scinote-web/app/jobs/pdf_preview_job.rb

# frozen_string_literal: true

# Provides asynchronous generation of image previews for ActiveStorage::Blob records.
class PdfPreviewJob < ApplicationJob
  queue_as :assets

  discard_on StandardError do |job, error|
    asset = Asset.find_by(id: job.arguments.first)
    ActiveRecord::Base.no_touching do
      asset&.update(pdf_preview_processing: false)
    end
    Rails.logger.error("Couldn't generate PDF preview for Asset with id: #{job.arguments.first}. Error:\n #{error}")
  end

  discard_on ActiveRecord::RecordNotFound

  def perform(asset_id)
    asset = Asset.find(asset_id)
    blob = asset.file.blob
    blob.open(tmpdir: tempdir) do |input|
      work_dir = File.dirname(input.path)
      preview_filename = "#{File.basename(input.path, '.*')}.pdf"
      preview_file = File.join(work_dir, preview_filename)
      Rails.logger.info "Starting preparing document preview for file #{blob.filename.sanitized}..."

      ActiveRecord::Base.transaction do
        success = system(
          libreoffice_path, '--headless', '--invisible', '--convert-to', 'pdf', '--outdir', work_dir, input.path
        )
        unless success && File.file?(preview_file)
          raise StandardError, "There was an error generating PDF preview, blob id: #{blob.id}"
        end

        ActiveRecord::Base.no_touching do
          asset.file_pdf_preview.attach(io: File.open(preview_file), filename: "#{blob.filename.base}.pdf")
          asset.update(pdf_preview_processing: false)
        end
        Rails.logger.info("Finished preparing PDF preview for file #{blob.filename.sanitized}.")
      end
    ensure
      File.delete(preview_file) if File.file?(preview_file)
    end
  end

  private

  def tempdir
    Rails.root.join('tmp')
  end

  def libreoffice_path
    ENV['LIBREOFFICE_PATH'] || 'soffice'
  end
end