/*
* Copyright 2005 The Apache Software Foundation
*
* 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.
*/
using System;
namespace Lucene.Net.Search{
/// <summary>A Scorer for queries with a required subscorer and an excluding (prohibited) subscorer.
/// <br>
/// This <code>Scorer</code> implements {@link Scorer#SkipTo(int)},
/// and it uses the skipTo() on the given scorers.
/// </summary>
public class ReqExclScorer : Scorer
{
private Scorer reqScorer, exclScorer;
/// <summary>Construct a <code>ReqExclScorer</code>.</summary>
/// <param name="reqScorer">The scorer that must match, except where
/// </param>
/// <param name="exclScorer">indicates exclusion.
/// </param>
public ReqExclScorer(Scorer reqScorer, Scorer exclScorer) : base(null)
{ // No similarity used.
this.reqScorer = reqScorer;
this.exclScorer = exclScorer;
}
private bool firstTime = true;
public override bool Next()
{
if (firstTime)
{
if (!exclScorer.Next())
{
exclScorer = null; // exhausted at start
}
firstTime = false;
}
if (reqScorer == null)
{
return false;
}
if (!reqScorer.Next())
{
reqScorer = null; // exhausted, nothing left
return false;
}
if (exclScorer == null)
{
return true; // reqScorer.next() already returned true
}
return ToNonExcluded();
}
/// <summary>Advance to non excluded doc.
/// <br>On entry:
/// <ul>
/// <li>reqScorer != null,
/// <li>exclScorer != null,
/// <li>reqScorer was advanced once via next() or skipTo()
/// and reqScorer.doc() may still be excluded.
/// </ul>
/// Advances reqScorer a non excluded required doc, if any.
/// </summary>
/// <returns> true iff there is a non excluded required doc.
/// </returns>
private bool ToNonExcluded()
{
int exclDoc = exclScorer.Doc();
do
{
int reqDoc = reqScorer.Doc(); // may be excluded
if (reqDoc < exclDoc)
{
return true; // reqScorer advanced to before exclScorer, ie. not excluded
}
else if (reqDoc > exclDoc)
{
if (!exclScorer.SkipTo(reqDoc))
{
exclScorer = null; // exhausted, no more exclusions
return true;
}
exclDoc = exclScorer.Doc();
if (exclDoc > reqDoc)
{
return true; // not excluded
}
}
}
while (reqScorer.Next());
reqScorer = null; // exhausted, nothing left
return false;
}
public override int Doc()
{
return reqScorer.Doc(); // reqScorer may be null when next() or skipTo() already return false
}
/// <summary>Returns the score of the current document matching the query.
/// Initially invalid, until {@link #Next()} is called the first time.
/// </summary>
/// <returns> The score of the required scorer.
/// </returns>
public override float Score()
{
return reqScorer.Score(); // reqScorer may be null when next() or skipTo() already return false
}
/// <summary>Skips to the first match beyond the current whose document number is
/// greater than or equal to a given target.
/// <br>When this method is used the {@link #Explain(int)} method should not be used.
/// </summary>
/// <param name="target">The target document number.
/// </param>
/// <returns> true iff there is such a match.
/// </returns>
public override bool SkipTo(int target)
{
if (firstTime)
{
firstTime = false;
if (!exclScorer.SkipTo(target))
{
exclScorer = null; // exhausted
}
}
if (reqScorer == null)
{
return false;
}
if (exclScorer == null)
{
return reqScorer.SkipTo(target);
}
if (!reqScorer.SkipTo(target))
{
reqScorer = null;
return false;
}
return ToNonExcluded();
}
public override Explanation Explain(int doc)
{
Explanation res = new Explanation();
if (exclScorer.SkipTo(doc) && (exclScorer.Doc() == doc))
{
res.SetDescription("excluded");
}
else
{
res.SetDescription("not excluded");
res.AddDetail(reqScorer.Explain(doc));
}
return res;
}
}
}
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