src/contrib/Regex/CSharpRegexCapabilities.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;

namespace Contrib.Regex
{
    /// <summary>
    /// C# Regex based implementation of <see cref="IRegexCapabilities"/>.
    /// </summary>
    /// <remarks>http://www.java2s.com/Open-Source/Java-Document/Net/lucene-connector/org/apache/lucene/search/regex/JavaUtilRegexCapabilities.java.htm</remarks>
    public class CSharpRegexCapabilities : IRegexCapabilities, IEquatable<CSharpRegexCapabilities>
    {
        private System.Text.RegularExpressions.Regex _rPattern;

        /// <summary>
        /// Called by the constructor of <see cref="RegexTermEnum"/> allowing implementations to cache 
        /// a compiled version of the regular expression pattern.
        /// </summary>
        /// <param name="pattern">regular expression pattern</param>
        public void Compile(string pattern)
        {
            _rPattern = new System.Text.RegularExpressions.Regex(pattern, 
                System.Text.RegularExpressions.RegexOptions.Compiled);
        }

        /// <summary>
        /// True on match.
        /// </summary>
        /// <param name="s">text to match</param>
        /// <returns>true on match</returns>
        public bool Match(string s)
        {
            return _rPattern.IsMatch(s);
        }

        /// <summary>
        /// A wise prefix implementation can reduce the term enumeration (and thus performance)
        /// of RegexQuery dramatically.
        /// </summary>
        /// <returns>static non-regex prefix of the pattern last passed to <see cref="IRegexCapabilities.Compile"/>.
        ///   May return null</returns>
        public string Prefix()
        {
            return null;
        }

        /// <summary>
        /// Indicates whether the current object is equal to another object of the same type.
        /// </summary>
        /// <returns>
        /// true if the current object is equal to the <paramref name="other"/> parameter; otherwise, false.
        /// </returns>
        /// <param name="other">An object to compare with this object</param>
        public bool Equals(CSharpRegexCapabilities other)
        {
            if (other == null) return false;
            if (this == other) return true;

            if (_rPattern != null ? !_rPattern.Equals(other._rPattern) : other._rPattern != null)
                return false;

            return true;
        }

        public override bool Equals(object obj)
        {
            if (obj as CSharpRegexCapabilities == null) return false;
            return Equals((CSharpRegexCapabilities) obj);
        }

        public override int GetHashCode()
        {
            return (_rPattern != null ? _rPattern.GetHashCode() : 0);
        }
    }
}