require 'leap'

module BrighterPlanet
  module Diet
    module CarbonModel
      def self.included(base)
        base.extend ::Leap::Subject
        base.decide :emission, :with => :characteristics do
          committee :emission do # returns kg CO2
            quorum 'from intensity and size', :needs => [:intensity, :size, :active_subtimeframe] do |characteristics|
              #( grams CO2 / kcal food   ) * (   kcal food         )
              (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 group balance', :needs => :food_group_balance do |characteristics|
              FoodGroup.names.collect do |group|
                characteristics[:food_group_balance]["#{group}_share".to_sym] * FoodGroup.find_by_name(group).intensity
              end.sum
            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
              Diet.diet_model.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