package com.mindprod.welcome;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Arrays;
import java.util.HashSet;
/**
 * A persistent cache people who have posted to a given newsgroup.
 * @since 2002 April 20
 */
public class Posters
   {
   /* constructor */
   public Posters( String newsgroup )
      {
      this.newsgroup = newsgroup;
      fireup();
      }
   /**
    * Get list of everyone who has ever posted.
    *
    * @return
    */
   public String[] getAllPosters()
      {
      String[] result = (String[])(cache.toArray(new String[cache.size()]));
      Arrays.sort(result);
      return result;
      }
   private String newsgroup;
   /* allow saving where we are in newsgroup headers as part of serialisation file */
   private long lastHeaderNumber;
   public long getLastHeaderNumber ()
      {
      return this.lastHeaderNumber;
      }
   public void setLastHeaderNumber (long lastHeaderNumber)
      {
      this.lastHeaderNumber = lastHeaderNumber;
      }
   /**
    * collection of people who have posted to a given newsgroup
    * raw names and emails exactly as they posted in FROM: field without any cleanup.
    */
   private HashSet cache;
   /**
    * Has this person posted before?
    *
    * @param name   name/email as appears on FROM: in newsgroup
    *               posting.
    * @return true if has posted in that newsgroup before.
    */
   public boolean hasPostedBefore(String name)
      {
      return cache.contains(name);
      }
   /**
   * Record the fact this person has posted to this newsgroup
   * It is ok to  call hasPosted even if he hasPostedBefore,
   * though doing so is pointless.
   *
   * @param name   name/email as appears on FROM: in newsgroup
   *               posting.
   * @return true if has posted in that newsgroup before.
   */
   public void hasPosted(String name)
      {
      if ( ! cache.contains(name) )
         {
         cache.add(name);
         }
      }
   public void hasBeenRead(long headerNumber)
      {
      if ( headerNumber > lastHeaderNumber )
         {
         lastHeaderNumber = headerNumber;
         }
      }
   /**
    * Called when class is loaded to reconstitute the
    * serialised cache.
    */
   private  void fireup()
      {
      try
         {
         // O P E N
         FileInputStream fis = new FileInputStream(newsgroup+".ser");
         ObjectInputStream ois = new ObjectInputStream(fis);
         // R E A D
         lastHeaderNumber = ((Long)ois.readObject()).longValue();
         cache = (HashSet) ois.readObject();
         // C L O S E
         ois.close();
         }
      catch ( Exception e )
         {
         System.out.println("Troubles restoring the newsgroup.ser file. Not to worry, starting afresh.");
         e.printStackTrace();
         cache = new HashSet(2053, 0.75f);
         lastHeaderNumber = 0;
         }
      } // end fireup
   /**
   * Called to save the cache
   * in serialised form
   * so you won't lose what you have so fare
   */
   public void flush()
      {
      try
         {
         // O P E N
         FileOutputStream fos = new FileOutputStream(newsgroup+".ser", false /* append */);
         ObjectOutputStream oos = new ObjectOutputStream(fos);
         // W R I T E
         oos.writeObject(new Long(lastHeaderNumber));
         oos.writeObject(cache);
         // C L O S E
         oos.close();
         }
      catch ( IOException e )
         {
         System.out.println("Troubles writing out the domaincache.ser file");
         e.printStackTrace();
         }
      }
   /**
    * Called when class is shut down to save the cache
    * in serialised form.
    */
   public  void close()
      {
      flush();
      }  // end close
   }