language-learning-app/frontend/src/hooks.server.ts

import { decodeJwt, jwtVerify } from 'jose';
import { redirect, type Handle } from '@sveltejs/kit';
import { PRIVATE_JWT_SECRET } from '$env/static/private';
import { client } from './lib/apiClient.ts';
import { COOKIE_NAME_AUTH_TOKEN } from '$lib/auth/index.ts';

async function verifyJwt(token: string, secret: string): Promise<boolean> {
	const encodedSecret = new TextEncoder().encode(secret);
	return await jwtVerify(token, encodedSecret)
		.then(() => true)
		.catch((e) => {
			console.log(`Caught error while validating JWT: ${e}`);
			return false;
		});
}

function getJwtPayload(jwt: string): { isAdmin: boolean } {
	const decodeResult = decodeJwt<{ is_admin: boolean }>(jwt);
	return { isAdmin: decodeResult.is_admin };
}

export const handle: Handle = async ({ event, resolve }) => {
	event.locals.apiClient = client;

	const rawToken = event.cookies.get(COOKIE_NAME_AUTH_TOKEN);
	const isValid = rawToken ? await verifyJwt(rawToken, PRIVATE_JWT_SECRET) : false;
	event.locals.authToken = isValid ? rawToken! : null;

	if (isValid && rawToken) {
		const payload = getJwtPayload(rawToken);
		event.locals.isAdmin = payload.isAdmin;
	} else {
		event.locals.isAdmin = false;
		console.log(`Not valid and no token`);
	}

	const { pathname } = event.url;
	if ((pathname.startsWith('/app') || pathname.startsWith('/admin')) && !isValid) {
		console.log(`Redirecting to login`);
		return redirect(307, '/login');
	}

	return resolve(event);
};