Hosting a Reddit API Discord app on Cloudflare Workers

$ wrangler secret put DISCORD_TOKEN
$ wrangler secret put DISCORD_PUBLIC_KEY
$ wrangler secret put DISCORD_APPLICATION_ID

$ wrangler secret put DISCORD_TEST_GUILD_ID

$ npm install

├── .github/workflows/ci.yaml -> GitHub Action configuration
├── src
├── ├── commands.js           -> JSON payloads for commands
├── ├── reddit.js             -> Interactions with the Reddit API
├── ├── register.js           -> Sets up commands with the Discord API
├── ├── server.js             -> Discord app logic and routing
├── test
├── ├── test.js               -> Tests for app
├── wrangler.toml             -> Configuration for Cloudflare Workers
├── package.json
├── README.md
├── renovate.json             -> Configuration for repo automation
├── .eslintrc.json
├── .prettierignore
├── .prettierrc.json
└── .gitignore

export const AWW_COMMAND = {
  name: 'awwww',
  description: 'Drop some cuteness on this channel.',
};

export const INVITE_COMMAND = {
  name: 'invite',
  description: 'Get an invite link to add the bot to your server',
};

import { AWW_COMMAND, INVITE_COMMAND } from './commands.js';
import fetch from 'node-fetch';

/**
 * This file is meant to be run from the command line, and is not used by the
 * application server.  It's allowed to use node.js primitives, and only needs
 * to be run once.
 */

const token = process.env.DISCORD_TOKEN;
const applicationId = process.env.DISCORD_APPLICATION_ID;

if (!token) {
  throw new Error('The DISCORD_TOKEN environment variable is required.');
}
if (!applicationId) {
  throw new Error(
    'The DISCORD_APPLICATION_ID environment variable is required.'
  );
}

/**
 * Register all commands globally.  This can take o(minutes), so wait until
 * you're sure these are the commands you want.
 */
async function registerGlobalCommands() {
  const url = `https://discord.com/api/v10/applications/${applicationId}/commands`;
  await registerCommands(url);
}

async function registerCommands(url) {
  const response = await fetch(url, {
    headers: {
      'Content-Type': 'application/json',
      Authorization: `Bot ${token}`,
    },
    method: 'PUT',
    body: JSON.stringify([AWW_COMMAND, INVITE_COMMAND]),
  });

  if (response.ok) {
    console.log('Registered all commands');
  } else {
    console.error('Error registering commands');
    const text = await response.text();
    console.error(text);
  }
  return response;
}

await registerGlobalCommands();

$ DISCORD_TOKEN=**** DISCORD_APPLICATION_ID=**** node src/register.js

$ npm run dev

$ npm run ngrok

release:
  if: github.ref == 'refs/heads/main'
  runs-on: ubuntu-latest
  needs: [test, lint]
  steps:
    - uses: actions/checkout@v2
    - uses: actions/setup-node@v2
      with:
        node-version: 16
    - run: npm install
    - run: npm run publish
      env:
        CF_API_TOKEN: ${{ secrets.CF_API_TOKEN }}
        CF_ACCOUNT_ID: ${{ secrets.CF_ACCOUNT_ID }}

export default {
  /**
   * Every request to a worker will start in the `fetch` method.
   * Verify the signature with the request, and dispatch to the router.
   * @param {*} request A Fetch Request object
   * @param {*} env A map of key/value pairs with env vars and secrets from the cloudflare env.
   * @returns
   */
  async fetch(request, env) {
    if (request.method === 'POST') {
      // Using the incoming headers, verify this request actually came from discord.
      const signature = request.headers.get('x-signature-ed25519');
      const timestamp = request.headers.get('x-signature-timestamp');
      const body = await request.clone().arrayBuffer();
      const isValidRequest = verifyKey(
        body,
        signature,
        timestamp,
        env.DISCORD_PUBLIC_KEY
      );
      if (!isValidRequest) {
        console.error('Invalid Request');
        return new Response('Bad request signature.', { status: 401 });
      }
    }

    // Dispatch the request to the appropriate route
    return router.handle(request, env);
  },
};

/**
 * Main route for all requests sent from Discord.  All incoming messages will
 * include a JSON payload described here:
 * /developers/docs/interactions/receiving-and-responding#interaction-object
 */
router.post('/', async (request, env) => {
  const message = await request.json();
  console.log(message);
  if (message.type === InteractionType.PING) {
    // The `PING` message is used during the initial webhook handshake, and is
    // required to configure the webhook in the developer portal.
    console.log('Handling Ping request');
    return new JsonResponse({
      type: InteractionResponseType.PONG,
    });
  }

  if (message.type === InteractionType.APPLICATION_COMMAND) {
    // Most user commands will come as `APPLICATION_COMMAND`.
    switch (message.data.name.toLowerCase()) {
      case AWW_COMMAND.name.toLowerCase(): {
        console.log('handling cute request');
        const cuteUrl = await getCuteUrl();
        return new JsonResponse({
          type: InteractionResponseType.CHANNEL_MESSAGE_WITH_SOURCE,
          data: {
            content: cuteUrl,
          },
        });
      }
      case INVITE_COMMAND.name.toLowerCase(): {
        const applicationId = env.DISCORD_APPLICATION_ID;
        const INVITE_URL = `https://discord.com/oauth2/authorize?client_id=${applicationId}&scope=applications.commands`;
        return new JsonResponse({
          type: InteractionResponseType.CHANNEL_MESSAGE_WITH_SOURCE,
          data: {
            content: INVITE_URL,
            flags: InteractionResponseFlags.EPHEMERAL,
          },
        });
      }
      default:
        console.error('Unknown Command');
        return new JsonResponse({ error: 'Unknown Type' }, { status: 400 });
    }
  }

  console.error('Unknown Type');
  return new JsonResponse({ error: 'Unknown Type' }, { status: 400 });
});