Basic minimax recursion

gistfile1.rb

def minimax(max_player = true, ply = 0, min_score = 1000, max_score = -1000)                                                                                                                           
  if board.winner?
    return(max_player ? (-1000 + ply) : (1000 - ply)) 
  elsif board.draw_game?
    return 0
  end

  best_move = 0
  
  available_moves.each do |index| 
    board[index]   = ( max_player ? side : opposite_side(side) )
    score          = minimax(!max_player, ply + 1, min_score, max_score)
    undo_move(index)
    if max_player && score > max_score 
      max_score  = score
      best_move  = index
    elsif !max_player && score < min_score
      min_score = score
    end
  end

  return( ply == 0 ? best_move : ( max_player ? max_score : min_score ) )
end