Balance teams automatically

import { createRoom } from 'ball2d/node';

const TEAM_SIZE = 3;

const room = await createRoom({
  apiKey: process.env.BALL2D_API_KEY,
  roomName: '3v3 balanced',
  noPlayer: true,
  maxPlayers: 10,
  public: true,
});

const team = (id) =>
  room.getPlayerList().filter((p) => p.team === id);

async function balance() {
  // Fill the smaller team from the spectators, oldest first.
  for (const spectator of team(0)) {
    const [red, blue] = [team(1).length, team(2).length];
    if (Math.min(red, blue) >= TEAM_SIZE) break;
    await room.setPlayerTeam(spectator.id, red <= blue ? 1 : 2);
  }
  // Move one player across if the teams differ by two or more.
  const [red, blue] = [team(1), team(2)];
  if (Math.abs(red.length - blue.length) >= 2) {
    const larger = red.length > blue.length ? red : blue;
    await room.setPlayerTeam(
      larger.at(-1).id,
      larger === red ? 2 : 1,
    );
  }
  if (
    team(1).length > 0 &&
    team(2).length > 0 &&
    room.getScores() === null
  )
    await room.startGame();
}

let queue = Promise.resolve();
const rebalance = () => {
  queue = queue
    .then(balance)
    .catch((error) => console.error('Balance failed:', error));
};

room.onPlayerJoin = rebalance;
room.onPlayerLeave = rebalance;
room.onGameStop = rebalance;

await room.setTeamsLock(true);
await room.setDefaultStadium('Classic');
console.log(room.roomLink);