package org.eclipse.jetty.continuation;
   
   import java.io.IOException;
   import javax.servlet.Filter;
   import javax.servlet.FilterChain;
   import javax.servlet.FilterConfig;
   import javax.servlet.ServletContext;
   import javax.servlet.ServletException;
   import javax.servlet.ServletRequest;
  import javax.servlet.ServletResponse;
  
  
  
  /* ------------------------------------------------------------ */
  /**
   * <p>ContinuationFilter must be applied to servlet paths that make use of
   * the asynchronous features provided by {@link Continuation} APIs, but that
   * are deployed in servlet containers that are neither Jetty (>= 7) nor a
   * compliant Servlet 3.0 container.</p>
   * <p>The following init parameters may be used to configure the filter (these are mostly for testing):</p>
   * <dl>
   * <dt>debug</dt><dd>Boolean controlling debug output</dd>
   * <dt>jetty6</dt><dd>Boolean to force use of Jetty 6 continuations</dd>
   * <dt>faux</dt><dd>Boolean to force use of faux continuations</dd>
   * </dl>
   * <p>If the servlet container is not Jetty (either 6 or 7) nor a Servlet 3
   * container, then "faux" continuations will be used.</p>
   * <p>Faux continuations will just put the thread that called {@link Continuation#suspend()}
   * in wait, and will notify that thread when {@link Continuation#resume()} or
   * {@link Continuation#complete()} is called.</p>
   * <p>Faux continuations are not threadless continuations (they are "faux" - fake - for this reason)
   * and as such they will scale less than proper continuations.</p>
   */
  public class ContinuationFilter implements Filter
  {
      static boolean _initialized;
      static boolean __debug; // shared debug status
      private boolean _faux;
      private boolean _jetty6;
      private boolean _filtered;
      ServletContext _context;
      private boolean _debug;
  
      public void init(FilterConfig filterConfig) throws ServletException
      {
          boolean jetty_7_or_greater="org.eclipse.jetty.servlet".equals(filterConfig.getClass().getPackage().getName());
          _context = filterConfig.getServletContext();
  
          String param=filterConfig.getInitParameter("debug");
          _debug=param!=null&&Boolean.parseBoolean(param);
          if (_debug)
              __debug=true;
  
          param=filterConfig.getInitParameter("jetty6");
          if (param==null)
              param=filterConfig.getInitParameter("partial");
          if (param!=null)
              _jetty6=Boolean.parseBoolean(param);
          else
              _jetty6=ContinuationSupport.__jetty6 && !jetty_7_or_greater;
  
          param=filterConfig.getInitParameter("faux");
          if (param!=null)
              _faux=Boolean.parseBoolean(param);
          else
              _faux=!(jetty_7_or_greater || _jetty6 || _context.getMajorVersion()>=3);
  
          _filtered=_faux||_jetty6;
          if (_debug)
              _context.log("ContinuationFilter "+
                      " jetty="+jetty_7_or_greater+
                      " jetty6="+_jetty6+
                      " faux="+_faux+
                      " filtered="+_filtered+
                      " servlet3="+ContinuationSupport.__servlet3);
          _initialized=true;
      }
  
      public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException
      {
          if (_filtered)
          {
              Continuation c = (Continuation) request.getAttribute(Continuation.ATTRIBUTE);
              FilteredContinuation fc;
              if (_faux && (c==null || !(c instanceof FauxContinuation)))
              {
                  fc = new FauxContinuation(request);
                  request.setAttribute(Continuation.ATTRIBUTE,fc);
              }
              else
                  fc=(FilteredContinuation)c;
  
              boolean complete=false;
              while (!complete)
              {
                  try
                  {
                      if (fc==null || (fc).enter(response))
                          chain.doFilter(request,response);
                 }
                 catch (ContinuationThrowable e)
                 {
                     debug("faux",e);
                 }
                 finally
                 {
                     if (fc==null)
                         fc = (FilteredContinuation) request.getAttribute(Continuation.ATTRIBUTE);
 
                     complete=fc==null || (fc).exit();
                 }
             }
         }
         else
         {
             try
             {
                 chain.doFilter(request,response);
             }
             catch (ContinuationThrowable e)
             {
                 debug("caught",e);
             }
         }
     }
 
     private void debug(String string)
     {
         if (_debug)
         {
             _context.log(string);
         }
     }
 
     private void debug(String string, Throwable th)
     {
         if (_debug)
         {
             if (th instanceof ContinuationThrowable)
                 _context.log(string+":"+th);
             else
                 _context.log(string,th);
         }
     }
 
     public void destroy()
     {
     }
 
     public interface FilteredContinuation extends Continuation
     {
         boolean enter(ServletResponse response);
         boolean exit();
     }
 }