SpanFirstQuery.cs

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/* 
 * 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.Generic;
using Lucene.Net.Index;
using Lucene.Net.Support;
using IndexReader = Lucene.Net.Index.IndexReader;
using ToStringUtils = Lucene.Net.Util.ToStringUtils;
using Query = Lucene.Net.Search.Query;

namespace Lucene.Net.Search.Spans
{
    
    /// <summary>Matches spans near the beginning of a field. </summary>
    [Serializable]
    public class SpanFirstQuery : SpanQuery, System.ICloneable
    {
        private class AnonymousClassSpans : Spans
        {
            public AnonymousClassSpans(Lucene.Net.Index.IndexReader reader, SpanFirstQuery enclosingInstance)
            {
                InitBlock(reader, enclosingInstance);
            }
            private void  InitBlock(Lucene.Net.Index.IndexReader reader, SpanFirstQuery enclosingInstance)
            {
                this.reader = reader;
                this.enclosingInstance = enclosingInstance;
                spans = Enclosing_Instance.match.GetSpans(reader);
            }
            private Lucene.Net.Index.IndexReader reader;
            private SpanFirstQuery enclosingInstance;
            public SpanFirstQuery Enclosing_Instance
            {
                get
                {
                    return enclosingInstance;
                }
                
            }
            private Spans spans;
            
            public override bool Next()
            {
                while (spans.Next())
                {
                    // scan to next match
                    if (End() <= Enclosing_Instance.end)
                        return true;
                }
                return false;
            }
            
            public override bool SkipTo(int target)
            {
                if (!spans.SkipTo(target))
                    return false;
                
                return spans.End() <= Enclosing_Instance.end || Next();
            }
            
            public override int Doc()
            {
                return spans.Doc();
            }
            public override int Start()
            {
                return spans.Start();
            }
            public override int End()
            {
                return spans.End();
            }
            
            // TODO: Remove warning after API has been finalized

            public override ICollection<byte[]> GetPayload()
            {
                System.Collections.Generic.ICollection<byte[]> result = null;
                if (spans.IsPayloadAvailable())
                {
                    result = spans.GetPayload();
                }
                return result; //TODO: any way to avoid the new construction?
            }

            // TODO: Remove warning after API has been finalized

            public override bool IsPayloadAvailable()
            {
                return spans.IsPayloadAvailable();
            }

            public override System.String ToString()
            {
                return "spans(" + Enclosing_Instance.ToString() + ")";
            }
        }
        private SpanQuery match;
        private int end;
        
        /// <summary>Construct a SpanFirstQuery matching spans in <c>match</c> whose end
        /// position is less than or equal to <c>end</c>. 
        /// </summary>
        public SpanFirstQuery(SpanQuery match, int end)
        {
            this.match = match;
            this.end = end;
        }

        /// <summary>Return the SpanQuery whose matches are filtered. </summary>
        public virtual SpanQuery Match
        {
            get { return match; }
        }

        /// <summary>Return the maximum end position permitted in a match. </summary>
        public virtual int End
        {
            get { return end; }
        }

        public override string Field
        {
            get { return match.Field; }
        }

        public override System.String ToString(System.String field)
        {
            System.Text.StringBuilder buffer = new System.Text.StringBuilder();
            buffer.Append("spanFirst(");
            buffer.Append(match.ToString(field));
            buffer.Append(", ");
            buffer.Append(end);
            buffer.Append(")");
            buffer.Append(ToStringUtils.Boost(Boost));
            return buffer.ToString();
        }
        
        public override System.Object Clone()
        {
            SpanFirstQuery spanFirstQuery = new SpanFirstQuery((SpanQuery) match.Clone(), end);
            spanFirstQuery.Boost = Boost;
            return spanFirstQuery;
        }
        
        public override void  ExtractTerms(System.Collections.Generic.ISet<Term> terms)
        {
            match.ExtractTerms(terms);
        }
        
        public override Spans GetSpans(IndexReader reader)
        {
            return new AnonymousClassSpans(reader, this);
        }
        
        public override Query Rewrite(IndexReader reader)
        {
            SpanFirstQuery clone = null;
            
            SpanQuery rewritten = (SpanQuery) match.Rewrite(reader);
            if (rewritten != match)
            {
                clone = (SpanFirstQuery) this.Clone();
                clone.match = rewritten;
            }
            
            if (clone != null)
            {
                return clone; // some clauses rewrote
            }
            else
            {
                return this; // no clauses rewrote
            }
        }
        
        public  override bool Equals(System.Object o)
        {
            if (this == o)
                return true;
            if (!(o is SpanFirstQuery))
                return false;
            
            SpanFirstQuery other = (SpanFirstQuery) o;
            return this.end == other.end && this.match.Equals(other.match) && this.Boost == other.Boost;
        }
        
        public override int GetHashCode()
        {
            int h = match.GetHashCode();
            h ^= ((h << 8) | (Number.URShift(h, 25))); // reversible
            h ^= System.Convert.ToInt32(Boost) ^ end;
            return h;
        }
    }
}