/**
* Copyright 2010 Google Inc.
*
* 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 org.waveprotocol.wave.model.conversation;
import org.waveprotocol.wave.model.util.StringMap;
import java.util.Iterator;
public class WrapperIterator<M extends HasId, W> implements Iterator<W> {
// The invariant for this iterator is that 'next' always contains the next
// manifest to return, if there is one, and the manifest iterator is ready to
// return the manifest immediately after the one corresponding to 'next',
// possibly one that has no backing overlay object.
private final Iterator<? extends M> manifestIterator;
private final StringMap<W> wrapperMap;
private W next;
private WrapperIterator(Iterator<? extends M> manifestIterator, StringMap<W> wrapperMap) {
this.manifestIterator = manifestIterator;
this.wrapperMap = wrapperMap;
advance();
}
/**
* Create a new wrapper iterator for the given series of manifests, using the
* associated wrapper map to fetch wrappers.
*/
public static <M extends HasId, W> WrapperIterator<M, W> create(
Iterator<? extends M> manifestIterator, StringMap<W> wrapperMap) {
return new WrapperIterator<M, W>(manifestIterator, wrapperMap);
}
private void advance() {
while (manifestIterator.hasNext()) {
M nextManifest = manifestIterator.next();
W nextWrapper = wrapperMap.get(nextManifest.getId());
if (nextWrapper != null) {
next = nextWrapper;
return;
}
}
next = null;
}
@Override
public boolean hasNext() {
return next != null;
}
@Override
public W next() {
W result = next;
advance();
return result;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
}