gistfile1.rb

module CalorieCalculator
  def caloric_need
    caloric_need_without_goal + calorie_need
  end

private

  # formula from http://www.bodybuilding.com/fun/issa64.htm
  def caloric_need_without_goal
    (weight * gender_multiplier * weight_multiplier * bodyfat_multiplier * activity_multiplier).round
  end

  def calorie_need
    case goal
    when -2 then -500
    when -1 then -200
    when 1 then 200
    when 2 then 500
    else
      0
    end
  end

  def gender_multiplier
    male? ? 1.0 : 0.9
  end

  def weight_multiplier
    24
  end

  def bodyfat_multiplier
    case bodyfat
    when very_low_bodyfat  then 1.0
    when low_bodyfat       then 0.95
    when high_bodyfat      then 0.90
    when very_high_bodyfat then 0.85
    else 1
    end
  end

  def activity_multiplier
    case activity_level
    when 'very_light' then 1.3
    when 'light'      then 1.55
    when 'average'    then 1.65
    when 'fit'        then 1.8
    when 'athlete'    then 2.0
    else 1
    end
  end

  def very_low_bodyfat
    male? ? 0.0..0.14 : 0.14..0.18
  end

  def low_bodyfat
    male? ? 0.14..0.20 : 0.18..0.28
  end

  def high_bodyfat
    male? ? 0.20..0.28 : 0.28..0.38
  end

  def very_high_bodyfat
    male? ? 0.28..1 : 0.38..1
  end

  def male?; gender == 'm'; end
end