/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.wicket.markup.head;
import java.io.Serializable;
import java.util.Comparator;
import org.apache.wicket.Page;
import org.apache.wicket.markup.head.ResourceAggregator.RecordedHeaderItem;
import org.apache.wicket.markup.head.ResourceAggregator.RecordedHeaderItemLocation;
/**
* Implements the default sorting algorithm for {@link HeaderItem}s. {@link PriorityHeaderItem}s are
* moved to the front, inverting the component order to convert the child-first into a parent-first
* order. If {@code renderPageFirst} is true, the head from the markup of a page is moved to the
* front of the header, directly after the priority header items.
*
* @author papegaaij
*/
public class PriorityFirstComparator implements Comparator<RecordedHeaderItem>, Serializable
{
protected static enum HeaderItemType {
PRIORITY, PAGE, COMPONENT;
}
private final boolean renderPageFirst;
/**
* Construct.
*
* @param renderPageFirst
* when true, the header of the page is moved to the front.
*/
public PriorityFirstComparator(boolean renderPageFirst)
{
this.renderPageFirst = renderPageFirst;
}
@Override
public int compare(RecordedHeaderItem o1, RecordedHeaderItem o2)
{
HeaderItemType o1Type = getItemType(o1);
HeaderItemType o2Type = getItemType(o2);
if (o1Type != o2Type)
return o1Type.ordinal() - o2Type.ordinal();
if (o1Type == HeaderItemType.PRIORITY)
{
return inversedComponentOrder(o1, o2);
}
return compareWithinGroup(o1, o2);
}
/**
* Compares two header items that belong in the same group.
*
* @param o1
* @param o2
* @return 0 by default to preserve the order
*/
protected int compareWithinGroup(RecordedHeaderItem o1, RecordedHeaderItem o2)
{
return 0;
}
/**
* Compares two priority header items, converting the child-first order into parent-first.
*
* @param o1
* @param o2
* @return -1, 0 or 1 if o1 needs to be rendered before, unchanged or after o2.
*/
protected int inversedComponentOrder(RecordedHeaderItem o1, RecordedHeaderItem o2)
{
RecordedHeaderItemLocation lastO1Location = o1.getLocations().get(
o1.getLocations().size() - 1);
RecordedHeaderItemLocation lastO2Location = o2.getLocations().get(
o2.getLocations().size() - 1);
// within a component, preserve order
if (lastO1Location.getRenderBase() == lastO2Location.getRenderBase())
return 0;
return lastO1Location.getIndexInRequest() < lastO2Location.getIndexInRequest() ? 1 : -1;
}
/**
* Determines the type of the item: priority, page or component.
*
* @param item
* @return the type of the item
*/
protected HeaderItemType getItemType(RecordedHeaderItem item)
{
if (item.getItem() instanceof PriorityHeaderItem)
return HeaderItemType.PRIORITY;
if (renderPageFirst)
{
if (item.getItem() instanceof PageHeaderItem)
return HeaderItemType.PAGE;
for (RecordedHeaderItemLocation curLocation : item.getLocations())
if (curLocation.getRenderBase() instanceof Page)
return HeaderItemType.PAGE;
}
return HeaderItemType.COMPONENT;
}
}