SpanNearQuery.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.Linq;
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 which are near one another.  One can specify <i>slop</i>, the
    /// maximum number of intervening unmatched positions, as well as whether
    /// matches are required to be in-order. 
    /// </summary>
    [Serializable]
    public class SpanNearQuery : SpanQuery, System.ICloneable
    {
        protected internal System.Collections.Generic.IList<SpanQuery> clauses;
        protected internal int internalSlop;
        protected internal bool inOrder;
        
        protected internal System.String internalField;
        private readonly bool collectPayloads;
        
        /// <summary>Construct a SpanNearQuery.  Matches spans matching a span from each
        /// clause, with up to <c>slop</c> total unmatched positions between
        /// them.  * When <c>inOrder</c> is true, the spans from each clause
        /// must be * ordered as in <c>clauses</c>. 
        /// </summary>
        public SpanNearQuery(SpanQuery[] clauses, int slop, bool inOrder):this(clauses, slop, inOrder, true)
        {
        }
        
        public SpanNearQuery(SpanQuery[] clauses, int slop, bool inOrder, bool collectPayloads)
        {
            
            // copy clauses array into an ArrayList
            this.clauses = new System.Collections.Generic.List<SpanQuery>(clauses.Length);
            for (int i = 0; i < clauses.Length; i++)
            {
                SpanQuery clause = clauses[i];
                if (i == 0)
                {
                    // check field
                    internalField = clause.Field;
                }
                else if (!clause.Field.Equals(internalField))
                {
                    throw new System.ArgumentException("Clauses must have same field.");
                }
                this.clauses.Add(clause);
            }
            this.collectPayloads = collectPayloads;
            this.internalSlop = slop;
            this.inOrder = inOrder;
        }
        
        /// <summary>Return the clauses whose spans are matched. </summary>
        public virtual SpanQuery[] GetClauses()
        {
            // Return a copy
            return clauses.ToArray();
        }

        /// <summary>Return the maximum number of intervening unmatched positions permitted.</summary>
        public virtual int Slop
        {
            get { return internalSlop; }
        }

        /// <summary>Return true if matches are required to be in-order.</summary>
        public virtual bool IsInOrder
        {
            get { return inOrder; }
        }

        public override string Field
        {
            get { return internalField; }
        }

        public override void  ExtractTerms(System.Collections.Generic.ISet<Term> terms)
        {
            foreach (SpanQuery clause in clauses)
            {
                clause.ExtractTerms(terms);
            }
        }

        public override System.String ToString(System.String field)
        {
            System.Text.StringBuilder buffer = new System.Text.StringBuilder();
            buffer.Append("spanNear([");
            System.Collections.Generic.IEnumerator<SpanQuery> i = clauses.GetEnumerator();
            while (i.MoveNext())
            {
                SpanQuery clause = i.Current;
                buffer.Append(clause.ToString(field));
                buffer.Append(", ");
            }
            if (clauses.Count > 0) buffer.Length -= 2;
            buffer.Append("], ");
            buffer.Append(internalSlop);
            buffer.Append(", ");
            buffer.Append(inOrder);
            buffer.Append(")");
            buffer.Append(ToStringUtils.Boost(Boost));
            return buffer.ToString();
        }
        
        public override Spans GetSpans(IndexReader reader)
        {
            if (clauses.Count == 0)
            // optimize 0-clause case
                return new SpanOrQuery(GetClauses()).GetSpans(reader);
            
            if (clauses.Count == 1)
            // optimize 1-clause case
                return clauses[0].GetSpans(reader);
            
            return inOrder?(Spans) new NearSpansOrdered(this, reader, collectPayloads):(Spans) new NearSpansUnordered(this, reader);
        }
        
        public override Query Rewrite(IndexReader reader)
        {
            SpanNearQuery clone = null;
            for (int i = 0; i < clauses.Count; i++)
            {
                SpanQuery c = clauses[i];
                SpanQuery query = (SpanQuery) c.Rewrite(reader);
                if (query != c)
                {
                    // clause rewrote: must clone
                    if (clone == null)
                        clone = (SpanNearQuery) this.Clone();
                    clone.clauses[i] = query;
                }
            }
            if (clone != null)
            {
                return clone; // some clauses rewrote
            }
            else
            {
                return this; // no clauses rewrote
            }
        }
        
        public override System.Object Clone()
        {
            int sz = clauses.Count;
            SpanQuery[] newClauses = new SpanQuery[sz];
            
            for (int i = 0; i < sz; i++)
            {
                SpanQuery clause = clauses[i];
                newClauses[i] = (SpanQuery) clause.Clone();
            }
            SpanNearQuery spanNearQuery = new SpanNearQuery(newClauses, internalSlop, inOrder);
            spanNearQuery.Boost = Boost;
            return spanNearQuery;
        }
        
        /// <summary>Returns true iff <c>o</c> is equal to this. </summary>
        public  override bool Equals(System.Object o)
        {
            if (this == o)
                return true;
            if (!(o is SpanNearQuery))
                return false;
            
            SpanNearQuery spanNearQuery = (SpanNearQuery) o;
            
            if (inOrder != spanNearQuery.inOrder)
                return false;
            if (internalSlop != spanNearQuery.internalSlop)
                return false;
            if (clauses.Count != spanNearQuery.clauses.Count)
                return false;
            System.Collections.IEnumerator iter1 = clauses.GetEnumerator();
            System.Collections.IEnumerator iter2 = spanNearQuery.clauses.GetEnumerator();
            while (iter1.MoveNext() && iter2.MoveNext())
            {
                SpanQuery item1 = (SpanQuery)iter1.Current;
                SpanQuery item2 = (SpanQuery)iter2.Current;
                if (!item1.Equals(item2))
                    return false;
            }
            
            return Boost == spanNearQuery.Boost;
        }
        
        public override int GetHashCode()
        {
            long result = 0;
            //mgarski .NET uses the arraylist's location, not contents to calculate the hash
            // need to start with result being the hash of the contents.
            foreach (SpanQuery sq in clauses)
            {
                result += sq.GetHashCode();
            }
            // Mix bits before folding in things like boost, since it could cancel the
            // last element of clauses.  This particular mix also serves to
            // differentiate SpanNearQuery hashcodes from others.
            result ^= ((result << 14) | (Number.URShift(result, 19))); // reversible
            result += System.Convert.ToInt32(Boost);
            result += internalSlop;
            result ^= (inOrder ? (long) 0x99AFD3BD : 0);
            return (int) result;
        }
    }
}