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.kafka.timeline;
  
  import java.util.Iterator;
  
  
  /**
   * This is a mutable long which can be snapshotted.
   * <br>
   * This class requires external synchronization.
   */
  public final class TimelineLong implements Revertable {
      public static final long INIT = 0;
  
      static class LongContainer implements Delta {
          private long value = INIT;
  
          long value() {
              return value;
          }
  
          void setValue(long value) {
              this.value = value;
          }
  
          @Override
          public void mergeFrom(long destinationEpoch, Delta delta) {
              // Nothing to do
          }
      }
  
      private final SnapshotRegistry snapshotRegistry;
      private long value;
  
      public TimelineLong(SnapshotRegistry snapshotRegistry) {
          this.snapshotRegistry = snapshotRegistry;
          this.value = INIT;
  
          snapshotRegistry.register(this);
      }
  
      public long get() {
          return value;
      }
  
      public long get(long epoch) {
          if (epoch == SnapshotRegistry.LATEST_EPOCH) return value;
          Iterator<Snapshot> iterator = snapshotRegistry.iterator(epoch);
          while (iterator.hasNext()) {
              Snapshot snapshot = iterator.next();
              LongContainer container = snapshot.getDelta(TimelineLong.this);
              if (container != null) return container.value();
          }
          return value;
      }
  
      public void set(long newValue) {
          Iterator<Snapshot> iterator = snapshotRegistry.reverseIterator();
          if (iterator.hasNext()) {
              Snapshot snapshot = iterator.next();
              LongContainer prevContainer = snapshot.getDelta(TimelineLong.this);
              if (prevContainer == null) {
                  prevContainer = new LongContainer();
                  snapshot.setDelta(TimelineLong.this, prevContainer);
                  prevContainer.setValue(value);
              }
          }
          this.value = newValue;
      }
  
      public void increment() {
          set(get() + 1L);
      }
  
      public void decrement() {
          set(get() - 1L);
      }
  
      @Override
      public void executeRevert(long targetEpoch, Delta delta) {
          LongContainer container = (LongContainer) delta;
          this.value = container.value();
      }
  
      @Override
      public void reset() {
          set(INIT);
      }
  
      @Override
      public int hashCode() {
          return ((int) value) ^ (int) (value >>> 32);
      }
  
      @Override
      public boolean equals(Object o) {
          if (!(o instanceof TimelineLong other)) return false;
          return value == other.value;
      }
  
      @Override
      public String toString() {
          return Long.toString(value);
      }
  }
  