/*
    * 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.shardingsphere.sqlfederation.executor.enumerator;
  
  import org.apache.calcite.linq4j.Enumerator;
  import org.apache.shardingsphere.infra.database.core.type.DatabaseType;
  import org.apache.shardingsphere.infra.metadata.database.schema.model.ShardingSphereColumn;
  import org.apache.shardingsphere.infra.metadata.statistics.ShardingSphereRowData;
  import org.apache.shardingsphere.sqlfederation.executor.utils.EnumeratorUtils;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.Map;
  
  /**
   * Memory row enumerator.
   */
  public final class MemoryRowEnumerator implements Enumerator<Object> {
      
      private final Collection<ShardingSphereRowData> rows;
      
      private final Map<Integer, Class<?>> columnTypes;
      
      private Iterator<ShardingSphereRowData> iterator;
      
      private Object current;
      
      public MemoryRowEnumerator(final Collection<ShardingSphereRowData> rows, final Collection<ShardingSphereColumn> columns, final DatabaseType databaseType) {
          this.rows = rows;
          columnTypes = EnumeratorUtils.createColumnTypes(new ArrayList<>(columns), databaseType);
          iterator = rows.iterator();
      }
      
      @Override
      public Object current() {
          return current;
      }
      
      @Override
      public boolean moveNext() {
          if (iterator.hasNext()) {
              current = EnumeratorUtils.convertToTargetType(columnTypes, iterator.next().getRows().toArray());
              return true;
          }
          current = null;
          iterator = rows.iterator();
          return false;
      }
      
      @Override
      public void reset() {
      }
      
      @Override
      public void close() {
          iterator = rows.iterator();
          current = null;
      }
  }