/*
    *    Copyright 2009-2021 the original author or authors.
    *
    *    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.apache.ibatis.executor.loader;
  
  import java.sql.SQLException;
  import java.util.List;
  
  import javax.sql.DataSource;
  
  import org.apache.ibatis.cache.CacheKey;
  import org.apache.ibatis.executor.Executor;
  import org.apache.ibatis.executor.ExecutorException;
  import org.apache.ibatis.executor.ResultExtractor;
  import org.apache.ibatis.mapping.BoundSql;
  import org.apache.ibatis.mapping.Environment;
  import org.apache.ibatis.mapping.MappedStatement;
  import org.apache.ibatis.reflection.factory.ObjectFactory;
  import org.apache.ibatis.session.Configuration;
  import org.apache.ibatis.session.ExecutorType;
  import org.apache.ibatis.session.RowBounds;
  import org.apache.ibatis.transaction.Transaction;
  import org.apache.ibatis.transaction.TransactionFactory;
  
  /**
   * @author Clinton Begin
   */
  public class ResultLoader {
  
    protected final Configuration configuration;
    protected final Executor executor;
    protected final MappedStatement mappedStatement;
    protected final Object parameterObject;
    protected final Class<?> targetType;
    protected final ObjectFactory objectFactory;
    protected final CacheKey cacheKey;
    protected final BoundSql boundSql;
    protected final ResultExtractor resultExtractor;
    protected final long creatorThreadId;
  
    protected boolean loaded;
    protected Object resultObject;
  
    public ResultLoader(Configuration config, Executor executor, MappedStatement mappedStatement, Object parameterObject, Class<?> targetType, CacheKey cacheKey, BoundSql boundSql) {
      this.configuration = config;
      this.executor = executor;
      this.mappedStatement = mappedStatement;
      this.parameterObject = parameterObject;
      this.targetType = targetType;
      this.objectFactory = configuration.getObjectFactory();
      this.cacheKey = cacheKey;
      this.boundSql = boundSql;
      this.resultExtractor = new ResultExtractor(configuration, objectFactory);
      this.creatorThreadId = Thread.currentThread().getId();
    }
  
    public Object loadResult() throws SQLException {
      List<Object> list = selectList();
      resultObject = resultExtractor.extractObjectFromList(list, targetType);
      return resultObject;
    }
  
    private <E> List<E> selectList() throws SQLException {
      Executor localExecutor = executor;
      if (Thread.currentThread().getId() != this.creatorThreadId || localExecutor.isClosed()) {
        localExecutor = newExecutor();
      }
      try {
        return localExecutor.query(mappedStatement, parameterObject, RowBounds.DEFAULT, Executor.NO_RESULT_HANDLER, cacheKey, boundSql);
      } finally {
        if (localExecutor != executor) {
          localExecutor.close(false);
        }
      }
    }
  
    private Executor newExecutor() {
      final Environment environment = configuration.getEnvironment();
      if (environment == null) {
        throw new ExecutorException("ResultLoader could not load lazily.  Environment was not configured.");
      }
      final DataSource ds = environment.getDataSource();
      if (ds == null) {
        throw new ExecutorException("ResultLoader could not load lazily.  DataSource was not configured.");
      }
      final TransactionFactory transactionFactory = environment.getTransactionFactory();
      final Transaction tx = transactionFactory.newTransaction(ds, null, false);
     return configuration.newExecutor(tx, ExecutorType.SIMPLE);
   }
 
   public boolean wasNull() {
     return resultObject == null;
   }
 
 }