/**
 * $Id$
 *
 * Undo system for painting and sculpting.
 * 
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

#include <stdlib.h>
#include <string.h>

#include "MEM_guardedalloc.h"

#include "DNA_userdef_types.h"

#include "BLI_listbase.h"

#include "BKE_context.h"
#include "BKE_global.h"

#include "ED_sculpt.h"

#include "paint_intern.h"

#define MAXUNDONAME	64

typedef struct UndoElem {
	struct UndoElem *next, *prev;
	char name[MAXUNDONAME];
	uintptr_t undosize;

	ListBase elems;

	UndoRestoreCb restore;
	UndoFreeCb free;
} UndoElem;

typedef struct UndoStack {
	int type;
	ListBase elems;
	UndoElem *current;
} UndoStack;

static UndoStack ImageUndoStack = {UNDO_PAINT_IMAGE, {NULL, NULL}, NULL};
static UndoStack MeshUndoStack = {UNDO_PAINT_MESH, {NULL, NULL}, NULL};

/* Generic */

static void undo_restore(bContext *C, UndoStack *stack, UndoElem *uel)
{
	if(uel && uel->restore)
		uel->restore(C, &uel->elems);
}

static void undo_elem_free(UndoStack *stack, UndoElem *uel)
{
	if(uel && uel->free) {
		uel->free(&uel->elems);
		BLI_freelistN(&uel->elems);
	}
}

static void undo_stack_push_begin(UndoStack *stack, const char *name, UndoRestoreCb restore, UndoFreeCb free)
{
	UndoElem *uel;
	int nr;
	
	/* Undo push is split up in begin and end, the reason is that as painting
	 * happens more tiles/nodes are added to the list, and at the very end we
	 * know how much memory the undo used to remove old undo elements */

	/* remove all undos after (also when stack->current==NULL) */
	while(stack->elems.last != stack->current) {
		uel= stack->elems.last;
		undo_elem_free(stack, uel);
		BLI_freelinkN(&stack->elems, uel);
	}
	
	/* make new */
	stack->current= uel= MEM_callocN(sizeof(UndoElem), "undo file");
	uel->restore= restore;
	uel->free= free;
	BLI_addtail(&stack->elems, uel);

	/* name can be a dynamic string */
	strncpy(uel->name, name, MAXUNDONAME-1);
	
	/* limit amount to the maximum amount*/
	nr= 0;
	uel= stack->elems.last;
	while(uel) {
		nr++;
		if(nr==U.undosteps) break;
		uel= uel->prev;
	}
	if(uel) {
		while(stack->elems.first!=uel) {
			UndoElem *first= stack->elems.first;
			undo_elem_free(stack, first);
			BLI_freelinkN(&stack->elems, first);
		}
	}
}

static void undo_stack_push_end(UndoStack *stack)
{
	UndoElem *uel;
	uintptr_t totmem, maxmem;

	if(U.undomemory != 0) {
		/* limit to maximum memory (afterwards, we can't know in advance) */
		totmem= 0;
		maxmem= ((uintptr_t)U.undomemory)*1024*1024;

		uel= stack->elems.last;
		while(uel) {
			totmem+= uel->undosize;
			if(totmem>maxmem) break;
			uel= uel->prev;
		}

		if(uel) {
			while(stack->elems.first!=uel) {
				UndoElem *first= stack->elems.first;
				undo_elem_free(stack, first);
				BLI_freelinkN(&stack->elems, first);
			}
		}
	}
}

static int undo_stack_step(bContext *C, UndoStack *stack, int step, const char *name)
{
	UndoElem *undo;

	if(step==1) {
		if(stack->current==NULL);
		else {
			if(!name || strcmp(stack->current->name, name) == 0) {
				if(G.f & G_DEBUG) printf("undo %s\n", stack->current->name);
				undo_restore(C, stack, stack->current);
				stack->current= stack->current->prev;
				return 1;
			}
		}
	}
	else if(step==-1) {
		if((stack->current!=NULL && stack->current->next==NULL) || stack->elems.first==NULL);
		else {
			if(!name || strcmp(stack->current->name, name) == 0) {
				undo= (stack->current && stack->current->next)? stack->current->next: stack->elems.first;
				undo_restore(C, stack, undo);
				stack->current= undo;
				if(G.f & G_DEBUG) printf("redo %s\n", undo->name);
				return 1;
			}
		}
	}

	return 0;
}

static void undo_stack_free(UndoStack *stack)
{
	UndoElem *uel;
	
	for(uel=stack->elems.first; uel; uel=uel->next)
		undo_elem_free(stack, uel);

	BLI_freelistN(&stack->elems);
	stack->current= NULL;
}

/* Exported Functions */

void undo_paint_push_begin(int type, const char *name, UndoRestoreCb restore, UndoFreeCb free)
{
	if(type == UNDO_PAINT_IMAGE)
		undo_stack_push_begin(&ImageUndoStack, name, restore, free);
	else if(type == UNDO_PAINT_MESH)
		undo_stack_push_begin(&MeshUndoStack, name, restore, free);
}

ListBase *undo_paint_push_get_list(int type)
{
	if(type == UNDO_PAINT_IMAGE) {
		if(ImageUndoStack.current)
			return &ImageUndoStack.current->elems;
	}
	else if(type == UNDO_PAINT_MESH) {
		if(MeshUndoStack.current)
			return &MeshUndoStack.current->elems;
	}
	
	return NULL;
}

void undo_paint_push_count_alloc(int type, int size)
{
	if(type == UNDO_PAINT_IMAGE)
		ImageUndoStack.current->undosize += size;
	else if(type == UNDO_PAINT_MESH)
		MeshUndoStack.current->undosize += size;
}

void undo_paint_push_end(int type)
{
	if(type == UNDO_PAINT_IMAGE)
		undo_stack_push_end(&ImageUndoStack);
	else if(type == UNDO_PAINT_MESH)
		undo_stack_push_end(&MeshUndoStack);
}

int ED_undo_paint_step(bContext *C, int type, int step, const char *name)
{
	if(type == UNDO_PAINT_IMAGE)
		return undo_stack_step(C, &ImageUndoStack, step, name);
	else if(type == UNDO_PAINT_MESH)
		return undo_stack_step(C, &MeshUndoStack, step, name);
	
	return 0;
}

void ED_undo_paint_free(void)
{
	undo_stack_free(&ImageUndoStack);
	undo_stack_free(&MeshUndoStack);
}

