content: /*
   * Copyright (C) 2012-2023 52°North Spatial Information Research GmbH
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 as published
   * by the Free Software Foundation.
   *
   * If the program is linked with libraries which are licensed under one of
   * the following licenses, the combination of the program with the linked
   * library is not considered a "derivative work" of the program:
   *
   *     - Apache License, version 2.0
   *     - Apache Software License, version 1.0
   *     - GNU Lesser General Public License, version 3
   *     - Mozilla Public License, versions 1.0, 1.1 and 2.0
   *     - Common Development and Distribution License (CDDL), version 1.0
   *
   * Therefore the distribution of the program linked with libraries licensed
   * under the aforementioned licenses, is permitted by the copyright holders
   * if the distribution is compliant with both the GNU General Public
   * License version 2 and the aforementioned licenses.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
   * Public License for more details.
   */
  package org.n52.sos.ds.hibernate.util;
  
  import java.io.Closeable;
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  
  import org.hibernate.Criteria;
  import org.hibernate.ScrollableResults;
  
  import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
  
  /**
   * @author <a href="mailto:c.autermann@52north.org">Christian Autermann</a>
   *
   * @since 4.0.0
   */
  @SuppressFBWarnings({"EI_EXPOSE_REP", "EI_EXPOSE_REP2"})
  public class ScrollableIterable<T> implements Iterable<T>, Closeable {
      private final ScrollableResults results;
  
      private Iterator<T> iterator;
  
      public ScrollableIterable(ScrollableResults results) {
          this.results = results;
      }
  
      public static <T> ScrollableIterable<T> fromResults(ScrollableResults sr) {
          return new ScrollableIterable<>(sr);
      }
  
      public static <T> ScrollableIterable<T> fromCriteria(Criteria c) {
          return new ScrollableIterable<>(c.scroll());
      }
  
      @Override
      public Iterator<T> iterator() {
          if (iterator != null) {
              throw new IllegalStateException("this is a one time iterable");
          }
          iterator = new ScrollableIterator();
          return iterator;
      }
  
      @Override
      public void close() {
          results.close();
      }
  
      private class ScrollableIterator implements Iterator<T> {
          private Boolean hasNext;
  
          @Override
          public boolean hasNext() {
              if (hasNext == null) {
                  // only proceed once
                  hasNext = results.next();
              }
              return hasNext;
          }
  
          @Override
          @SuppressWarnings("unchecked")
          public T next() {
              if (hasNext != null && hasNext) {
                  hasNext = null;
                  return (T) results.get(0);
              } else {
                  throw new NoSuchElementException();
              }
  
          }
  
          @Override
          public void remove() {
              throw new UnsupportedOperationException();
          }
      }
  }
  