/***************************************************************
 *  This file is part of the [fleXive](R) framework.
 *
 *  Copyright (c) 1999-2010
 *  UCS - unique computing solutions gmbh (http://www.ucs.at)
 *  All rights reserved
 *
 *  The [fleXive](R) project is free software; you can redistribute
 *  it and/or modify it under the terms of the GNU Lesser General Public
 *  License version 2.1 or higher as published by the Free Software Foundation.
 *
 *  The GNU Lesser General Public License can be found at
 *  http://www.gnu.org/licenses/lgpl.html.
 *  A copy is found in the textfile LGPL.txt and important notices to the
 *  license from the author are found in LICENSE.txt distributed with
 *  these libraries.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  For further information about UCS - unique computing solutions gmbh,
 *  please see the company website: http://www.ucs.at
 *
 *  For further information about [fleXive](R), please see the
 *  project website: http://www.flexive.org
 *
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 *  This copyright notice MUST APPEAR in all copies of the file!
 ***************************************************************/
package com.flexive.cms.war.filters;

import com.flexive.cms.war.CmsRequestUtils;
import com.flexive.cms.war.facelets.CmsResourceResolver;

import java.io.IOException;
import java.util.regex.Pattern;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Set cache headers of XHTML files served by the CMS (except edit mode pages).
 *
 * <h4>Init parameters</h4>
 *
 * <ul>
 * <li><strong>excludePattern</strong>: a regexp for URLs that should never have cache headers</li>
 * </ul>
 *
 * @author Daniel Lichtenberger
 * @version $Rev: 58 $
 */
public class CmsPageHeadersFilter implements Filter {
    private static final Log LOG = LogFactory.getLog(CmsPageHeadersFilter.class);
    /**
     * The maximum age of a static page served by the CMS in minutes
     * 
     * To prevent problem with JSF forms, this is set to the same
     * value as the session timeout in web.xml.
     */
    private static final long MAXAGE_STATIC_PAGE = 30;
    private Pattern excludePattern;

    public void destroy() {
        // nop
    }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        //noinspection PointlessBooleanExpression
        if (request instanceof HttpServletRequest && MAXAGE_STATIC_PAGE > 0
                && (excludePattern == null || !excludePattern.matcher(((HttpServletRequest) request).getRequestURI()).find())) {
            final HttpServletRequest httpRequest = (HttpServletRequest) request;
            final String uri = httpRequest.getRequestURI().replace(httpRequest.getContextPath(), "");

            final HttpServletResponse httpResponse = (HttpServletResponse) response;
            if (!CmsRequestUtils.isWebsiteRequest(request)
                    || CmsRequestUtils.getRequestedURI(request).startsWith(CmsResourceResolver.ADMIN_PATH)) {
                // disable cache for edit mode, /admin
                httpResponse.setDateHeader("Expires", 0);
                httpResponse.setHeader("Pragma", "no-cache");
            } else {
                // public page - cache for MAXAGE_STATIC_PAGE minutes
                // set one hour expiry in edit mode
                httpResponse.setDateHeader(
                        "Expires",
                        System.currentTimeMillis() + MAXAGE_STATIC_PAGE * 60 * 1000
                );

                // play safe
                httpResponse.setHeader("Cache-Control", "private");
                httpResponse.setHeader("Pragma", "cache");
            }
        }
        chain.doFilter(request, response);
    }

    public void init(FilterConfig filterConfig) throws ServletException {
        final String patternParam = filterConfig.getInitParameter("excludePattern");
        if (StringUtils.isNotBlank(patternParam)) {
            try {
                this.excludePattern = Pattern.compile(patternParam);
                if (LOG.isInfoEnabled()) {
                    LOG.info("Set exclude path for CMS caching filter: " + patternParam);
                }
            } catch (Exception e) {
                if (LOG.isWarnEnabled()) {
                    LOG.warn("Failed to parse excludePattern: " + e.getMessage());
                }
            }
        }
    }


}