package com.atlassian.plugin.servlet;
   
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   
   public class ResourceDownloadUtils {
       private static final long ONE_YEAR_SECONDS = 60L * 60L * 24L * 365L;
       private static final long ONE_YEAR_MILLISECONDS = 1000 * ONE_YEAR_SECONDS;
   
      /**
       * Set 'expire' headers to cache for one year. Also adds the additional cache control values passed in.
       * Note, this method resets the cache control headers if set previously.
       *
       * If caches are disabled (via the system property atlassian.disable.caches), this method sets 'expires' to 0.
       */
      public static void addCachingHeaders(HttpServletRequest httpServletRequest, final HttpServletResponse httpServletResponse, final String... cacheControls) {
          boolean cacheDisabledByQueryParam = "false".equals(httpServletRequest.getParameter("cache"));
          if (Boolean.getBoolean("atlassian.disable.caches")) {
              httpServletResponse.setDateHeader("Expires", 0);
              httpServletResponse.setHeader("Cache-Control", "no-cache, must-revalidate");
          } else if (!cacheDisabledByQueryParam) {
              httpServletResponse.setDateHeader("Expires", System.currentTimeMillis() + ONE_YEAR_MILLISECONDS);
              httpServletResponse.setHeader("Cache-Control", "max-age=" + ONE_YEAR_SECONDS);
              for (final String cacheControl : cacheControls) {
                  httpServletResponse.addHeader("Cache-Control", cacheControl);
              }
          }
      }
  
      /**
       * Sets caching headers with public cache control. Applications should call this method from urlrewrite.xml to
       * decorate urls like <code>/s/{build num}/.../_/resourceurl</code>.
       *
       * @see <a href="http://tuckey.org/urlrewrite/manual/2.6/">http://tuckey.org/urlrewrite/manual/2.6/</a>
       */
      public static void addPublicCachingHeaders(final HttpServletRequest httpServletRequest, final HttpServletResponse httpServletResponse) {
          addCachingHeaders(httpServletRequest, httpServletResponse, "public");
      }
  
      /**
       * Sets caching headers with private cache control. Applications should call this method from urlrewrite.xml to
       * decorate urls like <code>/sp/{build num}/.../_/resourceurl</code>.
       *
       * @see <a href="http://tuckey.org/urlrewrite/manual/2.6/">http://tuckey.org/urlrewrite/manual/2.6/</a>
       */
      public static void addPrivateCachingHeaders(final HttpServletRequest httpServletRequest, final HttpServletResponse httpServletResponse) {
          addCachingHeaders(httpServletRequest, httpServletResponse, "private");
      }
  }