/* dia-undo_manager.c
 * Copyright (C) 2003 Arjan Molenaar
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 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 Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include "dia-undo-manager.h"
#include "diamarshal.h"
#include "../config.h"

/**
 * dia_undo_action_new:
 * @sizeof_undo_action: Size of the real undo entry
 * @undo: function called on an undo operation
 * @redo: function called in a redo operation
 * @destroy: function called to free the resources held by this undo entry
 *
 * Create a new DiaUndoAction. DiaUndoAction is the object that is passed to
 * the UndoManager. This "class" is normally subclassed, so specific attributes
 * can be stored (this struct is an "abstract class"). 
 *
 * Return value: 
 **/
DiaUndoAction*
dia_undo_action_new (gsize sizeof_undo_action, DiaUndoFunc undo,
		    DiaUndoFunc redo, GDestroyNotify destroy)
{
	DiaUndoAction *entry;

	g_return_val_if_fail (sizeof_undo_action >= sizeof(DiaUndoAction), NULL);

	entry = g_malloc0 (sizeof_undo_action);
	entry->undo = undo;
	entry->redo = redo;
	entry->destroy = destroy;

	return entry;
}

void
dia_undo_action_undo (DiaUndoAction *entry)
{
	g_return_if_fail (entry != NULL);

	if (entry->undo)
		entry->undo (entry);
}

void
dia_undo_action_redo (DiaUndoAction *entry)
{
	g_return_if_fail (entry != NULL);

	if (entry->redo)
		entry->redo (entry);
}

void
dia_undo_action_destroy (DiaUndoAction *entry)
{
	g_return_if_fail (entry != NULL);

	if (entry->destroy)
		entry->destroy (entry);
	g_free (entry);
}


enum
{
	BEGIN_TRANSACTION,
	COMMIT_TRANSACTION,
	DISCARD_TRANSACTION,
	ADD_UNDO_ACTION,
	UNDO_TRANSACTION,
	REDO_TRANSACTION,
	CLEAR_UNDO_STACK,
	CLEAR_REDO_STACK,
	LAST_SIGNAL
};

static void dia_undo_manager_base_init (gpointer klass);

static guint undo_manager_signals[LAST_SIGNAL] = { 0 };

GType
dia_undo_manager_get_type (void)
{
	static GType undo_manager_type = 0;

	if (!undo_manager_type) {
		static const GTypeInfo undo_manager_info =
		{
			sizeof (DiaUndoManagerIface), /* class_size */
			dia_undo_manager_base_init,   /* base_init */
			NULL,           /* base_finalize */
			NULL,
			NULL,           /* class_finalize */
			NULL,           /* class_data */
			0,
			0,              /* n_preallocs */
			NULL
		};

		undo_manager_type = g_type_register_static (G_TYPE_INTERFACE,
							 "DiaUndoManager",
							 &undo_manager_info, 0);
		g_type_interface_add_prerequisite (undo_manager_type,
						   G_TYPE_OBJECT);
	}

	return undo_manager_type;
}

static void
dia_undo_manager_base_init (gpointer iface)
{
	static gboolean initialized = FALSE;

	if (!initialized) {
		undo_manager_signals[BEGIN_TRANSACTION] =
			  g_signal_new ("begin_transaction",
					G_TYPE_FROM_INTERFACE (iface),
					G_SIGNAL_RUN_LAST,
					G_STRUCT_OFFSET (DiaUndoManagerIface, begin_transaction),
					NULL, NULL,
					dia_marshal_VOID__VOID,
					G_TYPE_NONE, 0);
		undo_manager_signals[COMMIT_TRANSACTION] =
			  g_signal_new ("commit_transaction",
					G_TYPE_FROM_INTERFACE (iface),
					G_SIGNAL_RUN_LAST,
					G_STRUCT_OFFSET (DiaUndoManagerIface, commit_transaction),
					NULL, NULL,
					dia_marshal_VOID__VOID,
					G_TYPE_NONE, 0);
		undo_manager_signals[DISCARD_TRANSACTION] =
			  g_signal_new ("discard_transaction",
					G_TYPE_FROM_INTERFACE (iface),
					G_SIGNAL_RUN_LAST,
					G_STRUCT_OFFSET (DiaUndoManagerIface, discard_transaction),
					NULL, NULL,
					dia_marshal_VOID__VOID,
					G_TYPE_NONE, 0);
		undo_manager_signals[ADD_UNDO_ACTION] =
			  g_signal_new ("add_undo_action",
					G_TYPE_FROM_INTERFACE (iface),
					G_SIGNAL_RUN_LAST,
					G_STRUCT_OFFSET (DiaUndoManagerIface, add_undo_action),
					NULL, NULL,
					dia_marshal_VOID__POINTER,
					G_TYPE_NONE, 1,
					G_TYPE_POINTER);
		undo_manager_signals[UNDO_TRANSACTION] =
			  g_signal_new ("undo_transaction",
					G_TYPE_FROM_INTERFACE (iface),
					G_SIGNAL_RUN_LAST,
					G_STRUCT_OFFSET (DiaUndoManagerIface, undo_transaction),
					NULL, NULL,
					dia_marshal_VOID__VOID,
					G_TYPE_NONE, 0);
		undo_manager_signals[REDO_TRANSACTION] =
			  g_signal_new ("redo_transaction",
					G_TYPE_FROM_INTERFACE (iface),
					G_SIGNAL_RUN_LAST,
					G_STRUCT_OFFSET (DiaUndoManagerIface, redo_transaction),
					NULL, NULL,
					dia_marshal_VOID__VOID,
					G_TYPE_NONE, 0);
		initialized = TRUE;
	}
}

/**
 * dia_undo_manager_in_transaction:
 * @undo_manager: 
 *
 * This function returns TRUE if there is an open transaction.
 *
 * Return value: 
 **/
gboolean
dia_undo_manager_in_transaction (DiaUndoManager *undo_manager)
{
	g_return_if_fail (DIA_IS_UNDO_MANAGER (undo_manager));
	
	if (!DIA_UNDO_MANAGER_GET_IFACE (undo_manager)->in_transaction)
		return FALSE;

	return DIA_UNDO_MANAGER_GET_IFACE (undo_manager)->in_transaction (undo_manager);
}

/**
 * dia_undo_manager_can_undo:
 * @undo_manager: 
 *
 * 
 *
 * Return value: TRUE if there are transactions that can be undone.
 **/
gboolean
dia_undo_manager_can_undo (DiaUndoManager *undo_manager)
{
	g_return_if_fail (DIA_IS_UNDO_MANAGER (undo_manager));
	
	if (!DIA_UNDO_MANAGER_GET_IFACE (undo_manager)->can_undo)
		return FALSE;

	return DIA_UNDO_MANAGER_GET_IFACE (undo_manager)->can_undo (undo_manager);
}

/**
 * dia_undo_manager_can_redo:
 * @undo_manager: 
 *
 *
 *
 * Return value: TRUE if there are transactions that can be redone.
 **/
gboolean
dia_undo_manager_can_redo (DiaUndoManager *undo_manager)
{
	g_return_if_fail (DIA_IS_UNDO_MANAGER (undo_manager));
	
	if (!DIA_UNDO_MANAGER_GET_IFACE (undo_manager)->can_redo)
		return FALSE;

	return DIA_UNDO_MANAGER_GET_IFACE (undo_manager)->can_redo (undo_manager);
}

/**
 * dia_undo_manager_begin_transaction:
 * @undo_manager: 
 *
 * Begin a new transaction. 
 **/
void
dia_undo_manager_begin_transaction (DiaUndoManager *undo_manager)
{
	g_return_if_fail (DIA_IS_UNDO_MANAGER (undo_manager));

	g_signal_emit (undo_manager, undo_manager_signals[BEGIN_TRANSACTION], 0);
}

/**
 * dia_undo_manager_commit_transaction:
 * @undo_manager: 
 *
 * Store the transaction on the undo stack. If there are no actions to be
 * undone, a specific implementation may consider no storing it.
 **/
void
dia_undo_manager_commit_transaction (DiaUndoManager *undo_manager)
{
	g_return_if_fail (DIA_IS_UNDO_MANAGER (undo_manager));

	g_signal_emit (undo_manager, undo_manager_signals[COMMIT_TRANSACTION], 0);
}

/**
 * dia_undo_manager_discard_transaction:
 * @undo_manager: 
 *
 * Discard the current transaction. It is not stored on the undo stack.
 **/
void
dia_undo_manager_discard_transaction (DiaUndoManager *undo_manager)
{
	g_return_if_fail (DIA_IS_UNDO_MANAGER (undo_manager));

	g_signal_emit (undo_manager, undo_manager_signals[DISCARD_TRANSACTION], 0);
}

/**
 * dia_undo_manager_add_undo_action:
 * @undo_manager: 
 * @entry: 
 *
 * Add an entry to the current transaction. A transaction should have been
 * started by calling dia_undo_manager_begin_transaction().
 **/
void
dia_undo_manager_add_undo_action (DiaUndoManager *undo_manager, DiaUndoAction *entry)
{
	g_return_if_fail (DIA_IS_UNDO_MANAGER (undo_manager));

	g_signal_emit (undo_manager, undo_manager_signals[ADD_UNDO_ACTION], 0,
		       entry);
}

/**
 * dia_undo_manager_undo_transaction:
 * @undo_manager: 
 *
 * Undo the actions in the last commited transaction.
 **/
void
dia_undo_manager_undo_transaction (DiaUndoManager *undo_manager)
{
	g_return_if_fail (DIA_IS_UNDO_MANAGER (undo_manager));

	g_signal_emit (undo_manager, undo_manager_signals[UNDO_TRANSACTION], 0);
}

void
dia_undo_manager_redo_transaction (DiaUndoManager *undo_manager)
{
	g_return_if_fail (DIA_IS_UNDO_MANAGER (undo_manager));

	g_signal_emit (undo_manager, undo_manager_signals[REDO_TRANSACTION], 0);
}