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.cassandra.io.sstable;
  
  import java.nio.ByteBuffer;
  import java.util.Objects;
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.function.Supplier;
  import java.util.regex.Pattern;
  import java.util.stream.Stream;
  
  import com.google.common.base.Preconditions;
  
  /**
   * Generation identifier based on sequence of integers.
   * This has been the standard implementation in C* since inception.
   */
  public class SequenceBasedSSTableId implements SSTableId, Comparable<SequenceBasedSSTableId>
  {
      public final int generation;
  
      public SequenceBasedSSTableId(final int generation)
      {
          assert generation >= 0;
  
          this.generation = generation;
      }
  
      @Override
      public int compareTo(SequenceBasedSSTableId o)
      {
          if (o == null)
              return 1;
          else if (o == this)
              return 0;
  
          return Integer.compare(this.generation, o.generation);
      }
  
      @Override
      public boolean equals(Object o)
      {
          if (this == o) return true;
          if (o == null || getClass() != o.getClass())
              return false;
          SequenceBasedSSTableId that = (SequenceBasedSSTableId) o;
          return generation == that.generation;
      }
  
      @Override
      public int hashCode()
      {
          return Objects.hash(generation);
      }
  
      @Override
      public ByteBuffer asBytes()
      {
          ByteBuffer bytes = ByteBuffer.allocate(Integer.BYTES);
          bytes.putInt(0, generation);
          return bytes;
      }
  
      @Override
      public String toString()
      {
          return String.valueOf(generation);
      }
  
      public static class Builder implements SSTableId.Builder<SequenceBasedSSTableId>
      {
          public final static Builder instance = new Builder();
  
          private final static Pattern PATTERN = Pattern.compile("\\d+");
  
          /**
           * Generates a sequential number to represent an sstables identifier. The first generated identifier will be
           * greater by one than the largest generation number found across the provided existing identifiers.
           */
          @Override
          public Supplier<SequenceBasedSSTableId> generator(Stream<SSTableId> existingIdentifiers)
          {
              int value = existingIdentifiers.filter(SequenceBasedSSTableId.class::isInstance)
                                             .map(SequenceBasedSSTableId.class::cast)
                                             .mapToInt(id -> id.generation)
                                             .max()
                                             .orElse(0);
  
              AtomicInteger fileIndexGenerator = new AtomicInteger(value);
              return () -> new SequenceBasedSSTableId(fileIndexGenerator.incrementAndGet());
          }
  
          @Override
          public boolean isUniqueIdentifier(String str)
          {
              return str != null && !str.isEmpty() && str.length() <= 10 && PATTERN.matcher(str).matches();
          }
  
          @Override
          public boolean isUniqueIdentifier(ByteBuffer bytes)
          {
              return bytes != null && bytes.remaining() == Integer.BYTES && bytes.getInt(0) >= 0;
          }
  
          @Override
          public SequenceBasedSSTableId fromString(String token) throws IllegalArgumentException
          {
              return new SequenceBasedSSTableId(Integer.parseInt(token));
          }
  
          @Override
          public SequenceBasedSSTableId fromBytes(ByteBuffer bytes) throws IllegalArgumentException
          {
              Preconditions.checkArgument(bytes.remaining() == Integer.BYTES, "Buffer does not have a valid number of bytes remaining. Expecting: %s but was: %s", Integer.BYTES, bytes.remaining());
              return new SequenceBasedSSTableId(bytes.getInt(0));
          }
      }
  }
  