app.js

import dotenv from "dotenv";
import fs from "fs";
import http from "http";
import { App } from "octokit";
import { createNodeMiddleware } from "@octokit/webhooks";

// Load environment variables from .env file
dotenv.config();

// Set configured values
const appId = process.env.APP_ID;
const privateKeyPath = process.env.PRIVATE_KEY_PATH;
const privateKey = fs.readFileSync(privateKeyPath, "utf8");
const secret = process.env.WEBHOOK_SECRET;
const enterpriseHostname = process.env.ENTERPRISE_HOSTNAME;
const messageForNewPRs = fs.readFileSync("./message.md", "utf8");

// Create an authenticated Octokit client authenticated as a GitHub App
const app = new App({
  appId: appId,
  privateKey: privateKey,
  webhooks: {
    secret: secret
  },
  ...(enterpriseHostname && {
    Octokit: Octokit.defaults({
      baseUrl: `https://${enterpriseHostname}/api/v3`,
    }),
  }),
})

// Optional: Get & log the authenticated app's name
const { data } = await app.octokit.request("/app");

// Read more about custom logging: https://github.com/octokit/core.js#logging
app.octokit.log.debug(`Authenticated as '${ data.name }'`);

// Subscribe to the "pull_request.opened" webhook event
app.webhooks.on("pull_request.opened", async ({ octokit, payload }) => {
  console.log(`Received a pull request event for #${ payload.pull_request.number }`);
  await octokit.rest.issues.createComment({
    owner: payload.repository.owner.login,
    repo: payload.repository.name,
    issue_number: payload.pull_request.number,
    body: messageForNewPRs,
  });
});

// Optional: Handle errors
app.webhooks.onError((error) => {
  if (error.name === "AggregateError") {
    // Log Secret verification errors
    console.log(`Error processing request: ${ error.event }`);
  } else {
    console.log(error);
  }
});

// Launch a web server to listen for GitHub webhooks
const port = process.env.PORT || 3000;
const path = "/api/webhook";
const localWebhookUrl = `http://localhost:${ port }${ path }`;

// See https://github.com/octokit/webhooks.js/#createnodemiddleware for all options
const middleware = createNodeMiddleware(app.webhooks, { path });

http.createServer(middleware).listen(port, () => { 
  console.log(`Server is listening for events at: ${localWebhookUrl}`);
  console.log('Press Ctrl + C to quit.')
});