TermRangeTermEnum.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 StringHelper = Lucene.Net.Util.StringHelper;

namespace Lucene.Net.Search
{
    
    /// <summary> Subclass of FilteredTermEnum for enumerating all terms that match the
    /// specified range parameters.
    /// <p/>
    /// Term enumerations are always ordered by Term.compareTo().  Each term in
    /// the enumeration is greater than all that precede it.
    /// </summary>
    /// <since> 2.9
    /// </since>
    public class TermRangeTermEnum:FilteredTermEnum
    {
        
        private System.Globalization.CompareInfo collator = null;
        private bool endEnum = false;
        private System.String field;
        private System.String upperTermText;
        private System.String lowerTermText;
        private bool includeLower;
        private bool includeUpper;
        
        /// <summary> Enumerates all terms greater/equal than <c>lowerTerm</c>
        /// but less/equal than <c>upperTerm</c>. 
        /// 
        /// If an endpoint is null, it is said to be "open". Either or both 
        /// endpoints may be open.  Open endpoints may not be exclusive 
        /// (you can't select all but the first or last term without 
        /// explicitly specifying the term to exclude.)
        /// 
        /// </summary>
        /// <param name="reader">
        /// </param>
        /// <param name="field">An interned field that holds both lower and upper terms.
        /// </param>
        /// <param name="lowerTermText">The term text at the lower end of the range
        /// </param>
        /// <param name="upperTermText">The term text at the upper end of the range
        /// </param>
        /// <param name="includeLower">If true, the <c>lowerTerm</c> is included in the range.
        /// </param>
        /// <param name="includeUpper">If true, the <c>upperTerm</c> is included in the range.
        /// </param>
        /// <param name="collator">The collator to use to collate index Terms, to determine their
        /// membership in the range bounded by <c>lowerTerm</c> and
        /// <c>upperTerm</c>.
        /// 
        /// </param>
        /// <throws>  IOException </throws>
        public TermRangeTermEnum(IndexReader reader, System.String field, System.String lowerTermText, System.String upperTermText, bool includeLower, bool includeUpper, System.Globalization.CompareInfo collator)
        {
            this.collator = collator;
            this.upperTermText = upperTermText;
            this.lowerTermText = lowerTermText;
            this.includeLower = includeLower;
            this.includeUpper = includeUpper;
            this.field = StringHelper.Intern(field);
            
            // do a little bit of normalization...
            // open ended range queries should always be inclusive.
            if (this.lowerTermText == null)
            {
                this.lowerTermText = "";
                this.includeLower = true;
            }
            
            if (this.upperTermText == null)
            {
                this.includeUpper = true;
            }
            
            System.String startTermText = collator == null?this.lowerTermText:"";
            SetEnum(reader.Terms(new Term(this.field, startTermText)));
        }
        
        public override float Difference()
        {
            return 1.0f;
        }
        
        public override bool EndEnum()
        {
            return endEnum;
        }

        protected internal override bool TermCompare(Term term)
        {
            if (collator == null)
            {
                // Use Unicode code point ordering
                bool checkLower = !includeLower;
                if (term != null && (System.Object) term.Field == (System.Object) field)
                {
                    // interned comparison
                    if (!checkLower || null == lowerTermText || String.CompareOrdinal(term.Text, lowerTermText) > 0)
                    {
                        checkLower = false;
                        if (upperTermText != null)
                        {
                            int compare = String.CompareOrdinal(upperTermText, term.Text);
                            /*
                            * if beyond the upper term, or is exclusive and this is equal to
                            * the upper term, break out
                            */
                            if ((compare < 0) || (!includeUpper && compare == 0))
                            {
                                endEnum = true;
                                return false;
                            }
                        }
                        return true;
                    }
                }
                else
                {
                    // break
                    endEnum = true;
                    return false;
                }
                return false;
            }
            else
            {
                if (term != null && (System.Object) term.Field == (System.Object) field)
                {
                    // interned comparison
                    if ((lowerTermText == null || (includeLower?collator.Compare(term.Text.ToString(), lowerTermText.ToString()) >= 0:collator.Compare(term.Text.ToString(), lowerTermText.ToString()) > 0)) && (upperTermText == null || (includeUpper?collator.Compare(term.Text.ToString(), upperTermText.ToString()) <= 0:collator.Compare(term.Text.ToString(), upperTermText.ToString()) < 0)))
                    {
                        return true;
                    }
                    return false;
                }
                endEnum = true;
                return false;
            }
        }
    }
}