/*
* Copyright 2015-2016 Red Hat, Inc. and/or its affiliates
* and other contributors as indicated by the @author tags.
*
* 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.hawkular.inventory.api.paging;
import java.util.Iterator;
/**
* Holds the lambda function to be able to correctly calculate the total size, once the
* iterator is depleted
*
* @author Jirka Kremser
* @since 0.3.4
*/
public class SizeAwarePage<T> extends Page<T> {
private HasTotalSize hasTotalSize;
private long totalSize;
public SizeAwarePage(Iterator<T> wrapped, PageContext pageContext, HasTotalSize hasTotalSize) {
super(wrapped, pageContext, HasTotalSize.NOT_DEPLETED);
this.totalSize = HasTotalSize.NOT_DEPLETED;
if (hasTotalSize == null) {
throw new IllegalArgumentException("hasTotalSize can't be null");
}
this.hasTotalSize = hasTotalSize;
}
/**
* This returns <ul>
* <li>-1 if the iterator hasn't been depleted</li>
* <li>the total size otherwise</li>
* </ul>
*
* @return the total number of results of which this page is a subset of
*/
@Override
public long getTotalSize() {
if (totalSize == HasTotalSize.NOT_DEPLETED && !hasNext()) {
totalSize = hasTotalSize == null ? HasTotalSize.NOT_DEPLETED : hasTotalSize.getTotalSize();
}
return totalSize;
}
@Override public boolean hasNext() {
return super.hasNext();
}
@Override
public T next() {
return super.next();
}
@Override public void close() {
getTotalSize();
this.hasTotalSize = null;
super.close();
}
@FunctionalInterface
public interface HasTotalSize {
int NOT_DEPLETED = -1;
long getTotalSize();
}
}