package com.atlassian.plugin.servlet;
   
   
   import org.slf4j.Logger;
   import org.slf4j.LoggerFactory;
   
   import javax.servlet.http.HttpServlet;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  import java.util.List;
  
  public abstract class AbstractFileServerServlet extends HttpServlet {
      public static final String PATH_SEPARATOR = "/";
      public static final String RESOURCE_URL_PREFIX = "resources";
      public static final String SERVLET_PATH = "download";
      private static final Logger log = LoggerFactory.getLogger(AbstractFileServerServlet.class);
  
      @Override
      protected final void doGet(final HttpServletRequest httpServletRequest, final HttpServletResponse httpServletResponse) throws IOException {
          final DownloadStrategy downloadStrategy = getDownloadStrategy(httpServletRequest);
          if (downloadStrategy == null) {
              httpServletResponse.sendError(HttpServletResponse.SC_NOT_FOUND, "The file you were looking for was not found");
              return;
          }
  
          try {
              downloadStrategy.serveFile(httpServletRequest, httpServletResponse);
          } catch (final DownloadException e) {
              log.debug("Error while serving file for request:" + httpServletRequest.getRequestURI(), e);
              if (!httpServletResponse.isCommitted()) {
                  httpServletResponse.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "Error while serving file");
              }
          }
      }
  
      /**
       * Returns a list of {@link DownloadStrategy} objects in the order that they will be matched against.
       * The list returned should be cached as this method is called for every request.
       */
      protected abstract List<DownloadStrategy> getDownloadStrategies();
  
      private DownloadStrategy getDownloadStrategy(final HttpServletRequest httpServletRequest) {
          final String url = httpServletRequest.getRequestURI();
          DownloadStrategy strategy = findStrategy(url);
  
          if (strategy == null) {
              strategy = findStrategy(url.toLowerCase());
          }
  
          return strategy;
      }
  
      private DownloadStrategy findStrategy(String url) {
          for (final DownloadStrategy downloadStrategy : getDownloadStrategies()) {
              if (downloadStrategy.matches(url)) {
                  return downloadStrategy;
              }
          }
          return null;
      }
  }