module Coverable
  extend ActiveSupport::Concern

  COVER_IMAGE_TYPES = %w[image/png image/jpeg image/webp].freeze
  MAX_COVER_BYTES = 5.megabytes

  included do
    has_one_attached :cover_image
    has_one_attached :cover_slate

    validate :cover_image_file_type, if: -> { cover_image.attached? && cover_image.blob&.new_record? }
    validate :cover_image_file_size, if: -> { cover_image.attached? && cover_image.blob&.new_record? }
  end

  def cover_image_attached?
    cover_image.attached?
  end

  def cover_url
    return unless cover_image.attached?

    Rails.application.routes.url_helpers.rails_blob_path(cover_image, only_path: true)
  end

  def effective_cover_url
    if cover_image.attached?
      cover_url
    else
      cover_parent&.effective_cover_url
    end
  end

  private

  def cover_parent
    nil
  end

  def cover_image_file_type
    return if cover_image.content_type.in?(COVER_IMAGE_TYPES)

    errors.add(:cover_image, I18n.t("coverable.errors.invalid_type"))
  end

  def cover_image_file_size
    return if cover_image.byte_size <= MAX_COVER_BYTES

    errors.add(:cover_image, I18n.t("coverable.errors.too_large"))
  end
end