# Based on https://github.com/Shopify/sorbet/blob/master/gems/sorbet-runtime/lib/types/private/class_utils.rb
module CacheKeeper
  class ReplaceMethod
    class << self
      def replace(cached_method, &block)
        klass = cached_method.klass
        method_name = cached_method.method_name
        alias_for_original_method = cached_method.alias_for_original_method
        original_visibility = visibility_method_name(klass, method_name)

        define_method_with_visibility klass, method_name, alias_for_original_method, original_visibility, &block
      end

      private

      # `name` must be an instance method (for class methods, pass in mod.singleton_class)
      def visibility_method_name(klass, method_name)
        if klass.public_method_defined? method_name
          :public
        elsif klass.protected_method_defined? method_name
          :protected
        elsif klass.private_method_defined? method_name
          :private
        else
          raise NameError.new("undefined method `#{method_name}` for `#{klass}`")
        end
      end

      def define_method_with_visibility(klass, method_name, alias_for_original_method, visibility, &block)
        klass.module_exec do
          alias_method alias_for_original_method, method_name
          private alias_for_original_method

          # Start a visibility (public/protected/private) region, so that
          # all of the method redefinitions happen with the right visibility
          # from the beginning. This ensures that any other code that is
          # triggered by `method_added`, sees the redefined method with the
          # right visibility.
          send visibility

          define_method method_name, &block

          if block && block.arity < 0 && respond_to?(:ruby2_keywords, true)
            ruby2_keywords method_name
          end
        end
      end
    end
  end
end