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<?php

/**

 * @file

 * Code to compute the dates that match an iCal RRULE.

 *

 * Moved to a separate file since it is not used on most pages

 * so the code is not parsed unless needed.

 *

 * Extensive simpletests have been created to test the RRULE calculation

 * results against official examples from RFC 2445.

 *

 * These calculations are expensive and results should be stored or cached

 * so the calculation code is not called more often than necessary.

 *

 * Currently implemented:

 * INTERVAL, UNTIL, COUNT, EXDATE, RDATE, BYDAY, BYMONTHDAY, BYMONTH,

 * YEARLY, MONTHLY, WEEKLY, DAILY

 *

 * Currently not implemented:

 *

 * BYYEARDAY, MINUTELY, HOURLY, SECONDLY, BYMINUTE, BYHOUR, BYSECOND

 *   These could be implemented in the future.

 *

 * BYSETPOS

 *   Seldom used anywhere, so no reason to complicated the code.

 */

/**

 * Private implementation of date_repeat_calc().

 *

 * Compute dates that match the requested rule, within a specified date range.

 */

function _date_repeat_calc($rrule, $start, $end, $exceptions, $timezone, $additions) {

  module_load_include('inc', 'date_api', 'date_api_ical');

  if (empty($timezone)) {

    $timezone = date_default_timezone();

  }

  // Make sure the 'EXCEPTIONS' string isn't appended to the rule.

  $parts = explode("\n", $rrule);

  if (count($parts)) {

    $rrule = $parts[0];

  }

  // Get the parsed array of rule values.

  $rrule = date_ical_parse_rrule('RRULE:', $rrule);

  // These default values indicate there is no RRULE here.

  if ($rrule['FREQ'] == 'NONE' || (isset($rrule['INTERVAL']) && $rrule['INTERVAL'] == 0)) {

    return array();

  }

  // Create a date object for the start and end dates.

  $start_date = new DateObject($start, $timezone);

  // Versions of PHP greater than PHP 5.3.5 require that we set an explicit time when

  // using date_modify() or the time may not match the original value. Adding this

  // modifier gives us the same results in both older and newer versions of PHP.

  $modify_time = ' ' . $start_date->format('g:ia');

  // If the rule has an UNTIL, see if that is earlier than the end date.

  if (!empty($rrule['UNTIL'])) {

    $end_date = new DateObject($end, $timezone);

    $until_date = date_ical_date($rrule['UNTIL'], $timezone);

    if (date_format($until_date, 'U') < date_format($end_date, 'U')) {

      $end_date = $until_date;

    }

  }

  // The only valid option for an empty end date is when we have a count.

  elseif (empty($end)) {

    if (!empty($rrule['COUNT'])) {

      $end_date = NULL;

    }

    else {

      return array();

    }

  }

  else {

    $end_date = new DateObject($end, $timezone);

  }

  // Get an integer value for the interval, if none given, '1' is implied.

  if (empty($rrule['INTERVAL'])) {

    $rrule['INTERVAL'] = 1;

  }

  $interval = max(1, $rrule['INTERVAL']);

  $count = isset($rrule['COUNT']) ? $rrule['COUNT'] : NULL;

  if (empty($rrule['FREQ'])) {

    $rrule['FREQ'] = 'DAILY';

  }

  // Make sure DAILY frequency isn't used in places it won't work;

  if (!empty($rrule['BYMONTHDAY']) && !in_array($rrule['FREQ'], array('MONTHLY', 'YEARLY'))) {

    $rrule['FREQ'] = 'MONTHLY';

  }

  elseif (!empty($rrule['BYDAY']) && !in_array($rrule['FREQ'], array('MONTHLY', 'WEEKLY', 'YEARLY'))) {

    $rrule['FREQ'] = 'WEEKLY';

   }

  // Find the time period to jump forward between dates.

  switch ($rrule['FREQ']) {

   case 'DAILY':

     $jump = $interval . ' days';

     break;

   case 'WEEKLY':

     $jump = $interval . ' weeks';

     break;

   case 'MONTHLY':

     $jump = $interval . ' months';

     break;

   case 'YEARLY':

     $jump = $interval . ' years';

     break;

  }

  $rrule = date_repeat_adjust_rrule($rrule, $start_date);

  // The start date always goes into the results, whether or not it meets

  // the rules. RFC 2445 includes examples where the start date DOES NOT

  // meet the rules, but the expected results always include the start date.

  $days = array(date_format($start_date, DATE_FORMAT_DATETIME));

  // BYMONTHDAY will look for specific days of the month in one or more months.

  // This process is only valid when frequency is monthly or yearly.

  if (!empty($rrule['BYMONTHDAY'])) {

    $finished = FALSE;

    $current_day = clone($start_date);

    $direction_days = array();

    // Deconstruct the day in case it has a negative modifier.

    foreach ($rrule['BYMONTHDAY'] as $day) {

      preg_match("@(-)?([0-9]{1,2})@", $day, $regs);

      if (!empty($regs[2])) {

        // Convert parameters into full day name, count, and direction.

        $direction_days[$day] = array(

          'direction' => !empty($regs[1]) ? $regs[1] : '+',

          'direction_count' => $regs[2],

          );

      }

    }

    while (!$finished) {

      $period_finished = FALSE;

      while (!$period_finished) {

        foreach ($rrule['BYMONTHDAY'] as $monthday) {

          $day = $direction_days[$monthday];

          $current_day = date_repeat_set_month_day($current_day, NULL, $day['direction_count'], $day['direction'], $timezone, $modify_time);

          date_repeat_add_dates($days, $current_day, $start_date, $end_date, $exceptions, $rrule);

          if ($finished = date_repeat_is_finished($current_day, $days, $count, $end_date)) {

            $period_finished = TRUE;

          }

        }

        // If it's monthly, keep looping through months, one INTERVAL at a time.

        if ($rrule['FREQ'] == 'MONTHLY') {

          if ($finished = date_repeat_is_finished($current_day, $days, $count, $end_date)) {

            $period_finished = TRUE;

          }

          // Back up to first of month and jump.

          $current_day = date_repeat_set_month_day($current_day, NULL, 1, '+', $timezone, $modify_time);

          date_modify($current_day, '+' . $jump . $modify_time);

        }

        // If it's yearly, break out of the loop at the

        // end of every year, and jump one INTERVAL in years.

        else {

          if (date_format($current_day, 'n') == 12) {

            $period_finished = TRUE;

          }

          else {

            // Back up to first of month and jump.

            $current_day = date_repeat_set_month_day($current_day, NULL, 1, '+', $timezone, $modify_time);

            date_modify($current_day, '+1 month' . $modify_time);

          }

        }

      }

      if ($rrule['FREQ'] == 'YEARLY') {

        // Back up to first of year and jump.

        $current_day = date_repeat_set_year_day($current_day, NULL, 1, '+', $timezone, $modify_time);

        date_modify($current_day, '+' . $jump . $modify_time);

      }

      $finished = date_repeat_is_finished($current_day, $days, $count, $end_date);

    }

  }

  // This is the simple fallback case, not looking for any BYDAY,

  // just repeating the start date. Because of imputed BYDAY above, this

  // will only test TRUE for a DAILY or less frequency (like HOURLY).

  elseif (empty($rrule['BYDAY'])) {

    // $current_day will keep track of where we are in the calculation.

    $current_day = clone($start_date);

    $finished = FALSE;

    $months = !empty($rrule['BYMONTH']) ? $rrule['BYMONTH'] : array();

    while (!$finished) {

      date_repeat_add_dates($days, $current_day, $start_date, $end_date, $exceptions, $rrule);

      $finished = date_repeat_is_finished($current_day, $days, $count, $end_date);

      date_modify($current_day, '+' . $jump . $modify_time);

    }

  }

  else {

    // More complex searches for day names and criteria like '-1SU' or '2TU,2TH',

    // require that we interate through the whole time period checking each BYDAY.

    // Create helper array to pull day names out of iCal day strings.

    $day_names = date_repeat_dow_day_options(FALSE);

    $days_of_week = array_keys($day_names);

    // Parse out information about the BYDAYs and separate them

    // depending on whether they have directional parameters like -1SU or 2TH.

    $month_days = array();

    $week_days = array();

    // Find the right first day of the week to use, iCal rules say Monday

    // should be used if none is specified.

    $week_start_rule = !empty($rrule['WKST']) ? trim($rrule['WKST']) : 'MO';

    $week_start_day = $day_names[$week_start_rule];

    // Make sure the week days array is sorted into week order,

    // we use the $ordered_keys to get the right values into the key

    // and force the array to that order. Needed later when we

    // iterate through each week looking for days so we don't

    // jump to the next week when we hit a day out of order.

    $ordered = date_repeat_days_ordered($week_start_rule);

    $ordered_keys = array_flip($ordered);

    foreach ($rrule['BYDAY'] as $day) {

      preg_match("@(-)?([0-9]+)?([SU|MO|TU|WE|TH|FR|SA]{2})@", trim($day), $regs);

      if (!empty($regs[2])) {

        // Convert parameters into full day name, count, and direction.

        $direction_days[] = array(

          'day' => $day_names[$regs[3]],

          'direction' => !empty($regs[1]) ? $regs[1] : '+',

          'direction_count' => $regs[2],

          );

      }

      else {

        $week_days[$ordered_keys[$regs[3]]] = $day_names[$regs[3]];

      }

    }

    ksort($week_days);

    // BYDAYs with parameters like -1SU (last Sun) or 2TH (second Thur)

    // need to be processed one month or year at a time.

    if (!empty($direction_days) && in_array($rrule['FREQ'], array('MONTHLY', 'YEARLY'))) {

      $finished = FALSE;

      $current_day = clone($start_date);

      while (!$finished) {

        foreach ($direction_days as $day) {

          // Find the BYDAY date in the current month.

          if ($rrule['FREQ'] == 'MONTHLY') {

            $current_day = date_repeat_set_month_day($current_day, $day['day'], $day['direction_count'], $day['direction'], $timezone, $modify_time);

          }

          else {

            $current_day = date_repeat_set_year_day($current_day, $day['day'], $day['direction_count'], $day['direction'], $timezone, $modify_time);

          }

          date_repeat_add_dates($days, $current_day, $start_date, $end_date, $exceptions, $rrule);

        }

        $finished = date_repeat_is_finished($current_day, $days, $count, $end_date);

        // Reset to beginning of period before jumping to next period.

        // Needed especially when working with values like 'last Saturday'

        // to be sure we don't skip months like February.

        $year = date_format($current_day, 'Y');

        $month = date_format($current_day, 'n');

        if ($rrule['FREQ'] == 'MONTHLY') {

          date_date_set($current_day, $year, $month, 1);

        }

        else {

          date_date_set($current_day, $year, 1, 1);

        }

        // Jump to the next period.

        date_modify($current_day, '+' . $jump . $modify_time);

      }

    }

    // For BYDAYs without parameters,like TU,TH (every Tues and Thur),

    // we look for every one of those days during the frequency period.

    // Iterate through periods of a WEEK, MONTH, or YEAR, checking for

    // the days of the week that match our criteria for each week in the

    // period, then jumping ahead to the next week, month, or year,

    // an INTERVAL at a time.

    if (!empty($week_days) && in_array($rrule['FREQ'], array('MONTHLY', 'WEEKLY', 'YEARLY'))) {

      $finished = FALSE;

      $current_day = clone($start_date);

      $format = $rrule['FREQ'] == 'YEARLY' ? 'Y' : 'n';

      $current_period = date_format($current_day, $format);

      // Back up to the beginning of the week in case we are somewhere in the

      // middle of the possible week days, needed so we don't prematurely

      // jump to the next week. The date_repeat_add_dates() function will

      // keep dates outside the range from getting added.

      if (date_format($current_day, 'l') != $day_names[$day]) {

        date_modify($current_day, '-1 ' . $week_start_day . $modify_time);

      }

      while (!$finished) {

        $period_finished = FALSE;

        while (!$period_finished) {

          $moved = FALSE;

          foreach ($week_days as $delta => $day) {

            // Find the next occurence of each day in this week, only add it

            // if we are still in the current month or year. The date_repeat_add_dates

            // function is insufficient to test whether to include this date

            // if we are using a rule like 'every other month', so we must

            // explicitly test it here.

            // If we're already on the right day, don't jump or we

            // will prematurely move into the next week.

            if (date_format($current_day, 'l') != $day) {

              date_modify($current_day, '+1 ' . $day . $modify_time);

              $moved = TRUE;

            }

            if ($rrule['FREQ'] == 'WEEKLY' || date_format($current_day, $format) == $current_period) {

              date_repeat_add_dates($days, $current_day, $start_date, $end_date, $exceptions, $rrule);

            }

          }

          $finished = date_repeat_is_finished($current_day, $days, $count, $end_date);

          // Make sure we don't get stuck in endless loop if the current

          // day never got changed above.

          if (!$moved) {

            date_modify($current_day, '+1 day' . $modify_time);

          }

          // If this is a WEEKLY frequency, stop after each week,

          // otherwise, stop when we've moved outside the current period.

          // Jump to the end of the week, then test the period.

          if ($finished || $rrule['FREQ'] == 'WEEKLY') {

            $period_finished = TRUE;

          }

          elseif ($rrule['FREQ'] != 'WEEKLY' && date_format($current_day, $format) != $current_period) {

            $period_finished = TRUE;

          }

        }

        if ($finished) {

          continue;

        }

        // We'll be at the end of a week, month, or year when

        // we get to this point in the code.

        // Go back to the beginning of this period before we jump, to

        // ensure we jump to the first day of the next period.

        switch ($rrule['FREQ']) {

          case 'WEEKLY':

            date_modify($current_day, '+1 ' . $week_start_day . $modify_time);

            date_modify($current_day, '-1 week' . $modify_time);

            break;

          case 'MONTHLY':

            date_modify($current_day, '-' . (date_format($current_day, 'j') - 1) . ' days' . $modify_time);

            date_modify($current_day, '-1 month' . $modify_time);

            break;

          case 'YEARLY':

            date_modify($current_day, '-' . date_format($current_day, 'z') . ' days' . $modify_time);

            date_modify($current_day, '-1 year' . $modify_time);

            break;

        }

        // Jump ahead to the next period to be evaluated.

        date_modify($current_day, '+' . $jump . $modify_time);

        $current_period = date_format($current_day, $format);

        $finished = date_repeat_is_finished($current_day, $days, $count, $end_date);

      }

    }

  }

  // add additional dates

  foreach ($additions as $addition) {

    $date = new dateObject($addition . ' ' . $start_date->format('H:i:s'), $timezone);

    $days[] = date_format($date, DATE_FORMAT_DATETIME);

  }

  sort($days);

  return $days;

}

/**

 * See if the RRULE needs some imputed values added to it.

 */

function date_repeat_adjust_rrule($rrule, $start_date) {

  // If this is not a valid value, do nothing;

  if (empty($rrule) || empty($rrule['FREQ'])) {

    return array();

  }

  // RFC 2445 says if no day or monthday is specified when creating repeats for

  // weeks, months, or years, impute the value from the start date.

  if (empty($rrule['BYDAY']) && $rrule['FREQ'] == 'WEEKLY') {

    $rrule['BYDAY'] = array(date_repeat_dow2day(date_format($start_date, 'w')));

  }

  elseif (empty($rrule['BYDAY']) && empty($rrule['BYMONTHDAY']) && $rrule['FREQ'] == 'MONTHLY') {

    $rrule['BYMONTHDAY'] = array(date_format($start_date, 'j'));

  }

  elseif (empty($rrule['BYDAY']) && empty($rrule['BYMONTHDAY']) && empty($rrule['BYYEARDAY']) && $rrule['FREQ'] == 'YEARLY') {

    $rrule['BYMONTHDAY'] = array(date_format($start_date, 'j'));

    if (empty($rrule['BYMONTH'])) {

      $rrule['BYMONTH'] = array(date_format($start_date, 'n'));

    }

  }

  // If we are processing rules for period other than YEARLY or MONTHLY

  // and have BYDAYS like 2SU or -1SA, simplify them to SU or SA since the

  // position rules make no sense in other periods and just add complexity.

  elseif (!empty($rrule['BYDAY']) && !in_array($rrule['FREQ'], array('MONTHLY', 'YEARLY'))) {

    foreach ($rrule['BYDAY'] as $delta => $BYDAY) {

      $rrule['BYDAY'][$delta] = substr($BYDAY, -2);

    }

  }

  return $rrule;

}

/**

 * Helper function to add found date to the $dates array.

 *

 * Check that the date to be added is between the start and end date

 * and that it is not in the $exceptions, nor already in the $days array,

 * and that it meets other criteria in the RRULE.

 */

function date_repeat_add_dates(&$days, $current_day, $start_date, $end_date, $exceptions, $rrule) {

  if (isset($rrule['COUNT']) && sizeof($days) >= $rrule['COUNT']) {

    return FALSE;

  }

  $formatted = date_format($current_day, DATE_FORMAT_DATETIME);

  if (!empty($end_date) && $formatted > date_format($end_date, DATE_FORMAT_DATETIME)) {

    return FALSE;

  }

  if ($formatted < date_format($start_date, DATE_FORMAT_DATETIME)) {

    return FALSE;

  }

  if (in_array(date_format($current_day, 'Y-m-d'), $exceptions)) {

    return FALSE;

  }

  if (!empty($rrule['BYDAY'])) {

    $BYDAYS = $rrule['BYDAY'];

    foreach ($BYDAYS as $delta => $BYDAY) {

      $BYDAYS[$delta] = substr($BYDAY, -2);

    }

    if (!in_array(date_repeat_dow2day(date_format($current_day, 'w')), $BYDAYS)) {

      return FALSE;

    }}

  if (!empty($rrule['BYYEAR']) && !in_array(date_format($current_day, 'Y'), $rrule['BYYEAR'])) {

    return FALSE;

  }

  if (!empty($rrule['BYMONTH']) && !in_array(date_format($current_day, 'n'), $rrule['BYMONTH'])) {

    return FALSE;

  }

  if (!empty($rrule['BYMONTHDAY'])) {

    // Test month days, but only if there are no negative numbers.

    $test = TRUE;

    $BYMONTHDAYS = array();

    foreach ($rrule['BYMONTHDAY'] as $day) {

      if ($day > 0) {

        $BYMONTHDAYS[] = $day;

      }

      else {

        $test = FALSE;

        break;

      }

    }

    if ($test && !empty($BYMONTHDAYS) && !in_array(date_format($current_day, 'j'), $BYMONTHDAYS)) {

      return FALSE;

    }

  }

  // Don't add a day if it is already saved so we don't throw the count off.

  if (in_array($formatted, $days)) {

    return TRUE;

  }

  else {

    $days[] = $formatted;

  }

}

/**

 * Stop when $current_day is greater than $end_date or $count is reached.

 */

function date_repeat_is_finished($current_day, $days, $count, $end_date) {

  if (($count && sizeof($days) >= $count)

  || (!empty($end_date) && date_format($current_day, 'U') > date_format($end_date, 'U'))) {

    return TRUE;

  }

  else {

    return FALSE;

  }

}

/**

 * Set a date object to a specific day of the month.

 *

 * Example,

 *   date_set_month_day($date, 'Sunday', 2, '-')

 *   will reset $date to the second to last Sunday in the month.

 *   If $day is empty, will set to the number of days from the

 *   beginning or end of the month.

 */

function date_repeat_set_month_day($date_in, $day, $count = 1, $direction = '+', $timezone = 'UTC', $modify_time) {

  if (is_object($date_in)) {

    $current_month = date_format($date_in, 'n');

    // Reset to the start of the month.

    // We should be able to do this with date_date_set(), but

    // for some reason the date occasionally gets confused if run

    // through this function multiple times. It seems to work

    // reliably if we create a new object each time.

    $datetime = date_format($date_in, DATE_FORMAT_DATETIME);

    $datetime = substr_replace($datetime, '01', 8, 2);

    $date = new DateObject($datetime, $timezone);

    if ($direction == '-') {

      // For negative search, start from the end of the month.

      date_modify($date, '+1 month' . $modify_time);

    }

    else {

      // For positive search, back up one day to get outside the

      // current month, so we can catch the first of the month.

      date_modify($date, '-1 day' . $modify_time);

    }

    if (empty($day)) {

      date_modify($date, $direction . $count . ' days' . $modify_time);

    }

    else {

      // Use the English text for order, like First Sunday

      // instead of +1 Sunday to overcome PHP5 bug, (see #369020).

      $order = date_order();

      $step = $count <= 5 ? $order[$direction . $count] : $count;

      date_modify($date, $step . ' ' . $day . $modify_time);

    }

    // If that takes us outside the current month, don't go there.

    if (date_format($date, 'n') == $current_month) {

      return $date;

    }

  }

  return $date_in;

}

/**

 * Set a date object to a specific day of the year.

 *

 * Example,

 *   date_set_year_day($date, 'Sunday', 2, '-')

 *   will reset $date to the second to last Sunday in the year.

 *   If $day is empty, will set to the number of days from the

 *   beginning or end of the year.

 */

function date_repeat_set_year_day($date_in, $day, $count = 1, $direction = '+', $timezone = 'UTC', $modify_time) {

  if (is_object($date_in)) {

    $current_year = date_format($date_in, 'Y');

    // Reset to the start of the month.

    // See note above.

    $datetime = date_format($date_in, DATE_FORMAT_DATETIME);

    $datetime = substr_replace($datetime, '01-01', 5, 5);

    $date = new DateObject($datetime, $timezone);

    if ($direction == '-') {

      // For negative search, start from the end of the year.

      date_modify($date, '+1 year' . $modify_time);

    }

    else {

      // For positive search, back up one day to get outside the

      // current year, so we can catch the first of the year.

      date_modify($date, '-1 day' . $modify_time);

    }

    if (empty($day)) {

      date_modify($date, $direction . $count . ' days' . $modify_time);

    }

    else {

      // Use the English text for order, like First Sunday

      // instead of +1 Sunday to overcome PHP5 bug, (see #369020).

      $order = date_order();

      $step = $count <= 5 ? $order[$direction . $count] : $count;

      date_modify($date, $step . ' ' . $day . $modify_time);

    }

    // If that takes us outside the current year, don't go there.

    if (date_format($date, 'Y') == $current_year) {

      return $date;

    }

  }

  return $date_in;

}