把每一筆線上預約，自動寫進店家的私人 Google 行事曆。

const CONFIG = {
  SECRET_TOKEN: 'replace-with-your-secret-token',
  DEFAULT_DURATION_MINUTES: 60,

  // true：寫入登入帳號的主要行事曆
  USE_DEFAULT_CALENDAR: true,

  // 若 USE_DEFAULT_CALENDAR 改為 false，請填入指定行事曆 ID
  CALENDAR_ID: ''
};

function doGet() {
  return jsonOutput({
    status: 'ok',
    message: 'Google Calendar webhook is ready.'
  });
}

function doPost(e) {
  try {
    const body = JSON.parse((e.postData && e.postData.contents) || '{}');

    if (body.token !== CONFIG.SECRET_TOKEN) {
      return jsonOutput({
        status: 'error',
        message: 'Token 驗證失敗'
      });
    }

    const action = body.action || 'create';
    const calendar = getTargetCalendar();

    if (action === 'cancel') {
      return cancelBookingEvent(calendar, body);
    }

    return createBookingEvent(calendar, body);
  } catch (error) {
    return jsonOutput({
      status: 'error',
      message: error.message
    });
  }
}

function getTargetCalendar() {
  if (CONFIG.USE_DEFAULT_CALENDAR) {
    return CalendarApp.getDefaultCalendar();
  }

  const calendar = CalendarApp.getCalendarById(CONFIG.CALENDAR_ID);
  if (!calendar) {
    throw new Error('找不到 Google 行事曆，請確認 CALENDAR_ID');
  }

  return calendar;
}

function createBookingEvent(calendar, body) {
  const date = body.date || '';
  const time = body.time || '';
  const serviceName = body.service_name || '預約服務';
  const customerName = body.name || '未填姓名';
  const phone = body.phone || '未填電話';
  const duration = Number(body.duration_minutes || CONFIG.DEFAULT_DURATION_MINUTES);

  const start = new Date(`${date}T${time}:00+08:00`);
  const end = new Date(start.getTime() + duration * 60 * 1000);
  const title = `[LINE預約] ${serviceName} - ${customerName}`;
  const description = [
    `服務項目：${serviceName}`,
    `客戶姓名：${customerName}`,
    `聯絡電話：${phone}`,
    `預約編號：${body.booking_id || ''}`
  ].join('\n');

  const event = calendar.createEvent(title, start, end, {
    description: description
  });

  return jsonOutput({
    status: 'success',
    action: 'create',
    event_id: event.getId()
  });
}

function cancelBookingEvent(calendar, body) {
  if (!body.event_id) {
    return jsonOutput({
      status: 'error',
      message: '缺少 event_id，無法取消 Google 行事曆事件'
    });
  }

  const event = calendar.getEventById(body.event_id);
  if (!event) {
    return jsonOutput({
      status: 'not_found',
      action: 'cancel',
      message: 'Google 行事曆事件不存在，可能已經刪除'
    });
  }

  event.deleteEvent();

  return jsonOutput({
    status: 'success',
    action: 'cancel',
    event_id: body.event_id
  });
}

function jsonOutput(payload) {
  return ContentService
    .createTextOutput(JSON.stringify(payload))
    .setMimeType(ContentService.MimeType.JSON);
}