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RemoveEmptyNonLeafQueryNodeProcessor.cs
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RemoveEmptyNonLeafQueryNodeProcessor.cs
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using Lucene.Net.QueryParsers.Flexible.Core.Nodes;
using Lucene.Net.QueryParsers.Flexible.Core.Processors;
using Lucene.Net.Util;
using System.Collections.Generic;
using JCG = J2N.Collections.Generic;
namespace Lucene.Net.QueryParsers.Flexible.Standard.Processors
{
/*
* 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.
*/
/// <summary>
/// This processor removes every <see cref="IQueryNode"/> that is not a leaf and has not
/// children. If after processing the entire tree the root node is not a leaf and
/// has no children, a <see cref="MatchNoDocsQueryNode"/> object is returned.
/// <para/>
/// This processor is used at the end of a pipeline to avoid invalid query node
/// tree structures like a <see cref="GroupQueryNode"/> or <see cref="ModifierQueryNode"/>
/// with no children.
/// </summary>
/// <seealso cref="IQueryNode"/>
/// <seealso cref="MatchNoDocsQueryNode"/>
public class RemoveEmptyNonLeafQueryNodeProcessor : QueryNodeProcessor
{
private readonly JCG.List<IQueryNode> childrenBuffer = new JCG.List<IQueryNode>(); // LUCENENET: marked readonly
public RemoveEmptyNonLeafQueryNodeProcessor()
{
// empty constructor
}
public override IQueryNode Process(IQueryNode queryTree)
{
queryTree = base.Process(queryTree);
if (!queryTree.IsLeaf)
{
IList<IQueryNode> children = queryTree.GetChildren();
if (children is null || children.Count == 0)
{
return new MatchNoDocsQueryNode();
}
}
return queryTree;
}
protected override IQueryNode PostProcessNode(IQueryNode node)
{
return node;
}
protected override IQueryNode PreProcessNode(IQueryNode node)
{
return node;
}
protected override IList<IQueryNode> SetChildrenOrder(IList<IQueryNode> children)
{
try
{
foreach (IQueryNode child in children)
{
if (!child.IsLeaf)
{
IList<IQueryNode> grandChildren = child.GetChildren();
if (grandChildren != null && grandChildren.Count > 0)
{
this.childrenBuffer.Add(child);
}
}
else
{
this.childrenBuffer.Add(child);
}
}
children.Clear();
children.AddRange(this.childrenBuffer);
}
finally
{
this.childrenBuffer.Clear();
}
return children;
}
}
}