class Ingredient < ActiveRecord::Base

  validates :name, presence: true
  validates :density, density: true, allow_blank: true

  def set_usda_food(food)
    self.ndbn = food.ndbn
    self.density = calculate_density(food.gram_weight_1, food.gram_weight_desc_1) || calculate_density(food.gram_weight_2, food.gram_weight_desc_2)
  end

  def calculate_density(grams, description)
    return nil if grams.blank? || description.blank?

    # replace 'fl oz' with 'floz'
    description = description.gsub(/fl oz/i, 'floz')

    begin
      unit = UnitConversion.parse(description)
      if UnitConversion.volume?(unit)
        mass = Unitwise(grams, 'g')
        density = (mass / unit).convert_to(UnitConversion.normalize_unit_names('oz/cup'))
        return "#{density.value.round(4)} oz/cup"
      else
        return nil
      end
    rescue UnitConversion::UnparseableUnitError
      return nil
    end
  end

end