/*
    * Copyright 2010-2022 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
    *
    *    https://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.mybatis.spring.batch;
  
  import static org.springframework.util.Assert.notNull;
  import static org.springframework.util.ClassUtils.getShortName;
  
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.Map;
  import java.util.Optional;
  import java.util.function.Supplier;
  
  import org.apache.ibatis.cursor.Cursor;
  import org.apache.ibatis.session.ExecutorType;
  import org.apache.ibatis.session.SqlSession;
  import org.apache.ibatis.session.SqlSessionFactory;
  import org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader;
  import org.springframework.beans.factory.InitializingBean;
  
  /**
   * @author Guillaume Darmont / guillaume@dropinocean.com
   */
  public class MyBatisCursorItemReader<T> extends AbstractItemCountingItemStreamItemReader<T>
      implements InitializingBean {
  
    private String queryId;
  
    private SqlSessionFactory sqlSessionFactory;
    private SqlSession sqlSession;
  
    private Map<String, Object> parameterValues;
    private Supplier<Map<String, Object>> parameterValuesSupplier;
  
    private Cursor<T> cursor;
    private Iterator<T> cursorIterator;
  
    public MyBatisCursorItemReader() {
      setName(getShortName(MyBatisCursorItemReader.class));
    }
  
    @Override
    protected T doRead() throws Exception {
      T next = null;
      if (cursorIterator.hasNext()) {
        next = cursorIterator.next();
      }
      return next;
    }
  
    @Override
    protected void doOpen() throws Exception {
      Map<String, Object> parameters = new HashMap<>();
      if (parameterValues != null) {
        parameters.putAll(parameterValues);
      }
  
      Optional.ofNullable(parameterValuesSupplier).map(Supplier::get).ifPresent(parameters::putAll);
  
      sqlSession = sqlSessionFactory.openSession(ExecutorType.SIMPLE);
      cursor = sqlSession.selectCursor(queryId, parameters);
      cursorIterator = cursor.iterator();
    }
  
    @Override
    protected void doClose() throws Exception {
      if (cursor != null) {
        cursor.close();
      }
      if (sqlSession != null) {
        sqlSession.close();
      }
      cursorIterator = null;
    }
  
    /**
     * Check mandatory properties.
     *
     * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet()
     */
    @Override
    public void afterPropertiesSet() throws Exception {
      notNull(sqlSessionFactory, "A SqlSessionFactory is required.");
      notNull(queryId, "A queryId is required.");
    }
  
   /**
    * Public setter for {@link SqlSessionFactory} for injection purposes.
    *
    * @param sqlSessionFactory
    *          a factory object for the {@link SqlSession}.
    */
   public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
     this.sqlSessionFactory = sqlSessionFactory;
   }
 
   /**
    * Public setter for the statement id identifying the statement in the SqlMap configuration file.
    *
    * @param queryId
    *          the id for the statement
    */
   public void setQueryId(String queryId) {
     this.queryId = queryId;
   }
 
   /**
    * The parameter values to be used for the query execution.
    *
    * @param parameterValues
    *          the values keyed by the parameter named used in the query string.
    */
   public void setParameterValues(Map<String, Object> parameterValues) {
     this.parameterValues = parameterValues;
   }
 
   /**
    * The parameter supplier used to get parameter values for the query execution.
    *
    * @param parameterValuesSupplier
    *          the supplier used to get values keyed by the parameter named used in the query string.
    *
    * @since 2.1.0
    */
   public void setParameterValuesSupplier(Supplier<Map<String, Object>> parameterValuesSupplier) {
     this.parameterValuesSupplier = parameterValuesSupplier;
   }
 }