ChessBot

This is a Slack bot that allows players to challenge each other to a game of Chess.

Hosted Version

Requirements

• Go 1.12 - Older versions will work, but go mod is being used to manage dependencies.

Quick Start

cp .env.sample .env
export $(cat .env | xargs) && go run cmd/web/web.go

Configuration

Environment Variable	Default	Description
PORT	8080	Port that the web server will listen
HOSTNAME	localhost:8080	Used for generating links to render the game board state images
SIGNINGKEY	N/A	Key used to sign the signature for board rendering URLs
SQLITEPATH	N/A	Path to a sqlite3 database file. If not included, falls back to memory store.
SLACKAPPID	N/A	The app ID that operates the slack bot.
SLACKCLIENTID	N/A	Slack app client ID
SLACKCLIENTSECRET	N/A	Slack app client secret
SLACKSIGNINGKEY	N/A	Used to verify the request signature originates from slack

Installing

https://slack.com/oauth/authorize?client_id=<client_id_here>&scope=bot

Endpoints

GET /board?fen=&signature=&from=&to=&check=

Renders the game board based on the state of a game by FEN.

POST /slack

All slack event subscription callbacks flow through this.

• This is used for all typed commands mentioning @ChessBot in the channel.

POST /slack/action

All slack interactive component callbacks flow through this.

• This is used for accepting/rejecting challenges.

GET /slack/oauth

Slack app installation requests flow through here. A bot token is generated as part of the key exchange and stored keyed by team ID.

GET /analyze?game_id=

• This endpoint is used to generate an analysis of a game. It will redirect the user upon successful import to an analysis provider.

Testing with Slack

In order to do end-to-end testing with Slack, you will need to use a service that exposes your environment to Slack to allow webhooks to enter your application. I use ngrok, but any local tunnelling software should work.

Because our application needs to know what the external hostname is, you'll need to start the tunneling service first to get a provided hostname from the service:

ngrok http 8080

The 8080 port is what we specify by default in .env. Once the service is started and established, copy the hostname into .env for HOSTNAME environment variable, then start the application.

You will then need to enter the hostname into slack and allow them to prob your application with a challenge to ensure your app is authorized with the correct API tokens.

Finally, configure the interactive components to point to the action endpoint:

See the Slack integration docs for more info.

Testing the Chess Engine

go run cmd/repl/main.go

λ go run cmd/repl/main.go
Game REPL
Note: piece colors may appear reversed on dark background terminals.
Game ID: jcghocxkvgakyefcjgsd

 A B C D E F G H
8♜ ♞ ♝ ♛ ♚ ♝ ♞ ♜
7♟ ♟ ♟ ♟ ♟ ♟ ♟ ♟
6- - - - - - - -
5- - - - - - - -
4- - - - - - - -
3- - - - - - - -
2♙ ♙ ♙ ♙ ♙ ♙ ♙ ♙
1♖ ♘ ♗ ♕ ♔ ♗ ♘ ♖

player2's turn (White)

> d2d4

 A B C D E F G H
8♜ ♞ ♝ ♛ ♚ ♝ ♞ ♜
7♟ ♟ ♟ ♟ ♟ ♟ ♟ ♟
6- - - - - - - -
5- - - - - - - -
4- - - ♙ - - - -
3- - - - - - - -
2♙ ♙ ♙ - ♙ ♙ ♙ ♙
1♖ ♘ ♗ ♕ ♔ ♗ ♘ ♖

player1's turn (Black)

> export
[Site "Slack ChessBot match"]
[White "player2"]
[Black "player1"]

1.d4 *

> fen
rnbqkbnr/pppppppp/8/8/3P4/8/PPP1PPPP/RNBQKBNR b KQkq d3 0 1

>

Why not use Slack's RTM API?

1. We do not need realtime communication, webhooks perform perfectly fine for the asynchonous nature of Chess.
2. We have to implement a web server anyways for serving the game board as a PNG to be unfurled by Slack.
3. RTM messages don't support attachments.