<?php
// CRON_FUNCTIONS.PHP (functions for the cron script)

/**
 * Updates the nextrun field of a cron task, calculating what the
 * next execution of the task would be based on the other fields.
 * 
 * @param int - ID of the cron task to update
 * @param array - Optional array of cron task data from the database
 *                result. Will be queried for otherwise.
 * @return int - Timestamp of the next cron run
 */
function cron_update($cronid, $cronstuff = null)
{
    $cronid = intval($cronid);
    if (!is_array($cronstuff))
    {
        $cronstuff = mysql_fetch_assoc(mysql_query("
            SELECT * FROM cron
            WHERE cronid = " . $cronid
        ));
    }

    $minutenow  = date('i', TIME);
    $hournow    = date('H', TIME);
    $daynow     = date('d', TIME);
    $monthnow   = date('m', TIME);
    $yearnow    = date('Y', TIME);
    $weekdaynow = date('w', TIME);

    // calculate the next two times to run this task in the future
    if ($cronstuff['weekday'] == -1)
    {
        if ($cronstuff['day'] == -1)
        {
            $firstday = $daynow;
            $secondday = $daynow + 1;
        }
        else
        { // specific day of month
            $firstday = $cronstuff['day'];
            // same plus the number of days in this month
            $secondday = $cronstuff['day'] + date('t', TIME);
        }
    }
    else
    { // specific weekday
        $firstday = $daynow + ($cronstuff['weekday'] - $weekdaynow);
        $secondday = $firstday + 7;
    }
    
    if ($firstday < $daynow)
    { // this has passed, so use the day after that
        $firstday = $secondday;
    }
    
    // check if the next run is supposed to happen today
    if ($firstday == $daynow)
    {
        // see if possible to run this task today
        $todaytime = cron_next_run($cronstuff);
        
        if ($todaytime['hour'] == -1 && $todaytime['minute'] == -1)
        {
            // can't run it today
            $cronstuff['day'] = $secondday;
            
            $newtime = cron_next_run($cronstuff, 0, -1);
            $cronstuff['hour'] = $newtime['hour'];
            $cronstuff['minute'] = $newtime['minute'];
        }
        else
        {
            // it's ok, will be run today
            $cronstuff['day'] = $firstday;
            $cronstuff['hour'] = $todaytime['hour'];
            $cronstuff['minute'] = $todaytime['minute'];
        }
    }
    else
    {
        $cronstuff['day'] = $firstday;
        
        // work out first run time that day
        $newtime = cron_next_run($cronstuff, 0, -1);
        
        $cronstuff['hour'] = $newtime['hour'];
        $cronstuff['minute'] = $newtime['minute'];
    }
    
    // generate a timestamp for the next run from this information
    $nextrun = mktime(
        $cronstuff['hour'],
        $cronstuff['minute'],
        0,
        $monthnow,
        $cronstuff['day'],
        $yearnow
    );

    // update the cron database entry - again, run your own code here if
    // you don't use a MySQL database
    mysql_query("
        UPDATE cron SET nextrun = '" . $nextrun . "'
        WHERE cronid = '" . $cronid . "' 
            AND nextrun = '" . $cronstuff['nextrun'] . "'
    ");
    
    if (mysql_affected_rows() > 0) { return $nextrun; }
    else { return 0; }
}

/**
 * Calculates the next task run time today after a specified hour and minute.
 * 
 * @param array - Array of the cron task data from the database result.
 * @param int - Hour (-2 for current hour, -1 for every hour)
 * @param int - Minute (-2 for current minute, -1 for every minute)
 */
function cron_next_run($cronstuff, $hour = -2, $minute = -2)
{
    if ($hour == -2) { $hour = date('H', TIME); }
    if ($minute == -2) { $minute = date('i', TIME); }
    
    // allow the minute value to be a serialized array, to execute tasks
    // on more than one occasion during an hour (e.g. every 15 mins)
    if (!is_numeric($cronstuff['minute']))
    {
        $cronstuff['minute'] = unserialize($cronstuff['minute']);
    }
    else
    {
        $cronstuff['minute'] = array(0 => $cronstuff['minute']);
    }
    
    // every hour and minute
    if ($cronstuff['hour'] == -1 && $cronstuff['minute'][0] == -1)
    {
        $newstuff['hour'] = $hour;
        $newstuff['minute'] = $minute + 1;
    }
    
    // every hour, specific minutes
    elseif ($cronstuff['hour'] == -1 && $cronstuff['minute'][0] != -1)
    {
        $newstuff['hour'] = $hour;
        $nextminute = cron_next_minute($cronstuff['minute'], $minute);
        if ($nextminute === false)
        { // impossible to do this hour, skip to the next
            ++$newstuff['hour'];
            $nextminute = $cronstuff['minute'][0];
        }
        $newstuff['minute'] = $nextminute;
    }
    
    // every minute during some hours
    elseif ($cronstuff['hour'] != -1 && $cronstuff['minute'][0] == -1)
    {
        if ($cronstuff['hour'] < $hour)
        { // too late to run the task today
            $newstuff['hour'] = -1;
            $newstuff['minute'] = -1;
        }
        elseif ($cronstuff['hour'] == $hour)
        { // this hour
            $newstuff['hour'] = $cronstuff['hour'];
            $newstuff['minute'] = $minute + 1;
        }
        else
        { // some time in future, schedule check at 0th minute
            $newstuff['hour'] = $cronstuff['hour'];
            $newstuff['minute'] = 0;
        }
    }
    
    // some other time
    elseif ($cronstuff['hour'] != -1 && $cronstuff['minute'][0] != -1)
    {
        $nextminute = fetch_next_minute($cronstuff['minute'], $minute);
		
        if ($cronstuff['hour'] < $hour ||
          ($cronstuff['hour'] == $hour && $nextminute === false)
        )
        { // it's not going to run today
            $newstuff['hour'] = -1;
            $newstuff['minute'] = -1;
        }
        else
        {
            $newstuff['hour'] = $cronstuff['hour'];
            $newstuff['minute'] = $nextminute;
        }
    }
    return $newstuff;
}

/**
 * Loops through an array of numbers and returns the first number
 * greater than the second parameter.
 *
 * @param array - An array of numerical values
 * @param int - A number to compare against the array values
 * @return int - First greater number found
 */
function cron_next_minute($minutearray, $minute)
{
    foreach ($minutearray as $nextminute)
    {
        if ($nextminute > $minute)
        {
            return $nextminute;
        }
    }
    return false;
}

?>