@Override
    public final Mono<PermissionSet> getPermissions(Member member) {
        Map<Snowflake, PermissionOverwrite> effectiveOverwrites = getEffectiveOverwrites(getPermissionOverwrites(), member.getId(), member.getGuildId(), member.getRoleIds());

        return member.getPermissions()
                .filter(permissions -> !permissions.contains(Permission.ADMINISTRATOR))
                .map(permissions -> applyOverwrites(permissions, effectiveOverwrites, Collections.singleton(member.getGuildId())))
                .map(permissions -> applyOverwrites(permissions, effectiveOverwrites, member.getRoleIds()))
                .map(permissions -> applyOverwrites(permissions, effectiveOverwrites, Collections.singleton(member.getId())))
                .switchIfEmpty(Mono.just(PermissionSet.all()));
    }

    public static Map<Snowflake, PermissionOverwrite> getEffectiveOverwrites(Set<PermissionOverwrite> overwrites, Snowflake member, Snowflake guild, Set<Snowflake> roles) {
        return overwrites.stream()
                .filter(overwrite -> overwrite.getRoleId().map(r -> r.equals(guild) || roles.contains(r)).orElse(true))
                .filter(overwrite -> overwrite.getUserId().map(member::equals).orElse(true))
                .collect(Collectors.toMap(
                        overwrite -> (Snowflake) overwrite.getRoleId().orElseGet(overwrite.getUserId()::get),
                        Function.identity(),
                        (id1, id2) -> id1, // impossible?
                        LinkedHashMap::new));
    }

    public static PermissionSet applyOverwrites(PermissionSet current, Map<Snowflake, PermissionOverwrite> overwrites, Iterable<Snowflake> ids) {
        int allow = 0;
        int deny = 0;
        for (Snowflake id : ids) {
            PermissionOverwrite overwrite = overwrites.get(id);
            if (overwrite != null) {
                allow |= overwrite.getAllowed().getRawValue();
                deny |= overwrite.getDenied().getRawValue();
            }
        }
        return PermissionSet.of((current.getRawValue() & ~deny) | allow);
    }