<?php

/**
 * @file
 * JobSchedulerCronTab class.
 */

/**
 * Jose's cron tab parser = Better try only simple crontab strings.
 *
 * Usage:
 *   // Run 23 minutes after midn, 2am, 4am ..., everyday
 *   $crontab = new JobSchedulerCronTab('23 0-23/2 * * *');
 *   // When this needs to run next, from current time?
 *   $next_time = $crontab->nextTime(time());
 *
 * I hate Sundays.
 */
class JobSchedulerCronTab {
  // Original crontab elements
  public $crontab;
  // Parsed numeric values indexed by type
  public $cron;

  /**
   * Constructor
   *
   * About crontab strings, see all about possible formats
   * http://linux.die.net/man/5/crontab
   *
   * @param $crontab string
   *   Crontab text line: minute hour day-of-month month day-of-week
   */
  public function __construct($crontab) {
    $this->crontab = $crontab;
    $this->cron = is_array($crontab) ? $this->values($crontab) : $this->parse($crontab);
  }

  /**
   * Parse full crontab string into an array of type => values
   *
   * Note this one is static and can be used to validate values
   */
  public static function parse($crontab) {
    // Crontab elements, names match PHP date indexes (getdate)
    $keys = array('minutes', 'hours', 'mday', 'mon', 'wday');
    // Replace multiple spaces by single space
    $crontab = preg_replace('/(\s+)/', ' ', $crontab);
    // Expand into elements and parse all
    $values = explode(' ', trim($crontab));
    return self::values($values);
  }

  /**
   * Parse array of values, check whether this is valid
   */
  public static function values($array) {
    if (count($array) == 5) {
      $values = array_combine(array('minutes', 'hours', 'mday', 'mon', 'wday'), array_map('trim', $array));
      $elements = array();
      foreach ($values as $type => $string) {
        $elements[$type] = self::parseElement($type, $string, TRUE);
      }
      // Return only if we have the right number of elements
      // Dangerous means works running every second or things like that.
      if (count(array_filter($elements)) == 5) {
        return $elements;
      }
    }
    return NULL;
  }

  /**
   * Find the next occurrence within the next year as unix timestamp
   *
   * @param $start_time timestamp
   *   Starting time
   */
  public function nextTime($start_time = NULL, $limit = 366) {
    $start_time = isset($start_time) ? $start_time : time();
    $start_date = getdate($start_time); // Get minutes, hours, mday, wday, mon, year
    if ($date = $this->nextDate($start_date, $limit)) {
      return mktime($date['hours'], $date['minutes'], 0, $date['mon'], $date['mday'], $date['year']);
    }
    else {
      return 0;
    }
  }

  /**
   * Find the next occurrence within the next year as a date array,
   *
   * @see getdate()
   *
   * @param $date
   *   Date array with: 'mday', 'mon', 'year', 'hours', 'minutes'
   */
  public function nextDate($date, $limit = 366) {
    $date['seconds'] = 0;
    // It is possible that the current date doesn't match
    if ($this->checkDay($date) && ($nextdate = $this->nextHour($date))) {
      return $nextdate;
    }
    elseif ($nextdate = $this->nextDay($date, $limit)) {
      return $nextdate;
    }
    else {
      return FALSE;
    }
  }

  /**
   * Check whether date's day is a valid one
   */
  protected function checkDay($date) {
    foreach (array('wday', 'mday', 'mon') as $key) {
      if (!in_array($date[$key], $this->cron[$key])) {
        return FALSE;
      }
    }
    return TRUE;
  }

  /**
   * Find the next day from date that matches with cron parameters
   *
   * Maybe it's possible that it's within the next years, maybe no day of a year matches all conditions.
   * However, to prevent infinite loops we restrict it to the next year.
   */
  protected function nextDay($date, $limit = 366) {
    $i = 0; // Safety check, we love infinite loops...
    while ($i++ <= $limit) {
      // This should fix values out of range, like month > 12, day > 31....
      // So we can trust we get the next valid day, can't we?
      $time = mktime(0, 0, 0, $date['mon'], $date['mday'] + 1, $date['year']);
      $date = getdate($time);
      if ($this->checkDay($date)) {
        $date['hours'] = reset($this->cron['hours']);
        $date['minutes'] = reset($this->cron['minutes']);
        return $date;
      }
    }
  }
  /**
   * Find the next available hour within the same day
   */
  protected function nextHour($date) {
    $cron = $this->cron;
    while ($cron['hours']) {
      $hour = array_shift($cron['hours']);
      // Current hour; next minute.
      if ($date['hours'] == $hour) {
        foreach ($cron['minutes'] as $minute) {
          if ($date['minutes'] < $minute) {
            $date['hours'] = $hour;
            $date['minutes'] = $minute;
            return $date;
          }
        }
      }
      // Next hour; first avaiable minute.
      elseif ($date['hours'] < $hour) {
        $date['hours'] = $hour;
        $date['minutes'] = reset($cron['minutes']);
        return $date;
      }
    }
    return FALSE;
  }

  /**
   * Parse each text element. Recursive up to some point...
   */
  protected static function parseElement($type, $string, $translate = FALSE) {
    $string = trim($string);
    if ($translate) {
      $string = self::translateNames($type, $string);
    }
    if ($string === '*') {
      // This means all possible values, return right away, no need to double check
      return self::possibleValues($type);
    }
    elseif (strpos($string, '/')) {
      // Multiple. Example */2, for weekday will expand into 2, 4, 6
      list($values, $multiple) = explode('/', $string);
      $values = self::parseElement($type, $values);
      foreach ($values as $value) {
        if (!($value % $multiple)) {
          $range[] = $value;
        }
      }
    }
    elseif (strpos($string, ',')) {
      // Now process list parts, expand into items, process each and merge back
      $list = explode(',', $string);
      $range = array();
      foreach ($list as $item) {
        if ($values = self::parseElement($type, $item)) {
          $range = array_merge($range, $values);
        }
      }
    }
    elseif (strpos($string, '-')) {
      // This defines a range. Example 1-3, will expand into 1,2,3
      list($start, $end) = explode('-', $string);
      // Double check the range is within possible values
      $range = range($start, $end);
    }
    elseif (is_numeric($string)) {
      // This looks like a single number, double check it's int
      $range = array((int)$string);
    }

    // Return unique sorted values and double check they're within possible values
    if (!empty($range)) {
      $range = array_intersect(array_unique($range), self::possibleValues($type));
      sort($range);
      // Sunday validation. We need cron values to match PHP values, thus week day 7 is not allowed, must be 0
      if ($type == 'wday' && in_array(7, $range)) {
        array_pop($range);
        array_unshift($range, 0);
      }
      return $range;
    }
    else {
      // No match found for this one, will produce an error with validation
      return array();
    }
  }

  /**
   * Get values for each type
   */
  public static function possibleValues($type) {
    switch ($type) {
      case 'minutes':
        return range(0, 59);
      case 'hours':
        return range(0, 23);
      case 'mday':
        return range(1, 31);
      case 'mon':
        return range(1, 12);
      case 'wday':
        // These are PHP values, not *nix ones
        return range(0, 6);

    }
  }

  /**
   * Replace element names by values
   */
  public static function translateNames($type, $string) {
    switch ($type) {
      case 'wday':
        $replace = array_merge(
          // Tricky, tricky, we need sunday to be zero at the beginning of a range, but 7 at the end
          array('-sunday' => '-7', '-sun' => '-7', 'sunday-' => '0-', 'sun-' => '0-'),
          array_flip(array('sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday')),
          array_flip(array('sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat'))
        );
        break;
      case 'mon':
        $replace = array_merge(
          array_flip(array('nomonth1', 'january', 'february', 'march', 'april', 'may', 'june', 'july', 'august', 'september', 'october', 'november', 'december')),
          array_flip(array('nomonth2', 'jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul', 'aug', 'sep', 'oct', 'nov', 'dec')),
          array('sept' => 9)
        );
        break;
    }
    if (empty($replace)) {
      return $string;
    }
    else {
      return strtr($string, $replace);
    }
  }
}