content: /*
   This file is part of Airsonic.
  
   Airsonic is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
  
   Airsonic is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
  
   You should have received a copy of the GNU General Public License
   along with Airsonic.  If not, see <http://www.gnu.org/licenses/>.
  
   Copyright 2016 (C) Airsonic Authors
   Based upon Subsonic, Copyright 2009 (C) Sindre Mehus
   */
  package org.airsonic.player.filter;
  
  import org.airsonic.player.service.SettingsService;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import javax.servlet.*;
  import javax.servlet.http.HttpServletRequest;
  
  import java.io.File;
  import java.io.IOException;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  /**
   * This filter is executed very early in the filter chain. It verifies that
   * the Airsonic home directory (c:\airsonic or /var/airsonic) exists and
   * is writable. If not, a proper error message is given to the user.
   * <p/>
   * (The Airsonic home directory is usually created automatically, but a common
   * problem on Linux is that the Tomcat user does not have the necessary
   * privileges).
   *
   * @author Sindre Mehus
   */
  public class BootstrapVerificationFilter implements Filter {
  
      private static final Logger LOG = LoggerFactory.getLogger(BootstrapVerificationFilter.class);
      private boolean airsonicHomeVerified = false;
      private final AtomicBoolean serverInfoLogged = new AtomicBoolean();
  
      public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
              throws IOException, ServletException {
  
          // Already verified?
          if (airsonicHomeVerified) {
              chain.doFilter(req, res);
              return;
          }
  
          File home = SettingsService.getAirsonicHome();
          if (!directoryExists(home)) {
              error(res, "<p>The directory <b>" + home + "</b> does not exist. Please create it and make it writable, " +
                         "then restart the servlet container.</p>" +
                         "<p>(You can override the directory location by specifying -Dairsonic.home=... when " +
                         "starting the servlet container.)</p>");
  
          } else if (!directoryWritable(home)) {
              error(res, "<p>The directory <b>" + home + "</b> is not writable. Please change file permissions, " +
                         "then restart the servlet container.</p>" +
                         "<p>(You can override the directory location by specifying -Dairsonic.home=... when " +
                         "starting the servlet container.)</p>");
  
          } else {
              airsonicHomeVerified = true;
              logServerInfo(req);
              chain.doFilter(req, res);
          }
      }
  
      private void logServerInfo(ServletRequest req) {
          if (!serverInfoLogged.getAndSet(true) && req instanceof HttpServletRequest) {
              String serverInfo = ((HttpServletRequest) req).getSession().getServletContext().getServerInfo();
              LOG.info("Servlet container: " + serverInfo);
          }
      }
  
      private boolean directoryExists(File dir) {
          return dir.exists() && dir.isDirectory();
      }
  
      private boolean directoryWritable(File dir) {
          try {
              File tempFile = File.createTempFile("test", null, dir);
              return tempFile.delete();
          } catch (IOException x) {
              return false;
          }
      }
  
      private void error(ServletResponse res, String error) throws IOException {
          ServletOutputStream out = res.getOutputStream();
          out.println("<html>" +
                      "<head><title>Airsonic Error</title></head>" +
                      "<body>" +
                      "<h2>Airsonic Error</h2>" +
                      error +
                      "</body>" +
                      "</html>");
      }
  
      public void init(FilterConfig filterConfig) {
      }
  
      public void destroy() {
      }
  }
  