package org.paneris.bibliomania.metasearch.bob;
   
   import java.io.FileOutputStream;
   import java.io.IOException;
   import java.io.OutputStream;
   import java.net.URL;
   
   import org.apache.oro.text.regex.MalformedPatternException;
   import org.apache.oro.text.regex.Perl5Compiler;
  import org.apache.oro.text.regex.Perl5Matcher;
  import org.apache.oro.text.regex.Perl5Pattern;
  import org.apache.oro.text.regex.StringSubstitution;
  import org.apache.oro.text.regex.Util;
  import org.melati.util.IoUtils;
  import org.melati.util.MelatiRuntimeException;
  import org.melati.util.UnexpectedExceptionException;
  import org.paneris.bibliomania.metasearch.util.HackParser;
  import org.paneris.bibliomania.metasearch.util.TimeoutThread;
  
  public class Session {
    public static final String frontPageURL =
      "http://bookshop.blackwell.co.uk/cgi-bin/BOB2?BV_Operation=Dyn_LoginReceive&BV_ServiceName=BOB&form%25login_type=guest&form%25failure=/service_error.html&form%25success=/bob/bob_main.html.tmpl";
  
    public String sessionID, engineID;
  
    public Session(String sessionID, String engineID) {
      this.sessionID = sessionID;
      this.engineID = engineID;
    }
  
    public String queryParams() {
      return "BV_SessionID=" + sessionID + "&BV_EngineID=" + engineID;
    }
  
    public String toString() {
      return queryParams();
    }
  
    private static final Object bobSessionMon = new Object();
  
    private static Session bobSession = null;
  
    private static Exception bobSessionException = null;
  
    public static class NoSessionIDException extends MelatiRuntimeException {
      /**
       * 
       */
      private static final long serialVersionUID = 1L;
  
      public String getMessage() {
        return "Couldn't extract session ID from front page";
      }
    }
  
    private static void newSession() throws OpenException {
      System.err.println("BOB: establishing new session");
      try {
        TimeoutThread timeout = TimeoutThread.forCurrentThread(20000);
        try {
          FrontPage fp =
            new FrontPage(IoUtils.slurp(new URL(frontPageURL), 32768));
          if (fp.sessionID == null)
            throw new NoSessionIDException();
  
          bobSession = new Session(fp.sessionID, fp.engineID);
          bobSessionException = null;
        } finally {
          timeout.stop();
        }
      } catch (Exception e) {
        bobSessionException = e;
        throw new OpenException(e);
      }
    }
  
    private static class SessionRenewer extends Thread {
      public SessionRenewer() {
        setDaemon(true);
      }
  
      public void run() {
        try {
          for (;;) {
            try {
              newSession();
            } catch (Exception e) {
              System.err.println("BOB SessionRenewer:");
              e.printStackTrace();
            } finally {
              synchronized (bobSessionMon) {
                bobSessionMon.notifyAll();
              }
            }
  
            Thread.sleep(5 * 60 * 1000);
          }
        } catch (InterruptedException e) {
        } finally {
         sessionRenewer = null;
       }
     }
   }
 
   private static SessionRenewer sessionRenewer = null;
 
   private static synchronized void checkSessionRenewer() {
     if (sessionRenewer == null)
        (sessionRenewer = new SessionRenewer()).start();
   }
 
   static Session bobSession() {
     checkSessionRenewer();
 
     if (bobSession == null) {
       try {
         synchronized (bobSessionMon) {
           if (bobSession == null)
             bobSessionMon.wait();
         }
       } catch (InterruptedException e) {
         throw new OpenException(e);
       }
     }
 
     if (bobSession == null)
       throw new OpenException(bobSessionException);
 
     return bobSession;
   }
 
   private static Perl5Pattern bv__IDParam;
 
   static {
     try {
       bv__IDParam =
         (Perl5Pattern) (new Perl5Compiler()).compile(
           "BV_(Session|Engine)ID=[^&]*&?",
           0);
     } catch (MalformedPatternException e) {
       throw new UnexpectedExceptionException(e);
     }
   }
 
   private static final StringSubstitution empty = new StringSubstitution();
 
   public static String urlInCurrentSession(String url) {
     String urlWithoutSession =
       Util.substitute(
         new Perl5Matcher(),
         bv__IDParam,
         empty,
         url,
         Util.SUBSTITUTE_ALL);
 
     return urlWithoutSession + '&' + bobSession().queryParams();
   }
 
   private static String contentDumpPrefix = null;
   private static int contentDumpIndex = 0;
 
   private static byte[] contentUsingCurrentSession(
     String url,
     int estimate,
     int limit)
     throws IOException {
     byte[] content = IoUtils.slurp(new URL(urlInCurrentSession(url)), 32768);
 
     String dp = contentDumpPrefix;
     if (dp != null) {
       try {
         OutputStream o =
           new FileOutputStream(contentDumpPrefix + contentDumpIndex++ +".html");
         try {
           o.write(content);
         } finally {
           try {
             o.close();
           } catch (IOException e) {
           }
         }
       } catch (Exception e) {
         System.err.println("Can't write dump!");
       }
     }
 
     return content;
   }
 
   private static final byte[] timeoutExplan =
     "current session timing out".getBytes();
 
   public static byte[] content(String url, int estimate, int limit)
     throws IOException {
     byte[] it = contentUsingCurrentSession(url, estimate, limit);
     if (HackParser.indexOf(it, timeoutExplan) != -1) {
       newSession();
       return contentUsingCurrentSession(url, estimate, limit);
     } else
       return it;
   }
 }