net.mindengine.galen.parser.MathParser.java Source code

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Here is the source code for net.mindengine.galen.parser.MathParser.java

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/*******************************************************************************
* 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 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 String convertExpression(String initialValue, String expression) {
        String number = expression.substring(1);
        if (!StringUtils.isNumeric(number)) {
            throw new SyntaxException("Expected a number: " + number);
        }

        if (StringUtils.isNumeric(initialValue)) {
            char operationSymbol = expression.charAt(0);

            int initial = Integer.parseInt(initialValue);
            int added = Integer.parseInt(number);

            if (operationSymbol == '+') {
                return Integer.toString(initial + added);
            } else if (operationSymbol == '-') {
                return Integer.toString(initial - added);
            } else if (operationSymbol == '*') {
                return Integer.toString(initial * added);
            } else if (operationSymbol == '/') {
                return Integer.toString(initial / added);
            } else if (operationSymbol == '%') {
                return Integer.toString(initial % added);
            } else
                throw new SyntaxException("Unknown operation: " + operationSymbol);
        } else {
            return initialValue;
        }
    }

}