package com.atlassian.plugin.webresource.cache;
   
   import com.atlassian.plugin.cache.filecache.FileCache;
   import com.atlassian.plugin.cache.filecache.FileCacheStreamProvider;
   import com.atlassian.plugin.servlet.DownloadException;
   import com.atlassian.plugin.webresource.ResourceUtils;
   
   import java.io.OutputStream;
   import java.util.Map;
  import java.util.TreeMap;
  
  /**
   * A small facarde around a FileCacheStreamProvider, that captures both the cache key
   * and FileCache, saving having to pass them around seperately
   *
   * @since v2.13
   */
  public interface CacheHandle {
      void stream(OutputStream out, FileCacheStreamProvider streamProvider) throws DownloadException;
  
      public static class Builder {
          /** does not cache, calls the stream provider directly */
          public static CacheHandle passthrough() {
              return new CacheHandle() {
                  @Override
                  public void stream(OutputStream out, FileCacheStreamProvider streamProvider) throws DownloadException {
                      streamProvider.writeStream(out);
                  }
              };
          }
  
          /**
           * inspects the request, and if appropriate, returns a CacheHandle that will
           * cache resources to the cache.
           * If not approriate, a passthrough() handle is returned.
           */
          public static CacheHandle forRequest(final FileCache<FileCacheKey> cache, String downloadtype, String path, final Map<String, String> params)
          {
              if (!ResourceUtils.canRequestedResourcesContentBeAssumedConstant(params))
              {
                  return passthrough();
              }
  
              final FileCacheKey cacheKey = new FileCacheKey(new TreeMap<String, String>(params), downloadtype, path);
              return new CacheHandle() {
                  @Override
                  public void stream(OutputStream out, FileCacheStreamProvider streamProvider) throws DownloadException {
                      cache.stream(cacheKey, out, streamProvider);
                  }
              };
          }
  
      }
  
  }