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/*
* Copyright 2000-2014 Vaadin Ltd.
*
* 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 com.vaadin.sass.internal.expression;
import static com.vaadin.sass.internal.parser.SCSSLexicalUnit.SCSS_VARIABLE;
import java.util.Stack;
import com.vaadin.sass.internal.expression.exception.ArithmeticException;
import com.vaadin.sass.internal.parser.LexicalUnitImpl;
import com.vaadin.sass.internal.parser.SCSSLexicalUnit;
public class ArithmeticExpressionEvaluator {
private static ArithmeticExpressionEvaluator instance;
public static ArithmeticExpressionEvaluator get() {
if (instance == null) {
instance = new ArithmeticExpressionEvaluator();
}
return instance;
}
private void createNewOperand(BinaryOperator operator,
Stack<Object> operands) {
Object rightOperand = operands.pop();
operands.push(new BinaryExpression(operands.pop(), operator,
rightOperand));
}
public boolean containsArithmeticalOperator(LexicalUnitImpl term) {
LexicalUnitImpl current = term;
while (current != null) {
for (BinaryOperator operator : BinaryOperator.values()) {
/*
* '/' is treated as an arithmetical operator when one of its
* operands is Variable, or there is another binary operator.
* Otherwise, '/' is treated as a CSS operator.
*/
if (current.getLexicalUnitType() == operator.type) {
if (current.getLexicalUnitType() != BinaryOperator.DIV.type) {
return true;
} else {
if (current.getPreviousLexicalUnit()
.getLexicalUnitType() == SCSS_VARIABLE
|| current.getNextLexicalUnit()
.getLexicalUnitType() == SCSS_VARIABLE) {
return true;
}
}
}
}
current = current.getNextLexicalUnit();
}
return false;
}
private Object createExpression(LexicalUnitImpl term) {
LexicalUnitImpl current = term;
boolean afterOperand = false;
Stack<Object> operands = new Stack<Object>();
Stack<Object> operators = new Stack<Object>();
inputTermLoop: while (current != null) {
if (afterOperand) {
if (current.getLexicalUnitType() == SCSSLexicalUnit.SCSS_OPERATOR_RIGHT_PAREN) {
Object operator = null;
while (!operators.isEmpty()
&& ((operator = operators.pop()) != Parentheses.LEFT)) {
createNewOperand((BinaryOperator) operator, operands);
}
current = current.getNextLexicalUnit();
continue;
}
afterOperand = false;
for (BinaryOperator operator : BinaryOperator.values()) {
if (current.getLexicalUnitType() == operator.type) {
while (!operators.isEmpty()
&& (operators.peek() != Parentheses.LEFT)
&& (((BinaryOperator) operators.peek()).precedence >= operator.precedence)) {
createNewOperand((BinaryOperator) operators.pop(),
operands);
}
operators.push(operator);
current = current.getNextLexicalUnit();
continue inputTermLoop;
}
}
throw new ArithmeticException("Illegal arithmetic expression",
term);
}
if (current.getLexicalUnitType() == SCSSLexicalUnit.SCSS_OPERATOR_LEFT_PAREN) {
operators.push(Parentheses.LEFT);
current = current.getNextLexicalUnit();
continue;
}
afterOperand = true;
operands.push(current);
current = current.getNextLexicalUnit();
}
while (!operators.isEmpty()) {
Object operator = operators.pop();
if (operator == Parentheses.LEFT) {
throw new ArithmeticException("Unexpected \"(\" found", term);
}
createNewOperand((BinaryOperator) operator, operands);
}
Object expression = operands.pop();
if (!operands.isEmpty()) {
LexicalUnitImpl operand = (LexicalUnitImpl) operands.peek();
throw new ArithmeticException("Unexpected operand "
+ operand.toString() + " found", term);
}
return expression;
}
public LexicalUnitImpl evaluate(LexicalUnitImpl term) {
Object result = ArithmeticExpressionEvaluator.get().createExpression(
term);
if (result instanceof BinaryExpression) {
return ((BinaryExpression) result).eval();
}
return term;
}
}
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