require 'google/cloud/vision'

module GoogleCloudVision
  class OcrPdfService
    attr_accessor :pdf_filename

    def initialize(pdf_filename)
      fail "GOOGLE_CLOUD_KEYFILE env variable required" unless ENV['GOOGLE_CLOUD_KEYFILE']
      fail "Input must be PDF" unless pdf_filename&.split('.')&.last&.downcase == 'pdf'
      self.pdf_filename = pdf_filename
    end

    def perform
      [].tap do |pages|
        Magick::ImageList.new(self.pdf_filename).each_with_index do |page_img, i|
          tempfile = Tempfile.new(%w(image .jpg))
          begin
            log :writing_image, tempfile.path
            page_img.write(tempfile.path)
            image = vision.image(tempfile.path)
            annotation = vision.annotate(image, document: true)
            text = annotation.text.to_s
            log self.pdf_filename, i, text
            pages << text
          ensure
            tempfile.close
            tempfile.unlink
          end
        end
      end
    end

    private

      def vision
        @vision ||= Google::Cloud::Vision.new(project: ENV['GOOGLE_CLOUD_PROJECT_ID'])
      end
  end
end