/*******************************************************************************
* Copyright 2014 Ivan Shubin http://mindengine.net
*
* 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 net.mindengine.galen.parser;
import net.mindengine.galen.javascript.GalenJsExecutor;
import org.apache.commons.lang3.StringUtils;
import net.mindengine.galen.specs.reader.StringCharReader;
public class MathParser {
private char mathSymbol = '@';
public String parse(String template, String initialValue) {
StringCharReader reader = new StringCharReader(template);
StringBuffer text = new StringBuffer();
while(reader.hasMore()) {
char ch = reader.next();
if (ch == mathSymbol) {
if (reader.hasMore()) {
char nextCh = reader.next();
if (nextCh == mathSymbol) {
text.append(mathSymbol);
}
else if (nextCh == '{') {
String expression = reader.readUntilSymbol('}').replace(" ", "");
if (expression.length() < 2) {
throw new SyntaxException("Can't parse expression: " + expression);
}
text.append(convertExpression(initialValue, expression));
}
else {
text.append(initialValue);
text.append(nextCh);
}
}
else {
text.append(initialValue);
}
}
else {
text.append(ch);
}
}
return text.toString();
}
private static final char[] mathOperations = {'+', '-', '/', '*','%'};
private String convertExpression(String initialValue, String expression) {
int index = Integer.parseInt(initialValue);
if (startsWithOneOfTheseSymbols(expression, mathOperations)) {
expression = "index" + expression;
}
return Integer.toString(execJavascript(index, expression));
}
private int execJavascript(int index, String expression) {
GalenJsExecutor jsExecutor = new GalenJsExecutor();
jsExecutor.putObject("index", index);
Number number = (Number)jsExecutor.eval(expression);
return number.intValue();
}
private boolean startsWithOneOfTheseSymbols(String expression, char[] mathOperations) {
if (expression.length() > 0) {
char firstSymbol = expression.charAt(0);
for (char symbol: mathOperations) {
if (firstSymbol == symbol) {
return true;
}
}
}
return false;
}
}