catstodon/app/services/translate_status_service.rb

# frozen_string_literal: true

class TranslateStatusService < BaseService
  CACHE_TTL = 1.day.freeze

  include ERB::Util
  include FormattingHelper

  def call(status, target_language)
    @status = status
    @source_texts = source_texts

    target_language = target_language.split(/[_-]/).first unless target_languages.include?(target_language)
    @target_language = target_language

    raise Mastodon::NotPermittedError unless permitted?

    status_translation = Rails.cache.fetch("v2:translations/#{@status.language}/#{@target_language}/#{content_hash}", expires_in: CACHE_TTL) do
      translations = translation_backend.translate(@source_texts.values, @status.language, @target_language)
      build_status_translation(translations)
    end

    status_translation.status = @status

    status_translation
  end

  private

  def translation_backend
    @translation_backend ||= TranslationService.configured
  end

  def permitted?
    return false unless @status.distributable? && TranslationService.configured?

    target_languages.include?(@target_language)
  end

  def languages
    Rails.cache.fetch('translation_service/languages', expires_in: 7.days, race_condition_ttl: 1.hour) { translation_backend.languages }
  end

  def target_languages
    languages[@status.language] || []
  end

  def content_hash
    Digest::SHA256.base64digest(@source_texts.transform_keys { |key| key.respond_to?(:id) ? "#{key.class}-#{key.id}" : key }.to_json)
  end

  def source_texts
    texts = {}
    texts[:content] = wrap_emoji_shortcodes(status_content_format(@status)) if @status.content.present?
    texts[:spoiler_text] = wrap_emoji_shortcodes(html_escape(@status.spoiler_text)) if @status.spoiler_text.present?

    @status.preloadable_poll&.loaded_options&.each do |option|
      texts[option] = wrap_emoji_shortcodes(html_escape(option.title))
    end

    @status.media_attachments.each do |media_attachment|
      texts[media_attachment] = html_escape(media_attachment.description)
    end

    texts
  end

  def build_status_translation(translations)
    status_translation = Translation.new(
      detected_source_language: translations.first&.detected_source_language,
      language: @target_language,
      provider: translations.first&.provider,
      content: '',
      spoiler_text: '',
      poll_options: [],
      media_attachments: []
    )

    @source_texts.keys.each_with_index do |source, index|
      translation = translations[index]

      case source
      when :content
        node = unwrap_emoji_shortcodes(translation.text)
        Sanitize.node!(node, Sanitize::Config::MASTODON_STRICT)
        status_translation.content = node.to_html
      when :spoiler_text
        status_translation.spoiler_text = unwrap_emoji_shortcodes(translation.text).content
      when Poll::Option
        status_translation.poll_options << Translation::Option.new(
          title: unwrap_emoji_shortcodes(translation.text).content
        )
      when MediaAttachment
        status_translation.media_attachments << Translation::MediaAttachment.new(
          id: source.id,
          description: html_entities.decode(translation.text)
        )
      end
    end

    status_translation
  end

  def wrap_emoji_shortcodes(text)
    EmojiFormatter.new(text, @status.emojis, { raw_shortcode: true }).to_s
  end

  def unwrap_emoji_shortcodes(html)
    fragment = Nokogiri::HTML5.fragment(html)
    fragment.css('span[translate="no"]').each do |element|
      element.remove_attribute('translate')
      element.replace(element.children) if element.attributes.empty?
    end
    fragment
  end

  def html_entities
    HTMLEntities.new
  end
end