/*
* Copyright 2015, 2016 Tagir Valeev
*
* 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 one.util.streamex;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.Spliterators.AbstractSpliterator;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.Supplier;
import java.util.stream.Stream;
import static one.util.streamex.StreamExInternals.*;
/**
* @author Tagir Valeev
*/
/*package*/ final class HeadTailSpliterator<T, U> extends AbstractSpliterator<U> implements TailSpliterator<U> {
private Spliterator<T> source;
private BiFunction<? super T, ? super StreamEx<T>, ? extends Stream<U>> mapper;
private Supplier<? extends Stream<U>> emptyMapper;
private Spliterator<U> target;
StreamContext context;
HeadTailSpliterator(Spliterator<T> source, BiFunction<? super T, ? super StreamEx<T>, ? extends Stream<U>> mapper,
Supplier<? extends Stream<U>> emptyMapper) {
super(Long.MAX_VALUE, ORDERED);
this.source = source;
this.mapper = mapper;
this.emptyMapper = emptyMapper;
}
@Override
public boolean tryAdvance(Consumer<? super U> action) {
if(!init())
return false;
target = TailSpliterator.tryAdvanceWithTail(target, action);
if(target == null) {
context = null;
return false;
}
return true;
}
@Override
public Spliterator<U> tryAdvanceOrTail(Consumer<? super U> action) {
if(!init())
return null;
Spliterator<U> tail = target;
target = null;
context = null;
return tail;
}
@Override
public void forEachRemaining(Consumer<? super U> action) {
if(!init())
return;
TailSpliterator.forEachWithTail(target, action);
target = null;
context = null;
}
@Override
public Spliterator<U> forEachOrTail(Consumer<? super U> action) {
return tryAdvanceOrTail(action);
}
private boolean init() {
if(context == null)
return false;
if(target == null) {
Box<T> first = new Box<>();
source = TailSpliterator.tryAdvanceWithTail(source, first);
Stream<U> stream = source == null ? emptyMapper.get() : mapper.apply(first.a, StreamEx.of(source));
source = null;
mapper = null;
emptyMapper = null;
if(stream == null) {
target = Spliterators.emptySpliterator();
} else {
StreamContext ctx = StreamContext.of(stream);
if(ctx.closeHandler != null)
context.onClose(ctx.closeHandler);
target = stream.spliterator();
}
}
return true;
}
@Override
public long estimateSize() {
if(context == null)
return 0;
return (target == null ? source : target).estimateSize();
}
}