カレンダーのイベントの終了時刻を通知する。無限に user properties が増えるのでエラーが出たら掃除するといい

end-time-notification.gs

function remind() {
  const calendars = CalendarApp.getAllCalendars();
  for (const calendar of calendars) {
    const now = new Date();
    for (const event of calendar.getEventsForDay(now)) {
      const endTime = event.getEndTime();
      const minutesBefore = (minutes) => {
        const date = new Date(endTime);
        date.setMinutes(endTime.getMinutes() - minutes);
        return date;
      };

      const description = event.getDescription();
      const keyword = "[remind end time]";
      const keywordIndex = description.indexOf(keyword);
      if (keywordIndex === -1) {
        continue;
      }
      const minutes = description
        .slice(keywordIndex + keyword.length)
        .match(/^ (?<minutes>\d+)min$/).groups.minutes;

      const userProperties = PropertiesService.getUserProperties();
      if (!userProperties.getProperty(event.getId()) && minutesBefore(minutes) < now && now < endTime) {
        MailApp.sendEmail({
          to: Session.getActiveUser().getEmail(),
          subject: `[終了時刻通知] 「${event.getTitle()}」終了${minutes}分前`,
          body: `カレンダー「${calendar.getName()}」のイベント「${event.getTitle()}」の終了${minutes}分前をお知らせします。`,
        });
        userProperties.setProperty(event.getId(), true);
      }
    }
  }
}