ทำบอทเช็คสลิปใน LINE OA ของร้าน ด้วย Checkslip API

import crypto from "node:crypto";
import express from "express";

const app = express();
app.use(express.raw({ type: "application/json" }));

function signatureOk(rawBody, signature) {
  const expected = crypto
    .createHmac("sha256", process.env.LINE_CHANNEL_SECRET)
    .update(rawBody)
    .digest("base64");
  return signature === expected;
}

async function getSlipImage(messageId) {
  const res = await fetch(
    `https://api-data.line.me/v2/bot/message/${messageId}/content`,
    { headers: { Authorization: `Bearer ${process.env.LINE_CHANNEL_ACCESS_TOKEN}` } },
  );
  if (!res.ok) throw new Error(`LINE content ${res.status}`);
  return new Blob([await res.arrayBuffer()], { type: res.headers.get("content-type") });
}

async function checkSlip(image, messageId) {
  const form = new FormData();
  form.append("image", image, "slip.jpg");
  const res = await fetch("https://api.checkslip.com/api/slips/lookup", {
    method: "POST",
    headers: {
      Authorization: `Bearer ${process.env.CHECKSLIP_API_KEY}`,
      "Idempotency-Key": `line-${messageId}`,
    },
    body: form,
  });
  return res.json();
}

function replyText(result) {
  switch (result.outcome) {
    case "FOUND": {
      const baht = (result.slip.amount.satang / 100).toFixed(2);
      return `พบรายการ ${baht} บาท ร้านจะตรวจยอดกับออเดอร์ให้นะครับ`;
    }
    case "DUPLICATE":
      return "สลิปนี้เคยส่งเข้ามาแล้ว แอดมินจะตรวจให้อีกครั้งครับ";
    case "NOT_FOUND":
      return "ยังไม่พบรายการนี้ที่ธนาคาร แอดมินจะติดต่อกลับครับ";
    default:
      return "ได้รับสลิปแล้ว แอดมินจะตรวจให้ครับ";
  }
}

async function reply(replyToken, text) {
  await fetch("https://api.line.me/v2/bot/message/reply", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${process.env.LINE_CHANNEL_ACCESS_TOKEN}`,
    },
    body: JSON.stringify({ replyToken, messages: [{ type: "text", text }] }),
  });
}

app.post("/line/webhook", async (req, res) => {
  if (!signatureOk(req.body, req.get("x-line-signature"))) {
    return res.sendStatus(401);
  }
  res.sendStatus(200);
  const { events } = JSON.parse(req.body.toString("utf8"));
  for (const event of events) {
    if (event.type !== "message" || event.message.type !== "image") continue;
    try {
      const image = await getSlipImage(event.message.id);
      const result = await checkSlip(image, event.message.id);
      await reply(event.replyToken, replyText(result));
    } catch (err) {
      console.error("slip check failed", err);
    }
  }
});

app.listen(3000);