001/*-------------------------------------------------------------------------+
002|                                                                          |
003| Copyright 2005-2011 the ConQAT Project                                   |
004|                                                                          |
005| Licensed under the Apache License, Version 2.0 (the "License");          |
006| you may not use this file except in compliance with the License.         |
007| You may obtain a copy of the License at                                  |
008|                                                                          |
009|    http://www.apache.org/licenses/LICENSE-2.0                            |
010|                                                                          |
011| Unless required by applicable law or agreed to in writing, software      |
012| distributed under the License is distributed on an "AS IS" BASIS,        |
013| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
014| See the License for the specific language governing permissions and      |
015| limitations under the License.                                           |
016+-------------------------------------------------------------------------*/
017package eu.cqse.check.framework.util.tokens;
018
019import java.util.Arrays;
020
021/**
022 * Tries to match the given subpatterns in order, if possible. If not, an empty
023 * match is returned.
024 */
025public class OptionalPattern extends TokenPatternBase {
026
027        /** The patterns to match in order. */
028        private final TokenPatternBase[] matchers;
029
030        /** Constructor */
031        public OptionalPattern(TokenPatternBase[] matchers) {
032                this.matchers = matchers;
033        }
034
035        /** {@inheritDoc} */
036        @Override
037        protected TokenPatternMatch matchesLocally(TokenStream stream) {
038                int beforeOptional = stream.getPosition();
039                TokenPatternMatch parentMatch = createMatch(stream);
040                for (TokenPatternBase matcher : matchers) {
041                        TokenPatternMatch match = matcher.matches(stream);
042                        if (match == null) {
043                                stream.setPosition(beforeOptional);
044                                return createMatch(stream);
045                        }
046                        parentMatch.mergeFrom(match);
047                }
048                return parentMatch;
049        }
050
051        /** {@inheritDoc} */
052        @Override
053        public String toString() {
054                return "Optional " + Arrays.toString(matchers);
055        }
056}