/*
    * 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.TypedValue;
  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 the boolean AND operation.
   *
   * @author Andy Clement
   * @author Mark Fisher
   * @author Oliver Becker
   * @since 3.0
   */
  public class OpAnd extends Operator {
  
  	public OpAnd(int pos, SpelNodeImpl... operands) {
  		super("and", pos, operands);
  		this.exitTypeDescriptor = "Z";
  	}
  
  
  	@Override
  	public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
  		if (getBooleanValue(state, getLeftOperand()) == false) {
  			// no need to evaluate right operand
  			return BooleanTypedValue.FALSE;
  		}
  		return BooleanTypedValue.forValue(getBooleanValue(state, getRightOperand()));
  	}
  
  	private boolean getBooleanValue(ExpressionState state, SpelNodeImpl operand) {
  		try {
  			Boolean value = operand.getValue(state, Boolean.class);
  			assertValueNotNull(value);
  			return value;
  		}
  		catch (SpelEvaluationException ex) {
  			ex.setPosition(operand.getStartPosition());
  			throw ex;
  		}
  	}
  
  	private void assertValueNotNull(Boolean value) {
  		if (value == null) {
  			throw new SpelEvaluationException(SpelMessage.TYPE_CONVERSION_ERROR, "null", "boolean");
  		}
  	}
  
  	@Override
  	public boolean isCompilable() {
  		SpelNodeImpl left = getLeftOperand();
  		SpelNodeImpl right = getRightOperand();
  		return (left.isCompilable() && right.isCompilable() &&
  				CodeFlow.isBooleanCompatible(left.exitTypeDescriptor) &&
  				CodeFlow.isBooleanCompatible(right.exitTypeDescriptor));
  	}
  	
  	@Override
  	public void generateCode(MethodVisitor mv, CodeFlow cf) {
  		// Pseudo: if (!leftOperandValue) { result=false; } else { result=rightOperandValue; }
  		Label elseTarget = new Label();
  		Label endOfIf = new Label();
  		cf.enterCompilationScope();
  		getLeftOperand().generateCode(mv, cf);
  		cf.unboxBooleanIfNecessary(mv);
  		cf.exitCompilationScope();
  		mv.visitJumpInsn(IFNE, elseTarget);
  		mv.visitLdcInsn(0); // FALSE
  		mv.visitJumpInsn(GOTO,endOfIf);
  		mv.visitLabel(elseTarget);
  		cf.enterCompilationScope();
  		getRightOperand().generateCode(mv, cf);
  		cf.unboxBooleanIfNecessary(mv);
  		cf.exitCompilationScope();
  		mv.visitLabel(endOfIf);
  		cf.pushDescriptor(this.exitTypeDescriptor);
 	}
 
 }