<?php
/*

	© Copyright 2007 Ben Boyter (http://www.boyter.org)

	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 3 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, see <http://www.gnu.org/licenses/>.
    
*/


class spamchecker {

	/**
	 * Trains the spam checker on the given text. It allows you to train on either spam or ham.
	 * @param text the test to train the filter on
	 * @param boolen value, true if the text is spam, false if it is ham
	 */
	function train($text,$spam) {
		
		$result = mysql_query('SELECT totalsid, totalspam, totalham FROM totals');
			
		while ($line = mysql_fetch_array($result)) {
			$totalsid 	= $line[0];
			$totalspam 	= $line[1];
			$totalham 	= $line[2];
		}
			
		if($spam) {
			$totalspam++;
			mysql_query("UPDATE `totals` SET `totalspam` = '".$totalspam."' WHERE `totalsid` =1 LIMIT 1");
		}
		else {
			$totalham++;
			mysql_query("UPDATE `totals` SET `totalham` = '".$totalham."' WHERE `totalsid` =1 LIMIT 1");
		}
			
		$text = str_replace('"','',str_replace(',','',str_replace('.','',strtolower(strip_tags(trim($text))))));
		$temparray = explode(' ',$text);
			
		foreach ($temparray as $token) {
			$token = trim($token);
				
			$result = mysql_query('SELECT spamid FROM spam WHERE token="'.$token.'"');
				
			while ($line = mysql_fetch_array($result)) {
				$spamid = $line[0];
			}
				
			if(mysql_num_rows($result) == 1) {
						
				if($spam) {
					$result2 = mysql_query('SELECT token,spamcount,hamcount FROM spam WHERE spamid='.$spamid);
					while ($line = mysql_fetch_array($result2)) {
						$token = $line[0];
						$spamcount = $line[1];
						$hamcount = $line[2];
							
						$spamcount++;
						$spamrating = 0.4;
							
						// Work out spam rating
						if($totalham != 0 && $totalspam !=0) {
							$hamprob = $hamcount/$totalham;
							$spamprob = $spamcount/$totalspam;
							
							$spamrating = $spamprob/($hamprob+$spamprob);
								
							if($hamcount == 0){
								$spamrating = 1;
							}
								
						}

						mysql_query("UPDATE `spam` SET `spamcount` = '".$spamcount."', `spamrating`='".$spamrating."' WHERE `spamid` =".$spamid." LIMIT 1");
					}
				}
				else {
					$result2 = mysql_query('SELECT token,spamcount,hamcount FROM spam WHERE spamid='.$spamid.' LIMIT 0,1');
					while ($line = mysql_fetch_array($result2)) {
						$token = $line[0];
						$spamcount = $line[1];
						$hamcount = $line[2];
							
						$hamcount++;
							
						//work out spam rating
						if($totalham != 0 && $totalspam !=0) {
							$hamprob = $hamcount/$totalham;
							$spamprob = $spamcount/$totalspam;
							
							$spamrating = $spamprob/($hamprob+$spamprob);
								
							if($spamcount == 0){
								$spamrating = 0;
							}
						}
							
						mysql_query("UPDATE `spam` SET `hamcount` = '".$hamcount."', `spamrating`='".$spamrating."' WHERE `spamid` =".$spamid." LIMIT 1");
						
							
					}
						
				}
			}
			else { // not in the database
				
				if($spam) {
					mysql_query("INSERT INTO `spam` ( `spamid` , `token` , `spamcount` , `hamcount` , `spamrating` ) VALUES ( NULL , '".$token."', '1', '0', '1')");
				}
				else {
					mysql_query("INSERT INTO `spam` ( `spamid` , `token` , `spamcount` , `hamcount` , `spamrating` ) VALUES ( NULL , '".$token."', '0', '1', '0')");
				}
			}
		}
		
	}

	
	/**
	 * Checks the given text and returns a value from 0 to 1 indicating spamicty level.
	 * @param text to test if it is spam or not
	 * @return double from 0 to 1
	 */
	function checkSpam($text) {
		$text = str_replace('"','',str_replace(',','',str_replace('.','',strtolower(strip_tags(trim($text))))));
		$temparray = explode(' ',$text);
		
		$spamratings = array();
		$count = 0;		
		
		foreach ($temparray as $token) {
			$result = mysql_query('SELECT spamrating FROM spam WHERE token="'.$token.'"');
			while ($line = mysql_fetch_array($result)) {
				
				$spamratings[$count]=$line[0];
			}
			
			if(mysql_num_rows($result) == 0) {
				$spamratings[$count]='0.4';
			}		
			$count++;
		}
		
		$a = null;
		$b = null;
	
		
		foreach ($spamratings as $token) {
			if($a == null)
				$a = (double)$token;
			else
				$a = $a * $token;	
			
			if($b == null)
				$b = 1-(double)$token;
			else
				$b = $b * (1-(double)$token);			
			
		}
	
		$spam = $a/($a+$b);
		
		return $spam;	
	}
	
	/**
	 * Resets the spam filter. This will then require a full retrain to identify spam.
	 */
	function resetSpam() {
		mysql_query("UPDATE `totals` SET `totalspam` = '0',`totalham` = '0' WHERE `totalsid` =1 LIMIT 1;");
		mysql_query("TRUNCATE TABLE `spam`;");
	}
	

}
	
?>