# frozen_string_literal: true

module Nanoc
  module Core
    module CompilationStages
      class DetermineOutdatedness < Nanoc::Core::CompilationStage
        include Nanoc::Core::ContractsSupport

        def initialize(reps:, outdatedness_checker:, outdatedness_store:)
          @reps = reps
          @outdatedness_checker = outdatedness_checker
          @outdatedness_store = outdatedness_store
        end

        contract C::None => C::Any
        def run
          outdated_items = select_outdated_items
          outdated_reps = reps_of_items(outdated_items)

          store_outdated_reps(outdated_reps)

          outdated_items
        end

        private

        def store_outdated_reps(reps)
          @outdatedness_store.clear
          reps.each { |r| @outdatedness_store.add(r) }
        end

        def select_outdated_items
          @reps
            .select { |r| outdated?(r) }
            .map(&:item)
            .uniq
        end

        def reps_of_items(items)
          Set.new(items.flat_map { |i| @reps[i] })
        end

        def outdated?(rep)
          if @outdatedness_store.include?(rep)
            # We determined previously that this rep is outdated.
            true
          else
            !@outdatedness_checker.outdatedness_reasons_for(rep).empty?
          end
        end
      end
    end
  end
end
