const firebaseAuthMiddleware = async function (request, reply) {
    const authHeader = request.headers['authorization'];

    // HEADER NOT PROVIDED
    if (!authHeader)
        return notAuthorized(reply);

    const [protocol, token] = authHeader.split(' ');

    // TOKEN NOT PROVIDED
    if (!token)
        return notAuthorized(reply);

    const started = Date.now();

    try {

        const decodedToken = await firebaseAdminSDK.auth().verifyIdToken(token);
        const firebaseUser = await firebaseAdminSDK.auth().getUser(decodedToken.uid);

        request.firebaseUser = firebaseUser;
        request.authTime = Date.now() - started;
        return;

    } catch (error) {

        if (error.code === FIREBASE_TOKEN_EXPIRED) {
            reply.code(440);
            reply.send({ code: errorTypes.SESSION_EXPIRED });
            return;
        }

        reply.code(401);
        reply.send({ code: FIREBASE_AUTH_ERROR, error });
        return;

    }
};