content: /*
   * Copyright [2021-present] [ahoo wang <ahoowang@qq.com> (https://github.com/Ahoo-Wang)].
   * Licensed 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 me.ahoo.cosid.segment;
  
  import me.ahoo.cosid.segment.grouped.GroupedAccessor;
  import me.ahoo.cosid.segment.grouped.GroupedKey;
  import me.ahoo.cosid.util.Clock;
  
  import com.google.common.base.Preconditions;
  
  import java.util.concurrent.atomic.AtomicLongFieldUpdater;
  
  /**
   * Default Id Segment.
   *
   * @author ahoo wang
   */
  public class DefaultIdSegment implements IdSegment {
      
      public static final DefaultIdSegment OVERFLOW = new DefaultIdSegment(IdSegment.SEQUENCE_OVERFLOW, 0, Clock.SYSTEM.secondTime(), TIME_TO_LIVE_FOREVER, GroupedKey.NEVER);
      
      /**
       * include.
       */
      private final long maxId;
      private final long offset;
      private final long step;
      private volatile long sequence;
      private final long fetchTime;
      private final long ttl;
      private final GroupedKey group;
      private static final AtomicLongFieldUpdater<DefaultIdSegment> S = AtomicLongFieldUpdater.newUpdater(DefaultIdSegment.class, "sequence");
      
      public DefaultIdSegment(long maxId, long step) {
          this(maxId, step, Clock.SYSTEM.secondTime(), TIME_TO_LIVE_FOREVER, GroupedKey.NEVER);
      }
      
      public DefaultIdSegment(long maxId, long step, long fetchTime, long ttl, GroupedKey group) {
          Preconditions.checkArgument(ttl > 0, "ttl:[%s] must be greater than 0.", ttl);
          this.maxId = maxId;
          this.step = step;
          this.offset = maxId - step;
          this.sequence = offset;
          this.fetchTime = fetchTime;
          this.ttl = ttl;
          this.group = group;
      }
      
      @Override
      public GroupedKey group() {
          return group;
      }
      
      @Override
      public long getFetchTime() {
          return fetchTime;
      }
      
      @Override
      public long getTtl() {
          return ttl;
      }
      
      @Override
      public long getMaxId() {
          return maxId;
      }
      
      @Override
      public long getOffset() {
          return offset;
      }
      
      @Override
      public long getSequence() {
          return sequence;
      }
      
      @Override
      public long getStep() {
          return step;
      }
      
      @Override
      public long incrementAndGet() {
          if (isOverflow()) {
              return SEQUENCE_OVERFLOW;
          }
          
          final long nextSeq = S.incrementAndGet(this);
          
          if (isOverflow(nextSeq)) {
              return SEQUENCE_OVERFLOW;
          }
          GroupedAccessor.setIfNotNever(group());
          return nextSeq;
      }
      
      @Override
      public String toString() {
          return "DefaultIdSegment{"
              + "maxId=" + maxId
              + ", offset=" + offset
              + ", step=" + step
              + ", sequence=" + sequence
              + ", fetchTime=" + fetchTime
              + ", ttl=" + ttl
              + '}';
      }
  }
  