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 been sent a message, any newsgroup.
 * @since 2002-05-3
 */
public class Informed
   {
   /**
    * constructor
    *
    * @param group  name of newsgroup collection e.g.
    *               comp.lang.java to handle comp.lang.java.help
    *               and comp.lang.java.programmer.
    */
   public Informed( String group )
      {
      this.group = group;
      fireup();
      }
   /**
    * name of newsgroup collection e.g.
    * comp.lang.java to handle comp.lang.java.help
    * and comp.lang.java.programmer.
    */
   private String group;
   /**
    * Get list of everyone who has ever posted.
    *
    * @return
    */
   public String[] getAllPeople()
      {
      String[] result = (String[])(cache.toArray(new String[cache.size()]));
      Arrays.sort(result);
      return result;
      }
   /**
    * collection of people who been informed already.
    * cleaned up email address, unlike Poster class.
    */
   private HashSet cache;
   /**
    * Has this person posted before?
    *
    * @param   email email address cleaned up
    *
    * @return true if person has been informed before.
    */
   public boolean wasInformed(String email)
      {
      return cache.contains(email);
      }
   /**
   * 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 email  email address cleaned up
   *
   * @return true if has posted in that newsgroup before.
   */
   public void markInformed(String email)
      {
      if ( ! cache.contains(email) )
         {
         cache.add(email);
         }
      }
   /**
    * Called when class is loaded to reconstitute the
    * serialised cache.
    */
   private  void fireup()
      {
      try
         {
         // O P E N
         FileInputStream fis = new FileInputStream(group+".group.ser");
         ObjectInputStream ois = new ObjectInputStream(fis);
         // R E A D
         cache = (HashSet) ois.readObject();
         // C L O S E
         ois.close();
         }
      catch ( Exception e )
         {
         System.out.println("Troubles restoring the group.ser file. Not to worry, starting afresh.");
         e.printStackTrace();
         cache = new HashSet(2053, 0.75f);
         }
      } // 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(group+".group.ser", false /* append */);
         ObjectOutputStream oos = new ObjectOutputStream(fos);
         // W R I T E
         oos.writeObject(cache);
         // C L O S E
         oos.close();
         }
      catch ( IOException e )
         {
         System.out.println("Troubles writing out the group.ser file");
         e.printStackTrace();
         }
      }
   /**
    * Called when class is shut down to save the cache
    * in serialised form.
    */
   public  void close()
      {
      flush();
      }  // end close
   }