/*
    * Copyright 2022 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty5.buffer.api.internal;
  
  import io.netty5.buffer.api.ComponentIterator;
  import io.netty5.buffer.api.ComponentIterator.Next;
  import io.netty5.util.Resource;
  
  import java.lang.ref.Reference;
  
  import static java.util.Objects.requireNonNull;
  
  public final class SingleComponentIterator<T extends Next> implements ComponentIterator<T> {
      private final Resource<?> lifecycle;
      private final T singleComponent;
  
      @SuppressWarnings("unchecked")
      public SingleComponentIterator(Resource<?> lifecycle, Object singleComponent) {
          this.lifecycle = requireNonNull(lifecycle, "lifecycle");
          // The singleComponent may be null if there is nothing to iterate.
          this.singleComponent = (T) singleComponent;
      }
  
      @Override
      public T first() {
          return singleComponent;
      }
  
      @Override
      public void close() {
          lifecycle.close();
          Reference.reachabilityFence(lifecycle);
      }
  }