/*
 * CPSortDescriptor.j
 * Foundation
 *
 * Created by Francisco Tolmasky.
 * Copyright 2008, 280 North, Inc.
 *
 * 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 2.1 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
 * Lesser 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 02110-1301 USA
 */

@import "CPObject.j"
@import "CPObjJRuntime.j"


/*!
    The left operand is smaller than the right.
    @global
    @group CPComparisonResult
*/
CPOrderedAscending      = -1;
/*!
    The left and right operands are equal.
    @global
    @group CPComparisonResult
*/
CPOrderedSame           =  0;
/*!
    The left operand is greater than the right.
    @global
    @group CPComparisonResult
*/
CPOrderedDescending     =  1;

/*! 
    @class CPSortDescriptor
    @ingroup foundation
    @brief Holds attributes necessary to describe how to sort a set of objects.

    A CPSortDescriptor holds the attributes necessary to describe how
    to sort a set of objects. The sort descriptor instance holds a property key path
    to the sort item of the objects to compare, the method selector to call for sorting and the sort order.
*/
@implementation CPSortDescriptor : CPObject
{
    CPString    _key;
    SEL         _selector;
    BOOL        _ascending;
}

+ (id)sortDescriptorWithKey:(CPString)aKey ascending:(BOOL)isAscending
{
    return [[self alloc] initWithKey:aKey ascending:isAscending];
}

// Initializing a sort descriptor
/*!
    Initializes the sort descriptor.
    @param aKey the property key path to sort
    @param isAscending the sort order
    @return the initialized sort descriptor
*/
- (id)initWithKey:(CPString)aKey ascending:(BOOL)isAscending
{
    return [self initWithKey:aKey ascending:isAscending selector:@selector(compare:)];
}

+ (id)sortDescriptorWithKey:(CPString)aKey ascending:(BOOL)isAscending selector:(SEL)aSelector
{
    return [[self alloc] initWithKey:aKey ascending:isAscending selector:aSelector];
}

/*!
    Initializes the sort descriptor
    @param aKey the property key path to sort
    @param isAscending the sort order
    @param aSelector this method gets called to compare objects. The method will take one argument 
    (the object to compare against itself, and must return a CPComparisonResult.
*/
- (id)initWithKey:(CPString)aKey ascending:(BOOL)isAscending selector:(SEL)aSelector
{
    self = [super init];
    
    if (self)
    {
        _key = aKey;
        _ascending = isAscending;
        _selector = aSelector;
    }
    
    return self;
}

// Getting information about a sort descriptor
/*!
    Returns \c YES if the sort descriptor's order is ascending.
*/
- (BOOL)ascending
{
    return _ascending;
}

/*!
    Returns the descriptor's property key
*/
- (CPString)key
{
    return _key;
}

/*!
    Returns the selector of the method to call when comparing objects.
*/
- (SEL)selector
{
    return _selector;
}

// Using sort descriptors
/*!
    Compares two objects.
    @param lhsObject the left hand side object to compre
    @param rhsObject the right hand side object to compare
    @return the comparison result
*/
- (CPComparisonResult)compareObject:(id)lhsObject withObject:(id)rhsObject
{
    return (_ascending ? 1 : -1) * [[lhsObject valueForKey:_key] performSelector:_selector withObject:[rhsObject valueForKey:_key]];
}

/*!
    Makes a copy of this sort descriptor with a reversed sort order.
    @return the reversed copy of the sort descriptor
*/
- (id)reversedSortDescriptor
{
    return [[[self class] alloc] initWithKey:_key ascending:!_ascending selector:_selector];
}

@end