rails--rails/activestorage/app/models/active_storage/blob/identifiable.rb

# frozen_string_literal: true

module ActiveStorage::Blob::Identifiable
  def identify
    update! content_type: identify_content_type, identified: true unless identified?
  end

  def identified?
    identified
  end

  private
    def identify_content_type
      Marcel::MimeType.for download_identifiable_chunk, name: filename.to_s, declared_type: content_type
    end

    def download_identifiable_chunk
      service.download_chunk key, 0...4.kilobytes
    end
end