<?php

namespace Drupal\Core\Datetime;

use Drupal\Core\StringTranslation\TranslatableMarkup;

/**
 * Helper class for dealing with timezones.
 */
class TimeZoneFormHelper {

  /**
   * Generate an array of time zones names.
   *
   * This method retrieves the list of IANA time zones names that PHP is
   * configured to use, for display to users. It does not return the backward
   * compatible names (i.e., the ones defined in the back-zone file).
   *
   * @param bool $blank
   *   (optional) If TRUE, prepend an empty time zone option to the array.
   *
   * @return array
   *   An array or nested array containing time zones, keyed by the system name.
   *   The keys are valid time zone identifiers provided by
   *   \DateTimeZone::listIdentifiers()
   */
  public static function getOptionsList(bool $blank = FALSE): array {
    $zonelist = \DateTimeZone::listIdentifiers();
    $zones = $blank ? ['' => new TranslatableMarkup('- None selected -')] : [];
    foreach ($zonelist as $zone) {
      $zones[$zone] = new TranslatableMarkup(str_replace('_', ' ', $zone));
    }
    // Sort the translated time zones alphabetically.
    asort($zones);
    return $zones;
  }

  /**
   * Generate an array of time zones names grouped by region.
   *
   * This method retrieves the list of IANA time zones names that PHP is
   * configured to use, for display to users. It does not return the backward
   * compatible names (i.e., the ones defined in the back-zone file).
   *
   * @param bool $blank
   *   (optional) If TRUE, prepend an empty time zone option to the array.
   *
   * @return array
   *   An nested array containing time zones, keyed by the system name. The keys
   *   are valid time zone identifiers provided by
   *   \DateTimeZone::listIdentifiers()
   */
  public static function getOptionsListByRegion(bool $blank = FALSE): array {
    $zones = static::getOptionsList($blank);
    $grouped_zones = [];
    foreach ($zones as $key => $value) {
      $split = explode('/', $value);
      $city = array_pop($split);
      $region = array_shift($split);
      if (!empty($region)) {
        $grouped_zones[$region][$key] = empty($split) ? $city : $city . ' (' . implode('/', $split) . ')';
      }
      else {
        $grouped_zones[$key] = $value;
      }
    }
    foreach ($grouped_zones as $key => $value) {
      if (is_array($grouped_zones[$key])) {
        asort($grouped_zones[$key]);
      }
    }
    return $grouped_zones;
  }

}
