SlackAppをVercelにデプロイする

// lib/slack.ts
import pkg from "@slack/bolt";

const { App } = pkg;

export const slack = new App({
  token: process.env.SLACK_BOT_TOKEN,
  signingSecret: process.env.SLACK_SIGNING_SECRET,
});

// api/hello.ts
import type { VercelRequest, VercelResponse } from "@vercel/node";
import { slack } from "../lib/slack.js";
import { withSlackApi } from "../lib/api/withSlackApi.js";

export default withSlackApi(async function handler(
  _: VercelRequest,
  res: VercelResponse
) {
  await slack.client.chat.postMessage({
    channel: "C060MDTT9QX",
    text: "test message",
  });
  res.json("success");
  return;
});

// lib/slack.ts
import { VercelRequest } from "@vercel/node";
import { createHmac } from "crypto";
import tsscmp from "tsscmp";

// ------------------------------
// HTTP module independent methods
// ------------------------------

const verifyErrorPrefix = "Failed to verify authenticity";

/**
 * Verifies the signature of an incoming request from Slack.
 * If the request is invalid, this method throws an exception with the error details.
 */
export function verifySlackRequest(req: VercelRequest): void {
  const requestTimestampSecHeader = req.headers["x-slack-request-timestamp"];
  const signature = req.headers["x-slack-signature"];
  if (Number.isNaN(requestTimestampSecHeader)) {
    throw new Error(
      `${verifyErrorPrefix}: header x-slack-request-timestamp did not have the expected type (${requestTimestampSecHeader})`
    );
  }
  if (signature == null || Array.isArray(signature)) {
    throw new Error(
      `${verifyErrorPrefix}: header x-slack-signature did not have the expected type (${signature})`
    );
  }

  const requestTimestampSec = Number(requestTimestampSecHeader);

  // Calculate time-dependent values
  const nowMs = Date.now();
  const requestTimestampMaxDeltaMin = 5;
  const fiveMinutesAgoSec =
    Math.floor(nowMs / 1000) - 60 * requestTimestampMaxDeltaMin;

  // Enforce verification rules

  // Rule 1: Check staleness
  if (requestTimestampSec < fiveMinutesAgoSec) {
    throw new Error(
      `${verifyErrorPrefix}: x-slack-request-timestamp must differ from system time by no more than ${requestTimestampMaxDeltaMin} minutes or request is stale`
    );
  }

  // Rule 2: Check signature
  // Separate parts of signature
  const [signatureVersion, signatureHash] = signature.split("=");
  // Only handle known versions
  if (signatureVersion !== "v0") {
    throw new Error(`${verifyErrorPrefix}: unknown signature version`);
  }
  // Compute our own signature hash
  const hmac = createHmac("sha256", process.env.SLACK_SIGNING_SECRET ?? "");

  // We should detect the body have "toString" because the body parsed by vercel is mede by Object.create(null) or regular object.
  // the original shape of the body have "toString" is JSON.
  // the original shape of the body not have "toString" is URLSearchParams.
  // We should add the escape of slash because vercel remove the escape of slash when the body is JSON.
  const body =
    "toString" in req.body
      ? JSON.stringify(req.body).replaceAll("/", "\\/")
      : new URLSearchParams(req.body as Record<string, string>).toString();

  hmac.update(`${signatureVersion}:${requestTimestampSec}:${body}`);
  const ourSignatureHash = hmac.digest("hex");
  if (!signatureHash || !tsscmp(signatureHash, ourSignatureHash)) {
    throw new Error(`${verifyErrorPrefix}: signature mismatch`);
  }
}

  // We should detect the body have "toString" because the body parsed by vercel is mede by Object.create(null) or regular object.
  // the original shape of the body have "toString" is JSON.
  // the original shape of the body not have "toString" is URLSearchParams.
  // We should add the escape of slash because vercel remove the escape of slash when the body is JSON.
  const body =
    "toString" in req.body
      ? JSON.stringify(req.body).replaceAll("/", "\\/")
      : new URLSearchParams(req.body as Record<string, string>).toString();