Chris@0: /**
Chris@0:  * @file
Chris@0:  * Timezone detection.
Chris@0:  */
Chris@0: 
Chris@17: (function($, Drupal) {
Chris@0:   /**
Chris@0:    * Set the client's system time zone as default values of form fields.
Chris@0:    *
Chris@0:    * @type {Drupal~behavior}
Chris@0:    */
Chris@0:   Drupal.behaviors.setTimezone = {
Chris@0:     attach(context, settings) {
Chris@17:       const $timezone = $(context)
Chris@17:         .find('.timezone-detect')
Chris@17:         .once('timezone');
Chris@0:       if ($timezone.length) {
Chris@0:         const dateString = Date();
Chris@0:         // In some client environments, date strings include a time zone
Chris@0:         // abbreviation, between 3 and 5 letters enclosed in parentheses,
Chris@0:         // which can be interpreted by PHP.
Chris@0:         const matches = dateString.match(/\(([A-Z]{3,5})\)/);
Chris@0:         const abbreviation = matches ? matches[1] : 0;
Chris@0: 
Chris@0:         // For all other client environments, the abbreviation is set to "0"
Chris@0:         // and the current offset from UTC and daylight saving time status are
Chris@0:         // used to guess the time zone.
Chris@0:         const dateNow = new Date();
Chris@0:         const offsetNow = dateNow.getTimezoneOffset() * -60;
Chris@0: 
Chris@0:         // Use January 1 and July 1 as test dates for determining daylight
Chris@0:         // saving time status by comparing their offsets.
Chris@0:         const dateJan = new Date(dateNow.getFullYear(), 0, 1, 12, 0, 0, 0);
Chris@0:         const dateJul = new Date(dateNow.getFullYear(), 6, 1, 12, 0, 0, 0);
Chris@0:         const offsetJan = dateJan.getTimezoneOffset() * -60;
Chris@0:         const offsetJul = dateJul.getTimezoneOffset() * -60;
Chris@0: 
Chris@0:         let isDaylightSavingTime;
Chris@0:         // If the offset from UTC is identical on January 1 and July 1,
Chris@0:         // assume daylight saving time is not used in this time zone.
Chris@0:         if (offsetJan === offsetJul) {
Chris@0:           isDaylightSavingTime = '';
Chris@0:         }
Chris@0:         // If the maximum annual offset is equivalent to the current offset,
Chris@0:         // assume daylight saving time is in effect.
Chris@0:         else if (Math.max(offsetJan, offsetJul) === offsetNow) {
Chris@0:           isDaylightSavingTime = 1;
Chris@0:         }
Chris@0:         // Otherwise, assume daylight saving time is not in effect.
Chris@0:         else {
Chris@0:           isDaylightSavingTime = 0;
Chris@0:         }
Chris@0: 
Chris@0:         // Submit request to the system/timezone callback and set the form
Chris@0:         // field to the response time zone. The client date is passed to the
Chris@0:         // callback for debugging purposes. Submit a synchronous request to
Chris@0:         // avoid database errors associated with concurrent requests
Chris@0:         // during install.
Chris@0:         const path = `system/timezone/${abbreviation}/${offsetNow}/${isDaylightSavingTime}`;
Chris@0:         $.ajax({
Chris@0:           async: false,
Chris@0:           url: Drupal.url(path),
Chris@0:           data: { date: dateString },
Chris@0:           dataType: 'json',
Chris@0:           success(data) {
Chris@0:             if (data) {
Chris@0:               $timezone.val(data);
Chris@0:             }
Chris@0:           },
Chris@0:         });
Chris@0:       }
Chris@0:     },
Chris@0:   };
Chris@17: })(jQuery, Drupal);