package snake

/** m04 spawn: placing apples with the Random from Random.scala. */
object Spawn:

  def freeCells(state: GameState): List[Point] =
    for
      y <- Util.range(state.height)
      x <- Util.range(state.width)
      p = Point(x, y)
      if !Util.contains(state.snake, p, _ == _)
    yield p

  def spawnApple(state: GameState): GameState =
    if state.apple.isDefined || state.status != Status.Playing then state
    else
      val cells = freeCells(state)
      if cells.isEmpty then state.copy(status = Status.Won)
      else
        val (i, seed) = Random.intBelow(cells.length).run(state.seed)
        state.copy(apple = Some(cells(i)), seed = seed)

  def tick(state: GameState): GameState = spawnApple(Rules.advance(state))

  def newGame(seed: Long): GameState = spawnApple(Model.initialState(seed))