/*
 * Copyright 2002-2017 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.expression.EvaluationException;
import org.springframework.expression.Operation;
import org.springframework.expression.TypedValue;
import org.springframework.expression.spel.ExpressionState;
import org.springframework.expression.spel.SpelEvaluationException;
import org.springframework.expression.spel.SpelMessage;
import org.springframework.util.Assert;

/**
 * Increment operator. Can be used in a prefix or postfix form. This will throw
 * appropriate exceptions if the operand in question does not support increment.
 *
 * @author Andy Clement
 * @author Juergen Hoeller
 * @author Giovanni Dall'Oglio Risso
 * @since 3.2
 */
public class OpInc extends Operator {

	private final boolean postfix;  // false means prefix


	public OpInc(int pos, boolean postfix, SpelNodeImpl... operands) {
		super("++", pos, operands);
		this.postfix = postfix;
		Assert.notEmpty(operands, "Operands must not be empty");
	}


	@Override
	public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
		SpelNodeImpl operand = getLeftOperand();
		ValueRef valueRef = operand.getValueRef(state);

		TypedValue typedValue = valueRef.getValue();
		Object value = typedValue.getValue();
		TypedValue returnValue = typedValue;
		TypedValue newValue = null;

		if (value instanceof Number) {
			Number op1 = (Number) value;
			if (op1 instanceof BigDecimal) {
				newValue = new TypedValue(((BigDecimal) op1).add(BigDecimal.ONE), typedValue.getTypeDescriptor());
			}
			else if (op1 instanceof Double) {
				newValue = new TypedValue(op1.doubleValue() + 1.0d, typedValue.getTypeDescriptor());
			}
			else if (op1 instanceof Float) {
				newValue = new TypedValue(op1.floatValue() + 1.0f, typedValue.getTypeDescriptor());
			}
			else if (op1 instanceof BigInteger) {
				newValue = new TypedValue(((BigInteger) op1).add(BigInteger.ONE), typedValue.getTypeDescriptor());
			}
			else if (op1 instanceof Long) {
				newValue = new TypedValue(op1.longValue() + 1L, typedValue.getTypeDescriptor());
			}
			else if (op1 instanceof Integer) {
				newValue = new TypedValue(op1.intValue() + 1, typedValue.getTypeDescriptor());
			}
			else if (op1 instanceof Short) {
				newValue = new TypedValue(op1.shortValue() + (short) 1, typedValue.getTypeDescriptor());
			}
			else if (op1 instanceof Byte) {
				newValue = new TypedValue(op1.byteValue() + (byte) 1, typedValue.getTypeDescriptor());
			}
			else {
				// Unknown Number subtype -> best guess is double increment
				newValue = new TypedValue(op1.doubleValue() + 1.0d, typedValue.getTypeDescriptor());
			}
		}

		if (newValue == null) {
			try {
				newValue = state.operate(Operation.ADD, returnValue.getValue(), 1);
			}
			catch (SpelEvaluationException ex) {
				if (ex.getMessageCode() == SpelMessage.OPERATOR_NOT_SUPPORTED_BETWEEN_TYPES) {
					// This means the operand is not incrementable
					throw new SpelEvaluationException(operand.getStartPosition(),
							SpelMessage.OPERAND_NOT_INCREMENTABLE, operand.toStringAST());
				}
				throw ex;
			}
		}

		// set the name value
		try {
			valueRef.setValue(newValue.getValue());
		}
		catch (SpelEvaluationException see) {
			// If unable to set the value the operand is not writable (e.g. 1++ )
			if (see.getMessageCode() == SpelMessage.SETVALUE_NOT_SUPPORTED) {
				throw new SpelEvaluationException(operand.getStartPosition(), SpelMessage.OPERAND_NOT_INCREMENTABLE);
			}
			else {
				throw see;
			}
		}

		if (!this.postfix) {
			// The return value is the new value, not the original value
			returnValue = newValue;
		}

		return returnValue;
	}

	@Override
	public String toStringAST() {
		return getLeftOperand().toStringAST() + "++";
	}

	@Override
	public SpelNodeImpl getRightOperand() {
		throw new IllegalStateException("No right operand");
	}

}
