/*
    * 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.infra.merge.result.impl.memory;
  
  import org.apache.shardingsphere.infra.binder.context.statement.SQLStatementContext;
  import org.apache.shardingsphere.infra.executor.sql.execute.result.query.QueryResult;
  import org.apache.shardingsphere.infra.merge.result.MergedResult;
  import org.apache.shardingsphere.infra.metadata.database.schema.model.ShardingSphereSchema;
  import org.apache.shardingsphere.infra.rule.ShardingSphereRule;
  import org.apache.shardingsphere.infra.exception.core.ShardingSpherePreconditions;
  
  import java.io.InputStream;
  import java.io.Reader;
  import java.sql.Blob;
  import java.sql.Clob;
  import java.sql.SQLException;
  import java.sql.SQLFeatureNotSupportedException;
  import java.sql.SQLXML;
  import java.util.Arrays;
  import java.util.Calendar;
  import java.util.Collection;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.List;
  
  /**
   * Memory merged result.
   *
   * @param <T> type of rule
   */
  public abstract class MemoryMergedResult<T extends ShardingSphereRule> implements MergedResult {
      
      private static final Collection<Class<?>> INVALID_MEMORY_TYPES = new HashSet<>(Arrays.asList(Blob.class, Clob.class, Reader.class, InputStream.class, SQLXML.class));
      
      private final Iterator<MemoryQueryResultRow> memoryResultSetRows;
      
      private MemoryQueryResultRow currentResultSetRow;
      
      private boolean wasNull;
      
      protected MemoryMergedResult(final T rule, final ShardingSphereSchema schema, final SQLStatementContext sqlStatementContext, final List<QueryResult> queryResults) throws SQLException {
          List<MemoryQueryResultRow> memoryQueryResultRows = init(rule, schema, sqlStatementContext, queryResults);
          memoryResultSetRows = memoryQueryResultRows.iterator();
          if (!memoryQueryResultRows.isEmpty()) {
              currentResultSetRow = memoryQueryResultRows.get(0);
          }
      }
      
      protected abstract List<MemoryQueryResultRow> init(T rule, ShardingSphereSchema schema, SQLStatementContext sqlStatementContext, List<QueryResult> queryResults) throws SQLException;
      
      @Override
      public final boolean next() {
          if (memoryResultSetRows.hasNext()) {
              currentResultSetRow = memoryResultSetRows.next();
              return true;
          }
          return false;
      }
      
      @Override
      public final Object getValue(final int columnIndex, final Class<?> type) throws SQLException {
          ShardingSpherePreconditions.checkNotContains(INVALID_MEMORY_TYPES, type, () -> new SQLFeatureNotSupportedException(String.format("Get value from `%s`", type.getName())));
          Object result = currentResultSetRow.getCell(columnIndex);
          wasNull = null == result;
          return result;
      }
      
      @Override
      public final Object getCalendarValue(final int columnIndex, final Class<?> type, final Calendar calendar) {
          // TODO implement with calendar
          Object result = currentResultSetRow.getCell(columnIndex);
          wasNull = null == result;
          return result;
      }
      
      @Override
      public final InputStream getInputStream(final int columnIndex, final String type) throws SQLException {
          throw new SQLFeatureNotSupportedException(String.format("Get input stream from `%s`", type));
      }
      
      @Override
      public Reader getCharacterStream(final int columnIndex) throws SQLException {
          throw new SQLFeatureNotSupportedException("Get Character stream");
      }
     
     @Override
     public final boolean wasNull() {
         return wasNull;
     }
 }