/*
* Copyright 2003-2011 JetBrains s.r.o.
*
* 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 jetbrains.mps.util.iterable;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import java.util.Iterator;
/**
* Translate each element of first sequence to sequence of another elements, and serve these through {@link Iterator}
*/
public abstract class CollectManyIterator<IN, T> implements Iterable<T>, Iterator<T> {
private final Iterable<IN> myStart;
private Iterator<IN> myCurrentOuter;
private Iterator<T> myCurrentInner;
private T myNext;
public CollectManyIterator(@NotNull Iterable<IN> input) {
myStart = input;
reset(); // just in case it's used as Iterator, not Iterable, i.e. without #iterator() call
}
private void reset() {
myCurrentOuter = myStart.iterator();
myNext = nextInternal();
}
@Override
public boolean hasNext() {
return myNext != null;
}
@Override
public T next() {
T curr = myNext;
myNext = nextInternal();
return curr;
}
private T nextInternal() {
if (myCurrentInner != null && myCurrentInner.hasNext()) {
return myCurrentInner.next();
}
while (myCurrentOuter.hasNext()) {
IN element = myCurrentOuter.next();
myCurrentInner = element != null ? translate(element) : null;
if (myCurrentInner != null && myCurrentInner.hasNext()) {
return myCurrentInner.next();
}
}
return null;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
@Nullable
protected abstract Iterator<T> translate(IN node);
@Override
public Iterator<T> iterator() {
reset();
return this;
}
}