/*
* 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.openapi.editor.cells.traversal;
import jetbrains.mps.openapi.editor.cells.EditorCell;
import jetbrains.mps.openapi.editor.cells.EditorCell_Collection;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import org.jetbrains.mps.openapi.util.TreeIterator;
import java.util.ArrayDeque;
import java.util.Collections;
import java.util.Iterator;
import java.util.NoSuchElementException;
class CellSubtreeIterator implements TreeIterator<EditorCell> {
/**
* All iterators in the stack have {@code hasNext() == true}
*/
private final ArrayDeque<Iterator<EditorCell>> myIteratorStack = new ArrayDeque<Iterator<EditorCell>>();
private final Direction myDirection;
private EditorCell myCurrent;
/**
* Indicates whether {@link #myCurrent} has children and therefore its iterator was pushed onto {@link #myIteratorStack}. Used in {@link #skipChildren()}
* to know whether there are any children to skip.
*/
private boolean myCurrentHasChildren;
CellSubtreeIterator(EditorCell root, Direction direction) {
myDirection = direction;
pushCell(root);
}
private void pushCell(EditorCell cell) {
pushIterator(Collections.singleton(cell).iterator());
}
private void pushChildren(EditorCell cell) {
Iterator<EditorCell> iterator = childrenOf(cell);
myCurrentHasChildren = iterator != null && iterator.hasNext();
if (myCurrentHasChildren) {
pushIterator(iterator);
}
}
private void pushIterator(@NotNull Iterator<EditorCell> iterator) {
myIteratorStack.push(iterator);
}
private void moveNext() {
if (myIteratorStack.isEmpty()) {
throw new NoSuchElementException("attempt to move past the end of an iterator");
}
final Iterator<EditorCell> iterator = myIteratorStack.peek();
EditorCell next = iterator.next();
if (!iterator.hasNext()) {
myIteratorStack.pop();
}
myCurrent = next;
pushChildren(myCurrent);
}
@Nullable
private Iterator<EditorCell> childrenOf(@Nullable EditorCell cell) {
if (cell == null) {
return null;
}
if (!(cell instanceof EditorCell_Collection)) {
return null;
}
return myDirection.getChildren((EditorCell_Collection) cell);
}
@Override
public boolean hasNext() {
return !myIteratorStack.isEmpty();
}
@Override
public EditorCell next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
moveNext();
return myCurrent;
}
@Override
public void skipChildren() {
if (myCurrentHasChildren) {
myIteratorStack.pop();
}
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
}