/*
    * 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 java.math.BigDecimal;
  import java.math.BigInteger;
  
  import org.springframework.asm.MethodVisitor;
  import org.springframework.core.convert.TypeDescriptor;
  import org.springframework.expression.EvaluationException;
  import org.springframework.expression.Operation;
  import org.springframework.expression.TypeConverter;
  import org.springframework.expression.TypedValue;
  import org.springframework.expression.spel.CodeFlow;
  import org.springframework.expression.spel.ExpressionState;
  import org.springframework.util.Assert;
  import org.springframework.util.NumberUtils;
  
  /**
   * The plus operator will:
   * <ul>
   * <li>add numbers
   * <li>concatenate strings
   * </ul>
   *
   * <p>It can be used as a unary operator for numbers.
   * The standard promotions are performed when the operand types vary (double+int=double).
   * For other options it defers to the registered overloader.
   *
   * @author Andy Clement
   * @author Juergen Hoeller
   * @author Ivo Smid
   * @author Giovanni Dall'Oglio Risso
   * @since 3.0
   */
  public class OpPlus extends Operator {
  
  	public OpPlus(int pos, SpelNodeImpl... operands) {
  		super("+", pos, operands);
  		Assert.notEmpty(operands);
  	}
  
  
  	@Override
  	public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
  		SpelNodeImpl leftOp = getLeftOperand();
  		SpelNodeImpl rightOp = getRightOperand();
  
  		if (rightOp == null) {  // if only one operand, then this is unary plus
  			Object operandOne = leftOp.getValueInternal(state).getValue();
  			if (operandOne instanceof Number) {
  				if (operandOne instanceof Double) {
  					this.exitTypeDescriptor = "D";
  				}
  				else if (operandOne instanceof Float) {
  					this.exitTypeDescriptor = "F";
  				}
  				else if (operandOne instanceof Long) {
  					this.exitTypeDescriptor = "J";
  				}
  				else if (operandOne instanceof Integer) {
  					this.exitTypeDescriptor = "I";
  				}
  				return new TypedValue(operandOne);
  			}
  			return state.operate(Operation.ADD, operandOne, null);
  		}
  
  		TypedValue operandOneValue = leftOp.getValueInternal(state);
  		Object leftOperand = operandOneValue.getValue();
  		TypedValue operandTwoValue = rightOp.getValueInternal(state);
  		Object rightOperand = operandTwoValue.getValue();
  
  		if (leftOperand instanceof Number && rightOperand instanceof Number) {
  			Number leftNumber = (Number) leftOperand;
  			Number rightNumber = (Number) rightOperand;
  
  			if (leftNumber instanceof BigDecimal || rightNumber instanceof BigDecimal) {
  				BigDecimal leftBigDecimal = NumberUtils.convertNumberToTargetClass(leftNumber, BigDecimal.class);
  				BigDecimal rightBigDecimal = NumberUtils.convertNumberToTargetClass(rightNumber, BigDecimal.class);
  				return new TypedValue(leftBigDecimal.add(rightBigDecimal));
  			}
  			else if (leftNumber instanceof Double || rightNumber instanceof Double) {
  				if (leftNumber.getClass() == rightNumber.getClass()) {
  					this.exitTypeDescriptor = "D";
 				}
 				return new TypedValue(leftNumber.doubleValue() + rightNumber.doubleValue());
 			}
 			else if (leftNumber instanceof Float || rightNumber instanceof Float) {
 				if (leftNumber.getClass() == rightNumber.getClass()) {
 					this.exitTypeDescriptor = "F";
 				}
 				return new TypedValue(leftNumber.floatValue() + rightNumber.floatValue());
 			}
 			else if (leftNumber instanceof BigInteger || rightNumber instanceof BigInteger) {
 				BigInteger leftBigInteger = NumberUtils.convertNumberToTargetClass(leftNumber, BigInteger.class);
 				BigInteger rightBigInteger = NumberUtils.convertNumberToTargetClass(rightNumber, BigInteger.class);
 				return new TypedValue(leftBigInteger.add(rightBigInteger));
 			}
 			else if (leftNumber instanceof Long || rightNumber instanceof Long) {
 				if (leftNumber.getClass() == rightNumber.getClass()) {
 					this.exitTypeDescriptor = "J";
 				}
 				return new TypedValue(leftNumber.longValue() + rightNumber.longValue());
 			}
 			else if (CodeFlow.isIntegerForNumericOp(leftNumber) || CodeFlow.isIntegerForNumericOp(rightNumber)) {
 				if (leftNumber instanceof Integer && rightNumber instanceof Integer) {
 					this.exitTypeDescriptor = "I";
 				}
 				return new TypedValue(leftNumber.intValue() + rightNumber.intValue());
 			}
 			else {
 				// Unknown Number subtypes -> best guess is double addition
 				return new TypedValue(leftNumber.doubleValue() + rightNumber.doubleValue());
 			}
 		}
 
 		if (leftOperand instanceof String && rightOperand instanceof String) {
 			this.exitTypeDescriptor = "Ljava/lang/String";
 			return new TypedValue((String) leftOperand + rightOperand);
 		}
 
 		if (leftOperand instanceof String) {
 			return new TypedValue(
 					leftOperand + (rightOperand == null ? "null" : convertTypedValueToString(operandTwoValue, state)));
 		}
 
 		if (rightOperand instanceof String) {
 			return new TypedValue(
 					(leftOperand == null ? "null" : convertTypedValueToString(operandOneValue, state)) + rightOperand);
 		}
 
 		return state.operate(Operation.ADD, leftOperand, rightOperand);
 	}
 
 	@Override
 	public String toStringAST() {
 		if (this.children.length < 2) {  // unary plus
 			return "+" + getLeftOperand().toStringAST();
 		}
 		return super.toStringAST();
 	}
 
 	@Override
 	public SpelNodeImpl getRightOperand() {
 		if (this.children.length < 2) {
 			return null;
 		}
 		return this.children[1];
 	}
 
 	/**
 	 * Convert operand value to string using registered converter or using
 	 * {@code toString} method.
 	 * @param value typed value to be converted
 	 * @param state expression state
 	 * @return {@code TypedValue} instance converted to {@code String}
 	 */
 	private static String convertTypedValueToString(TypedValue value, ExpressionState state) {
 		TypeConverter typeConverter = state.getEvaluationContext().getTypeConverter();
 		TypeDescriptor typeDescriptor = TypeDescriptor.valueOf(String.class);
 		if (typeConverter.canConvert(value.getTypeDescriptor(), typeDescriptor)) {
 			return String.valueOf(typeConverter.convertValue(value.getValue(),
 					value.getTypeDescriptor(), typeDescriptor));
 		}
 		return String.valueOf(value.getValue());
 	}
 
 	@Override
 	public boolean isCompilable() {
 		if (!getLeftOperand().isCompilable()) {
 			return false;
 		}
 		if (this.children.length > 1) {
 			 if (!getRightOperand().isCompilable()) {
 				 return false;
 			 }
 		}
 		return (this.exitTypeDescriptor != null);
 	}
 
 	/**
 	 * Walk through a possible tree of nodes that combine strings and append
 	 * them all to the same (on stack) StringBuilder.
 	 */
 	private void walk(MethodVisitor mv, CodeFlow cf, SpelNodeImpl operand) {
 		if (operand instanceof OpPlus) {
 			OpPlus plus = (OpPlus)operand;
 			walk(mv,cf,plus.getLeftOperand());
 			walk(mv,cf,plus.getRightOperand());
 		}
 		else {
 			cf.enterCompilationScope();
 			operand.generateCode(mv,cf);
 			if (cf.lastDescriptor() != "Ljava/lang/String") {
 				mv.visitTypeInsn(CHECKCAST, "java/lang/String");
 			}
 			cf.exitCompilationScope();
 			mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);
 		}
 	}
 	
 	@Override
 	public void generateCode(MethodVisitor mv, CodeFlow cf) {
 		if (this.exitTypeDescriptor == "Ljava/lang/String") {
 			mv.visitTypeInsn(NEW, "java/lang/StringBuilder");
 			mv.visitInsn(DUP);
 			mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "()V", false);
 			walk(mv,cf,getLeftOperand());
 			walk(mv,cf,getRightOperand());
 			mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false);
 		}
 		else {
 			getLeftOperand().generateCode(mv, cf);
 			String leftDesc = getLeftOperand().exitTypeDescriptor;
 			if (!CodeFlow.isPrimitive(leftDesc)) {
 				CodeFlow.insertUnboxInsns(mv, this.exitTypeDescriptor.charAt(0), leftDesc);
 			}
 			if (this.children.length > 1) {
 				cf.enterCompilationScope();
 				getRightOperand().generateCode(mv, cf);
 				String rightDesc = getRightOperand().exitTypeDescriptor;
 				cf.exitCompilationScope();
 				if (!CodeFlow.isPrimitive(rightDesc)) {
 					CodeFlow.insertUnboxInsns(mv, this.exitTypeDescriptor.charAt(0), rightDesc);
 				}
 				switch (this.exitTypeDescriptor.charAt(0)) {
 					case 'I':
 						mv.visitInsn(IADD);
 						break;
 					case 'J':
 						mv.visitInsn(LADD);
 						break;
 					case 'F': 
 						mv.visitInsn(FADD);
 						break;
 					case 'D':
 						mv.visitInsn(DADD);
 						break;				
 					default:
 						throw new IllegalStateException(
 								"Unrecognized exit type descriptor: '" + this.exitTypeDescriptor + "'");
 				}
 			}
 		}
 		cf.pushDescriptor(this.exitTypeDescriptor);
 	}
 
 }