Explanation.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 System.Collections.Generic;

namespace Lucene.Net.Search
{
    
    /// <summary>Expert: Describes the score computation for document and query. </summary>
    [Serializable]
    public class Explanation
    {
        private float value;        // the value of this node
        private System.String description;  // what it represents
        private List<Explanation> details;  // sub-explanations
        
        public Explanation()
        {
        }
        
        public Explanation(float value, System.String description)
        {
            this.value = value;
            this.description = description;
        }

        /// <summary> Indicates whether or not this Explanation models a good match.
        /// 
        /// <p/>
        /// By default, an Explanation represents a "match" if the value is positive.
        /// <p/>
        /// </summary>
        /// <seealso cref="Value">
        /// </seealso>
        public virtual bool IsMatch
        {
            get { return (0.0f < Value); }
        }


        /// <summary>The value assigned to this explanation node. </summary>
        public virtual float Value
        {
            get { return value; }
            set { this.value = value; }
        }

        /// <summary>A description of this explanation node. </summary>
        public virtual string Description
        {
            get { return description; }
            set { this.description = value; }
        }

        /// <summary> A short one line summary which should contain all high level
        /// information about this Explanation, without the "Details"
        /// </summary>
        protected internal virtual string Summary
        {
            get { return Value + " = " + Description; }
        }

        /// <summary>The sub-nodes of this explanation node. </summary>
        public virtual Explanation[] GetDetails()
        {
            if (details == null)
                return null;
            return details.ToArray();
        }

        /// <summary>Adds a sub-node to this explanation node. </summary>
        public virtual void  AddDetail(Explanation detail)
        {
            if (details == null)
                details = new List<Explanation>();
            details.Add(detail);
        }
        
        /// <summary>Render an explanation as text. </summary>
        public override System.String ToString()
        {
            return ToString(0);
        }

        protected internal virtual System.String ToString(int depth)
        {
            System.Text.StringBuilder buffer = new System.Text.StringBuilder();
            for (int i = 0; i < depth; i++)
            {
                buffer.Append("  ");
            }
            buffer.Append(Summary);
            buffer.Append("\n");
            
            Explanation[] details = GetDetails();
            if (details != null)
            {
                for (int i = 0; i < details.Length; i++)
                {
                    buffer.Append(details[i].ToString(depth + 1));
                }
            }
            
            return buffer.ToString();
        }
        
        /// <summary>Render an explanation as HTML. </summary>
        public virtual System.String ToHtml()
        {
            System.Text.StringBuilder buffer = new System.Text.StringBuilder();
            buffer.Append("<list>\n");
            
            buffer.Append("<item>");
            buffer.Append(Summary);
            buffer.Append("<br />\n");
            
            Explanation[] details = GetDetails();
            if (details != null)
            {
                for (int i = 0; i < details.Length; i++)
                {
                    buffer.Append(details[i].ToHtml());
                }
            }
            
            buffer.Append("</item>\n");
            buffer.Append("</list>\n");
            
            return buffer.ToString();
        }
        
        /// <summary> Small Util class used to pass both an idf factor as well as an
        /// explanation for that factor.
        /// 
        /// This class will likely be held on a <see cref="Weight" />, so be aware 
        /// before storing any large or un-serializable fields.
        /// 
        /// </summary>
        [Serializable]
        public abstract class IDFExplanation
        {
            /// <value> the idf factor </value>
            public abstract float Idf { get; }

            /// <summary> This should be calculated lazily if possible.
            /// 
            /// </summary>
            /// <returns> the explanation for the idf factor.
            /// </returns>
            public abstract System.String Explain();
        }
    }
}