/*
 * 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 Lucene.Net.Search
{
	
	
	/// <summary> Encapsulates sort criteria for returned hits.
	/// 
	/// <p>The fields used to determine sort order must be carefully chosen.
	/// Documents must contain a single term in such a field,
	/// and the value of the term should indicate the document's relative position in
	/// a given sort order.  The field must be indexed, but should not be tokenized,
	/// and does not need to be stored (unless you happen to want it back with the
	/// rest of your document data).  In other words:
	/// 
	/// <p><code>document.add (new Field ("byNumber", Integer.toString(x), Field.Store.NO, Field.Index.UN_TOKENIZED));</code></p>
	/// 
	/// 
	/// <p><h3>Valid Types of Values</h3>
	/// 
	/// <p>There are three possible kinds of term values which may be put into
	/// sorting fields: Integers, Floats, or Strings.  Unless
	/// {@link SortField SortField} objects are specified, the type of value
	/// in the field is determined by parsing the first term in the field.
	/// 
	/// <p>Integer term values should contain only digits and an optional
	/// preceeding negative sign.  Values must be base 10 and in the range
	/// <code>Integer.MIN_VALUE</code> and <code>Integer.MAX_VALUE</code> inclusive.
	/// Documents which should appear first in the sort
	/// should have low value integers, later documents high values
	/// (i.e. the documents should be numbered <code>1..n</code> where
	/// <code>1</code> is the first and <code>n</code> the last).
	/// 
	/// <p>Float term values should conform to values accepted by
	/// {@link Float Float.valueOf(String)} (except that <code>NaN</code>
	/// and <code>Infinity</code> are not supported).
	/// Documents which should appear first in the sort
	/// should have low values, later documents high values.
	/// 
	/// <p>String term values can contain any valid String, but should
	/// not be tokenized.  The values are sorted according to their
	/// {@link Comparable natural order}.  Note that using this type
	/// of term value has higher memory requirements than the other
	/// two types.
	/// 
	/// <p><h3>Object Reuse</h3>
	/// 
	/// <p>One of these objects can be
	/// used multiple times and the sort order changed between usages.
	/// 
	/// <p>This class is thread safe.
	/// 
	/// <p><h3>Memory Usage</h3>
	/// 
	/// <p>Sorting uses of caches of term values maintained by the
	/// internal HitQueue(s).  The cache is static and contains an integer
	/// or float array of length <code>IndexReader.maxDoc()</code> for each field
	/// name for which a sort is performed.  In other words, the size of the
	/// cache in bytes is:
	/// 
	/// <p><code>4 * IndexReader.maxDoc() * (# of different fields actually used to sort)</code>
	/// 
	/// <p>For String fields, the cache is larger: in addition to the
	/// above array, the value of every term in the field is kept in memory.
	/// If there are many unique terms in the field, this could
	/// be quite large.
	/// 
	/// <p>Note that the size of the cache is not affected by how many
	/// fields are in the index and <i>might</i> be used to sort - only by
	/// the ones actually used to sort a result set.
	/// 
	/// <p>The cache is cleared each time a new <code>IndexReader</code> is
	/// passed in, or if the value returned by <code>maxDoc()</code>
	/// changes for the current IndexReader.  This class is not set up to
	/// be able to efficiently sort hits from more than one index
	/// simultaneously.
	/// 
	/// <p>Created: Feb 12, 2004 10:53:57 AM
	/// 
	/// </summary>
	/// <author>   Tim Jones (Nacimiento Software)
	/// </author>
	/// <since>   lucene 1.4
	/// </since>
	/// <version>  $Id: Sort.java 150618 2004-10-18 22:36:54Z dnaber $
	/// </version>
	[Serializable]
	public class Sort
	{
		
		/// <summary> Represents sorting by computed relevance. Using this sort criteria returns
		/// the same results as calling
		/// {@link Searcher#Search(Query) Searcher#search()}without a sort criteria,
		/// only with slightly more overhead.
		/// </summary>
		public static readonly Sort RELEVANCE = new Sort();
		
		/// <summary>Represents sorting by index order. </summary>
		public static readonly Sort INDEXORDER;
		
		// internal representation of the sort criteria
		internal SortField[] fields;
		
		/// <summary> Sorts by computed relevance. This is the same sort criteria as calling
		/// {@link Searcher#Search(Query) Searcher#search()}without a sort criteria,
		/// only with slightly more overhead.
		/// </summary>
		public Sort() : this(new SortField[] {SortField.FIELD_SCORE, SortField.FIELD_DOC})
		{
		}
		
		/// <summary> Sorts by the terms in <code>field</code> then by index order (document
		/// number). The type of value in <code>field</code> is determined
		/// automatically.
		/// 
		/// </summary>
		/// <seealso cref="SortField.AUTO">
		/// </seealso>
		public Sort(System.String field)
		{
			SetSort(field, false);
		}
		
		/// <summary> Sorts possibly in reverse by the terms in <code>field</code> then by
		/// index order (document number). The type of value in <code>field</code> is
		/// determined automatically.
		/// 
		/// </summary>
		/// <seealso cref="SortField.AUTO">
		/// </seealso>
		public Sort(System.String field, bool reverse)
		{
			SetSort(field, reverse);
		}
		
		/// <summary> Sorts in succession by the terms in each field. The type of value in
		/// <code>field</code> is determined automatically.
		/// 
		/// </summary>
		/// <seealso cref="SortField.AUTO">
		/// </seealso>
		public Sort(System.String[] fields)
		{
			SetSort(fields);
		}
		
		/// <summary>Sorts by the criteria in the given SortField. </summary>
		public Sort(SortField field)
		{
			SetSort(field);
		}
		
		/// <summary>Sorts in succession by the criteria in each SortField. </summary>
		public Sort(SortField[] fields)
		{
			SetSort(fields);
		}
		
		/// <summary> Sets the sort to the terms in <code>field</code> then by index order
		/// (document number).
		/// </summary>
		public void  SetSort(System.String field)
		{
			SetSort(field, false);
		}
		
		/// <summary> Sets the sort to the terms in <code>field</code> possibly in reverse,
		/// then by index order (document number).
		/// </summary>
		public virtual void  SetSort(System.String field, bool reverse)
		{
			SortField[] nfields = new SortField[]{new SortField(field, SortField.AUTO, reverse), SortField.FIELD_DOC};
			fields = nfields;
		}
		
		/// <summary>Sets the sort to the terms in each field in succession. </summary>
		public virtual void  SetSort(System.String[] fieldnames)
		{
			int n = fieldnames.Length;
			SortField[] nfields = new SortField[n];
			for (int i = 0; i < n; ++i)
			{
				nfields[i] = new SortField(fieldnames[i], SortField.AUTO);
			}
			fields = nfields;
		}
		
		/// <summary>Sets the sort to the given criteria. </summary>
		public virtual void  SetSort(SortField field)
		{
			this.fields = new SortField[]{field};
		}
		
		/// <summary>Sets the sort to the given criteria in succession. </summary>
		public virtual void  SetSort(SortField[] fields)
		{
			this.fields = fields;
		}
		
		/// <summary> Representation of the sort criteria.</summary>
		/// <returns> Array of SortField objects used in this sort criteria
		/// </returns>
		public virtual SortField[] GetSort()
		{
			return fields;
		}
		
		public override System.String ToString()
		{
			System.Text.StringBuilder buffer = new System.Text.StringBuilder();
			
			for (int i = 0; i < fields.Length; i++)
			{
				buffer.Append(fields[i].ToString());
				if ((i + 1) < fields.Length)
					buffer.Append(',');
			}
			
			return buffer.ToString();
		}
		static Sort()
		{
			INDEXORDER = new Sort(SortField.FIELD_DOC);
		}
	}
}