/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/*
 *  Authors: Iain Holmes <iain@gnome.org>
 *
 *  Copyright 2002 - 2006 Iain Holmes
 *
 *  This file is free software; you can redistribute it and/or
 *  modify it under the terms of version 2 of the GNU Library General Public
 *  License as published by the Free Software Foundation;
 *
 *  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.
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <glib/gi18n.h>

#include "koto-undo-manager.h"

G_DEFINE_TYPE (KotoUndoManager, koto_undo_manager, G_TYPE_OBJECT);

#define GET_PRIVATE(o)  \
   (G_TYPE_INSTANCE_GET_PRIVATE ((o), KOTO_TYPE_UNDO_MANAGER, KotoUndoManagerPrivate))

enum {
	CHANGED,
	LAST_SIGNAL
};

static guint signals[LAST_SIGNAL];

struct _KotoUndoManagerPrivate {
	GList *contexts, *undo, *redo;
	
	KotoUndoContext *working;
};

struct _KotoUndoContext {
	char *name;
	int count;

	GList *undoables;
};

static void
context_free (KotoUndoContext *ctxt)
{
	GList *u;

	g_free (ctxt->name);
	for (u = ctxt->undoables; u; u = u->next) {
		KotoUndoable *undoable = u->data;
		
		koto_undoable_free (undoable);
	}
	
	g_list_free (ctxt->undoables);

	g_free (ctxt);
}

static KotoUndoContext *
context_new (const char *name)
{
	KotoUndoContext *ctxt;

	ctxt = g_new (KotoUndoContext, 1);

	ctxt->name = g_strdup (name);
	ctxt->count = 0;
	ctxt->undoables = NULL;

	return ctxt;
}

static void
context_undo (KotoUndoContext *ctxt)
{
	GList *p;

	for (p = ctxt->undoables; p; p = p->next) {
		KotoUndoable *u = p->data;

		if (u->undo) {
			u->undo (u->closure);
		}
	}
}

static void
context_redo (KotoUndoContext *ctxt)
{
	GList *p;

	for (p = g_list_last (ctxt->undoables); p; p = p->prev) {
		KotoUndoable *u = p->data;

		if (u->redo) {
			u->redo (u->closure);
		}
	}
}

static void
finalize (GObject *object)
{
	KotoUndoManager *manager;
	KotoUndoManagerPrivate *priv;
	GList *p;

	manager = KOTO_UNDO_MANAGER (object);
	priv = manager->priv;

	for (p = priv->contexts; p; p = p->next) {
		KotoUndoContext *ctxt = p->data;
		context_free (ctxt);
	}
	g_list_free (priv->contexts);

	G_OBJECT_CLASS (koto_undo_manager_parent_class)->finalize (object);
}

static void
koto_undo_manager_class_init (KotoUndoManagerClass *klass)
{
	GObjectClass *object_class;

	g_type_class_add_private (klass, sizeof (KotoUndoManagerPrivate));

	object_class = G_OBJECT_CLASS (klass);

	object_class->finalize = finalize;

	signals[CHANGED] = g_signal_new ("changed",
					 G_TYPE_FROM_CLASS (klass),
					 G_SIGNAL_RUN_FIRST |
					 G_SIGNAL_NO_RECURSE,
					 G_STRUCT_OFFSET (KotoUndoManagerClass, changed),
					 NULL, NULL,
					 g_cclosure_marshal_VOID__VOID,
					 G_TYPE_NONE, 0);

}

static void
koto_undo_manager_init (KotoUndoManager *manager)
{
	manager->priv = GET_PRIVATE (manager);
}

KotoUndoManager *
koto_undo_manager_new (void)
{
	KotoUndoManager *manager;

	manager = g_object_new (KOTO_TYPE_UNDO_MANAGER, NULL);
	return manager;
}

gboolean
koto_undo_manager_can_undo (KotoUndoManager *manager)
{
	return (manager->priv->undo != NULL);
}

gboolean
koto_undo_manager_can_redo (KotoUndoManager *manager)
{
	return (manager->priv->redo != NULL);
}

/* FIXME: Should these return copies of the names 
   so that they're threadsafe? */
const char *
koto_undo_manager_get_undo_name (KotoUndoManager *manager)
{
	if (manager->priv->undo) {
		KotoUndoContext *ctxt = manager->priv->undo->data;
		return ctxt->name;
	} else {
		return "";
	}
}

const char *
koto_undo_manager_get_redo_name (KotoUndoManager *manager)
{
	if (manager->priv->redo) {
		KotoUndoContext *ctxt = manager->priv->redo->data;
		return ctxt->name;
	} else {
		return "";
	}
}

KotoUndoContext *
koto_undo_manager_context_begin (KotoUndoManager *manager,
				   const char *name)
{
	KotoUndoContext *ctxt;

	if (manager->priv->working != NULL) {
		manager->priv->working->count++;

		return manager->priv->working;
	}

	ctxt = context_new (name);
	ctxt->count++;
	manager->priv->working = ctxt;

	return ctxt;
}

KotoUndoContext *
koto_undo_manager_context_begin_formatted (KotoUndoManager *manager,
					   const char *format, ...)
{
	KotoUndoContext *ctxt;
	va_list args;
	char *name;
	
	va_start (args, format);
	
	name = g_strdup_vprintf (format, args);
	
	ctxt = koto_undo_manager_context_begin (manager, name);
	g_free (name);

	va_end (args);

	return ctxt;
}

void
koto_undo_manager_context_end (KotoUndoManager *manager,
				 KotoUndoContext *ctxt)
{
	/* TODO: handle start then end without any adds correctly */
	KotoUndoManagerPrivate *priv;

	priv = manager->priv;

	ctxt->count--;

	if (ctxt->count > 0) {
		return;
	}

	if (priv->contexts == NULL) {
		priv->contexts = g_list_append (NULL, ctxt);
		priv->undo = priv->contexts;
	} else {
		GList *pruned = priv->redo;
		GList *n;

		if (pruned != NULL) {
			GList *p;

			/* Disconnect pruned */
			if (priv->redo && priv->redo->prev) {
				priv->redo->prev->next = NULL;
			}

			/* If redo->prev == NULL then we've pruned everything */
			if (priv->redo && priv->redo->prev == NULL) {
				priv->contexts = NULL;
			}

			priv->redo = NULL;
			pruned->prev = NULL;

			for (p = pruned; p; p = p->next) {
				KotoUndoContext *c = p->data;

				context_free (c);
			}
			g_list_free (pruned);
		}

		/* Append our new context and move the position pointer on */
		n = g_list_append (priv->undo, ctxt);
		if (priv->undo == NULL) {
			priv->undo = n;
		} else {
			priv->undo = priv->undo->next;
		}
		/* If priv->contexts is NULL, then we pruned everything and need
		   to start a new list */
		if (priv->contexts == NULL) {
			priv->contexts = priv->undo;
		}
		priv->redo = NULL;
	}

	priv->working = NULL;

	g_signal_emit (manager, signals[CHANGED], 0);
}

void
koto_undo_manager_context_cancel (KotoUndoManager *manager,
				    KotoUndoContext *ctxt)
{
	g_return_if_fail (manager->priv->working == ctxt);

	manager->priv->working = NULL;
	context_free (ctxt);
}

void
koto_undo_manager_undo (KotoUndoManager *manager)
{
	
	if (manager->priv->undo) {
		context_undo ((KotoUndoContext *) manager->priv->undo->data);
		manager->priv->redo = manager->priv->undo;
		manager->priv->undo = manager->priv->undo->prev;

		g_signal_emit (manager, signals[CHANGED], 0);
	}
}

void
koto_undo_manager_redo (KotoUndoManager *manager)
{
	if (manager->priv->redo) {
		context_redo ((KotoUndoContext *) manager->priv->redo->data);
		manager->priv->undo = manager->priv->redo;
		manager->priv->redo = manager->priv->redo->next;

		g_signal_emit (manager, signals[CHANGED], 0);
	}
}

GList *
koto_undo_manager_get_history (KotoUndoManager *manager)
{
	GList *history = NULL;
	GList *p;
	KotoUndoHistory *hist;

	hist = g_new (KotoUndoHistory, 1);
	hist->name = g_strdup (_("Original Sample"));
	hist->current = FALSE;
	hist->ctxt = NULL;

 	history = g_list_prepend (history, hist);

	for (p = manager->priv->contexts; p; p = p->next) {
		KotoUndoContext *ctxt = p->data;

		hist = g_new (KotoUndoHistory, 1);
		hist->name = g_strdup (ctxt->name);
		hist->ctxt = ctxt;

 		history = g_list_append (history, hist);
		if (p == manager->priv->undo) {
			hist->current = TRUE;
		} else {
			hist->current = FALSE;
		}
	}

	return history;
}

void
koto_undo_context_add (KotoUndoContext *ctxt,
			 KotoUndoable *undoable)
{
	ctxt->undoables = g_list_prepend (ctxt->undoables, undoable);
}