src/Lucene.Net.Queries/Function/ValueSources/TermFreqValueSource.cs

/*
 * 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.
 */
using System;
using System.Collections;
using System.IO;
using Lucene.Net.Index;
using Lucene.Net.Queries.Function.DocValues;
using Lucene.Net.Search;
using Lucene.Net.Util;

namespace Lucene.Net.Queries.Function.ValueSources
{
    /// <summary>
    /// Function that returns <seealso cref="DocsEnum#freq()"/> for the
    /// supplied term in every document.
    /// <para>
    /// If the term does not exist in the document, returns 0.
    /// If frequencies are omitted, returns 1.
    /// </para>
    /// </summary>
    public class TermFreqValueSource : DocFreqValueSource
    {
        public TermFreqValueSource(string field, string val, string indexedField, BytesRef indexedBytes)
            : base(field, val, indexedField, indexedBytes)
        {
        }

        public override string Name
        {
            get { return "termfreq"; }
        }

        public override FunctionValues GetValues(IDictionary context, AtomicReaderContext readerContext)
        {
            Fields fields = readerContext.AtomicReader.Fields;
            Terms terms = fields.Terms(indexedField);

            return new IntDocValuesAnonymousInnerClassHelper(this, this, terms);
        }

        private class IntDocValuesAnonymousInnerClassHelper : IntDocValues
        {
            private readonly TermFreqValueSource outerInstance;

            private Terms terms;

            public IntDocValuesAnonymousInnerClassHelper(TermFreqValueSource outerInstance, TermFreqValueSource @this, Terms terms)
                : base(@this)
            {
                this.outerInstance = outerInstance;
                this.terms = terms;
                lastDocRequested = -1;
                Reset();
            }

            private DocsEnum docs;
            private int atDoc;
            private int lastDocRequested;

            public virtual void Reset()
            {
                // no one should call us for deleted docs?

                if (terms != null)
                {
                    TermsEnum termsEnum = terms.Iterator(null);
                    if (termsEnum.SeekExact(outerInstance.indexedBytes))
                    {
                        docs = termsEnum.Docs(null, null);
                    }
                    else
                    {
                        docs = null;
                    }
                }
                else
                {
                    docs = null;
                }

                if (docs == null)
                {
                    docs = new DocsEnumAnonymousInnerClassHelper(this);
                }
                atDoc = -1;
            }

            private class DocsEnumAnonymousInnerClassHelper : DocsEnum
            {
                private readonly IntDocValuesAnonymousInnerClassHelper outerInstance;

                public DocsEnumAnonymousInnerClassHelper(IntDocValuesAnonymousInnerClassHelper outerInstance)
                {
                    this.outerInstance = outerInstance;
                }

                public override int Freq()
                {
                    return 0;
                }

                public override int DocID()
                {
                    return DocIdSetIterator.NO_MORE_DOCS;
                }

                public override int NextDoc()
                {
                    return DocIdSetIterator.NO_MORE_DOCS;
                }

                public override int Advance(int target)
                {
                    return DocIdSetIterator.NO_MORE_DOCS;
                }

                public override long Cost()
                {
                    return 0;
                }
            }

            public override int IntVal(int doc)
            {
                try
                {
                    if (doc < lastDocRequested)
                    {
                        // out-of-order access.... reset
                        Reset();
                    }
                    lastDocRequested = doc;

                    if (atDoc < doc)
                    {
                        atDoc = docs.Advance(doc);
                    }

                    if (atDoc > doc)
                    {
                        // term doesn't match this document... either because we hit the
                        // end, or because the next doc is after this doc.
                        return 0;
                    }

                    // a match!
                    return docs.Freq();
                }
                catch (IOException e)
                {
                    throw new Exception("caught exception in function " + outerInstance.Description + " : doc=" + doc, e);
                }
            }
        }
    }
}