@line/bot-sdk Express Middleware: ตัวอย่างพร้อมใช้งานจริง พร้อม replyMessage & validateSignature

npm init -y
npm i express @line/bot-sdk
npm i -D typescript @types/express @types/node ts-node-dev

# .env
LINE_CHANNEL_ACCESS_TOKEN=...
LINE_CHANNEL_SECRET=...

import express from "express"
import { middleware, messagingApi, WebhookEvent } from "@line/bot-sdk"

const config = {
  channelAccessToken: process.env.LINE_CHANNEL_ACCESS_TOKEN!,
  channelSecret: process.env.LINE_CHANNEL_SECRET!,
}

const client = new messagingApi.MessagingApiClient({
  channelAccessToken: config.channelAccessToken,
})

const app = express()

// สำคัญ: อย่าเรียก express.json() ก่อน middleware()
app.post("/webhook", middleware(config), async (req, res) => {
  const events: WebhookEvent[] = req.body.events
  await Promise.all(events.map(handleEvent))
  res.status(200).end()
})

async function handleEvent(event: WebhookEvent) {
  if (event.type !== "message" || event.message.type !== "text") return
  const reply = await client.replyMessage({
    replyToken: event.replyToken,
    messages: [{ type: "text", text: `Echo: ${event.message.text}` }],
  })
  console.log("sent message ids:", reply.sentMessages.map(m => m.id))
}

app.listen(3000)

import crypto from "node:crypto"

function validateSignature(body, secret, signature) {
  const computed = crypto
    .createHmac("sha256", secret)
    .update(body)
    .digest("base64")
  return crypto.timingSafeEqual(
    Buffer.from(computed),
    Buffer.from(signature),
  )
}

await client.replyMessage({
  replyToken: event.replyToken,
  messages: [
    { type: "text", text: "สวัสดี!" },
    {
      type: "flex",
      altText: "ยืนยันการจอง",
      contents: {
        type: "bubble",
        body: {
          type: "box",
          layout: "vertical",
          contents: [
            { type: "text", text: "ยืนยันการจอง", weight: "bold", size: "lg" },
          ],
        },
      },
    },
  ],
})

type ReplyMessageResponse = {
  sentMessages: Array<{
    id: string
    quoteToken?: string
  }>
}