content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF 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
   *
   * 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.apache.calcite.adapter.geode.simple;
  
  import org.apache.calcite.linq4j.Enumerator;
  
  import org.apache.geode.cache.client.ClientCache;
  import org.apache.geode.cache.query.QueryService;
  import org.apache.geode.cache.query.SelectResults;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.Iterator;
  
  /**
   * Geode Simple Enumerator.
   *
   * @param <E> Element type
   */
  public abstract class GeodeSimpleEnumerator<E> implements Enumerator<E> {
  
    private @Nullable Iterator results;
  
    private E current;
  
    protected GeodeSimpleEnumerator(ClientCache clientCache, String regionName) {
      QueryService queryService = clientCache.getQueryService();
      String oql = "select * from /" + regionName.trim();
      try {
        results = ((SelectResults) queryService.newQuery(oql).execute()).iterator();
      } catch (Exception e) {
        e.printStackTrace();
        results = null;
      }
    }
  
    @Override public E current() {
      return current;
    }
  
    @Override public boolean moveNext() {
      if (results == null) {
        throw new IllegalStateException();
      }
      if (results.hasNext()) {
        current = convert(results.next());
        return true;
      }
      current = null;
      return false;
    }
  
    @Override public void reset() {
      throw new UnsupportedOperationException();
    }
  
    @Override public void close() {
      /*clientCache.close(); */
    }
  
    public abstract E convert(Object obj);
  }
  