/*
    * Copyright 2002-2014 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.springframework.expression.spel.ast;
  
  import org.springframework.asm.Label;
  import org.springframework.asm.MethodVisitor;
  import org.springframework.expression.EvaluationException;
  import org.springframework.expression.spel.CodeFlow;
  import org.springframework.expression.spel.ExpressionState;
  import org.springframework.expression.spel.SpelEvaluationException;
  import org.springframework.expression.spel.SpelMessage;
  import org.springframework.expression.spel.support.BooleanTypedValue;
  
  /**
   * Represents a NOT operation.
   *
   * @author Andy Clement
   * @author Mark Fisher
   * @author Oliver Becker
   * @since 3.0
   */
  public class OperatorNot extends SpelNodeImpl {  // Not is a unary operator so does not extend BinaryOperator
  
  	public OperatorNot(int pos, SpelNodeImpl operand) {
  		super(pos, operand);
  		this.exitTypeDescriptor = "Z";
  	}
  
  
  	@Override
  	public BooleanTypedValue getValueInternal(ExpressionState state) throws EvaluationException {
  		try {
  			Boolean value = this.children[0].getValue(state, Boolean.class);
  			if (value == null) {
  				throw new SpelEvaluationException(SpelMessage.TYPE_CONVERSION_ERROR, "null", "boolean");
  			}
  			return BooleanTypedValue.forValue(!value);
  		}
  		catch (SpelEvaluationException ex) {
  			ex.setPosition(getChild(0).getStartPosition());
  			throw ex;
  		}
  	}
  
  	@Override
  	public String toStringAST() {
  		return "!" + getChild(0).toStringAST();
  	}
  	
  	@Override
  	public boolean isCompilable() {
  		SpelNodeImpl child = this.children[0];
  		return (child.isCompilable() && CodeFlow.isBooleanCompatible(child.exitTypeDescriptor));
  	}
  	
  	@Override
  	public void generateCode(MethodVisitor mv, CodeFlow cf) {
  		this.children[0].generateCode(mv, cf);
  		cf.unboxBooleanIfNecessary(mv);
  		Label elseTarget = new Label();
  		Label endOfIf = new Label();
  		mv.visitJumpInsn(IFNE,elseTarget);		
  		mv.visitInsn(ICONST_1); // TRUE
  		mv.visitJumpInsn(GOTO,endOfIf);
  		mv.visitLabel(elseTarget);
  		mv.visitInsn(ICONST_0); // FALSE
  		mv.visitLabel(endOfIf);
  		cf.pushDescriptor(this.exitTypeDescriptor);
  	}
  
  }