protected Iterable openDataFile()

in parquet-cli/src/main/java/org/apache/parquet/cli/BaseCommand.java [332:402]
64 lines of code
6 McCabe index (conditional complexity)

  protected <D> Iterable<D> openDataFile(final String source, Schema projection)
      throws IOException {
    Formats.Format format = Formats.detectFormat(open(source));
    switch (format) {
      case PARQUET:
        Configuration conf = new Configuration(getConf());
        // TODO: add these to the reader builder
        AvroReadSupport.setRequestedProjection(conf, projection);
        AvroReadSupport.setAvroReadSchema(conf, projection);
        final ParquetReader<D> parquet = AvroParquetReader.<D>builder(qualifiedPath(source))
            .disableCompatibility()
            .withDataModel(GenericData.get())
            .withConf(conf)
            .build();
        return new Iterable<D>() {
          @Override
          public Iterator<D> iterator() {
            return new Iterator<D>() {
              private boolean hasNext = false;
              private D next = advance();

              @Override
              public boolean hasNext() {
                return hasNext;
              }

              @Override
              public D next() {
                if (!hasNext) {
                  throw new NoSuchElementException();
                }
                D toReturn = next;
                this.next = advance();
                return toReturn;
              }

              private D advance() {
                try {
                  D next = parquet.read();
                  this.hasNext = (next != null);
                  return next;
                } catch (IOException e) {
                  throw new RuntimeException(
                      "Failed while reading Parquet file: " + source, e);
                }
              }

              @Override
              public void remove() {
                throw new UnsupportedOperationException("Remove is not supported");
              }
            };
          }
        };

      case AVRO:
        Iterable<D> avroReader = (Iterable<D>) DataFileReader.openReader(
            openSeekable(source), new GenericDatumReader<>(projection));
        return avroReader;

      default:
        if (source.endsWith("json")) {
          return new AvroJsonReader<>(open(source), projection);
        } else {
          Preconditions.checkArgument(projection == null,
              "Cannot select columns from text files");
          Iterable text = CharStreams.readLines(new InputStreamReader(open(source)));
          return text;
        }
    }
  }