/*
    * 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 lombok.RequiredArgsConstructor;
  import lombok.SneakyThrows;
  import org.apache.calcite.linq4j.Enumerator;
  import org.apache.shardingsphere.infra.executor.sql.execute.result.query.QueryResultMetaData;
  import org.apache.shardingsphere.infra.executor.sql.execute.result.query.impl.driver.jdbc.type.util.ResultSetUtils;
  import org.apache.shardingsphere.infra.merge.result.MergedResult;
  import org.apache.shardingsphere.infra.exception.core.external.sql.type.wrapper.SQLWrapperException;
  
  import java.sql.SQLException;
  import java.sql.Statement;
  import java.sql.Timestamp;
  import java.time.LocalDateTime;
  import java.util.Collection;
  
  /**
   * JDBC row enumerator.
   */
  @RequiredArgsConstructor
  public final class JDBCRowEnumerator implements Enumerator<Object> {
      
      private final MergedResult queryResult;
      
      private final QueryResultMetaData metaData;
      
      private final Collection<Statement> statements;
      
      private Object currentRow;
      
      @Override
      public Object current() {
          return currentRow;
      }
      
      @SneakyThrows
      @Override
      public boolean moveNext() {
          return moveNext0();
      }
      
      private boolean moveNext0() throws SQLException {
          if (queryResult.next()) {
              setCurrentRow();
              return true;
          }
          return false;
      }
      
      private void setCurrentRow() throws SQLException {
          Object[] rowValues = new Object[metaData.getColumnCount()];
          for (int i = 0; i < metaData.getColumnCount(); i++) {
              rowValues[i] = getValue(i);
          }
          currentRow = 1 == metaData.getColumnCount() ? rowValues[0] : rowValues;
      }
      
      private Object getValue(final int index) throws SQLException {
          Object result = queryResult.getValue(index + 1, Object.class);
          return result instanceof LocalDateTime ? ResultSetUtils.convertValue(result, Timestamp.class) : result;
      }
      
      @Override
      public void reset() {
      }
      
      @Override
      public void close() {
          try {
              for (Statement each : statements) {
                  each.close();
              }
              currentRow = null;
          } catch (final SQLException ex) {
              throw new SQLWrapperException(ex);
          }
      }
  }