WildcardQuery.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 IndexReader = Lucene.Net.Index.IndexReader;
using Term = Lucene.Net.Index.Term;
using ToStringUtils = Lucene.Net.Util.ToStringUtils;

namespace Lucene.Net.Search
{
    
    /// <summary>Implements the wildcard search query. Supported wildcards are <c>*</c>, which
    /// matches any character sequence (including the empty one), and <c>?</c>,
    /// which matches any single character. Note this query can be slow, as it
    /// needs to iterate over many terms. In order to prevent extremely slow WildcardQueries,
    /// a Wildcard term should not start with one of the wildcards <c>*</c> or
    /// <c>?</c>.
    /// 
    /// <p/>This query uses the <see cref="MultiTermQuery.CONSTANT_SCORE_AUTO_REWRITE_DEFAULT" />
    ///
    /// rewrite method.
    /// 
    /// </summary>
    /// <seealso cref="WildcardTermEnum">
    /// </seealso>
    [Serializable]
    public class WildcardQuery : MultiTermQuery
    {
        private readonly bool _termContainsWildcard;
        private readonly bool _termIsPrefix;
        protected internal Term internalTerm;
        
        public WildcardQuery(Term term)
        { 
            this.internalTerm = term;
            string text = term.Text;
            _termContainsWildcard = (term.Text.IndexOf('*') != -1)
                                        || (term.Text.IndexOf('?') != -1);
            _termIsPrefix = _termContainsWildcard
                                && (text.IndexOf('?') == -1)
                                && (text.IndexOf('*') == text.Length - 1);
        }
        
        protected internal override FilteredTermEnum GetEnum(IndexReader reader)
        {
            if (_termContainsWildcard)
            {
                return new WildcardTermEnum(reader, Term);
            }
            else
            {
                return new SingleTermEnum(reader, Term);
            }
        }

        /// <summary> Returns the pattern term.</summary>
        public Term Term
        {
            get { return internalTerm; }
        }

        public override Query Rewrite(IndexReader reader)
        {
            if (_termIsPrefix)
            {
                MultiTermQuery rewritten =
                    new PrefixQuery(internalTerm.CreateTerm(internalTerm.Text.Substring(0, internalTerm.Text.IndexOf('*'))));
                rewritten.Boost = Boost;
                rewritten.RewriteMethod = RewriteMethod;
                return rewritten;
            }
            else
            {
                return base.Rewrite(reader);
            }
        }
        
        /// <summary>Prints a user-readable version of this query. </summary>
        public override System.String ToString(System.String field)
        {
            System.Text.StringBuilder buffer = new System.Text.StringBuilder();
            if (!internalTerm.Field.Equals(field))
            {
                buffer.Append(internalTerm.Field);
                buffer.Append(":");
            }
            buffer.Append(internalTerm.Text);
            buffer.Append(ToStringUtils.Boost(Boost));
            return buffer.ToString();
        }
        
        //@Override
        public override int GetHashCode()
        {
            int prime = 31;
            int result = base.GetHashCode();
            result = prime * result + ((internalTerm == null)?0:internalTerm.GetHashCode());
            return result;
        }
        
        //@Override
        public  override bool Equals(System.Object obj)
        {
            if (this == obj)
                return true;
            if (!base.Equals(obj))
                return false;
            if (GetType() != obj.GetType())
                return false;
            WildcardQuery other = (WildcardQuery) obj;
            if (internalTerm == null)
            {
                if (other.internalTerm != null)
                    return false;
            }
            else if (!internalTerm.Equals(other.internalTerm))
                return false;
            return true;
        }
    }
}