/*
* Copyright (C) 2009-2010 Mathias Doenitz
*
* 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.parboiled.matchervisitors;
import org.parboiled.matchers.*;
import org.parboiled.support.Characters;
import java.util.Random;
/**
* Returns the first character a given matcher can start a match with.
* For all complex matchers, i.e. the ones not always matching just one character, the visitor returns null.
*/
public class GetStarterCharVisitor extends DefaultMatcherVisitor<Character> {
@Override
public Character visit(AnyOfMatcher matcher) {
Characters characters = matcher.characters;
if (!characters.isSubtractive()) {
return characters.getChars()[0];
}
// for substractive sets we try to randomly choose a fitting character
Random random = new Random();
char c;
do {
c = (char) random.nextInt(Character.MAX_VALUE);
} while (!Character.isDefined(c) || !characters.contains(c));
return c;
}
@Override
public Character visit(CharIgnoreCaseMatcher matcher) {
return matcher.charLow;
}
@Override
public Character visit(CharMatcher matcher) {
return matcher.character;
}
@Override
public Character visit(CharRangeMatcher matcher) {
return matcher.cLow;
}
@Override
public Character visit(CustomMatcher matcher) {
return matcher.getStarterChar();
}
}