/*

   Derby - Class org.apache.derby.impl.sql.compile.IsNode

   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.derby.impl.sql.compile;

import java.util.List;
import org.apache.derby.iapi.error.StandardException;
import org.apache.derby.iapi.reference.ClassName;
import org.apache.derby.iapi.services.classfile.VMOpcode;
import org.apache.derby.iapi.services.compiler.MethodBuilder;
import org.apache.derby.iapi.services.context.ContextManager;

class IsNode extends BinaryLogicalOperatorNode
{
	private boolean		notMe;	// set to true if we're to negate the sense of this node

	/**
     * Constructor for an IsNode
	 *
	 * @param leftOperand	The left operand of the IS
	 * @param rightOperand	The right operand of the IS
	 * @param notMe			Whether to reverse the sense of this node.
     * @param cm            The context manager
	 */

    IsNode(ValueNode leftOperand,
           ValueNode rightOperand,
           boolean notMe,
           ContextManager cm)
	{
		// the false for shortCir
        super(leftOperand, rightOperand, "is", cm );
        this.notMe = notMe;
	}

	/**
	 * Bind this logical operator.  All that has to be done for binding
	 * a logical operator is to bind the operands, check that both operands
	 * are BooleanDataValue, and set the result type to BooleanDataValue.
	 *
	 * @param fromList			The query's FROM list
	 * @param subqueryList		The subquery list being built as we find SubqueryNodes
     * @param aggregates        The aggregate list being built as we find AggregateNodes
	 *
	 * @return	The new top of the expression tree.
	 *
	 * @exception StandardException		Thrown on error
	 */

    ValueNode bindExpression(
        FromList fromList, SubqueryList subqueryList, List<AggregateNode> aggregates)
			throws StandardException
	{
        super.bindExpression(fromList, subqueryList, aggregates);

		leftOperand.checkIsBoolean();
		rightOperand.checkIsBoolean();

		setType(leftOperand.getTypeServices());

		return this;
	}

	
	/**
	 * Eliminate NotNodes in the current query block. We just mark whether
	 * this IS node is under an eliminated NOT node.
	 *
	 * @param	underNotNode	Whether or not we are under a NotNode.
	 *							
	 *
	 * @return		The modified expression
	 *
	 * @exception StandardException		Thrown on error
	 */
	ValueNode eliminateNots(boolean underNotNode) 
					throws StandardException
	{
		if ( underNotNode ) { notMe = !notMe; }

		leftOperand = leftOperand.eliminateNots( false);
		rightOperand = rightOperand.eliminateNots( false );

		return this;
	}

	/**
	 * Do the 1st step in putting child expressions into conjunctive normal
	 * form.  This step ensures that the top level of the child expression is
	 * a chain of AndNodes terminated by a true BooleanConstantNode.
	 *
	 * @return		The modified expression
	 *
	 * @exception StandardException		Thrown on error
	 */
	public ValueNode putAndsOnTop() 
					throws StandardException
	{
		leftOperand = leftOperand.putAndsOnTop();
		rightOperand = rightOperand.putAndsOnTop();

		return this;
	}

	/**
	 * Verify that putAndsOnTop() did its job correctly.  Verify that the top level 
	 * of the expression is a chain of AndNodes terminated by a true BooleanConstantNode.
	 *
	 * @return		Boolean which reflects validity of the tree.
	 */
	public boolean verifyPutAndsOnTop()
	{
		return ( leftOperand.verifyPutAndsOnTop() && rightOperand.verifyPutAndsOnTop() );
	}

	/**
	 * Finish putting an expression into conjunctive normal
	 * form.  An expression tree in conjunctive normal form meets
	 * the following criteria:
	 *		o  If the expression tree is not null,
	 *		   the top level will be a chain of AndNodes terminating
	 *		   in a true BooleanConstantNode.
	 *		o  The left child of an AndNode will never be an AndNode.
	 *		o  Any right-linked chain that includes an AndNode will
	 *		   be entirely composed of AndNodes terminated by a true BooleanConstantNode.
	 *		o  The left child of an OrNode will never be an OrNode.
	 *		o  Any right-linked chain that includes an OrNode will
	 *		   be entirely composed of OrNodes terminated by a false BooleanConstantNode.
	 *		o  ValueNodes other than AndNodes and OrNodes are considered
	 *		   leaf nodes for purposes of expression normalization.
	 *		   In other words, we won't do any normalization under
	 *		   those nodes.
	 *
	 * In addition, we track whether or not we are under a top level AndNode.  
	 * SubqueryNodes need to know this for subquery flattening.
	 *
	 * @param	underTopAndNode		Whether or not we are under a top level AndNode.
	 *							
	 *
	 * @return		The modified expression
	 *
	 * @exception StandardException		Thrown on error
	 */
	public ValueNode changeToCNF(boolean underTopAndNode) 
					throws StandardException
	{
		leftOperand = leftOperand.changeToCNF(false );
		rightOperand = rightOperand.changeToCNF(false );

		return this;
	}

	/**
	 * Verify that changeToCNF() did its job correctly.  Verify that:
	 *		o  AndNode  - rightOperand is not instanceof OrNode
	 *				      leftOperand is not instanceof AndNode
	 *		o  OrNode	- rightOperand is not instanceof AndNode
	 *					  leftOperand is not instanceof OrNode
	 *
	 * @return		Boolean which reflects validity of the tree.
	 */
	public boolean verifyChangeToCNF()
	{
		return	( leftOperand.verifyChangeToCNF() && rightOperand.verifyChangeToCNF() );
	}


	/**
	 * Do code generation for this logical binary operator.
	 *
	 * @param acb	The ExpressionClassBuilder for the class we're generating
	 * @param mb the method  the expression will go into
	 *
	 * @exception StandardException		Thrown on error
	 */

    void generateExpression(ExpressionClassBuilder acb, MethodBuilder mb)
		throws StandardException
	{
		String				evaluatorMethodName;

		/*
		** Generate the return value. Generated code is:
		**
		**	<fieldLeft>.<evaluatorMethodName>(<fieldRight>)
		*/

		if ( notMe ) { evaluatorMethodName = "isNot"; }
		else { evaluatorMethodName = "is"; }

		leftOperand.generateExpression(acb, mb);
		rightOperand.generateExpression(acb, mb);
		mb.callMethod(VMOpcode.INVOKEINTERFACE, ClassName.BooleanDataValue, evaluatorMethodName,
							ClassName.BooleanDataValue, 1);
	}
}
