/* -*- Mode: C; indent-tabs-mode: t; c-basic-offset: 8; tab-width: 8 -*- */

/*

 * GData Client

 * Copyright (C) Philip Withnall 2010 <philip@tecnocode.co.uk>

 *

 * GData Client 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.

 *

 * GData Client 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 GData Client.  If not, see <http://www.gnu.org/licenses/>.

 */

/**

 * SECTION:gdata-comparable

 * @short_description: GData comparable interface

 * @stability: Stable

 * @include: gdata/gdata-comparable.h

 *

 * #GDataComparable is an interface which can be implemented by any object which needs to be compared to another object of the same type or of a

 * derived type.

 *

 * When implementing the interface, classes must implement the <function>compare_with</function> function, and the implementation must be

 * <ulink type="http" url="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#index-g_t_0040code_007bpure_007d-function-attribute-2413">pure

 * </ulink>.

 *

 * Since: 0.7.0

 */

#include <glib.h>

#include <glib-object.h>

#include "gdata-comparable.h"

GType

gdata_comparable_get_type (void)

{

	static GType comparable_type = 0;

	if (!comparable_type) {

		comparable_type = g_type_register_static_simple (G_TYPE_INTERFACE, "GDataComparable",

		                                                 sizeof (GDataComparableIface),

		                                                 NULL, 0, NULL, 0);

	}

	return comparable_type;

}

/**

 * gdata_comparable_compare:

 * @self: (allow-none): a #GDataComparable, or %NULL

 * @other: (allow-none): another #GDataComparable of the same type, or %NULL

 *

 * Compares the two objects, returning -1 if @self is "less than" @other by some metric, 0

 * if they're equal, or 1 if @self is "greater than" @other.

 *

 * %NULL values are handled gracefully, with 0 returned if both @self and @other are %NULL,

 * -1 if @self is %NULL and 1 if @other is %NULL.

 *

 * The @other object must be of the same type as @self, or of a type derived from @self's type.

 *

 * Return value: %TRUE on success, %FALSE otherwise

 *

 * Since: 0.7.0

 */

gint

gdata_comparable_compare (GDataComparable *self, GDataComparable *other)

{

	GDataComparableIface *iface;

	g_return_val_if_fail (self == NULL || GDATA_IS_COMPARABLE (self), 0);

	g_return_val_if_fail (other == NULL || GDATA_IS_COMPARABLE (other), 0);

	g_return_val_if_fail (self == NULL || other == NULL || g_type_is_a (G_OBJECT_TYPE (other), G_OBJECT_TYPE (self)), 0);

	/* Deal with NULL values */

	if (self == NULL && other != NULL)

		return -1;

	else if (self != NULL && other == NULL)

		return 1;

	if (self == other)

		return 0;

	/* Use the comparator method for non-NULL values */

	iface = GDATA_COMPARABLE_GET_IFACE (self);

	g_assert (iface->compare_with != NULL);

	return iface->compare_with (self, other);

}