module Hyrax
  module LocalFileDownloadsControllerBehavior
    protected

      # Handle the HTTP show request
      def send_local_content
        response.headers['Accept-Ranges'] = 'bytes'
        if request.head?
          local_content_head
        elsif request.headers['Range']
          send_range_for_local_file
        else
          send_local_file_contents
        end
      end

      # render an HTTP Range response
      def send_range_for_local_file
        _, range = request.headers['Range'].split('bytes=')
        from, to = range.split('-').map(&:to_i)
        to = local_file_size - 1 unless to
        length = to - from + 1
        response.headers['Content-Range'] = "bytes #{from}-#{to}/#{local_file_size}"
        response.headers['Content-Length'] = length.to_s
        self.status = 206
        prepare_local_file_headers
        # For derivatives stored on the local file system
        send_data IO.binread(file, length, from), local_derivative_download_options.merge(status: status)
      end

      def send_local_file_contents
        self.status = 200
        prepare_local_file_headers
        # For derivatives stored on the local file system
        send_file file, local_derivative_download_options
      end

      def local_file_size
        File.size(file)
      end

      def local_file_mime_type
        mime_type_for(file)
      end

      # @return [String] the filename
      def local_file_name
        params[:filename] || File.basename(file) || (asset.respond_to?(:label) && asset.label)
      end

      def local_file_last_modified
        File.mtime(file) if file.is_a? String
      end

      # Override
      # render an HTTP HEAD response
      def local_content_head
        response.headers['Content-Length'] = local_file_size.to_s
        head :ok, content_type: local_file_mime_type
      end

      # Override
      def prepare_local_file_headers
        send_file_headers! local_content_options
        response.headers['Content-Type'] = local_file_mime_type
        response.headers['Content-Length'] ||= local_file_size.to_s
        # Prevent Rack::ETag from calculating a digest over body
        response.headers['Last-Modified'] = local_file_last_modified.utc.strftime("%a, %d %b %Y %T GMT")
        self.content_type = local_file_mime_type
      end

    private

      # Override the Hydra::Controller::DownloadBehavior#content_options so that
      # we have an attachement rather than 'inline'
      def local_content_options
        { type: local_file_mime_type, filename: local_file_name, disposition: 'attachment' }
      end

      # Override this method if you want to change the options sent when downloading
      # a derivative file
      def local_derivative_download_options
        { type: local_file_mime_type, filename: local_file_name, disposition: 'inline' }
      end
  end
end