/*
* 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 java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
/**
* {@link java.lang.Iterable} to walk recursive sequences of identical objects.
*/
public abstract class RecursiveIterator<T> implements Iterable<T>, Iterator<T> {
private final Iterable<T> myRoot;
private final boolean myLeavesOnly;
private final Set<T> mySeen = new HashSet<T>();
private final Deque<Iterator<T>> myStack = new ArrayDeque<Iterator<T>>();
private T myNext;
public RecursiveIterator(@NotNull Iterable<T> root, boolean leavesOnly) {
myRoot = root;
myLeavesOnly = leavesOnly;
}
protected T nextElement() {
while(!myStack.isEmpty()) {
final Iterator<T> top = myStack.peek();
if(top.hasNext()) {
final T next = top.next();
if(next == null || !mySeen.add(next)) {
continue;
}
Iterator<T> new_ = children(next);
if(new_ != null) {
myStack.push(new_);
if(myLeavesOnly) {
continue;
}
}
return next;
}
myStack.pop();
}
return null;
}
@Override
public final boolean hasNext() {
return myNext != null;
}
@Override
public final T next() {
final T result = myNext;
myNext = nextElement();
return result;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
@Override
public Iterator<T> iterator() {
mySeen.clear();
myStack.clear();
myStack.push(myRoot.iterator());
myNext = nextElement();
return this;
}
protected abstract Iterator<T> children(T node);
}