rock-paper-scissors/src/main/kotlin/rps/Game.kt

package rps

fun main() {
  println("Hello, world")
}

/**
 * A possible move in a game of rock-paper-scissors.
 *
 * [strongAgainst] is a function for lazy evaluation because otherwise we can’t access SCISSORS before it’s been defined.
 * If the game needs to be expanded (e.g. the somewhat common “rock, paper, scissors, salamander, spock”),
 * this argument could be a List<Move> instead.
 */
enum class Move(val strongAgainst: () -> Move) {
  ROCK({ SCISSORS }),
  PAPER({ ROCK }),
  SCISSORS({ PAPER })
}

// purposely not calling this Result to avoid confusion with kotlin.Result and similar
enum class Outcome {
  WIN,
  DRAW,
  LOSS
}

/** Determine the [Outcome] of [first] vs [second] from the perspective of [first]. */
fun determineOutcome(first: Move, second: Move): Outcome = when {
  first.strongAgainst() == second -> Outcome.WIN
  first == second -> Outcome.DRAW
  else -> Outcome.LOSS
}