content: package allen.town.podcast.parser.feed.util;
  
  import android.webkit.MimeTypeMap;
  import androidx.annotation.Nullable;
  import org.apache.commons.io.FilenameUtils;
  
  import java.util.Arrays;
  import java.util.HashSet;
  import java.util.Set;
  
  /**
   * Utility class for handling MIME-Types of enclosures.
   * */
  public class MimeTypeUtils {
      public static final String OCTET_STREAM = "application/octet-stream";
  
      // based on https://developer.android.com/guide/topics/media/media-formats
      static final Set<String> AUDIO_FILE_EXTENSIONS = new HashSet<>(Arrays.asList(
              "3gp", "aac", "amr", "flac", "imy", "m4a", "m4b", "mid", "mkv", "mp3", "mp4", "mxmf", "oga",
              "ogg", "ogx", "opus", "ota", "rtttl", "rtx", "wav", "xmf"
      ));
  
      static final Set<String> VIDEO_FILE_EXTENSIONS = new HashSet<>(Arrays.asList(
              "3gp", "mkv", "mp4", "ogg", "ogv", "ogx", "webm"
      ));
  
      private MimeTypeUtils() {
  
      }
  
      @Nullable
      public static String getMimeType(@Nullable String type, @Nullable String filename) {
          if (isMediaFile(type) && !OCTET_STREAM.equals(type)) {
              return type;
          }
          String filenameType = MimeTypeUtils.getMimeTypeFromUrl(filename);
          if (isMediaFile(filenameType)) {
              return filenameType;
          }
          return type;
      }
  
      public static boolean isMediaFile(String type) {
          if (type == null) {
              return false;
          } else {
              return type.startsWith("audio/")
                      || type.startsWith("video/")
                      || type.equals("application/ogg")
                      || type.equals("application/octet-stream");
          }
      }
  
      public static boolean isImageFile(String type) {
          if (type == null) {
              return false;
          } else {
              return type.startsWith("image/");
          }
      }
  
      /**
       * Should be used if mime-type of enclosure tag is not supported. This
       * method will return the mime-type of the file extension.
       */
      private static String getMimeTypeFromUrl(String url) {
          if (url == null) {
              return null;
          }
          String extension = FilenameUtils.getExtension(url);
          String mapResult = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
          if (mapResult != null) {
              return mapResult;
          }
  
          if (AUDIO_FILE_EXTENSIONS.contains(extension)) {
              return "audio/*";
          } else if (VIDEO_FILE_EXTENSIONS.contains(extension)) {
              return "video/*";
          }
          return null;
      }
  }
  