<?php

class CronExp {
	public function match($expression, $time = NULL){
		if(empty($time)){
			$time = time() - time() % 60; // rounded to current minute
		}elseif(is_string($time)){
			$time = strtotime($time);
		}

		$tmp = self::replaceSpecialStrings($expression);
		if($tmp){
			$expression = $tmp;
		}

		$cronpart = self::checkValid($expression);
		if(!$cronpart){
			return FALSE;
		}

		$procs = [
			['i', 0, 59],
			['G', 0, 23],
			['j', 0, 31],
			['n', 1, 12],
			['w', 0, 6]
		];

		foreach($cronpart as $i => $match){
			foreach(explode(",", $match) as $expr){
				if(!self::checkCronParam(
					$expr, $time,
					$procs[$i][0], $procs[$i][1], $procs[$i][2])
				){
					return FALSE;
				}
			}
		}
		return TRUE;
	}

	private function replaceSpecialStrings($expression){
		$strings = [
			'yearly'   => '0 0 1 1 *',
			'annually' => '0 0 1 1 *',
			'monthly'  => '0 0 1 * *',
			'weekly'   => '0 0 * * 0',
			'daily'    => '0 0 * * *',
			'midnight' => '0 0 * * *',
			'hourly'   => '0 * * * *'
		];

		$expression = str_replace("@", "", $expression);
		if(array_key_exists($expression, $strings)){
			return $strings[$expression];
		}
		return FALSE;
	}

	public function checkValid($expression){
		$r = preg_match_all('/(([*\-\,\/\d]+)(\s+|$))/', $expression, $matches, PREG_PATTERN_ORDER);
		// If not 5 matches, not valid cron.
		if($r != 5){ return FALSE; }
		return $matches[2];
	}

	private function checkCronParam($expr, $time, $datesel, $mmin, $mmax){
		$dmatch = (int) date($datesel, $time);

		if(in_array($expr, ['*', '*/1'])){ return TRUE; }
		if(is_numeric($expr)){
			return ( (int) $expr == $dmatch );
		}
		if(preg_match('/^\*\/(\d{1,2})$/', $expr, $matches)){
			// Data 00 always match.
			if($dmatch === 0){ return TRUE; }
			return ($dmatch % (int) $matches[1] == 0);
		}elseif(preg_match('/^(\d{1,2})-(\d{1,2})$/', $expr, $matches)){
			$min = (int) $matches[1];
			$max = (int) $matches[2];
			// Not match if invalid.
			if(
				$min > $max or
				$min < $mmin or
				$max > $mmax
			){ return FALSE; }

			return ($dmatch >= $min and $dmatch <= $max);
		}

		// Others or not meeting get FALSE.
		return FALSE;
	}
}

?>