Building a Discord Bot
- Go to https://discord.com/developers/applications (login using your discord account if required).
- Click on New Application button available at left side of your profile picture.
- Name your application and click on Create.
- Go to Bot section, click on Add Bot, and finally on Yes, do it! to confirm.
That's it. A new application is created which will hold our Slash Command. Don't close the tab as we need information from this application page throughout our development.
Before we can write some code, we need to curl a discord endpoint to register a Slash Command in our app.
Fill DISCORD_BOT_TOKEN
with the token available in the Bot section and CLIENT_ID
with the ID available on the General Information section of the page and run the command on your terminal.
_10BOT_TOKEN='replace_me_with_bot_token'
_10CLIENT_ID='replace_me_with_client_id'
_10-H 'Content-Type: application/json' \
_10-H "Authorization: Bot $BOT_TOKEN" \
_10-d '{"name":"hello","description":"Greet a person","options":[{"name":"name","description":"The name of the person","type":3,"required":true}]}' \
_10"https://discord.com/api/v8/applications/$CLIENT_ID/commands"
This will register a Slash Command named hello
that accepts a parameter named name
of type string.
_94// Sift is a small routing library that abstracts away details like starting a
_94// listener on a port, and provides a simple function (serve) that has an API
_94// to invoke a function for a specific path.
_94import { json, serve, validateRequest } from 'https://deno.land/x/sift@0.6.0/mod.ts'
_94// TweetNaCl is a cryptography library that we use to verify requests
_94import nacl from 'https://cdn.skypack.dev/tweetnacl@v1.0.3?dts'
_94enum DiscordCommandType {
_94 ApplicationCommand = 2,
_94// For all requests to "/" endpoint, we want to invoke home() handler.
_94 '/discord-bot': home,
_94// The main logic of the Discord Slash Command is defined in this function.
_94async function home(request: Request) {
_94 // validateRequest() ensures that a request is of POST method and
_94 // has the following headers.
_94 const { error } = await validateRequest(request, {
_94 headers: ['X-Signature-Ed25519', 'X-Signature-Timestamp'],
_94 return json({ error: error.message }, { status: error.status })
_94 // verifySignature() verifies if the request is coming from Discord.
_94 // When the request's signature is not valid, we return a 401 and this is
_94 // important as Discord sends invalid requests to test our verification.
_94 const { valid, body } = await verifySignature(request)
_94 { error: 'Invalid request' },
_94 const { type = 0, data = { options: [] } } = JSON.parse(body)
_94 // Discord performs Ping interactions to test our application.
_94 // Type 1 in a request implies a Ping interaction.
_94 if (type === DiscordCommandType.Ping) {
_94 type: 1, // Type 1 in a response is a Pong interaction response type.
_94 // Type 2 in a request is an ApplicationCommand interaction.
_94 // It implies that a user has issued a command.
_94 if (type === DiscordCommandType.ApplicationCommand) {
_94 const { value } = data.options.find(
_94 (option: { name: string; value: string }) => option.name === 'name'
_94 // Type 4 responds with the below message retaining the user's
_94 content: `Hello, ${value}!`,
_94 // We will return a bad request error as a valid Discord request
_94 // shouldn't reach here.
_94 return json({ error: 'bad request' }, { status: 400 })
_94/** Verify whether the request is coming from Discord. */
_94async function verifySignature(request: Request): Promise<{ valid: boolean; body: string }> {
_94 const PUBLIC_KEY = Deno.env.get('DISCORD_PUBLIC_KEY')!
_94 // Discord sends these headers with every request.
_94 const signature = request.headers.get('X-Signature-Ed25519')!
_94 const timestamp = request.headers.get('X-Signature-Timestamp')!
_94 const body = await request.text()
_94 const valid = nacl.sign.detached.verify(
_94 new TextEncoder().encode(timestamp + body),
_94 hexToUint8Array(signature),
_94 hexToUint8Array(PUBLIC_KEY)
_94 return { valid, body }
_94/** Converts a hexadecimal string to Uint8Array. */
_94function hexToUint8Array(hex: string) {
_94 return new Uint8Array(hex.match(/.{1,2}/g)!.map((val) => parseInt(val, 16)))
_10supabase functions deploy discord-bot --no-verify-jwt
_10supabase secrets set DISCORD_PUBLIC_KEY=your_public_key
Navigate to your Function details in the Supabase Dashboard to get your Endpoint URL.
- Go back to your application (Greeter) page on Discord Developer Portal
- Fill INTERACTIONS ENDPOINT URL field with the URL and click on Save Changes.
The application is now ready. Let's proceed to the next section to install it.
So to use the hello
Slash Command, we need to install our Greeter application on our Discord server. Here are the steps:
- Go to OAuth2 section of the Discord application page on Discord Developer Portal
- Select
applications.commands
scope and click on the Copy button below.
- Now paste and visit the URL on your browser. Select your server and click on Authorize.
Open Discord, type /Promise
and press Enter.
_10supabase functions serve discord-bot --no-verify-jwt --env-file ./supabase/.env.local