src/Lucene.Net.QueryParser/Flexible/Core/Nodes/SlopQueryNode.cs

using Lucene.Net.QueryParsers.Flexible.Core.Messages;
using Lucene.Net.QueryParsers.Flexible.Core.Parser;
using Lucene.Net.QueryParsers.Flexible.Messages;

namespace Lucene.Net.QueryParsers.Flexible.Core.Nodes
{
    /*
     * 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.
     */

    /// <summary>
    /// A <see cref="SlopQueryNode"/> represents phrase query with a slop.
    /// 
    /// From Lucene FAQ: Is there a way to use a proximity operator (like near or
    /// within) with Lucene? There is a variable called slop that allows you to
    /// perform NEAR/WITHIN-like queries. By default, slop is set to 0 so that only
    /// exact phrases will match. When using TextParser you can use this syntax to
    /// specify the slop: "doug cutting"~2 will find documents that contain
    /// "doug cutting" as well as ones that contain "cutting doug".
    /// </summary>
    public class SlopQueryNode : QueryNode, IFieldableNode
    {
        private int value = 0;

        /// <summary>
        /// 
        /// </summary>
        /// <param name="query">QueryNode Tree with the phrase</param>
        /// <param name="value">slop value</param>
        public SlopQueryNode(IQueryNode query, int value)
        {
            if (query == null)
            {
                throw new QueryNodeError(new Message(
                    QueryParserMessages.NODE_ACTION_NOT_SUPPORTED, "query", "null"));
            }

            this.value = value;
            IsLeaf = false;
            Allocate();
            Add(query);
        }

        public virtual IQueryNode GetChild()
        {
            return GetChildren()[0];
        }

        public virtual int Value => this.value;

        private string GetValueString()
        {
            float f = this.value;
            if (f == (long)f)
                return "" + (long)f;
            else
                return "" + f;
        }

        public override string ToString()
        {
            return "<slop value='" + GetValueString() + "'>" + "\n"
                + GetChild().ToString() + "\n</slop>";
        }

        public override string ToQueryString(IEscapeQuerySyntax escapeSyntaxParser)
        {
            if (GetChild() == null)
                return "";
            return GetChild().ToQueryString(escapeSyntaxParser) + "~"
                + GetValueString();
        }

        public override IQueryNode CloneTree()
        {
            SlopQueryNode clone = (SlopQueryNode)base.CloneTree();

            clone.value = this.value;

            return clone;
        }

        public virtual string Field
        {
            get
            {
                IQueryNode child = GetChild();

                if (child is IFieldableNode fieldableNode)
                {
                    return fieldableNode.Field;
                }

                return null;
            }
            set
            {
                IQueryNode child = GetChild();

                if (child is IFieldableNode fieldableNode)
                {
                    fieldableNode.Field = value;
                }
            }
        }
    }
}