module Inch
  module Evaluation
    # Role objects are assigned to evaluations of code objects. They describe
    # the object they are attached to.
    # @abstract
    class Role
      attr_reader :object

      class << self
        def applicable_if(symbol = nil, &block)
          @applicable_procs ||= {}
          @applicable_procs[to_s] = block || symbol.to_proc
        end

        def applicable_unless(symbol = nil, &block)
          @applicable_procs ||= {}
          @applicable_procs[to_s] = proc do |object|
            !(block || symbol.to_proc).call(object)
          end
        end

        def applicable?(object)
          @applicable_procs ||= {}
          @applicable_procs[to_s].call(object)
        end

        def priority(value)
          define_method(:priority) { value }
        end
      end

      # @param object [Codebase::Object] the object to evaluate
      # @param value [Float] a score that might be added by this role
      def initialize(object, value = nil)
        @object = object
        @value = value
      end

      # Returns a maximal score for the object.
      # The final score can not be higher than this.
      # @note Override this method to that a max_score for the evaluation.
      # @return [Float]
      def max_score
      end

      # Returns a minimal score for the object.
      # The final score can not be lower than this.
      # @note Override this method to that a min_score for the evaluation.
      # @return [Float]
      def min_score
      end

      # Returns a score that will be added to the associated object's
      # overall score.
      #
      # @note Override this method to assign a score for the role
      # @return [Float]
      def score
        @value.to_f
      end

      # Returns a potential score that would be added to the overall score
      # if the object had implemented the Role's subject.
      #
      # @see Role::Missing
      # @note Override this method to assign a potential score for the role
      # @return [Float]
      def potential_score
        nil
      end

      # Returns a priority that will be added to the associated object's
      # overall priority.
      #
      # @note Override this method to assign a priority for the role
      # @return [Fixnum]
      def priority
        0
      end

      # Returns a suggestion to achieve the potential score that would be
      # added to the overall score if the object had implemented the Role's
      # subject.
      #
      # @see Role::Missing
      # @return [String]
      def suggestion
        nil
      end

      # Returns the type of the +object+ that is being evaluated.
      #
      # @return [String]
      def object_type
        fail NotImplementedError
      end
    end
  end
end