demarches-normaliennes/app/jobs/titre_identite_watermark_job.rb

class TitreIdentiteWatermarkJob < ApplicationJob
  class FileNotScannedYetError < StandardError
  end

  # If by the time the job runs the blob has been deleted, ignore the error
  discard_on ActiveRecord::RecordNotFound
  # If the file is deleted during the scan, ignore the error
  discard_on ActiveStorage::FileNotFoundError
  # If the file is not analyzed or scanned for viruses yet, retry later
  # (to avoid modifying the file while it is being scanned).
  retry_on FileNotScannedYetError, wait: :exponentially_longer, attempts: 10

  def perform(blob)
    return if blob.watermark_done?
    raise FileNotScannedYetError if blob.virus_scanner.pending?

    blob.open do |file|
      Tempfile.create(["watermarked", File.extname(file)]) do |output|
        processed = WatermarkService.new.process(file, output)
        return if processed.blank?

        blob.upload(processed) # also update checksum & byte_size accordingly
        blob.watermarked_at = Time.current
        blob.save!
      end
    end
  end
end