Create a hash for the variants of a product based on the options value

product_varitans_by_option_values.rb

Spree::Product.class_eval do
  def variants_hash
    product_variants = self.variants.to_a
    color_hash = {}

    option_value_variants = -> (color_id) do
      sizes_hash = {}

      option_values_for('Size').map do |option_value|
        size_variants = option_value.variants.to_a.keep_if do |variant|
          product_variants.include? variant
        end

        size_variant = size_variants.keep_if do |variant|
          variant.option_values.map(&:id).include? color_id
        end.first # there should only be one left over

        size_variants.map do |size_variant|
          if size_variant.option_values.find_by(option_type_id: 1)
            sizes_hash[option_value.value_name.to_sym] = size_variant.gon_object
          end
        end
      end

      sizes_hash
    end

    option_values_for('Color').map do |option_value|
      color_hash[option_value.value_name.to_sym] = option_value_variants.call(option_value.id)
    end

    color_hash
  end
 end