impact_model.rb

module BrighterPlanet
  module Diet
    module ImpactModel
      def self.included(base)
        base.decide :impact, :with => :characteristics do
          committee :carbon do # returns kg CO2
            quorum 'from intensity and size', :needs => [:intensity, :size, :active_subtimeframe] do |characteristics|

              (characteristics[:intensity] * characteristics[:size]).grams.to(:kilograms) * characteristics[:active_subtimeframe].days
            end
            quorum 'default' do
              raise 'Diet emission committee default quorum should never be called'
            end
          end
      
          committee :intensity do # returns grams CO2 / kcal food
            quorum 'from food groups', :needs => [:red_meat_share, :poultry_share, :fish_share, :eggs_share, :nuts_share, :dairy_share, :cereals_and_grains_share, :fruit_share, :vegetables_share, :oils_and_sugars_share] do |characteristics|
              [:red_meat, :poultry, :fish, :eggs, :nuts, :dairy, :cereals_and_grains, :fruit, :vegetables, :oils_and_sugars].sum do |group|
                characteristics["#{group}_share".to_sym].to_f * FoodGroup[group].intensity.to_f
              end
            end
      
            quorum 'from diet class', :needs => :diet_class do |characteristics|
              characteristics[:diet_class].intensity
            end
          end
      
          committee :size do # returns kcal food
            quorum 'default' do
              base.fallback.size
            end
          end
      
          committee :diet_class do
            quorum 'default' do
              DietClass.fallback
            end
          end
      
          committee :active_subtimeframe do
            quorum 'from start and end dates', :needs => [:start_date, :end_date] do |characteristics, timeframe|
              Timeframe.constrained_new characteristics[:start_date], characteristics[:end_date], timeframe
            end
          end
          
          committee :start_date do
            quorum 'from end date', :appreciates => :end_date do |characteristics, timeframe|
              [ timeframe.from, characteristics[:end_date] ].compact.min
            end
          end
          
          committee :end_date do
            quorum 'from start date', :appreciates => :start_date do |characteristics, timeframe|
              [ timeframe.to, characteristics[:start_date] ].compact.max
            end
          end
        end
      end
    end
  end
end