/*==================================================================
 * SwamiUndo.c - Swami undo routines
 *
 * Swami
 * Copyright (C) 1999-2003 Josh Green <jgreen@users.sourceforge.net>
 *
 * 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., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA or point your web browser to http://www.gnu.org.
 *
 * To contact the author of this program:
 * Email: Josh Green <jgreen@users.sourceforge.net>
 * Swami homepage: http://swami.sourceforge.net
 *==================================================================*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdio.h>

#include "SwamiLog.h"
#include "SwamiObject.h"
#include "SwamiUndoFuncs.h"

#define ENTRY_CHUNK_OPTIMUM_AREA	64
#define ITEM_CHUNK_OPTIMUM_AREA		128

#define ERRMSG_NO_ACTIVE_UNDO_GROUP  "No active undo group"
#define ERRMSG_ACTIVE_UNDO_GROUP     "No undo group should be active"

/* --- private function prototypes --- */

static SwamiUndoItem *new_item (void);
static void free_item (SwamiUndoItem *doitem);
static void new_entry (SwamiObject *swami);
static void remove_curpos_entry (SwamiObject *swami);


/* --- private data --- */

static GMemChunk *entry_chunk;
static GMemChunk *item_chunk;
static gboolean undo_initialized = FALSE;

/* --- functions --- */

/**
 * swami_undo_system_init:
 *
 * Used internally to initialize undo system
 */
void
swami_undo_system_init (void)
{
  if (undo_initialized) return;

  entry_chunk = g_mem_chunk_create (SwamiUndoEntry, ENTRY_CHUNK_OPTIMUM_AREA,
				    G_ALLOC_AND_FREE);
  item_chunk = g_mem_chunk_create (SwamiUndoItem, ITEM_CHUNK_OPTIMUM_AREA,
				   G_ALLOC_AND_FREE);
  undo_initialized = TRUE;
}

#if 0
/* dump undo tree for debugging purposes */
void
sfdo_debug_dump (GNode *start, gint sibling, gboolean traverse,
		 gboolean detail)
{
  GList *l = NULL, *p, *p2;
  GNode *n;
  SwamiUndoEntry *entry;
  SwamiUndoItem *item;
  gint prev, next;

  if (!start)
    start = sfdo_tree.curpos;	/* no start specified, set to current pos */
  else if (sibling >= 0)
    {				/* start from the 'sibling' index of 'start' */
      n = start->parent;	/* get parent of 'start' */
      if (n)
	{
	  n = g_node_nth_child (n, sibling); /* find the sibling by index */
	  if (n) start = n;
	}
    }

  if (traverse)
    {
      /* traverse up the tree */
      n = start;
      while (n && n->data)
	{
	  entry = (SwamiUndoEntry *)(n->data);
	  l = g_list_prepend (l, n);
	  n = n->parent;
	}

      /* traverse down the tree via the default redo path */
      n = start;
      if (n) n = n->children;
      while (n && n->data)
	{
	  entry = (SwamiUndoEntry *)(n->data);
	  l = g_list_append (l, n);
	  n = n->children;
	}
    }
  else l = g_list_append (l, start); /* !traverse, show just one node */

  printf ("   %c    ROOT\n", (sfdo_tree.curpos == sfdo_tree.root) ? '+' : '/');

  p = l;
  prev = 0;
  next = 0;
  while (p)
    {
      n = (GNode *)(p->data);
      p = g_list_next (p);

      entry = (SwamiUndoEntry *)(n->data);

      if (n->parent)
	{
	  prev = g_node_child_position (n->parent, n);
	  next = g_node_n_children (n->parent) - prev - 1;
	}

      printf ("%c%-2d%c%2d%c (%lx) %s\n",
	      prev ? '<' : ' ', prev,
	      (n == sfdo_tree.curpos) ? '+' : '|',
	       next, next ? '>' : ' ',
	      (long)(n), entry->descr);

      if (!detail) continue;

      p2 = g_list_last (entry->items);

      if (!p2) printf ("\t<EMPTY>\n");

      while (p2)
	{
	  item = (SwamiUndoItem *)(p2->data);

	  printf ("\t| (state = %lx) %s\n", (long)(item->state),
		  sfdofuncs[item->type].descr);

	  p2 = g_list_previous (p2);
	}
    }
}
#endif

/**
 * swami_undo_group_start:
 * @swami: Swami object
 * @descr: Description of group action
 *
 * Start an undo group. Undo groups are used to group multiple actions. Groups
 * can be nested, but sub-groups are only remembered for the currently active
 * #SwamiUndoEntry.
 */
void
swami_undo_group_start (SwamiObject *swami, const char *descr)
{
  GList *p;
  SwamiUndo *undo;
  SwamiUndoEntry *entry;

  g_return_if_fail (swami != NULL);
  undo = swami->undo;

  if (undo->running) return;

  if (undo->groups)	/* sub group? */
    {				/* ? grouping already active? */
      /* ?: yes, get last GList * SwamiUndoItem of last group */
      entry = (SwamiUndoEntry *) (undo->curpos->data);
      p = entry->items;		/* first (most recent) group item */
    }
  else  /* top level group */
    {
      new_entry (swami);	/* ?: no, create new entry */
      p = NULL;			/* last GList * of previous group is NULL */

      /* copy the description to the entry if provided */
      if (descr) ((SwamiUndoEntry *)(undo->curpos->data))->descr
		   = g_strdup (descr);
    }

  undo->groups = g_list_prepend (undo->groups, p);
}

/**
 * swami_undo_group_end:
 * @swami: Swami object
 *
 * End an undo group
 */
void
swami_undo_group_end (SwamiObject *swami)
{
  GList *p;
  SwamiUndo *undo;

  g_return_if_fail (swami != NULL);
  undo = swami->undo;

  if (undo->running) return;

  if (undo->groups == NULL)
    {
      SWAMI_CRITICAL (ERRMSG_NO_ACTIVE_UNDO_GROUP);
      return;
    }

  p = undo->groups;	/* first (most recent) group item */

  /* remove and free group node */
  undo->groups = g_list_remove_link (undo->groups, p);
  g_list_free_1 (p);
}

/**
 * swami_undo_item_add:
 * @swami: Swami object
 * @type: Undo item type
 * @state: Pointer to state data for this item
 *
 * Add an item to the active open group entry
 */
void
swami_undo_item_add (SwamiObject *swami, int type, gpointer state)
{
  SwamiUndo *undo;
  SwamiUndoEntry *entry;
  SwamiUndoItem *item;

  g_return_if_fail (swami != NULL);
  undo = swami->undo;

  /* create a new group if there isn't one already open */
  if (undo->groups == NULL)
    new_entry (swami);

  if (type <= SWAMI_UNDO_NONE || type >= SWAMI_UNDO_LAST)
    {
      SWAMI_PARAM_ERROR ("type");
      return;
    }

  /* create and load the SwamiUndoItem */
  item = new_item ();
  item->type = type;
  item->state = state;

  entry = (SwamiUndoEntry *) (undo->curpos->data);
  entry->items = g_list_prepend (entry->items, item);
}

/**
 * swami_undo_retract:
 * @swami: Swami object
 *
 * Undo all items in current sub group and remove it. Does not store redo
 * information for any items. This function is useful when doing complex
 * operations with multiple actions that could fail.
 * See #swami_undo_retract_all to retract all nested group actions.
 */
void
swami_undo_retract (SwamiObject *swami)
{
  GList *p, *p2;
  SwamiUndo *undo;
  SwamiUndoEntry *entry;
  SwamiUndoItem *doitem;

  g_return_if_fail (swami != NULL);
  undo = swami->undo;

  if (undo->groups == NULL)
    {
      SWAMI_CRITICAL (ERRMSG_NO_ACTIVE_UNDO_GROUP);
      return;
    }

  undo->running = TRUE;		/* to stop recursive undo calls */

  entry = (SwamiUndoEntry *)(undo->curpos->data);  /* current entry */
  p = entry->items;  /* first item of current entry */

  /* loop while items and item isn't the last item of the previous group */
  while (p && p->data != undo->groups->data)
    {
      doitem = (SwamiUndoItem *)(p->data);

      /* call undo function */
      (*swami_undo_type_info[doitem->type].restore) (swami, doitem);

      /* call free state function */
      if (swami_undo_type_info[doitem->type].free)
	(*swami_undo_type_info[doitem->type].free) (swami, doitem);

      p2 = p;
      p = g_list_next (p);  /* must advance here, as p will be removed */

      /* remove SwamiUndoItem GList node */
      entry->items = g_list_remove_link (entry->items, p2);
      g_list_free_1 (p2);

      free_item (doitem);  /* free the SwamiUndoItem structure */
    }

  /* free last group SwamiUndoItem pointer, thereby destroying the group */
  undo->groups = g_list_remove_link (undo->groups,
				     undo->groups);

  if (!undo->groups)
    remove_curpos_entry (swami);

  undo->running = FALSE;
}

/**
 * swami_undo_retract_all:
 * @swami: Swami object
 *
 * Undo items in all current nested groups and remove them. Does not store redo
 * information for any items. This function is useful when doing complex
 * operations with multiple actions that could fail.
 * See #swami_undo_retract to retract only top level sub group.
 */
void
swami_undo_retract_all (SwamiObject *swami)
{
  SwamiUndo *undo;

  g_return_if_fail (swami != NULL);
  undo = swami->undo;

  if (undo->groups == NULL)
    {
      SWAMI_CRITICAL (ERRMSG_NO_ACTIVE_UNDO_GROUP);
      return;
    }

  while (undo->groups)
    swami_undo_retract (swami);
}

/**
 * swami_undo:
 * @swami: Swami Object
 *
 * Undo current entry in undo history
 */
void
swami_undo (SwamiObject *swami)
{
  GList *p;
  SwamiUndo *undo;
  SwamiUndoEntry *entry;
  SwamiUndoItem *undoitem, *newitem;

  g_return_if_fail (swami != NULL);
  undo = swami->undo;

  /* groups should not be active */
  if (undo->groups != NULL)
    {
      SWAMI_CRITICAL (ERRMSG_ACTIVE_UNDO_GROUP);
      return;
    }

  /* return if no entries to undo */
  if (undo->curpos == undo->root) return;

  undo->running = TRUE;		/* to stop recursive undo calls */

  entry = (SwamiUndoEntry *)(undo->curpos->data);  /* current entry */
  p = entry->items;  /* first item of current entry */

  /* loop while items */
  while (p)
    {
      undoitem = (SwamiUndoItem *)(p->data);  /* item to undo */
      newitem = new_item ();	/* new item to store redo state data */

      /* load redo item using undo item as reference */
      (*swami_undo_type_info[undoitem->type].restate) (swami, undoitem,
						       newitem);

      /* restore state from undo item */
      (*swami_undo_type_info[undoitem->type].restore) (swami, undoitem);

      /* free old undo item state and structure */
      if (swami_undo_type_info[undoitem->type].free)
	(*swami_undo_type_info[undoitem->type].free) (swami, undoitem);
      free_item (undoitem);

      p->data = newitem;  /* replace old undo GList data ptr with redo ptr */

      p = g_list_next (p);  /* advance forward in list (backwards in time) */
    }

  /* advance curpos up the tree */
  undo->curpos = undo->curpos->parent;

  undo->running = FALSE;
}

/**
 * swami_redo:
 * @swami: Swami object
 * @node: Child of current position in history or NULL to redo most
 *   recent entry
 *
 * Redo an entry in undo history tree
 */
void
swami_redo (SwamiObject *swami, GNode *node)
{
  GList *p;
  GNode *n;
  SwamiUndo *undo;
  SwamiUndoEntry *entry;
  SwamiUndoItem *redoitem, *newitem;

  g_return_if_fail (swami != NULL);
  undo = swami->undo;

  /* groups should not be active */
  if (undo->groups != NULL)
    {
      SWAMI_CRITICAL (ERRMSG_ACTIVE_UNDO_GROUP);
      return;
    }

  n = undo->curpos->children;

  if (node)  /* redo node specified? */
    {
      /* look for child node matching "node" */
      while (n && n != node)
	n = g_node_next_sibling (n);

      if (n == NULL)
	{
	  SWAMI_PARAM_ERROR ("node");
	  return;
	}
    }

  /* return if no entries to redo */
  if (undo->curpos->children == NULL) return;

  undo->running = TRUE;		/* to stop recursive undo calls */

  entry = (SwamiUndoEntry *)(n->data);  /* entry to redo */
  p = g_list_last (entry->items);  /* last item of entry to redo */

  /* loop while items */
  while (p)
    {
      redoitem = (SwamiUndoItem *)(p->data);  /* item to redo */
      newitem = new_item ();	/* new item to store undo state data */

      /* load undo item using redo item as reference */
      (*swami_undo_type_info[redoitem->type].restate) (swami, redoitem,
						       newitem);

      /* restore state from redo item */
      (*swami_undo_type_info[redoitem->type].restore) (swami, redoitem);

      /* free old redo item state and structure */
      if (swami_undo_type_info[redoitem->type].free)
	(*swami_undo_type_info[redoitem->type].free) (swami, redoitem);
      free_item (redoitem);

      p->data = newitem;  /* replace old redo GList data ptr with undo ptr */

      p = g_list_previous (p);  /* advance back in list (forwards in time) */
    }

  /* advance curpos to redone node */
  undo->curpos = n;

  undo->running = FALSE;
}

/**
 * swami_undo_jump:
 * @swami: Swami object
 * @node: #SwamiUndoEntry node in undo state history to jump to
 *
 * Jump to a position in undo state history, undoing and redoing items to
 * get to restore state.
 */
void
swami_undo_jump (SwamiObject *swami, GNode *node)
{
  GNode *n;
  GSList *srclist = NULL, *dstlist = NULL;
  GSList *srcp, *dstp;
  SwamiUndo *undo;

  g_return_if_fail (swami != NULL);
  undo = swami->undo;

  /* groups should not be active */
  if (undo->groups != NULL)
    {
      SWAMI_CRITICAL (ERRMSG_ACTIVE_UNDO_GROUP);
      return;
    }

  n = undo->curpos;
  while (n)			/* make a list of curpos ancestry */
    {
      srclist = g_slist_prepend (srclist, n);
      n = n->parent;
    }

  n = node;
  while (n)			/* make a list of destination ancestry */
    {
      dstlist = g_slist_prepend (dstlist, n);
      n = n->parent;
    }

  srcp = srclist;
  dstp = dstlist;
  while (srcp && dstp)		/* skip common ancestry */
    {
      if (srcp->data != dstp->data) break;
      srcp = g_slist_next (srcp);
      dstp = g_slist_next (dstp);
    }

  while (srcp)			/* undo from curpos up to common parent */
    {
      swami_undo (swami);
      srcp = g_slist_next (srcp);
    }

  while (dstp)			/* redo from common parent to destination */
    {
      swami_redo (swami, (GNode *)(dstp->data));
      dstp = g_slist_next (dstp);
    }

  g_slist_free (srclist);
  g_slist_free (dstlist);
}

/* allocate a new SwamiUndoItem and initialize to a NULL state */
static SwamiUndoItem *
new_item (void)
{
  SwamiUndoItem *item;
  item = g_chunk_new (SwamiUndoItem, item_chunk);
  item->type = SWAMI_UNDO_NONE;
  item->state = NULL;
  return (item);
}

static void
free_item (SwamiUndoItem *doitem)
{
  g_mem_chunk_free (item_chunk, doitem);
}

/* appends a new entry onto the curpos node, and makes it the curpos */
static void
new_entry (SwamiObject *swami)
{
  SwamiUndo *undo = swami->undo;
  SwamiUndoEntry *entry;

  /* grouping should not be active! */
  g_return_if_fail (undo->groups == NULL);

  entry = g_chunk_new (SwamiUndoEntry, entry_chunk);
  entry->descr = NULL;
  entry->items = NULL;
  undo->curpos = g_node_prepend_data (undo->curpos, entry);
}

/* removes the current entry which must have NO SwamiUndoItems and NO children
   (i.e. bottom of the tree) */
static void
remove_curpos_entry (SwamiObject *swami)
{
  GNode *n;
  SwamiUndo *undo = swami->undo;
  SwamiUndoEntry *entry;

  /* curpos should be the bottom of the tree (no GNode children!) */
  g_return_if_fail (undo->curpos->children == NULL);

  n = undo->curpos;		/* current position GNode */
  entry = (SwamiUndoEntry *)(n->data);  /* get current entry */

  g_return_if_fail (entry->items == NULL);  /* fail if it has SwamiUndoItems */

  undo->curpos = undo->curpos->parent; /* move curpos to parent */

  /* if this entry has a description, free it */
  if (entry->descr)
    g_free (entry->descr);

  g_mem_chunk_free (entry_chunk, entry);  /* free the SwamiUndoEntry atom */
  g_node_unlink (n);  /* unlink the node from the tree */
  g_node_destroy (n);  /* destroy node */
}