Google Apps ScriptでGmailをLINEに通知する方法

const lineToken = '<LINE Notifyのトークン>'
const searchOperators = '<Gmail検索演算子付き条件>'

const sendLine = (body, lineToken) => {
  UrlFetchApp.fetch('https://notify-api.line.me/api/notify', {
    'method' : 'post',
    'payload': {'message': body},
    'headers': {'Authorization': `Bearer ${lineToken}`},
  })
}

const setSearchCondition = () => {
  const intervalMinute = 3
  const term = Math.trunc(Date.now() / 1000) - (intervalMinute * 60)
  return `(is:unread after:${term} ${searchOperators})`
}

const searchMail = (searchCondition) => {
  return GmailApp.search(searchCondition)
}

const getMessages = (searchResult) => {
  const mails = GmailApp.getMessagesForThreads(searchResult)
  const detailMessages = []
  const formatter = new Intl.DateTimeFormat('ja-JP', {
    year: 'numeric',
    month: '2-digit',
    day: '2-digit',
    hour: '2-digit',
    minute: '2-digit',
  })
  for (const messages of mails) {
    const message = messages.pop()
    detailMessages.push(`
      【日付】: ${formatter.format(message.getDate())}
      【From】: ${message.getFrom()}
      【件名】: ${message.getSubject()}
      【本文】: ${message.getPlainBody().slice(0, 200)}
    `.replace(/^ +/gm, ''))
  }
  GmailApp.markThreadsRead(searchResult)
  return detailMessages
}

const gmailToLine = () => {
  const result = searchMail(setSearchCondition())
  if (result.length) {
    const messages = getMessages(result)
    messages.forEach(message => sendLine(message, lineToken))
  }
}