if (realm.isBruteForceProtected()) {
    //     if (session.getProvider(BruteForceProtector.class).isTemporarilyDisabled(session, realm, user)) {
    //         event.error(Errors.USER_TEMPORARILY_DISABLED);
    //         return ErrorPage.error(session, authSession, Response.Status.BAD_REQUEST, Messages.ACCOUNT_DISABLED);
    //     }
    // some logic

import org.jboss.logging.Logger;
import org.keycloak.authentication.AuthenticationFlowContext;
import org.keycloak.authentication.AuthenticationFlowError;
import org.keycloak.authentication.Authenticator;
import org.keycloak.authentication.authenticators.browser.AbstractUsernameFormAuthenticator;
import org.keycloak.events.Details;
import org.keycloak.events.Errors;
import org.keycloak.forms.login.LoginFormsProvider;
import org.keycloak.models.GroupModel;
import org.keycloak.models.KeycloakSession;
import org.keycloak.models.RealmModel;
import org.keycloak.models.UserModel;
import org.keycloak.models.utils.KeycloakModelUtils;
import org.keycloak.services.managers.AuthenticationManager;
import org.keycloak.services.messages.Messages;
import org.open.keycloak.authenticator.api.HttpResult;
import org.open.keycloak.authenticator.rest.AuthenticationRestAdapter;
import org.keycloak.services.managers.BruteForceProtector;

import java.util.List;

import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.core.Response;

import static javax.servlet.http.HttpServletResponse.SC_OK;
import static javax.servlet.http.HttpServletResponse.SC_UNAUTHORIZED;
import static javax.servlet.http.HttpServletResponse.SC_NOT_FOUND;
import static javax.servlet.http.HttpServletResponse.SC_INTERNAL_SERVER_ERROR;

public class CustomAuthenticator implements Authenticator {

    private static final Logger logger = Logger.getLogger(CustomAuthenticator.class);

    @Override
    public void action(AuthenticationFlowContext context) {
        MultivaluedMap<String, String> formData = context.getHttpRequest().getDecodedFormParameters();
        if (!authenticateUser(context, formData)) {
            return;
        }
        setUserToContext(context, formData);
        context.success();
    }

    @Override
    public void authenticate(AuthenticationFlowContext context) {
        LoginFormsProvider forms = context.form();
        Response challenge = forms.createLogin();
        context.challenge(challenge);
    }

    /**
     * @param context  Used to store detailed explanation about authentication process and results.
     * @param formData Form fields mapped by field names.
     * @return True if user is successfully authenticated, false if not.
     */
    private boolean authenticateUser(AuthenticationFlowContext context, MultivaluedMap<String, String> formData) {
        String username = formData.getFirst(AuthenticationManager.FORM_USERNAME);
        if (username == null || "".equals(username)) {
            context.getEvent().error(Errors.USERNAME_MISSING);
            Response challenge = context.form()
                .setError(Messages.MISSING_USERNAME)

                .createLogin();
            context.forceChallenge(challenge);
            return false;
        }

        String password = formData.getFirst("password");
        if (password == null || "".equals(password)) {
            context.getEvent().error(Errors.PASSWORD_MISSING);
            Response challenge = context.form()
                .setError(Messages.MISSING_PASSWORD)
                .createLogin();
            context.forceChallenge(challenge);
            return false;
        }
        KeycloakSession session = context.getSession();
        RealmModel realm = session.realms().getRealmByName("open");
        if (realm.isBruteForceProtected()) {
        //     if (session.getProvider(BruteForceProtector.class).isTemporarilyDisabled(session, realm, user)) {
        //         event.error(Errors.USER_TEMPORARILY_DISABLED);
        //         return ErrorPage.error(session, authSession, Response.Status.BAD_REQUEST, Messages.ACCOUNT_DISABLED);
        //     }
        // some logic

    }

    private void setUserToContext(AuthenticationFlowContext context, MultivaluedMap<String, String> formData) {
        String username = formData.getFirst("username");

        UserModel user = KeycloakModelUtils.findUserByNameOrEmail(
            context.getSession(),
            context.getRealm(),
            username
        );

        if (user == null) {
            KeycloakSession session = context.getSession();
            RealmModel realm = session.realms().getRealmByName("open");
            user = session.users().addUser(realm, username);
            user.setEmail(username);
            user.setEnabled(true);
            user.setEmailVerified(true);
            List<GroupModel> groups = realm.getGroups();
            for (GroupModel group: groups) {
                user.joinGroup(group);
            }
        }
        context.setUser(user);
    }

}