 
 module.exports = {