/*
* Copyright 2015, The Querydsl Team (http://www.querydsl.com/team)
*
* 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 com.querydsl.core.group;
/**
* {@code MixinGroupExpression} provides nesting support for {@link GroupExpression} instances
*
* @param <E>
* @param <F>
* @param <R>
*/
public class MixinGroupExpression<E, F, R> extends AbstractGroupExpression<E, R> {
private static final long serialVersionUID = -5419707469727395643L;
private class GroupCollectorImpl implements GroupCollector<E, R> {
private final GroupCollector<F, R> mixinGroupCollector;
private GroupCollector<E, F> groupCollector;
public GroupCollectorImpl() {
mixinGroupCollector = mixin.createGroupCollector();
}
@Override
public void add(E input) {
if (groupCollector == null) {
groupCollector = groupExpression.createGroupCollector();
}
groupCollector.add(input);
}
@Override
public R get() {
if (groupCollector != null) {
F output = groupCollector.get();
mixinGroupCollector.add(output);
groupCollector = null;
}
return mixinGroupCollector.get();
}
}
private final GroupExpression<F, R> mixin;
private final GroupExpression<E, F> groupExpression;
@SuppressWarnings({ "unchecked", "rawtypes" })
public MixinGroupExpression(GroupExpression<E, F> groupExpression, GroupExpression<F, R> mixin) {
super((Class) mixin.getType(), groupExpression.getExpression());
this.mixin = mixin;
this.groupExpression = groupExpression;
}
@Override
public GroupCollector<E, R> createGroupCollector() {
return new GroupCollectorImpl();
}
}