<?php

/**
 * 计划任务
 */
namespace Common\Server;

class CrontabServer {
   /**
     *  Finds next execution time(stamp) parsin crontab syntax, 
     *  after given starting timestamp (or current time if ommited)
     * 
     *  @param string $_cron_string:
     *
     *      0     1    2    3    4
     *      *     *    *    *    *  
     *      -     -    -    -    -
     *      |     |    |    |    |
     *      |     |    |    |    +----- day of week (0 - 6) (Sunday=0)
     *      |     |    |    +------- month (1 - 12)
     *      |     |    +--------- day of month (1 - 31)
     *      |     +----------- hour (0 - 23)
     *      +------------- min (0 - 59)
     *  @param int $_after_timestamp timestamp [default=current timestamp]
     *  @return int unix timestamp - next execution time will be greater 
     *              than given timestamp (defaults to the current timestamp)
     *  @throws InvalidArgumentException 
     */
    public static function parse($_cron_string,$_after_timestamp=null)
    {
        if(!preg_match('/^((\*(\/[0-9]+)?)|[0-9\-\,\/]+)\s+((\*(\/[0-9]+)?)|[0-9\-\,\/]+)\s+((\*(\/[0-9]+)?)|[0-9\-\,\/]+)\s+((\*(\/[0-9]+)?)|[0-9\-\,\/]+)\s+((\*(\/[0-9]+)?)|[0-9\-\,\/]+)$/i',trim($_cron_string))){
            return("Invalid cron string: ".$_cron_string);
        }
        if($_after_timestamp && !is_numeric($_after_timestamp)){
            return("\$_after_timestamp must be a valid unix timestamp ($_after_timestamp given)");
        }
        $cron   = preg_split("/[\s]+/i",trim($_cron_string));
        $start  = empty($_after_timestamp)?time():$_after_timestamp;
        $date   = array(    'minutes'   =>self::_parseCronNumbers($cron[0],0,59),
                            'hours'     =>self::_parseCronNumbers($cron[1],0,23),
                            'dom'       =>self::_parseCronNumbers($cron[2],1,31),
                            'month'     =>self::_parseCronNumbers($cron[3],1,12),
                            'dow'       =>self::_parseCronNumbers($cron[4],0,6),
                        );
        // limited to time()+366 - no need to check more than 1year ahead
        for($i=0;$i<=60*60*24*366;$i+=60){
            if( in_array(intval(date('j',$start+$i)),$date['dom']) &&
                in_array(intval(date('n',$start+$i)),$date['month']) &&
                in_array(intval(date('w',$start+$i)),$date['dow']) &&
                in_array(intval(date('G',$start+$i)),$date['hours']) &&
                in_array(intval(date('i',$start+$i)),$date['minutes'])
                ){
                    return $start+$i;
            }
        }
        return null;
    }
    /**
     * get a single cron style notation and parse it into numeric value
     *
     * @param string $s cron string element
     * @param int $min minimum possible value
     * @param int $max maximum possible value
     * @return int parsed number 
     */
    protected static function _parseCronNumbers($s,$min,$max)
    {
        $result = array();
        $v = explode(',',$s);
        foreach($v as $vv){
            $vvv  = explode('/',$vv);
            $step = empty($vvv[1])?1:$vvv[1];
            $vvvv = explode('-',$vvv[0]);
            $_min = count($vvvv)==2?$vvvv[0]:($vvv[0]=='*'?$min:$vvv[0]);
            $_max = count($vvvv)==2?$vvvv[1]:($vvv[0]=='*'?$max:$vvv[0]);
            for($i=$_min;$i<=$_max;$i+=$step){
                $result[$i]=intval($i);
            }
        }
        ksort($result);
        return $result;
    }    
}