/*
* Copyright 2016 Red Hat, Inc. and/or its affiliates.
*
* 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.optaplanner.core.impl.score.director.drools.testgen.mutation;
import java.util.List;
public class TestGenHeadCuttingMutator<T> {
private final List<T> list;
private double cutFactor = 0.8;
private int totalCutSize = 0;
private int revertIncrement = -1;
private int cutIncrement;
public TestGenHeadCuttingMutator(List<T> list) {
this.list = list;
updateIncrement(false);
}
public boolean canMutate() {
return cutIncrement > 0 && totalCutSize + cutIncrement <= list.size();
}
public List<T> mutate() {
totalCutSize += cutIncrement;
revertIncrement = cutIncrement;
updateIncrement(false);
return getResult();
}
public void revert() {
if (revertIncrement < 0) {
throw new IllegalStateException("Can't revert without performing mutation first");
}
// revert cut size
totalCutSize -= revertIncrement;
revertIncrement = -1;
// reduce cut factor
cutFactor /= 2;
updateIncrement(true);
}
private void updateIncrement(boolean revert) {
cutIncrement = (int) ((list.size() - totalCutSize) * cutFactor);
if (cutIncrement == 0 && !revert) {
cutIncrement = 1;
}
}
public List<T> getResult() {
return list.subList(totalCutSize, list.size());
}
}