/*
    * Copyright 2014 The Codehaus Foundation.
    *
    * 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 org.codehaus.plexus.components.io.resources.proxy;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  
  import org.codehaus.plexus.components.io.resources.PlexusIoResource;
  
  abstract class ForwardingIterator implements Iterator<PlexusIoResource>, Closeable {
      private final Object possiblyCloseable;
  
      private PlexusIoResource next = null;
  
      ForwardingIterator(Object possiblyCloseable) {
          this.possiblyCloseable = possiblyCloseable;
      }
  
      public boolean hasNext() {
          if (next == null) {
              try {
                  next = getNextResource();
              } catch (IOException e) {
                  throw new RuntimeException(e);
              }
          }
          return next != null;
      }
  
      public PlexusIoResource next() {
          if (!hasNext()) {
              throw new NoSuchElementException();
          }
          PlexusIoResource ret = next;
          next = null;
          return ret;
      }
  
      public void remove() {
          throw new UnsupportedOperationException();
      }
  
      public void close() throws IOException {
          if (possiblyCloseable instanceof Closeable) {
              ((Closeable) possiblyCloseable).close();
          }
      }
  
      /**
       * Returns the next resource or null if no next resource;
       */
      protected abstract PlexusIoResource getNextResource() throws IOException;
  }