Bloom.Book.BookData.SetUpDisplayOfTopicInBook C# (CSharp) Method

        private void SetUpDisplayOfTopicInBook(DataSet data)
        {
            var topicPageElement = this._dom.SelectSingleNode("//div[@data-derived='topic']");
            if (topicPageElement == null)
            {
                //old-style. here we don't have the data-derived, so we need to avoid picking from the datadiv
                topicPageElement = this._dom.SelectSingleNode("//div[not(id='bloomDataDiv')]//div[@data-book='topic']");
                if (topicPageElement == null)
                {
                    //most unit tests do not have complete books, so this not surprising. It just means we don't have anything to do
                    return;
                }
            }
            //clear it out what's there now
            topicPageElement.RemoveAttribute("lang");
            topicPageElement.InnerText = "";

            NamedMutliLingualValue topicData;

            var parentOfTopicDisplayElement = ((XmlElement)(topicPageElement.ParentNode));
            //this just lets us have css rules that vary if there is a topic (allows other text to be centered instead left-aligned)
            //we'll change it later if we find there is a topic
            parentOfTopicDisplayElement.SetAttribute("data-have-topic", "false");

            //if we have no topic element in the data-div
            //leave the field in the page with an empty text.
            if (!data.TextVariables.TryGetValue("topic", out topicData))
            {
                return;
            }

            //we use English as the "key" for topics.
            var englishTopic = topicData.TextAlternatives.GetExactAlternative("en");

            //if we have no topic, just clear it out from the page
            if (string.IsNullOrEmpty(englishTopic) || englishTopic == "NoTopic")
                return;

            parentOfTopicDisplayElement.SetAttribute("data-have-topic", "true");

            var stringId = "Topics." + englishTopic;

            //get the topic in the most prominent language for which we have a translation
            var langOfTopicToShowOnCover = _collectionSettings.Language1Iso639Code;
            if (LocalizationManager.GetIsStringAvailableForLangId(stringId, _collectionSettings.Language1Iso639Code))
            {
                langOfTopicToShowOnCover = _collectionSettings.Language1Iso639Code;
            }
            else if (LocalizationManager.GetIsStringAvailableForLangId(stringId, _collectionSettings.Language2Iso639Code))
            {
                langOfTopicToShowOnCover = _collectionSettings.Language2Iso639Code;
            }
            else if (LocalizationManager.GetIsStringAvailableForLangId(stringId, _collectionSettings.Language3Iso639Code))
            {
                langOfTopicToShowOnCover = _collectionSettings.Language3Iso639Code;
            }
            else
            {
                langOfTopicToShowOnCover = "en";
            }

            var bestTranslation = LocalizationManager.GetDynamicStringOrEnglish("Bloom", stringId, englishTopic,
                "this is a book topic", langOfTopicToShowOnCover);

            //NB: in a unit test environment, GetDynamicStringOrEnglish is going to give us the id back, which is annoying.
            if (bestTranslation == stringId)
                bestTranslation = englishTopic;

            topicPageElement.SetAttribute("lang", langOfTopicToShowOnCover);
            topicPageElement.InnerText = bestTranslation;
        }