https://gist.github.com/devsnek/77275f6e3f810a9545440931ed314dc1

index.ts

import { Hono } from 'hono';
import { InteractionType, InteractionResponseType } from 'discord-api-types/v9';

// Function to convert a hex string to binary format
function hex2bin(hex: string): Uint8Array {
  const buf = new Uint8Array(Math.ceil(hex.length / 2));
  for (let i = 0; i < buf.length; i++) {
    buf[i] = parseInt(hex.substr(i * 2, 2), 16);
  }
  return buf;
}

// Function to import the ED25519 public key
async function importPublicKey(publicKeyHex: string): Promise<CryptoKey> {
  const publicKeyData = hex2bin(publicKeyHex);
  return crypto.subtle.importKey(
    'raw',
    publicKeyData,
    {
      name: 'NODE-ED25519',
      namedCurve: 'NODE-ED25519',
      public: true,
    },
    true,
    ['verify']
  );
}

// Function to verify the ED25519 signature
async function verifySignature(
  publicKey: CryptoKey,
  signature: Uint8Array,
  timestamp: string,
  body: string
): Promise<boolean> {
  const encoder = new TextEncoder();
  const data = encoder.encode(timestamp + body);
  return crypto.subtle.verify(
    'NODE-ED25519',
    publicKey,
    signature,
    data
  );
}

const PUBLIC_KEY_HEX = 'YOUR_DISCORD_PUBLIC_KEY_HEX';
const publicKeyPromise = importPublicKey(PUBLIC_KEY_HEX);

// Initialize the Hono app
const app = new Hono();

// Middleware to verify the request signature
app.use('/interactions', async (c, next) => {
  const signature = c.req.header('X-Signature-Ed25519');
  const timestamp = c.req.header('X-Signature-Timestamp');
  const body = await c.req.text();

  if (!signature || !timestamp) {
    return c.text('Missing signature or timestamp', 401);
  }

  const isVerified = await verifySignature(
    await publicKeyPromise,
    hex2bin(signature),
    timestamp,
    body
  );

  if (!isVerified) {
    return c.text('Invalid request signature', 401);
  }

  // Store the parsed body for use in the next middleware or handler
  c.req.body = JSON.parse(body);
  return next();
});

// Route handler
app.post('/interactions', async (c) => {
  const data = c.req.body;
  if (data.type === InteractionType.Ping) {
    return c.json({ type: InteractionResponseType.Pong });
  }

  return c.text('Invalid request', 400);
});

// Export the fetch method of the app
export default {
  fetch: app.fetch.bind(app),
};