* @param userMessage the user's message
     * @param userId the user ID (can be null for anonymous users)
     * @return the chat response including session info and sources
     */
    public ChatResult chat(final String sessionId, final String userMessage, final String userId) {
        return chat(sessionId, userMessage, userId, Collections.emptyMap(), new String[0]);
    }

    /**

import org.apache.logging.log4j.Logger;
import org.codelibs.core.lang.StringUtil;
import org.codelibs.fess.Constants;
import org.codelibs.fess.api.BaseApiManager;
import org.codelibs.fess.chat.ChatClient.ChatResult;
import org.codelibs.fess.chat.ChatPhaseCallback;
import org.codelibs.fess.entity.ChatMessage.ChatSource;
import org.codelibs.fess.entity.FacetQueryView;
import org.codelibs.fess.entity.SearchRequestParams;