/**
    *    Copyright 2009-2019 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;
  
  import static org.apache.ibatis.executor.ExecutionPlaceholder.EXECUTION_PLACEHOLDER;
  
  import java.sql.Connection;
  import java.sql.SQLException;
  import java.sql.Statement;
  import java.util.List;
  import java.util.concurrent.ConcurrentLinkedQueue;
  
  import org.apache.ibatis.cache.CacheKey;
  import org.apache.ibatis.cache.impl.PerpetualCache;
  import org.apache.ibatis.cursor.Cursor;
  import org.apache.ibatis.executor.statement.StatementUtil;
  import org.apache.ibatis.logging.Log;
  import org.apache.ibatis.logging.LogFactory;
  import org.apache.ibatis.logging.jdbc.ConnectionLogger;
  import org.apache.ibatis.mapping.BoundSql;
  import org.apache.ibatis.mapping.MappedStatement;
  import org.apache.ibatis.mapping.ParameterMapping;
  import org.apache.ibatis.mapping.ParameterMode;
  import org.apache.ibatis.mapping.StatementType;
  import org.apache.ibatis.reflection.MetaObject;
  import org.apache.ibatis.reflection.factory.ObjectFactory;
  import org.apache.ibatis.session.Configuration;
  import org.apache.ibatis.session.LocalCacheScope;
  import org.apache.ibatis.session.ResultHandler;
  import org.apache.ibatis.session.RowBounds;
  import org.apache.ibatis.transaction.Transaction;
  import org.apache.ibatis.type.TypeHandlerRegistry;
  
  /**
   * @author Clinton Begin
   */
  public abstract class BaseExecutor implements Executor {
  
    private static final Log log = LogFactory.getLog(BaseExecutor.class);
  
    protected Transaction transaction;
    protected Executor wrapper;
  
    protected ConcurrentLinkedQueue<DeferredLoad> deferredLoads;
    protected PerpetualCache localCache;
    protected PerpetualCache localOutputParameterCache;
    protected Configuration configuration;
  
    protected int queryStack;
    private boolean closed;
  
    protected BaseExecutor(Configuration configuration, Transaction transaction) {
      this.transaction = transaction;
      this.deferredLoads = new ConcurrentLinkedQueue<>();
      this.localCache = new PerpetualCache("LocalCache");
      this.localOutputParameterCache = new PerpetualCache("LocalOutputParameterCache");
      this.closed = false;
      this.configuration = configuration;
      this.wrapper = this;
    }
  
    @Override
    public Transaction getTransaction() {
      if (closed) {
        throw new ExecutorException("Executor was closed.");
      }
      return transaction;
    }
  
    @Override
    public void close(boolean forceRollback) {
      try {
        try {
          rollback(forceRollback);
        } finally {
          if (transaction != null) {
            transaction.close();
          }
        }
      } catch (SQLException e) {
        // Ignore.  There's nothing that can be done at this point.
        log.warn("Unexpected exception on closing transaction.  Cause: " + e);
      } finally {
        transaction = null;
        deferredLoads = null;
        localCache = null;
       localOutputParameterCache = null;
       closed = true;
     }
   }
 
   @Override
   public boolean isClosed() {
     return closed;
   }
 
   @Override
   public int update(MappedStatement ms, Object parameter) throws SQLException {
     ErrorContext.instance().resource(ms.getResource()).activity("executing an update").object(ms.getId());
     if (closed) {
       throw new ExecutorException("Executor was closed.");
     }
     clearLocalCache();
     return doUpdate(ms, parameter);
   }
 
   @Override
   public List<BatchResult> flushStatements() throws SQLException {
     return flushStatements(false);
   }
 
   public List<BatchResult> flushStatements(boolean isRollBack) throws SQLException {
     if (closed) {
       throw new ExecutorException("Executor was closed.");
     }
     return doFlushStatements(isRollBack);
   }
 
   @Override
   public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException {
     BoundSql boundSql = ms.getBoundSql(parameter);
     CacheKey key = createCacheKey(ms, parameter, rowBounds, boundSql);
     return query(ms, parameter, rowBounds, resultHandler, key, boundSql);
   }
 
   @SuppressWarnings("unchecked")
   @Override
   public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
     ErrorContext.instance().resource(ms.getResource()).activity("executing a query").object(ms.getId());
     if (closed) {
       throw new ExecutorException("Executor was closed.");
     }
     if (queryStack == 0 && ms.isFlushCacheRequired()) {
       clearLocalCache();
     }
     List<E> list;
     try {
       queryStack++;
       list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;
       if (list != null) {
         handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);
       } else {
         list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);
       }
     } finally {
       queryStack--;
     }
     if (queryStack == 0) {
       for (DeferredLoad deferredLoad : deferredLoads) {
         deferredLoad.load();
       }
       // issue #601
       deferredLoads.clear();
       if (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {
         // issue #482
         clearLocalCache();
       }
     }
     return list;
   }
 
   @Override
   public <E> Cursor<E> queryCursor(MappedStatement ms, Object parameter, RowBounds rowBounds) throws SQLException {
     BoundSql boundSql = ms.getBoundSql(parameter);
     return doQueryCursor(ms, parameter, rowBounds, boundSql);
   }
 
   @Override
   public void deferLoad(MappedStatement ms, MetaObject resultObject, String property, CacheKey key, Class<?> targetType) {
     if (closed) {
       throw new ExecutorException("Executor was closed.");
     }
     DeferredLoad deferredLoad = new DeferredLoad(resultObject, property, key, localCache, configuration, targetType);
     if (deferredLoad.canLoad()) {
       deferredLoad.load();
     } else {
       deferredLoads.add(new DeferredLoad(resultObject, property, key, localCache, configuration, targetType));
     }
   }
 
   @Override
   public CacheKey createCacheKey(MappedStatement ms, Object parameterObject, RowBounds rowBounds, BoundSql boundSql) {
     if (closed) {
       throw new ExecutorException("Executor was closed.");
     }
     CacheKey.html#CacheKey">CacheKey cacheKey = new CacheKey();
     cacheKey.update(ms.getId());
     cacheKey.update(rowBounds.getOffset());
     cacheKey.update(rowBounds.getLimit());
     cacheKey.update(boundSql.getSql());
     List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
     TypeHandlerRegistry typeHandlerRegistry = ms.getConfiguration().getTypeHandlerRegistry();
     // mimic DefaultParameterHandler logic
     for (ParameterMapping parameterMapping : parameterMappings) {
       if (parameterMapping.getMode() != ParameterMode.OUT) {
         Object value;
         String propertyName = parameterMapping.getProperty();
         if (boundSql.hasAdditionalParameter(propertyName)) {
           value = boundSql.getAdditionalParameter(propertyName);
         } else if (parameterObject == null) {
           value = null;
         } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
           value = parameterObject;
         } else {
           MetaObject metaObject = configuration.newMetaObject(parameterObject);
           value = metaObject.getValue(propertyName);
         }
         cacheKey.update(value);
       }
     }
     if (configuration.getEnvironment() != null) {
       // issue #176
       cacheKey.update(configuration.getEnvironment().getId());
     }
     return cacheKey;
   }
 
   @Override
   public boolean isCached(MappedStatement ms, CacheKey key) {
     return localCache.getObject(key) != null;
   }
 
   @Override
   public void commit(boolean required) throws SQLException {
     if (closed) {
       throw new ExecutorException("Cannot commit, transaction is already closed");
     }
     clearLocalCache();
     flushStatements();
     if (required) {
       transaction.commit();
     }
   }
 
   @Override
   public void rollback(boolean required) throws SQLException {
     if (!closed) {
       try {
         clearLocalCache();
         flushStatements(true);
       } finally {
         if (required) {
           transaction.rollback();
         }
       }
     }
   }
 
   @Override
   public void clearLocalCache() {
     if (!closed) {
       localCache.clear();
       localOutputParameterCache.clear();
     }
   }
 
   protected abstract int doUpdate(MappedStatement ms, Object parameter)
       throws SQLException;
 
   protected abstract List<BatchResult> doFlushStatements(boolean isRollback)
       throws SQLException;
 
   protected abstract <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql)
       throws SQLException;
 
   protected abstract <E> Cursor<E> doQueryCursor(MappedStatement ms, Object parameter, RowBounds rowBounds, BoundSql boundSql)
       throws SQLException;
 
   protected void closeStatement(Statement statement) {
     if (statement != null) {
       try {
         statement.close();
       } catch (SQLException e) {
         // ignore
       }
     }
   }
 
   /**
    * Apply a transaction timeout.
    * @param statement a current statement
    * @throws SQLException if a database access error occurs, this method is called on a closed <code>Statement</code>
    * @since 3.4.0
    * @see StatementUtil#applyTransactionTimeout(Statement, Integer, Integer)
    */
   protected void applyTransactionTimeout(Statement statement) throws SQLException {
     StatementUtil.applyTransactionTimeout(statement, statement.getQueryTimeout(), transaction.getTimeout());
   }
 
   private void handleLocallyCachedOutputParameters(MappedStatement ms, CacheKey key, Object parameter, BoundSql boundSql) {
     if (ms.getStatementType() == StatementType.CALLABLE) {
       final Object cachedParameter = localOutputParameterCache.getObject(key);
       if (cachedParameter != null && parameter != null) {
         final MetaObject metaCachedParameter = configuration.newMetaObject(cachedParameter);
         final MetaObject metaParameter = configuration.newMetaObject(parameter);
         for (ParameterMapping parameterMapping : boundSql.getParameterMappings()) {
           if (parameterMapping.getMode() != ParameterMode.IN) {
             final String parameterName = parameterMapping.getProperty();
             final Object cachedValue = metaCachedParameter.getValue(parameterName);
             metaParameter.setValue(parameterName, cachedValue);
           }
         }
       }
     }
   }
 
   private <E> List<E> queryFromDatabase(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
     List<E> list;
     localCache.putObject(key, EXECUTION_PLACEHOLDER);
     try {
       list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);
     } finally {
       localCache.removeObject(key);
     }
     localCache.putObject(key, list);
     if (ms.getStatementType() == StatementType.CALLABLE) {
       localOutputParameterCache.putObject(key, parameter);
     }
     return list;
   }
 
   protected Connection getConnection(Log statementLog) throws SQLException {
     Connection connection = transaction.getConnection();
     if (statementLog.isDebugEnabled()) {
       return ConnectionLogger.newInstance(connection, statementLog, queryStack);
     } else {
       return connection;
     }
   }
 
   @Override
   public void setExecutorWrapper(Executor wrapper) {
     this.wrapper = wrapper;
   }
 
   private static class DeferredLoad {
 
     private final MetaObject resultObject;
     private final String property;
     private final Class<?> targetType;
     private final CacheKey key;
     private final PerpetualCache localCache;
     private final ObjectFactory objectFactory;
     private final ResultExtractor resultExtractor;
 
     // issue #781
     public DeferredLoad(MetaObject resultObject,
                         String property,
                         CacheKey key,
                         PerpetualCache localCache,
                         Configuration configuration,
                         Class<?> targetType) {
       this.resultObject = resultObject;
       this.property = property;
       this.key = key;
       this.localCache = localCache;
       this.objectFactory = configuration.getObjectFactory();
       this.resultExtractor = new ResultExtractor(configuration, objectFactory);
       this.targetType = targetType;
     }
 
     public boolean canLoad() {
       return localCache.getObject(key) != null && localCache.getObject(key) != EXECUTION_PLACEHOLDER;
     }
 
     public void load() {
       @SuppressWarnings("unchecked")
       // we suppose we get back a List
       List<Object> list = (List<Object>) localCache.getObject(key);
       Object value = resultExtractor.extractObjectFromList(list, targetType);
       resultObject.setValue(property, value);
     }
 
   }
 
 }