render_jpg_concern.rb

module RenderJpgConcern
  MIN_WIDTH = 20
  MAX_WIDTH = 1000
  MIN_HEIGHT = 20
  MAX_HEIGHT = 1000
  DEFAULT_WIDTH = 400
  DEFAULT_HEIGHT = 300

  def render_jpg(model)
    http_cache_forever(public: true) do
      image = model.image
      return render_blank_jpg unless image.attached?
      width = params.dig(:image, :width).presence
      height = params.dig(:image, :height).presence
      options = { format: :jpg, gravity: :center }

      if width || height
        width ||= DEFAULT_WIDTH
        height ||= DEFAULT_HEIGHT
        width = [MAX_WIDTH, [MIN_WIDTH, width.to_i].max].min
        height = [MAX_HEIGHT, [MIN_HEIGHT, height.to_i].max].min
        options[:resize] = "#{width.to_i}x#{height.to_i}^"
        options[:extent] = "#{width.to_i}x#{height.to_i}"
      end

      send_data(
        image.variant(**options).processed.download,
        filename: "#{model.slug}.jpg",
        disposition: :inline,
        type: "image/jpeg"
      )
    end
  rescue ActiveStorage::FileNotFoundError
    model.image.purge
    render_blank_jpg
  end

  def render_blank_jpg
    send_file(
      Rails.root.join("app/assets/images/blank.jpg"),
      filename: "blank.jpg",
      disposition: :inline,
      type: "image/jpeg"
    )
  end
end