Terminal Sudoku in Ruby

sudoku.rb

require 'colorize'

class Tile
  attr_reader :value, :given

  def initialize(value = 0)
    @value = value
    @given = value != 0
  end

  def value=(num)
    @value = num unless given
  end

  def to_s
    value.to_s.colorize(color)
  end

  def color
    if given
      :green
    elsif value == 0
      :red
    else
      :yellow
    end
  end
end

class Board
  attr_reader :grid

  def self.from_file(filename)
    tiles = File.read(filename).gsub(/\W/, '').split('').map do |num|
      Tile.new(num.to_i)
    end
    Board.new(tiles)
  end

  def initialize(grid)
    @grid = grid
  end

  def given?(pos)
    grid[pos].given
  end

  def render
    grid.each_slice(9) { |row| print_row(row) }
  end

  def print_row(row)
    row.each { |tile| print tile.to_s }
    print "\n"
  end

  def get_row(pos)
    (0...9).map { |i| pos / 9 * 9 + i }.map { |i| grid[i].value }
  end

  def get_col(pos)
    (0...9).map { |i| pos % 9 + i * 9 }.map { |i| grid[i].value }
  end

  def group_solved?(arr)
    ((1..9).to_a - arr).empty?
  end

  def get_box(pos)
    row_start = (pos / 9) / 3 * 3
    col_start = (pos % 9) / 3 * 3
    (0...3).map do |i|
      (0...3).map do |j|
        (row_start + i) * 9 + (col_start + j)
      end
    end.flatten.map { |i| grid[i].value }
  end

  def solved?
    (0...81).all? do |pos|
      group_solved?( get_row(pos) ) &&
      group_solved?( get_col(pos) ) &&
      group_solved?( get_box(pos) )
    end
  end

  def make_move(choice)
    pos = choice[0]
    val = choice[1]
    @grid[pos].value = val
  end
end

class Game
  attr_reader :board

  def initialize(filename)
    @board = Board.from_file(filename)
  end

  def play
    while !solved?
      board.render
      choice = get_input
      make_move(choice)
    end

    board.render
    game_over_message
  end

  def solved?
    board.solved?
  end

  def get_input
    pos = get_pos
    val = get_val
    [pos, val]
  end

  def valid_pos?(pos_str)
    pos = pos_str.to_i
    pos_str =~ /^\d+$/ && pos >= 0 && pos < 81   && !board.given?(pos.to_i)
  end

  def valid_val?(val_str)
    val_str =~ /^[1-9]$/
  end

  def get_pos
    loop do
      print "Enter position: "
      pos_str = gets.chomp
      return pos_str.to_i if valid_pos?(pos_str)
    end
  end

  def get_val
    loop do
      print "Enter value: "
      val_str = gets.chomp
      return val_str.to_i if valid_val?(val_str)
    end
  end

  def make_move(choice)
    board.make_move(choice)
  end

  def game_over_message
    puts "You win!!"
  end
end