# By alan snape
# All rights reserved.

class RockPaperScissors

  # Exceptions this class can raise:
  class NoSuchStrategyError < StandardError; end

  # check strategy is legal or not
  def self.checkStrategy(stg)
    if 'P' != stg && 'R' != stg && 'S' != stg then
      raise NoSuchStrategyError, 'Strategy must be one of R,P,S'
    end
  end

  # a single round game
  def self.winner(player1, player2)
    stg1, stg2 = player1[1], player2[1]
    self.checkStrategy(stg1)
    self.checkStrategy(stg2)
    if stg1 == stg2 then
      return player1
    elsif 'P' == stg1 && 'S' == stg2 then
      return player2
    elsif 'S' == stg1 && 'P' == stg2 then
      return player1
    else
      return stg1 < stg2 ? player1 : player2
    end
  end

  # if there is a sub game then returns the winner of it
  # else return this player himself
  def self.tournament_match(game)
    if game[0].kind_of?(Array) then
      return self.tournament_winner(game)
    else
      return game
    end
  end

  # tournament game rounds
  def self.tournament_winner(tournament)
    player1 = self.tournament_match(tournament[0])
    player2 = self.tournament_match(tournament[1])
    return self.winner(player1, player2)
  end

end