# frozen_string_literal: true

module Gitlab
  module Sanitizers
    class Exif
      # these tags are not removed from the image
      WHITELISTED_TAGS = %w(
        ResolutionUnit
        XResolution
        YResolution
        YCbCrSubSampling
        YCbCrPositioning
        BitsPerSample
        ImageHeight
        ImageWidth
        ImageSize
        Copyright
        CopyrightNotice
        Orientation
      ).freeze

      # these tags are common in exiftool output, these
      # do not contain any sensitive information, but
      # we don't need to preserve them when removing
      # exif tags
      IGNORED_TAGS = %w(
        ColorComponents
        EncodingProcess
        ExifByteOrder
        ExifToolVersion
        JFIFVersion
        Directory
        FileAccessDate
        FileInodeChangeDate
        FileModifyDate
        FileName
        FilePermissions
        FileSize
        SourceFile
        Megapixels
        FileType
        FileTypeExtension
        MIMEType
      ).freeze

      ALLOWED_TAGS = WHITELISTED_TAGS + IGNORED_TAGS
      EXCLUDE_PARAMS = WHITELISTED_TAGS.map { |tag| "-#{tag}" }

      attr_reader :logger

      def initialize(logger: Rails.logger)
        @logger = logger
      end

      # rubocop: disable CodeReuse/ActiveRecord
      def batch_clean(start_id: nil, stop_id: nil, dry_run: true, sleep_time: nil)
        relation = Upload.where('lower(path) like ? or lower(path) like ? or lower(path) like ?',
                                '%.jpg', '%.jpeg', '%.tiff')

        logger.info "running in dry run mode, no images will be rewritten" if dry_run

        find_params = {
          start: start_id.present? ? start_id.to_i : nil,
          finish: stop_id.present? ? stop_id.to_i : Upload.last&.id
        }

        relation.find_each(find_params) do |upload|
          clean(upload.build_uploader, dry_run: dry_run)
          sleep sleep_time if sleep_time
        rescue => err
          logger.error "failed to sanitize #{upload_ref(upload)}: #{err.message}"
          logger.debug err.backtrace.join("\n ")
        end
      end
      # rubocop: enable CodeReuse/ActiveRecord

      def clean(uploader, dry_run: true)
        Dir.mktmpdir('gitlab-exif') do |tmpdir|
          src_path = fetch_upload_to_file(uploader, tmpdir)

          to_remove = extra_tags(src_path)

          if to_remove.empty?
            logger.info "#{upload_ref(uploader.upload)}: only whitelisted tags present, skipping"
            break
          end

          logger.info "#{upload_ref(uploader.upload)}: found exif tags to remove: #{to_remove}"

          break if dry_run

          remove_and_store(tmpdir, src_path, uploader)
        end
      end

      def extra_tags(path)
        exif_tags(path).keys - ALLOWED_TAGS
      end

      private

      def remove_and_store(tmpdir, src_path, uploader)
        exec_remove_exif!(src_path)
        logger.info "#{upload_ref(uploader.upload)}: exif removed, storing"
        File.open(src_path, 'r') { |f| uploader.store!(f) }
      end

      def exec_remove_exif!(path)
        # IPTC and XMP-iptcExt groups may keep copyright information so
        # we always preserve them
        cmd = ["exiftool", "-all=", "-tagsFromFile", "@", *EXCLUDE_PARAMS, "--IPTC:all", "--XMP-iptcExt:all", path]
        output, status = Gitlab::Popen.popen(cmd)

        if status != 0
          raise "exiftool return code is #{status}: #{output}"
        end

        if File.size(path) == 0
          raise "size of file is 0"
        end

        # exiftool creates backup of the original file in filename_original
        old_path = "#{path}_original"
        if File.size(path) == File.size(old_path)
          raise "size of sanitized file is same as original size"
        end
      end

      def fetch_upload_to_file(uploader, dir)
        # upload is stored into the file with the original name - this filename
        # is used by carrierwave when storing the file back to the storage
        filename = File.join(dir, uploader.filename)

        File.open(filename, 'w') do |file|
          file.binmode
          file.write uploader.read
        end

        filename
      end

      def upload_ref(upload)
        "#{upload.id}:#{upload.path}"
      end

      def exif_tags(path)
        cmd = ["exiftool", "-all", "-j", "-sort", "--IPTC:all", "--XMP-iptcExt:all", path]
        output, status = Gitlab::Popen.popen(cmd)

        raise "failed to get exif tags: #{output}" if status != 0

        JSON.parse(output).first
      end
    end
  end
end
