content: package allen.town.podcast.core.feed;
  
  import android.text.TextUtils;
  import android.util.Log;
  import androidx.annotation.Nullable;
  import allen.town.podcast.model.feed.Chapter;
  
  import java.util.List;
  
  public class ChapterMerger {
      private static final String TAG = "ChapterMerger";
  
      private ChapterMerger() {
  
      }
  
      /**
       * This method might modify the input data.
       */
      @Nullable
      public static List<Chapter> merge(@Nullable List<Chapter> chapters1, @Nullable List<Chapter> chapters2) {
          if (chapters1 == null) {
              return chapters2;
          } else if (chapters2 == null) {
              return chapters1;
          } else if (chapters2.size() > chapters1.size()) {
              return chapters2;
          } else if (chapters2.size() < chapters1.size()) {
              return chapters1;
          } else {
              // Merge chapter lists of same length. Store in chapters2 array.
              // In case the lists can not be merged, return chapters1 array.
              for (int i = 0; i < chapters2.size(); i++) {
                  Chapter chapterTarget = chapters2.get(i);
                  Chapter chapterOther = chapters1.get(i);
  
                  if (Math.abs(chapterTarget.getStart() - chapterOther.getStart()) > 1000) {
                      Log.e(TAG, "Chapter lists are too different. Cancelling merge.");
                      return score(chapters1) > score(chapters2) ? chapters1 : chapters2;
                  }
  
                  if (TextUtils.isEmpty(chapterTarget.getImageUrl())) {
                      chapterTarget.setImageUrl(chapterOther.getImageUrl());
                  }
                  if (TextUtils.isEmpty(chapterTarget.getLink())) {
                      chapterTarget.setLink(chapterOther.getLink());
                  }
                  if (TextUtils.isEmpty(chapterTarget.getTitle())) {
                      chapterTarget.setTitle(chapterOther.getTitle());
                  }
              }
              return chapters2;
          }
      }
  
      /**
       * Tries to give a score that can determine which list of chapters a user might want to see.
       */
      private static int score(List<Chapter> chapters) {
          int score = 0;
          for (Chapter chapter : chapters) {
              score = score
                      + (TextUtils.isEmpty(chapter.getTitle()) ? 0 : 1)
                      + (TextUtils.isEmpty(chapter.getLink()) ? 0 : 1)
                      + (TextUtils.isEmpty(chapter.getImageUrl()) ? 0 : 1);
          }
          return score;
      }
  }
  