/* Interface for NSSortDescriptor for GNUStep
   Copyright (C) 2005 Free Software Foundation, Inc.

   Written by:  Saso Kiselkov <diablos@manga.sk>
   Date: 2005
   
   This file is part of the GNUstep Base Library.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 3 of the License, or (at your option) any later version.
   
   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.
   
   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, write to the Free
   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   Boston, MA 02111 USA.
   */ 

#ifndef __NSSortDescriptor_h_GNUSTEP_BASE_INCLUDE
#define __NSSortDescriptor_h_GNUSTEP_BASE_INCLUDE
#import	<GNUstepBase/GSVersionMacros.h>

#if OS_API_VERSION(100300,GS_API_LATEST)

#import	<Foundation/NSObject.h>
#import	<Foundation/NSArray.h>

#if	defined(__cplusplus)
extern "C" {
#endif

@class NSString;

/**
 * Instances of this class are used to perform multi-level sorts of
 * arrays containging collections or other objects whose properties
 * can be obtained using key names.
 */
@interface NSSortDescriptor : NSObject <NSCopying, NSCoding>
{
  NSString *_key;
  BOOL	_ascending;
  SEL	_selector;
}

/** Returns a flag indicating whether the sort descriptor sorts objects
 * in ascending order (YES) or descending order (NO).
 */
- (BOOL) ascending;

/** Returns the result of comparing object1 to object2 using the property
 * whose key is defined in the receiver and using the selector of the
 * receiver.  If the receiver performs a descending order sort, the
 * result of this comparison is the opposite of that prroduced by
 * applying the selector.
 */
- (NSComparisonResult) compareObject: (id)object1 toObject: (id)object2;

/** Initialises the receiver for comparisons using the 'compare:' selector
 * and the specified key and ordering.
 */
- (id) initWithKey: (NSString *)key
	 ascending: (BOOL)ascending;

/** <init />
 * Initialises the receiver to perform comparisons in the specified order
 * using selector to compar the property key of each object.
 */
- (id) initWithKey: (NSString *)key
         ascending: (BOOL)ascending
          selector: (SEL)selector;

/** Returns the key used to obtain the property on which comparisons are based.
 */
- (NSString *) key;

/** Returns the selector used to compare the properties of objects.
 */
- (SEL) selector;

/** Returns a copy of the receiver which compares and sorts in reversed
 * order.
 */
- (id) reversedSortDescriptor;
@end

@interface NSArray (NSSortDescriptorSorting)

/**
 * Produces a sorted array using the mechanism described for
 * [NSMutableArray-sortUsingDescriptors:]
 */
- (NSArray *) sortedArrayUsingDescriptors: (NSArray *)sortDescriptors;

@end

@interface NSMutableArray (NSSortDescriptorSorting)

/**
 * This method works like this: first, it sorts the entire
 * contents of the array using the first sort descriptor. Then,
 * after each sort-run, it looks whether there are sort
 * descriptors left to process, and if yes, looks at the partially
 * sorted array, finds all portions in it which are equal
 * (evaluate to NSOrderedSame) and applies the following
 * descriptor onto them. It repeats this either until all
 * descriptors have been applied or there are no more equal
 * portions (equality ranges) left in the array.
 */
- (void) sortUsingDescriptors: (NSArray *)sortDescriptors;

@end

#if	defined(__cplusplus)
}
#endif

#endif	/* 100400 */

#endif /* __NSSortDescriptor_h_GNUSTEP_BASE_INCLUDE */
