/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.shiro.web.tags;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/**
 * JSP tag that renders the tag body if the current user <em>is not</em> known to the system, either because they
 * haven't logged in yet, or because they have no 'RememberMe' identity.
 *
 * <p>The logically opposite tag of this one is the {@link UserTag}.  Please read that class's JavaDoc as it explains
 * more about the differences between Authenticated/Unauthenticated and User/Guest semantic differences.
 *
 * @since 0.9
 */
public class GuestTag extends SecureTag {

    private static final Logger LOGGER = LoggerFactory.getLogger(GuestTag.class);

    public int onDoStartTag() throws JspException {
        if (getSubject() == null || getSubject().getPrincipal() == null) {
            if (LOGGER.isTraceEnabled()) {
                LOGGER.trace("Subject does not exist or does not have a known identity (aka 'principal').  "
                        + "Tag body will be evaluated.");
            }
            return TagSupport.EVAL_BODY_INCLUDE;
        } else {
            if (LOGGER.isTraceEnabled()) {
                LOGGER.trace("Subject exists or has a known identity (aka 'principal').  "
                        + " Tag body will not be evaluated.");
            }
            return TagSupport.SKIP_BODY;
        }
    }

}
