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.examples.common;
  
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.MoreObjects.firstNonNull;
  
  import javax.annotation.Nullable;
  import org.apache.beam.sdk.io.FileBasedSink;
  import org.apache.beam.sdk.io.FileBasedSink.FilenamePolicy;
  import org.apache.beam.sdk.io.FileBasedSink.OutputFileHints;
  import org.apache.beam.sdk.io.TextIO;
  import org.apache.beam.sdk.io.fs.ResolveOptions.StandardResolveOptions;
  import org.apache.beam.sdk.io.fs.ResourceId;
  import org.apache.beam.sdk.transforms.DoFn;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.transforms.windowing.IntervalWindow;
  import org.apache.beam.sdk.transforms.windowing.PaneInfo;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PDone;
  import org.joda.time.format.DateTimeFormatter;
  import org.joda.time.format.ISODateTimeFormat;
  
  /**
   * A {@link DoFn} that writes elements to files with names deterministically derived from the lower
   * and upper bounds of their key (an {@link IntervalWindow}).
   *
   * <p>This is test utility code, not for end-users, so examples can be focused on their primary
   * lessons.
   */
  public class WriteOneFilePerWindow extends PTransform<PCollection<String>, PDone> {
    private static final DateTimeFormatter FORMATTER = ISODateTimeFormat.hourMinute();
    private String filenamePrefix;
    @Nullable private Integer numShards;
  
    public WriteOneFilePerWindow(String filenamePrefix, Integer numShards) {
      this.filenamePrefix = filenamePrefix;
      this.numShards = numShards;
    }
  
    @Override
    public PDone expand(PCollection<String> input) {
      ResourceId resource = FileBasedSink.convertToFileResourceIfPossible(filenamePrefix);
      TextIO.Write write =
          TextIO.write()
              .to(new PerWindowFiles(resource))
              .withTempDirectory(resource.getCurrentDirectory())
              .withWindowedWrites();
      if (numShards != null) {
        write = write.withNumShards(numShards);
      }
      return input.apply(write);
    }
  
    /**
     * A {@link FilenamePolicy} produces a base file name for a write based on metadata about the data
     * being written. This always includes the shard number and the total number of shards. For
     * windowed writes, it also includes the window and pane index (a sequence number assigned to each
     * trigger firing).
     */
    public static class PerWindowFiles extends FilenamePolicy {
  
      private final ResourceId baseFilename;
  
      public PerWindowFiles(ResourceId baseFilename) {
        this.baseFilename = baseFilename;
      }
  
      public String filenamePrefixForWindow(IntervalWindow window) {
        String prefix =
            baseFilename.isDirectory() ? "" : firstNonNull(baseFilename.getFilename(), "");
        return String.format(
            "%s-%s-%s", prefix, FORMATTER.print(window.start()), FORMATTER.print(window.end()));
      }
  
      @Override
      public ResourceId windowedFilename(
          int shardNumber,
          int numShards,
          BoundedWindow window,
          PaneInfo paneInfo,
          OutputFileHints outputFileHints) {
        IntervalWindow intervalWindow = (IntervalWindow) window;
        String filename =
            String.format(
                "%s-%s-of-%s%s",
                filenamePrefixForWindow(intervalWindow),
                shardNumber,
                numShards,
                outputFileHints.getSuggestedFilenameSuffix());
        return baseFilename
            .getCurrentDirectory()
            .resolve(filename, StandardResolveOptions.RESOLVE_FILE);
      }
  
      @Override
      public ResourceId unwindowedFilename(
          int shardNumber, int numShards, OutputFileHints outputFileHints) {
        throw new UnsupportedOperationException("Unsupported.");
      }
    }
  }
  