/* 
 * 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 Lucene.Net.Index;
using Lucene.Net.Search;

namespace Contrib.Regex
{
	/// <summary>
	/// Subclass of FilteredTermEnum for enumerating all terms that match the
	/// specified regular expression term using the specified regular expression
	/// implementation.
	/// <para>Term enumerations are always ordered by Term.compareTo().  Each term in
	/// the enumeration is greater than all that precede it.</para>
	/// </summary>
	/// <remarks>http://www.java2s.com/Open-Source/Java-Document/Net/lucene-connector/org/apache/lucene/search/regex/RegexTermEnum.java.htm</remarks>
	public class RegexTermEnum : FilteredTermEnum
	{
		private string _sField = "";
		private string _sPre = "";
		private bool _bEndEnum;
		private readonly IRegexCapabilities _regexImpl;

		public RegexTermEnum(IndexReader reader, Term term, IRegexCapabilities regexImpl)
		{
			_sField = term.Field;
			string sText = term.Text;
			
			_regexImpl = regexImpl;

			_regexImpl.Compile(sText);

			_sPre = _regexImpl.Prefix() ?? "";

			SetEnum(reader.Terms(new Term(term.Field, _sPre)));
		}

		/// <summary>Equality compare on the term </summary>
		protected override bool TermCompare(Term term)
		{
			if (_sField == term.Field)
			{
				string sSearchText = term.Text;
				if (sSearchText.StartsWith(_sPre)) return _regexImpl.Match(sSearchText);
			} //eif

			_bEndEnum = true;
			return false;
		}

		/// <summary>Equality measure on the term </summary>
		public override float Difference()
		{
			// TODO: adjust difference based on distance of searchTerm.text() and term().text()
			return 1.0F;
		}

		/// <summary>Indicates the end of the enumeration has been reached </summary>
		public override bool EndEnum()
		{
			return _bEndEnum;
		}

		//public override void Close()
		//{
		//    base.Close();
		//    _sField = null;
		//}
	}
}