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.runners.dataflow.worker;
  
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableList;
  
  /** Utilities for handling filepatterns. */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class Filepatterns {
    private static final Pattern AT_N_SPEC = Pattern.compile("@(?<N>\\d+)");
  
    /**
     * Expands the filepattern containing an {@code @N} wildcard.
     *
     * <p>Returns N filenames with the wildcard replaced with a string of the form {@code
     * 0000i-of-0000N}. For example, for "gs://bucket/file@2.ism", returns an iterable of two elements
     * "gs://bucket/file-00000-of-00002.ism" and "gs://bucket/file-00001-of-00002.ism".
     *
     * <p>The sequence number and N are formatted with the same number of digits (prepended by zeros).
     * with at least 5 digits. N must be smaller than 1 billion.
     *
     * <p>If the filepattern contains no wildcards, returns the filepattern unchanged.
     *
     * @throws IllegalArgumentException if more than one wildcard is detected.
     */
    public static Iterable<String> expandAtNFilepattern(String filepattern) {
      ImmutableList.Builder<String> builder = ImmutableList.builder();
      Matcher match = AT_N_SPEC.matcher(filepattern);
      if (!match.find()) {
        builder.add(filepattern);
      } else {
        int numShards = Integer.parseInt(match.group("N"));
        String formatString = "-%0" + getShardWidth(numShards, filepattern) + "d-of-%05d";
        for (int i = 0; i < numShards; ++i) {
          builder.add(
              AT_N_SPEC.matcher(filepattern).replaceAll(String.format(formatString, i, numShards)));
        }
        if (match.find()) {
          throw new IllegalArgumentException(
              "More than one @N wildcard found in filepattern: " + filepattern);
        }
      }
      return builder.build();
    }
  
    private static int getShardWidth(int numShards, String filepattern) {
      if (numShards < 100000) {
        return 5;
      }
      if (numShards < 1000000) {
        return 6;
      }
      if (numShards < 10000000) {
        return 7;
      }
      if (numShards < 100000000) {
        return 8;
      }
      if (numShards < 1000000000) {
        return 9;
      }
      throw new IllegalArgumentException(
          "Unsupported number of shards: " + numShards + " in filepattern: " + filepattern);
    }
  }
  