rounds.js

[
  [
    [a, b],
    [c, d]
  ],
  [
    [a, d]
  ]
]





const players = [a, b, c, d]
const rounds = 4

(1..rounds).reduce((accumulated) => {
  if (accumulated.length == rounds - 1) {
    return accumulated
  }
  return [...accumulated, generateRound(discoverWinners(accumulated))]
}, [generateRound(players)])


// Pairings = Array<VS>
// ReadyPlayers = Array<Player>
// RoundList => ReadyPlayers
function discoverWinners (rounds) {
  return rounds.last().map(battle)
}
// ReadyPlayers => Pairings
function generateRound (players) {
  return ...
}

// VS = [Player, Player]
// VS => Winner
function battle(vs) {
  ...
}