/**
 * Licensed to Apereo under one or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information regarding copyright ownership. Apereo
 * 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 the
 * following location:
 *
 * <p>http://www.apache.org/licenses/LICENSE-2.0
 *
 * <p>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.apereo.portal.portlet.container.cache;

import java.util.concurrent.TimeUnit;
import org.apereo.portal.portlet.rendering.PortletResourceOutputHandler;

/**
 * Utility for writing out portlet response caching related headers
 *
 */
public final class PortletCachingHeaderUtils {
    private static final int YEAR_OF_SECONDS = (int) TimeUnit.DAYS.toSeconds(365);

    private PortletCachingHeaderUtils() {}

    /**
     * @param cachedPortletData The {@link CachedPortletData} to base the headers on
     * @param portletResourceOutputHandler The handler to write the headers to
     * @see #setCachingHeaders(int, boolean, long, PortletResourceOutputHandler)
     * @see #setETag(String, PortletResourceOutputHandler)
     */
    public static void setCachingHeaders(
            CachedPortletData<?> cachedPortletData,
            PortletResourceOutputHandler portletResourceOutputHandler) {
        final long expirationTime = cachedPortletData.getExpirationTime();
        final int maxAge =
                (int) TimeUnit.MILLISECONDS.toSeconds(expirationTime - System.currentTimeMillis());
        final long timeStored = cachedPortletData.getTimeStored();
        final boolean publicScope = cachedPortletData.isPublicScope();

        setCachingHeaders(maxAge, publicScope, timeStored, portletResourceOutputHandler);
        final String etag = cachedPortletData.getEtag();
        if (etag != null) {
            setETag(etag, portletResourceOutputHandler);
        }
    }

    /**
     * Set the Last-Modified, CacheControl, and Expires headers based on the maxAge, publicScope and
     * lastModified.
     *
     * @param maxAge Maximum age for the content, follows the portlet rules (-1 cache forever, 0
     *     cache never, N cache seconds)
     * @param publicScope If the content is public
     * @param lastModified The last modification timestamp of the content
     * @param portletResourceOutputHandler The handler to write the headers to
     */
    public static void setCachingHeaders(
            int maxAge,
            boolean publicScope,
            long lastModified,
            PortletResourceOutputHandler portletResourceOutputHandler) {
        if (maxAge != 0) {
            portletResourceOutputHandler.setDateHeader("Last-Modified", lastModified);

            if (publicScope) {
                portletResourceOutputHandler.setHeader("CacheControl", "public");
            } else {
                portletResourceOutputHandler.setHeader("CacheControl", "private");
            }

            if (maxAge < 0) {
                //If caching "forever" set expires and max-age to 1 year
                maxAge = YEAR_OF_SECONDS;
            }

            portletResourceOutputHandler.setDateHeader(
                    "Expires", System.currentTimeMillis() + TimeUnit.SECONDS.toMillis(maxAge));
            portletResourceOutputHandler.addHeader("CacheControl", "max-age=" + maxAge);
        }
    }

    /**
     * Set the ETag header based on the specified token
     *
     * @param token ETag value
     * @param portletResourceOutputHandler The handler to write the header to
     */
    public static void setETag(
            String token, PortletResourceOutputHandler portletResourceOutputHandler) {
        portletResourceOutputHandler.setHeader("ETag", token);
    }
}