minecraft crafting data modeling exercise

recipe.rb

class Recipe
  attr_reader :recipe

  def initialize(recipe)
    @recipe = recipe
    standardize
  end

  private

  # There's no error checking for a recipe composed of nothing :empty cells
  def standardize
    rotate_cols while first_col_empty?
    rotate_rows while first_row_empty?
  end

  def rotate_cols
    @recipe.each &:rotate!
  end

  def rotate_rows
    @recipe[0], @recipe[1], @recipe[2] = @recipe[1], @recipe[2], @recipe[0]
  end

  def first_col_empty?
    @recipe.all?{|r| r[0] == :empty}
  end

  def first_row_empty?
    @recipe[0].all?{|c| c == :empty}
  end
end

standardized_input = [
  [:coal,  :empty, :empty, ],
  [:stick, :empty, :empty, ],
  [:empty, :empty, :empty, ],
]

inputs = [
  [
    [:coal,  :empty, :empty, ],
    [:stick, :empty, :empty, ],
    [:empty, :empty, :empty, ],
  ],
  [
    [:empty, :empty, :empty, ],
    [:coal,  :empty, :empty, ],
    [:stick, :empty, :empty, ],
  ],
  [
    [:empty, :coal,  :empty, ],
    [:empty, :stick, :empty, ],
    [:empty, :empty, :empty, ],
  ],
  [
    [:empty, :empty, :empty, ],
    [:empty, :coal,  :empty, ],
    [:empty, :stick, :empty, ],
  ],
  [
    [:empty, :empty, :coal,  ],
    [:empty, :empty, :stick, ],
    [:empty, :empty, :empty, ],
  ],
  [
    [:empty, :empty, :empty, ],
    [:empty, :empty, :coal,  ],
    [:empty, :empty, :stick, ],
  ],
]

inputs.each do |input|
  recipe = Recipe.new(input)
  puts recipe.recipe == standardized_input
end