Monkey patch for storing file changes in paper_trail version object

paper_trail.rb

module PaperTrail
  module Model
    module InstanceMethods
      private

      def changes_for_paper_trail
        notable_changes = changes.delete_if { |k, _v| !notably_changed.include?(k) }
        AttributeSerializers::ObjectChangesAttribute.
          new(self.class).
          serialize(notable_changes)
        if defined?(CarrierWave::Uploader::Base)
          changes_hash_with_carrierwave(notable_changes)
        else
          notable_changes.to_hash
        end
      end

      def changes_hash_with_carrierwave(notable_changes)
        Hash[
          notable_changes.to_hash.map do |attribute, values|
            values_formatter = ValuesFormatter.new(self, attribute, values.first, values.last)
            values_formatter.format!

            [
              attribute,
              [
                values_formatter.before,
                values_formatter.after
              ]
            ]
          end
        ]
      end

      class ValuesFormatter
        def initialize(model, attribute, before, after)
          self.model = model
          self.attribute = attribute
          self.before = before
          self.after = after
        end

        attr_accessor :model, :attribute, :before, :after

        def format!
          return if !(is_uploader?(before) || is_uploader?(after))

          self.before = format_before_value(before)
          self.after = format_after_value(after)
        end

        private

        def format_before_value(value)
          if is_uploader?(value)
            format_before_uploader_value(value)
          else
            format_non_uploader_value(value)
          end
        end

        def format_after_value(value)
          if is_uploader?(value)
            format_after_uploader_value(value)
          else
            format_non_uploader_value(value)
          end
        end

        def format_non_uploader_value(value)
          store_path(value)
        end

        def format_before_uploader_value(value)
          return unless value.file

          store_path(value.file.original_filename)
        end

        def format_after_uploader_value(value)
          return if model.public_send("remove_#{attribute}").to_bool

          store_path(value.file.original_filename)
        end

        def is_uploader?(value)
          value.is_a?(CarrierWave::Uploader::Base)
        end

        def store_path(filename)
          (is_uploader?(before) ? before : after).store_path(filename)
        end
      end
    end
  end
end