content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.beam.sdk.extensions.sql.meta.provider.text;
  
  import java.io.IOException;
  import org.apache.beam.sdk.annotations.Internal;
  import org.apache.beam.sdk.extensions.sql.impl.BeamTableStatistics;
  import org.apache.beam.sdk.extensions.sql.meta.BeamSqlTable;
  import org.apache.beam.sdk.extensions.sql.meta.SchemaBaseBeamTable;
  import org.apache.beam.sdk.io.TextIO;
  import org.apache.beam.sdk.io.TextRowCountEstimator;
  import org.apache.beam.sdk.options.PipelineOptions;
  import org.apache.beam.sdk.schemas.Schema;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.values.PBegin;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PDone;
  import org.apache.beam.sdk.values.Row;
  import org.apache.commons.csv.CSVFormat;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * {@link TextTable} is a {@link BeamSqlTable} that reads text files and converts them according to
   * the specified format.
   *
   * <p>Support formats are {@code "csv"} and {@code "lines"}.
   *
   * <p>{@link CSVFormat} itself has many dialects, check its javadoc for more info.
   */
  @Internal
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class TextTable extends SchemaBaseBeamTable {
  
    private final PTransform<PCollection<String>, PCollection<Row>> readConverter;
    private final PTransform<PCollection<Row>, PCollection<String>> writeConverter;
    private static final TextRowCountEstimator.SamplingStrategy DEFAULT_SAMPLING_STRATEGY =
        new TextRowCountEstimator.LimitNumberOfTotalBytes(1024 * 1024L);
    private final String filePattern;
    private BeamTableStatistics rowCountStatistics = null;
    private static final Logger LOG = LoggerFactory.getLogger(TextTable.class);
  
    /** Text table with the specified read and write transforms. */
    public TextTable(
        Schema schema,
        String filePattern,
        PTransform<PCollection<String>, PCollection<Row>> readConverter,
        PTransform<PCollection<Row>, PCollection<String>> writeConverter) {
      super(schema);
      this.filePattern = filePattern;
      this.readConverter = readConverter;
      this.writeConverter = writeConverter;
    }
  
    public String getFilePattern() {
      return filePattern;
    }
  
    @Override
    public BeamTableStatistics getTableStatistics(PipelineOptions options) {
      if (rowCountStatistics == null) {
        rowCountStatistics = getTextRowEstimate(options, getFilePattern());
      }
  
      return rowCountStatistics;
    }
  
    private static BeamTableStatistics getTextRowEstimate(
        PipelineOptions options, String filePattern) {
      TextRowCountEstimator textRowCountEstimator =
          TextRowCountEstimator.builder()
              .setFilePattern(filePattern)
              .setSamplingStrategy(DEFAULT_SAMPLING_STRATEGY)
              .build();
      try {
        Double rows = textRowCountEstimator.estimateRowCount(options);
        return BeamTableStatistics.createBoundedTableStatistics(rows);
      } catch (IOException | TextRowCountEstimator.NoEstimationException e) {
        LOG.warn("Could not get the row count for the text table " + filePattern, e);
      }
      return BeamTableStatistics.BOUNDED_UNKNOWN;
    }
  
    @Override
    public PCollection.IsBounded isBounded() {
      return PCollection.IsBounded.BOUNDED;
    }
  
    @Override
    public PCollection<Row> buildIOReader(PBegin begin) {
      return begin
          .apply("ReadTextFiles", TextIO.read().from(filePattern))
          .apply("StringToRow", readConverter);
    }
  
    @Override
    public PDone buildIOWriter(PCollection<Row> input) {
      return input
          .apply("RowToString", writeConverter)
          .apply("WriteTextFiles", TextIO.write().withDelimiter(new char[] {}).to(filePattern));
    }
  }
  