discourse/lib/upload_fixer.rb

class UploadFixer
  def self.fix_extensions
    Upload.where("uploads.extension IS NOT NULL").find_each do |upload|
      is_external = Discourse.store.external?
      previous_url = upload.url.dup

      source =
        if is_external
          "https:#{previous_url}"
        else
          Discourse.store.path_for(upload)
        end

      correct_extension = FastImage.type(source).to_s.downcase
      current_extension = upload.extension.to_s.downcase

      if correct_extension.present?
        correct_extension = 'jpg' if correct_extension == 'jpeg'
        current_extension = 'jpg' if current_extension == 'jpeg'

        if correct_extension != current_extension
          new_filename = change_extension(
            upload.original_filename,
            correct_extension
          )

          new_url = change_extension(previous_url, correct_extension)

          if is_external
            new_url = "/#{new_url}"
            source = Discourse.store.get_path_for_upload(upload)
            destination = change_extension(source, correct_extension)

            Discourse.store.copy_file(
              previous_url,
              source,
              destination
            )

            upload.update!(
              original_filename: new_filename,
              url: new_url,
              extension: correct_extension
            )

            DbHelper.remap(previous_url, upload.url)
            Discourse.store.remove_file(previous_url, source)
          else
            destination = change_extension(source, correct_extension)
            FileUtils.copy(source, destination)

            upload.update!(
              original_filename: new_filename,
              url: new_url,
              extension: correct_extension
            )

            DbHelper.remap(previous_url, upload.url)

            tombstone_path = source.sub("/uploads/", "/uploads/tombstone/")
            FileUtils.mkdir_p(File.dirname(tombstone_path))

            FileUtils.move(
              source,
              tombstone_path
            )
          end
        end
      end
    end
  end

  private

  def self.change_extension(path, extension)
    pathname = Pathname.new(path)
    dirname = pathname.dirname.to_s != "." ? "#{pathname.dirname}/" : ""
    basename = File.basename(path, File.extname(path))
    "#{dirname}#{basename}.#{extension}"
  end
end