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.GroupedKey;
  
  import com.google.errorprone.annotations.concurrent.GuardedBy;
  
  import java.util.function.Function;
  
  /**
   * Chained ID segment.
   *
   * @author ahoo wang
   */
  public class IdSegmentChain implements IdSegment {
      public static final int ROOT_VERSION = -1;
      public static final IdSegmentChain NOT_SET = null;
      
      private final long version;
      private final IdSegment idSegment;
      @GuardedBy("this")
      private volatile IdSegmentChain next;
      private final boolean allowReset;
  
      public IdSegmentChain(IdSegmentChain previousChain, IdSegment idSegment, boolean allowReset) {
          this(previousChain.getVersion() + 1, idSegment, allowReset);
      }
      
      public IdSegmentChain(long version, IdSegment idSegment, boolean allowReset) {
          this.version = version;
          this.idSegment = idSegment;
          this.allowReset = allowReset;
      }
      
      /**
       * try set next Chained ID segment.
       *
       * @param idSegmentChainSupplier {@link IdSegmentChain} supplier
       * @return true if set successfully
       * @throws NextIdSegmentExpiredException This exception is thrown
       *                                       if the provided {@link IdSegmentChain} has expired.
       */
      public boolean trySetNext(Function<IdSegmentChain, IdSegmentChain> idSegmentChainSupplier) throws NextIdSegmentExpiredException {
          if (NOT_SET != next) {
              return false;
          }
          
          synchronized (this) {
              if (NOT_SET != next) {
                  return false;
              }
              IdSegmentChain nextIdSegmentChain = idSegmentChainSupplier.apply(this);
              setNext(nextIdSegmentChain);
              return true;
          }
      }
      
      public void setNext(IdSegmentChain nextIdSegmentChain) {
          if (!allowReset) {
              ensureNextIdSegment(nextIdSegmentChain);
          }
          
          next = nextIdSegmentChain;
      }
      
      public IdSegmentChain ensureSetNext(Function<IdSegmentChain, IdSegmentChain> idSegmentChainSupplier) throws NextIdSegmentExpiredException {
          IdSegmentChain currentChain = this;
          while (!currentChain.trySetNext(idSegmentChainSupplier)) {
              currentChain = currentChain.getNext();
          }
          return currentChain;
      }
      
      public IdSegmentChain getNext() {
          return next;
      }
      
      public IdSegment getIdSegment() {
          return idSegment;
      }
      
      @Override
      public GroupedKey group() {
          return idSegment.group();
      }
      
      public long getVersion() {
          return version;
      }
      
      public int gap(IdSegmentChain end, long step) {
          return (int) ((end.getMaxId() - getSequence()) / step);
      }
      
      public static IdSegmentChain newRoot(boolean allowReset) {
          return new IdSegmentChain(IdSegmentChain.ROOT_VERSION, DefaultIdSegment.OVERFLOW, allowReset);
      }
      
      @Override
      public long getFetchTime() {
          return idSegment.getFetchTime();
      }
      
      @Override
      public long getTtl() {
          return idSegment.getTtl();
      }
      
      @Override
      public long getMaxId() {
          return idSegment.getMaxId();
      }
      
      @Override
      public long getOffset() {
          return idSegment.getOffset();
      }
      
      @Override
      public long getSequence() {
          return idSegment.getSequence();
      }
      
      @Override
      public long getStep() {
          return idSegment.getStep();
      }
      
      @Override
      public long incrementAndGet() {
          return idSegment.incrementAndGet();
      }
      
      @Override
      public String toString() {
          return "IdSegmentChain{"
              + "version=" + version
              + ", idSegment=" + idSegment
              + '}';
      }
  }
  