content: package allen.town.podcast.asynctask;
  
  import android.content.Context;
  import android.net.Uri;
  import androidx.annotation.NonNull;
  import androidx.documentfile.provider.DocumentFile;
  
  import java.io.IOException;
  import java.io.OutputStream;
  import java.io.OutputStreamWriter;
  import java.nio.charset.Charset;
  
  import allen.town.podcast.core.export.ExportWriter;
  import allen.town.podcast.core.storage.DBReader;
  import io.reactivex.Observable;
  
  /**
   * Writes an OPML file into the user selected export directory in the background.
   */
  public class DocumentFileExportWorker {
  
      private final @NonNull ExportWriter exportWriter;
      private @NonNull Context context;
      private @NonNull Uri outputFileUri;
  
      public DocumentFileExportWorker(@NonNull ExportWriter exportWriter, @NonNull Context context, @NonNull Uri outputFileUri) {
          this.exportWriter = exportWriter;
          this.context = context;
          this.outputFileUri = outputFileUri;
      }
  
      public Observable<DocumentFile> exportObservable() {
          DocumentFile output = DocumentFile.fromSingleUri(context, outputFileUri);
          return Observable.create(subscriber -> {
              OutputStream outputStream = null;
              OutputStreamWriter writer = null;
              try {
                  Uri uri = output.getUri();
                  outputStream = context.getContentResolver().openOutputStream(uri, "wt");
                  if (outputStream == null) {
                      throw new IOException();
                  }
                  writer = new OutputStreamWriter(outputStream, Charset.forName("UTF-8"));
                  exportWriter.writeDocument(DBReader.getFeedList(), writer, context);
                  subscriber.onNext(output);
              } catch (IOException e) {
                  subscriber.onError(e);
              } finally {
                  if (writer != null) {
                      try {
                          writer.close();
                      } catch (IOException e) {
                          subscriber.onError(e);
                      }
                  }
                  if (outputStream != null) {
                      try {
                          outputStream.close();
                      } catch (IOException e) {
                          subscriber.onError(e);
                      }
                  }
                  subscriber.onComplete();
              }
          });
      }
  
  }
  