<?php

// ----------------------------------------------------------------------------
//
// ccrotator.class.php - Concurrent Code Rotator class, ver.0.01 (May 17, 2005)
//
// Description:
//   This class allows randomly select one of PHP, HTML or JavaScript code
//   fragments that share same place on the page. It uses special random number
//   generation algorithm which allows to control the frequency and probability
//   of appearance per working cycle.
//
// Author:
//   Vagharshak Tozalakyan <hide@address.com>
//   This module was written by author on his free time.
//
// Warning:
//   This class is non commercial, non professional work. It should not have
//   unexpected results. However, if any damage is caused by this class the
//   author can not be responsible. The use of this class is at the risk of
//   the user.
//
// ----------------------------------------------------------------------------


define ( 'FROM_FILE', TRUE );

class CodeRotator
{


  var $tracker_file;  // The name of a file used to store display counters
  var $codes;  // Array of code fragments
  var $debug_mode; // TRUE if the code runs in debug mode


  /*
    Description:
      Class constructor.
    Prototype:
      void CodeRotator ( string tracker_file )
    Parameters:
      tracker_file -  The name of a file used to store display counters.
  */
  function CodeRotator ( $tracker_file )
  {

    $this->tracker_file = $tracker_file;
    $this->codes = array ( );
    $this->debug_mode = FALSE;

    // Seed the better random number generator for PHP < 4.2.0
    list ( $usec, $sec ) = explode ( ' ', microtime ( ) );
    mt_srand ( ( float ) $sec + ( ( float ) $usec * 100000 ) );

  }


  /*
    Description:
      Adds a new code fragment.
    Prototype:
      void AddCode ( string id, string code, int vpc[, bool from_file] )
    Parameters:
      id - unique identifier of code fragment
      code - code fragment or filename of it
      vpc - max views number per working cycle
      from_file - TRUE if filename specified instead of code
  */
  function AddCode ( $id, $code, $vpc, $from_file = FALSE )
  {

    $this->codes[$id]['code'] = $code;
    $this->codes[$id]['vpc'] = abs ( intval ( $vpc ) );
    $this->codes[$id]['from_file'] = $from_file;

  }


  /*
    Description:
      Selects and shows a code fragment.
    Prototype:
      void ShowCode ( )
  */
  function ShowCode ( )
  {

    $f = fopen ( $this->tracker_file, 'a+' );
    if ( ! $f )
    {
      trigger_error ( 'Failed to open tracker file!', E_USER_WARNING );
      return;
    }

    flock ( $f, LOCK_EX );

    $fsz = filesize ( $this->tracker_file );
    $counters = unserialize ( fread ( $f,  $fsz + 10 ) );
    if ( empty ( $counters ) )
      $counters = array ( );

    foreach ( $this->codes as $id => $code )
    {
      if ( ! isset ( $counters[$id] ) )
      {
        $counters[$id] = 0;
      }
    }

    $tmp = array ( );
    foreach ( $counters as $id => $count )
    {
      if ( $count < $this->codes[$id]['vpc'] )
      {
        $tmp[$id] = 0;
      }
    }

    if ( count ( $tmp ) == 0 )
    {
      foreach ( $counters as $id => $count )
      {
        $counters[$id] = 0;
        $tmp[$id] = 0;
      }
    }

    $s = 0;
    foreach ( $tmp as $id => $freq )
    {
      $s += $this->codes[$id]['vpc'];
    }

    foreach ( $tmp as $id => $freq )
    {
      $tmp[$id] = ceil ( ( $this->codes[$id]['vpc'] * 100 ) / $s );
    }

    $rand = mt_rand ( 0, 100 );

    $s = 0;
    foreach ( $tmp as $id => $freq )
    {
      $s += $freq;
      if ( $rand <  $s )
      {
        $code_id = $id;
        break;
      }
    }

    $counters[$code_id]++;

    ftruncate ( $f, 0 );
    fwrite ( $f, serialize ( $counters ) );

    flock ( $f, LOCK_UN );
    fclose ( $f );

    if ( $this->debug_mode )
    {
      echo '<table align="center" width="60%" border="0" cellspacing="10" ';
      echo 'cellpadding="0" bgcolor="#f0f0ff"><tr><td align="center">';
      echo '<b>Rough probability:</b><br />';
      foreach ( $tmp as $id => $freq )
      {
        echo "$id = $freq% <br />";
      }
      echo '<br /><b>Counters:</b><br />';
      foreach ( $counters as $id => $count )
      {
        echo "$id = $count <br />";
      }
      echo '</td></tr></table>';
    }

    if ( $this->codes[$code_id]['from_file'] == TRUE )
    {
      include $this->codes[$code_id]['code'];
    }
    else
    {
      echo $this->codes[$code_id]['code'];
    }

  }

}


/*
$ccr = new CodeRotator ( 'tracker' );
$ccr->AddCode ( 'b1', 'code1', 2, FALSE );
$ccr->AddCode ( 'b2', 'code2', 5, FALSE );
$ccr->AddCode ( 'b3', 'code3', 7, FALSE );
$ccr->AddCode ( 'b4', 'code4', 3, FALSE );
$ccr->AddCode ( 'b5', 'includes/code5.txt', 3, TRUE );
$ccr->debug_mode = TRUE;
$ccr->ShowCode ( );
*/

?>