/**
 * GuestbookDatabase.java
 * Pete Willemsen
 * CoolServlets.com
 * February 3, 2000
 * Version 1.0.3
 *
 * Any errors or feature requests can be reported on CoolServlets.com.
 * We hope you enjoy this program!
 *
 *    Copyright (C) 2000  Pete Willemsen
 *
 *    This program 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 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program 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 this program; if not, write to the Free Software
 *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package com.coolservlets.guestbook;

import java.io.*;
import java.util.*;

public class GuestbookDatabase implements Serializable {

    public GuestbookDatabase() {
	_database = new Hashtable();
    }

    /** 
     * Add a Guestbook entry to the database specified by key.  If
     * no "key" exists, a new entry will be created.  Note that
     * the hashtable stores a vector of Guestbook entries
     * at each entry. */
    public void addEntry( String key, GuestbookEntry e ) {

	if (_database.containsKey( key )) {
	    
	    // just lookup the key in the hash table and add the
	    // guestbook entry to the vector

	    Vector entry_vector = (Vector)_database.get( key );
	    
	    // Add a guestbook entry to the end of the vector.
	    // Presumably (unless I don't understand Java), this is
	    // faster than adding it to the beginning of the vector
	    // which if it happens would generally require that all
	    // items with greater index be copied.
	    entry_vector.addElement( e );

	}
	else {
	    
	    // add this key to the hashtable and create a new vector
	    // of guestbook entries for that key
	    Vector entry_vector = new Vector();
	    
	    // Add a guestbook entry to the end of the vector.
	    // Presumably (unless I don't understand Java), this is
	    // faster than adding it to the beginning of the vector
	    // which if it happens would generally require that all
	    // items with greater index be copied.
	    entry_vector.addElement( e );

	    _database.put( key, entry_vector );
	    
	}
	    
    }

    public GuestbookEntry getEntry( String key, int idx  ) {
	
	Vector entry_vector;

	// First, look up the guestbookentry vector from the hashtable
	if (_database.containsKey( key )) { 
	    entry_vector = (Vector)_database.get( key );
	}
	else {
	    // key does not exist in hashtable, so return null
	    return null;
	}

	// Now, it is necessary that guestbook entries be treated such
	// that database[0] is the most recent entry.  Since I append
	// entries onto the vector (for speed), re-map the indices to
	// achieve the correct order.

	if (idx >= 0 && idx < entry_vector.size()) {
	    int remap_idx = (entry_vector.size() - 1) - idx;
	    return (GuestbookEntry)entry_vector.elementAt( remap_idx );
	}
	else {
	    // should I really throw out of range exception, but until
	    // then, return null
	    return null;
	}
    }

    public int size( String key ) {
	Vector entry_vector;

	// Look up the guestbookentry vector from the hashtable and
	// return the size if found
	if (_database.containsKey( key )) {
	    entry_vector = (Vector)_database.get( key );
	    return entry_vector.size();
	}
	else 
	    return 0;
    }
    
    private Hashtable _database;
}