implement user authentication with login functionality and database integration

backend/services/database.js

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+import mysql from "mysql2";
+import dotenv from "dotenv";
+dotenv.config();
+
+// Ein einzelner Pool reicht; der zweite Pool benutzte fälschlich DB_TABLE als Datenbank
+const pool = mysql
+  .createPool({
+    host: process.env.DB_HOST,
+    user: process.env.DB_USER,
+    password: process.env.DB_PASSWORD,
+    database: process.env.DB_NAME,
+  })
+  .promise();
+
+export const loginFunc = async (username, password) => {
+  const [result] = await pool.query(
+    "SELECT * FROM users WHERE username = ? AND password = ?",
+    [username, password]
+  );
+  if (result.length > 0) return { success: true };
+  return { success: false };
+};
+
+export const getItemsFromDatabase = async () => {
+  const [result] = await pool.query("SELECT * FROM items");
+  if (result.length > 0) {
+    return { success: true, data: result };
+  }
+  return { success: false };
+};

backend/services/tokenService.js

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+import { SignJWT, jwtVerify } from "jose";
+import env from "dotenv";
+env.config();
+const secret = new TextEncoder().encode(process.env.SECRET_KEY);
+
+export async function generateToken(payload) {
+  const newToken = await new SignJWT(payload)
+    .setProtectedHeader({ alg: "HS256" })
+    .setIssuedAt()
+    .setExpirationTime("2h") // Token valid for 2 hours
+    .sign(secret);
+  console.log("Generated token: ", newToken);
+  return newToken;
+}
+
+export async function authenticate(req, res, next) {
+  const authHeader = req.headers["authorization"];
+  const token = authHeader && authHeader.split(" ")[1]; // Bearer <token>
+
+  if (token == null) return res.sendStatus(401); // No token present
+
+  const { payload } = await jwtVerify(token, secret);
+  req.user = payload;
+
+  next();
+}