require 'set'
class Surrogate

  # Reflects on the surrogate class to give info about methods that are useful for the comparer
  #
  # It might make sense to not treat instance and class differently, but instead let whoever wants to use this
  # instantiate it with both the class and the singleton class.
  class SurrogateClassReflector < Struct.new(:surrogate_class)
    def methods
      { instance: {
          api:            instance_api_methods,
          inherited:      instance_inherited_methods,
          other:          instance_other_methods,
          without_bodies: instance_without_bodies,
        },
        class: {
          api:            class_api_methods,
          inherited:      class_inherited_methods,
          other:          class_other_methods,
          without_bodies: class_without_bodies,
        },
      }
    end

    def instance_api_methods
      Set.new class_hatchery.api_method_names
    end

    def instance_inherited_methods
      Set.new surrogate_class.instance_methods - surrogate_class.instance_methods(false)
    end

    def instance_other_methods
      Set.new(surrogate_class.instance_methods false) - instance_api_methods
    end

    def instance_without_bodies
      Set.new class_hatchery.api_method_names.reject { |name| class_hatchery.api_method_for name }
    end

    def class_api_methods
      Set.new singleton_class_hatchery.api_method_names
    end

    def class_inherited_methods
      Set.new surrogate_class.singleton_class.instance_methods - surrogate_class.singleton_class.instance_methods(false)
    end

    def class_other_methods
      Set.new(surrogate_class.singleton_class.instance_methods false) - class_api_methods - class_inherited_methods
    end

    def class_without_bodies
      Set.new singleton_class_hatchery.api_method_names.reject { |name| singleton_class_hatchery.api_method_for name }
    end

    def class_hatchery
      @class_hatchery ||= surrogate_class.instance_variable_get :@hatchery
    end

    def singleton_class_hatchery
      @singleton_class_hatchery ||= surrogate_class.singleton_class.instance_variable_get :@hatchery
    end
  end
end