/*-
 * 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.sling.dynamicinclude;

import java.io.IOException;

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 org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.sling.SlingFilter;
import org.apache.felix.scr.annotations.sling.SlingFilterScope;
import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.SlingHttpServletResponse;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@SlingFilter(scope = {SlingFilterScope.REQUEST, SlingFilterScope.FORWARD}, order = 0)
public class CacheControlFilter implements Filter {

    private static final String HEADER_DATE = "Date";

    private static final String HEADER_CACHE_CONTROL = "Cache-Control";

    private static final Logger LOG = LoggerFactory.getLogger(CacheControlFilter.class);

    @Reference
    private ConfigurationWhiteboard configurationWhiteboard;

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException,
            ServletException {
        final SlingHttpServletRequest slingRequest = (SlingHttpServletRequest) request;
        final String resourceType = slingRequest.getResource().getResourceType();
        final Configuration config = configurationWhiteboard.getConfiguration(slingRequest, resourceType);

        if (config != null && config.hasTtlSet()) {
            SlingHttpServletResponse slingResponse = (SlingHttpServletResponse) response;
            slingResponse.setHeader(HEADER_CACHE_CONTROL, "max-age=" + config.getTtl());
            LOG.debug("set \"{}: max-age={}\" to {}", HEADER_CACHE_CONTROL, config.getTtl(), resourceType);
            if (!slingResponse.containsHeader(HEADER_DATE)) {
                slingResponse.setDateHeader(HEADER_DATE, System.currentTimeMillis());
            }
        }

        chain.doFilter(request, response);
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void destroy() {
    }
}