discord_chess_bot.py

import discord
import chess

token = "It's a secret *wink wink*"

class ChessClient(discord.Client):
    def __init__(self): 
        super().__init__() 
        self.chess_board = None
        self.players = None
        self.resigning = False

    async def on_ready(self): 
        print(f'logged on as {self.user}') 

    async def on_message(self, message):
        if message.author.id == self.user.id or message.channel.name.lower() != 'chess':
            return
        if self.chess_board:
            if message.author not in self.players:
                return
            elif message.content in ('/resign', '/quit'):
                if not self.resigning:
                    await message.channel.send('Are you sure you want to resign in this game? Type `/quit` again to confirm')
                    self.resigning = True
                else:
                    resigner = self.players[not self.players.index(message.author)]
                    await message.channel.send('Resign confirmed. '+resigner.mention + ', Your opponent has resigned')
                    self.resigning = False
                    self.chess_board = None
                    self.players = None
                    return
            elif message.author.id == self.players[1].id:
                pass
            m = message.content.strip()
            if m.startswith('m ') or m.startswith('move '):
                _, m, *_ = m.split()
                try:
                    self.chess_board.push_san(m)
                except ValueError as err:
                    if err.args[0].startswith('illegal'):
                        reply = f'Illegal move! `{m}`'
                    else:
                        reply = f'Malformed move notation `{m}`. Type `/help` to get help on how to write moves.'
                    await message.channel.send(reply)
                    return

                if self.chess_board.is_game_over():
                    await message.channel.send(f'Game over, GG!\n```{self.chess_board!s}```')
                    self.chess_board = None
                    self.players = None
                    return

                self.players = tuple(reversed(self.players))
                await message.channel.send('Your turn ' + self.players[0].mention)
        if message.content.count('challenge') > 0:
            if len(message.mentions) == 0:
                await message.channel.send(message.author.mention + ' You must mention someone to challenge them to a game of chess')
                return
            if not self.players:
                if message.mentions[0].id == self.user.id:
                    await message.channel.send('I\'m not very good at chess :flushed: Try challenging someone else!')
                    return
                self.players = (
                    message.author,
                    message.mentions[0],
                )
                await message.channel.send(message.author.mention + " Challenge initiated")
                print("Challenge initiated:", message.author.mention, message.mentions[0].mention)
            else:
                await message.channel.send(message.author.mention + " Sorry, a challenge has already been initiated")
        if message.content.count('accept') > 0:
            if not self.players:
                await message.channel.send(message.author.mention + " No one challenged *you*")
                return
            elif self.players[1].id != message.author.id:
                await message.channel.send(message.author.mention + " You can't just accept someone else's challenge like that! Rude...")
                return
            await message.channel.send("Challenge accepted! Prepare to play " + self.players[0].mention)
            self.chess_board = chess.Board()
            # The challenge acceptor goes first
            self.players = tuple(reversed(self.players))
            await message.channel.send(self.players[0].mention + ' You go first')

        if message.content.count('reject') > 0:
            if not self.players:
                await message.channel.send('Why do you reject me? :cry: (There is no challenge to reject)')
                return
            elif self.players[1].id != message.author.id:
                await message.channel.send("But what if they wanted to play...")
                return
            await message.channel.send("Maybe another time...\n" + self.players[0].mention + ' They don\'t want to play chess at the moment :disappointed:')
            self.players = None

        if message.content.startswith('/help'):
            await message.channel.send(
                'Welcome to the chess room!\n' \
                + 'You can challenge a user to a game of chess by typing `challenge` and mentioning the user in the same message (using @-NAME)\n' \
                + 'Accept a challenge by simply typing `accept` (you can reject with `reject`). The game now starts!\n' \
                + 'Move your pieces with `move MOVE` where MOVE is a move in Standard Algebraic Notation, SAN (trust me, it\'s easy!) You can read up on how it works here: http://cfajohnson.com/chess/SAN/\n' \
                + 'The game ends according to the normal rules of chess. Alternatively, you can end it early with `/resign` or `/quit`\n' \
                + 'show the board at any time with `show board`\n'
            )

        if message.content.count('show board') > 0:
            if not self.chess_board:
                await message.channel.send('''
```
 |a b c d e f g h
-+---------------
8|  I ' M
7|  W I N N I N G
6|  Y O U ' R E
5|  L O S I N G
4|  T O O   B A D
3|  S O   S A D
2|
1|  L O L   J K
```
*No game is playing right now*''')
                return
            board = str(self.chess_board)
            board = f' |a b c d e f g h\n-+{"-"*15}\n' + '\n'.join(str(8-i)+'|'+row for i, row in enumerate(board.split('\n')))
            await message.channel.send(f'```\n{board}\n```')
            return
        print(f'Message from {message.author}: {message.content}')

client = ChessClient()
client.run(token)