/*
 * 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.
 */

/** \file
 * \ingroup bke
 *
 * Contains management of ID's for remapping.
 */

#include "CLG_log.h"

#include "BLI_utildefines.h"

#include "DNA_collection_types.h"
#include "DNA_object_types.h"

#include "BKE_armature.h"
#include "BKE_collection.h"
#include "BKE_curve.h"
#include "BKE_layer.h"
#include "BKE_lib_id.h"
#include "BKE_lib_query.h"
#include "BKE_lib_remap.h"
#include "BKE_main.h"
#include "BKE_material.h"
#include "BKE_mball.h"
#include "BKE_modifier.h"
#include "BKE_multires.h"
#include "BKE_node.h"
#include "BKE_object.h"

#include "DEG_depsgraph.h"
#include "DEG_depsgraph_build.h"

#include "lib_intern.h" /* own include */

static CLG_LogRef LOG = {.identifier = "bke.lib_remap"};

BKE_library_free_notifier_reference_cb free_notifier_reference_cb = NULL;

void BKE_library_callback_free_notifier_reference_set(BKE_library_free_notifier_reference_cb func)
{
  free_notifier_reference_cb = func;
}

BKE_library_remap_editor_id_reference_cb remap_editor_id_reference_cb = NULL;

void BKE_library_callback_remap_editor_id_reference_set(
    BKE_library_remap_editor_id_reference_cb func)
{
  remap_editor_id_reference_cb = func;
}

typedef struct IDRemap {
  Main *bmain; /* Only used to trigger depsgraph updates in the right bmain. */
  ID *old_id;
  ID *new_id;
  /** The ID in which we are replacing old_id by new_id usages. */
  ID *id_owner;
  short flag;

  /* 'Output' data. */
  short status;
  /** Number of direct use cases that could not be remapped (e.g.: obdata when in edit mode). */
  int skipped_direct;
  /** Number of indirect use cases that could not be remapped. */
  int skipped_indirect;
  /** Number of skipped use cases that refcount the data-block. */
  int skipped_refcounted;
} IDRemap;

/* IDRemap->flag enums defined in BKE_lib.h */

/* IDRemap->status */
enum {
  /* *** Set by callback. *** */
  ID_REMAP_IS_LINKED_DIRECT = 1 << 0,    /* new_id is directly linked in current .blend. */
  ID_REMAP_IS_USER_ONE_SKIPPED = 1 << 1, /* There was some skipped 'user_one' usages of old_id. */
};

static int foreach_libblock_remap_callback(LibraryIDLinkCallbackData *cb_data)
{
  const int cb_flag = cb_data->cb_flag;

  if (cb_flag & IDWALK_CB_EMBEDDED) {
    return IDWALK_RET_NOP;
  }

  ID *id_owner = cb_data->id_owner;
  ID *id_self = cb_data->id_self;
  ID **id_p = cb_data->id_pointer;
  IDRemap *id_remap_data = cb_data->user_data;
  ID *old_id = id_remap_data->old_id;
  ID *new_id = id_remap_data->new_id;

  /* Those asserts ensure the general sanity of ID tags regarding 'embedded' ID data (root
   * nodetrees and co). */
  BLI_assert(id_owner == id_remap_data->id_owner);
  BLI_assert(id_self == id_owner || (id_self->flag & LIB_EMBEDDED_DATA) != 0);

  if (!old_id) { /* Used to cleanup all IDs used by a specific one. */
    BLI_assert(!new_id);
    old_id = *id_p;
  }

  if (*id_p && (*id_p == old_id)) {
    /* Better remap to NULL than not remapping at all,
     * then we can handle it as a regular remap-to-NULL case. */
    if ((cb_flag & IDWALK_CB_NEVER_SELF) && (new_id == id_self)) {
      new_id = NULL;
    }

    const bool is_reference = (cb_flag & IDWALK_CB_OVERRIDE_LIBRARY_REFERENCE) != 0;
    const bool is_indirect = (cb_flag & IDWALK_CB_INDIRECT_USAGE) != 0;
    const bool skip_indirect = (id_remap_data->flag & ID_REMAP_SKIP_INDIRECT_USAGE) != 0;
    /* Note: proxy usage implies LIB_TAG_EXTERN, so on this aspect it is direct,
     * on the other hand since they get reset to lib data on file open/reload it is indirect too.
     * Edit Mode is also a 'skip direct' case. */
    const bool is_obj = (GS(id_owner->name) == ID_OB);
    const bool is_obj_proxy = (is_obj &&
                               (((Object *)id_owner)->proxy || ((Object *)id_owner)->proxy_group));
    const bool is_obj_editmode = (is_obj && BKE_object_is_in_editmode((Object *)id_owner));
    const bool is_never_null = ((cb_flag & IDWALK_CB_NEVER_NULL) && (new_id == NULL) &&
                                (id_remap_data->flag & ID_REMAP_FORCE_NEVER_NULL_USAGE) == 0);
    const bool skip_reference = (id_remap_data->flag & ID_REMAP_SKIP_OVERRIDE_LIBRARY) != 0;
    const bool skip_never_null = (id_remap_data->flag & ID_REMAP_SKIP_NEVER_NULL_USAGE) != 0;

#ifdef DEBUG_PRINT
    printf(
        "In %s (lib %p): Remapping %s (%p) to %s (%p) "
        "(is_indirect: %d, skip_indirect: %d, is_reference: %d, skip_reference: %d)\n",
        id->name,
        id->lib,
        old_id->name,
        old_id,
        new_id ? new_id->name : "<NONE>",
        new_id,
        is_indirect,
        skip_indirect,
        is_reference,
        skip_reference);
#endif

    if ((id_remap_data->flag & ID_REMAP_FLAG_NEVER_NULL_USAGE) &&
        (cb_flag & IDWALK_CB_NEVER_NULL)) {
      id_owner->tag |= LIB_TAG_DOIT;
    }

    /* Special hack in case it's Object->data and we are in edit mode, and new_id is not NULL
     * (otherwise, we follow common NEVER_NULL flags).
     * (skipped_indirect too). */
    if ((is_never_null && skip_never_null) ||
        (is_obj_editmode && (((Object *)id_owner)->data == *id_p) && new_id != NULL) ||
        (skip_indirect && is_indirect) || (is_reference && skip_reference)) {
      if (is_indirect) {
        id_remap_data->skipped_indirect++;
        if (is_obj) {
          Object *ob = (Object *)id_owner;
          if (ob->data == *id_p && ob->proxy != NULL) {
            /* And another 'Proudly brought to you by Proxy Hell' hack!
             * This will allow us to avoid clearing 'LIB_EXTERN' flag of obdata of proxies... */
            id_remap_data->skipped_direct++;
          }
        }
      }
      else if (is_never_null || is_obj_editmode || is_reference) {
        id_remap_data->skipped_direct++;
      }
      else {
        BLI_assert(0);
      }
      if (cb_flag & IDWALK_CB_USER) {
        id_remap_data->skipped_refcounted++;
      }
      else if (cb_flag & IDWALK_CB_USER_ONE) {
        /* No need to count number of times this happens, just a flag is enough. */
        id_remap_data->status |= ID_REMAP_IS_USER_ONE_SKIPPED;
      }
    }
    else {
      if (!is_never_null) {
        *id_p = new_id;
        DEG_id_tag_update_ex(id_remap_data->bmain,
                             id_self,
                             ID_RECALC_COPY_ON_WRITE | ID_RECALC_TRANSFORM | ID_RECALC_GEOMETRY);
        if (id_self != id_owner) {
          DEG_id_tag_update_ex(id_remap_data->bmain,
                               id_owner,
                               ID_RECALC_COPY_ON_WRITE | ID_RECALC_TRANSFORM | ID_RECALC_GEOMETRY);
        }
      }
      if (cb_flag & IDWALK_CB_USER) {
        /* NOTE: We don't user-count IDs which are not in the main database.
         * This is because in certain conditions we can have data-blocks in
         * the main which are referencing data-blocks outside of it.
         * For example, BKE_mesh_new_from_object() called on an evaluated
         * object will cause such situation.
         */
        if ((old_id->tag & LIB_TAG_NO_MAIN) == 0) {
          id_us_min(old_id);
        }
        if (new_id != NULL && (new_id->tag & LIB_TAG_NO_MAIN) == 0) {
          /* We do not want to handle LIB_TAG_INDIRECT/LIB_TAG_EXTERN here. */
          new_id->us++;
        }
      }
      else if (cb_flag & IDWALK_CB_USER_ONE) {
        id_us_ensure_real(new_id);
        /* We cannot affect old_id->us directly, LIB_TAG_EXTRAUSER(_SET)
         * are assumed to be set as needed, that extra user is processed in final handling. */
      }
      if (!is_indirect || is_obj_proxy) {
        id_remap_data->status |= ID_REMAP_IS_LINKED_DIRECT;
      }
      /* We need to remap proxy_from pointer of remapped proxy... sigh. */
      if (is_obj_proxy && new_id != NULL) {
        Object *ob = (Object *)id_owner;
        if (ob->proxy == (Object *)new_id) {
          ob->proxy->proxy_from = ob;
        }
      }
    }
  }

  return IDWALK_RET_NOP;
}

static void libblock_remap_data_preprocess(IDRemap *r_id_remap_data)
{
  switch (GS(r_id_remap_data->id_owner->name)) {
    case ID_OB: {
      ID *old_id = r_id_remap_data->old_id;
      if (!old_id || GS(old_id->name) == ID_AR) {
        Object *ob = (Object *)r_id_remap_data->id_owner;
        /* Object's pose holds reference to armature bones. sic */
        /* Note that in theory, we should have to bother about linked/non-linked/never-null/etc.
         * flags/states.
         * Fortunately, this is just a tag, so we can accept to 'over-tag' a bit for pose recalc,
         * and avoid another complex and risky condition nightmare like the one we have in
         * foreach_libblock_remap_callback(). */
        if (ob->pose && (!old_id || ob->data == old_id)) {
          BLI_assert(ob->type == OB_ARMATURE);
          ob->pose->flag |= POSE_RECALC;
          /* We need to clear pose bone pointers immediately, some code may access those before
           * pose is actually recomputed, which can lead to segfault. */
          BKE_pose_clear_pointers(ob->pose);
        }
      }
      break;
    }
    default:
      break;
  }
}

/**
 * Can be called with both old_ob and new_ob being NULL,
 * this means we have to check whole Main database then.
 */
static void libblock_remap_data_postprocess_object_update(Main *bmain,
                                                          Object *old_ob,
                                                          Object *new_ob)
{
  if (new_ob == NULL) {
    /* In case we unlinked old_ob (new_ob is NULL), the object has already
     * been removed from the scenes and their collections. We still have
     * to remove the NULL children from collections not used in any scene. */
    BKE_collections_object_remove_nulls(bmain);
  }

  BKE_main_collection_sync_remap(bmain);

  if (old_ob == NULL) {
    for (Object *ob = bmain->objects.first; ob != NULL; ob = ob->id.next) {
      if (ob->type == OB_MBALL && BKE_mball_is_basis(ob)) {
        DEG_id_tag_update(&ob->id, ID_RECALC_GEOMETRY);
      }
    }
  }
  else {
    for (Object *ob = bmain->objects.first; ob != NULL; ob = ob->id.next) {
      if (ob->type == OB_MBALL && BKE_mball_is_basis_for(ob, old_ob)) {
        DEG_id_tag_update(&ob->id, ID_RECALC_GEOMETRY);
        break; /* There is only one basis... */
      }
    }
  }
}

/* Can be called with both old_collection and new_collection being NULL,
 * this means we have to check whole Main database then. */
static void libblock_remap_data_postprocess_collection_update(Main *bmain,
                                                              Collection *owner_collection,
                                                              Collection *UNUSED(old_collection),
                                                              Collection *new_collection)
{
  if (new_collection == NULL) {
    /* XXX Complex cases can lead to NULL pointers in other collections than old_collection,
     * and BKE_main_collection_sync_remap() does not tolerate any of those, so for now always check
     * whole existing collections for NULL pointers.
     * I'd consider optimizing that whole collection remapping process a TODO for later. */
    BKE_collections_child_remove_nulls(bmain, owner_collection, NULL /*old_collection*/);
  }
  else {
    /* Temp safe fix, but a "tad" brute force... We should probably be able to use parents from
     * old_collection instead? */
    BKE_main_collections_parent_relations_rebuild(bmain);
  }

  BKE_main_collection_sync_remap(bmain);
}

static void libblock_remap_data_postprocess_obdata_relink(Main *bmain, Object *ob, ID *new_id)
{
  if (ob->data == new_id) {
    switch (GS(new_id->name)) {
      case ID_ME:
        multires_force_sculpt_rebuild(ob);
        break;
      case ID_CU:
        BKE_curve_type_test(ob);
        break;
      default:
        break;
    }
    BKE_modifiers_test_object(ob);
    BKE_object_materials_test(bmain, ob, new_id);
  }
}

static void libblock_remap_data_postprocess_nodetree_update(Main *bmain, ID *new_id)
{
  /* Update all group nodes using a node group. */
  ntreeUpdateAllUsers(bmain, new_id);
}

/**
 * Execute the 'data' part of the remapping (that is, all ID pointers from other ID data-blocks).
 *
 * Behavior differs depending on whether given \a id is NULL or not:
 * - \a id NULL: \a old_id must be non-NULL, \a new_id may be NULL (unlinking \a old_id) or not
 *   (remapping \a old_id to \a new_id).
 *   The whole \a bmain database is checked, and all pointers to \a old_id
 *   are remapped to \a new_id.
 * - \a id is non-NULL:
 *   + If \a old_id is NULL, \a new_id must also be NULL,
 *     and all ID pointers from \a id are cleared
 *     (i.e. \a id does not references any other data-block anymore).
 *   + If \a old_id is non-NULL, behavior is as with a NULL \a id, but only within given \a id.
 *
 * \param bmain: the Main data storage to operate on (must never be NULL).
 * \param id: the data-block to operate on
 * (can be NULL, in which case we operate over all IDs from given bmain).
 * \param old_id: the data-block to dereference (may be NULL if \a id is non-NULL).
 * \param new_id: the new data-block to replace \a old_id references with (may be NULL).
 * \param r_id_remap_data: if non-NULL, the IDRemap struct to use
 * (uselful to retrieve info about remapping process).
 */
ATTR_NONNULL(1)
static void libblock_remap_data(
    Main *bmain, ID *id, ID *old_id, ID *new_id, const short remap_flags, IDRemap *r_id_remap_data)
{
  IDRemap id_remap_data;
  const int foreach_id_flags = ((remap_flags & ID_REMAP_NO_INDIRECT_PROXY_DATA_USAGE) != 0 ?
                                    IDWALK_NO_INDIRECT_PROXY_DATA_USAGE :
                                    IDWALK_NOP) |
                               ((remap_flags & ID_REMAP_FORCE_INTERNAL_RUNTIME_POINTERS) != 0 ?
                                    IDWALK_DO_INTERNAL_RUNTIME_POINTERS :
                                    IDWALK_NOP);

  if (r_id_remap_data == NULL) {
    r_id_remap_data = &id_remap_data;
  }
  r_id_remap_data->bmain = bmain;
  r_id_remap_data->old_id = old_id;
  r_id_remap_data->new_id = new_id;
  r_id_remap_data->id_owner = NULL;
  r_id_remap_data->flag = remap_flags;
  r_id_remap_data->status = 0;
  r_id_remap_data->skipped_direct = 0;
  r_id_remap_data->skipped_indirect = 0;
  r_id_remap_data->skipped_refcounted = 0;

  if (id) {
#ifdef DEBUG_PRINT
    printf("\tchecking id %s (%p, %p)\n", id->name, id, id->lib);
#endif
    r_id_remap_data->id_owner = id;
    libblock_remap_data_preprocess(r_id_remap_data);
    BKE_library_foreach_ID_link(
        NULL, id, foreach_libblock_remap_callback, (void *)r_id_remap_data, foreach_id_flags);
  }
  else {
    /* Note that this is a very 'brute force' approach,
     * maybe we could use some depsgraph to only process objects actually using given old_id...
     * sounds rather unlikely currently, though, so this will do for now. */
    ID *id_curr;

    FOREACH_MAIN_ID_BEGIN (bmain, id_curr) {
      if (BKE_library_id_can_use_idtype(id_curr, GS(old_id->name))) {
        /* Note that we cannot skip indirect usages of old_id here (if requested),
         * we still need to check it for the user count handling...
         * XXX No more true (except for debug usage of those skipping counters). */
        r_id_remap_data->id_owner = id_curr;
        libblock_remap_data_preprocess(r_id_remap_data);
        BKE_library_foreach_ID_link(NULL,
                                    id_curr,
                                    foreach_libblock_remap_callback,
                                    (void *)r_id_remap_data,
                                    foreach_id_flags);
      }
    }
    FOREACH_MAIN_ID_END;
  }

  if ((remap_flags & ID_REMAP_SKIP_USER_CLEAR) == 0) {
    /* XXX We may not want to always 'transfer' fake-user from old to new id...
     *     Think for now it's desired behavior though,
     *     we can always add an option (flag) to control this later if needed. */
    if (old_id && (old_id->flag & LIB_FAKEUSER)) {
      id_fake_user_clear(old_id);
      id_fake_user_set(new_id);
    }

    id_us_clear_real(old_id);
  }

  if (new_id && (new_id->tag & LIB_TAG_INDIRECT) &&
      (r_id_remap_data->status & ID_REMAP_IS_LINKED_DIRECT)) {
    new_id->tag &= ~LIB_TAG_INDIRECT;
    new_id->flag &= ~LIB_INDIRECT_WEAK_LINK;
    new_id->tag |= LIB_TAG_EXTERN;
  }

#ifdef DEBUG_PRINT
  printf("%s: %d occurrences skipped (%d direct and %d indirect ones)\n",
         __func__,
         r_id_remap_data->skipped_direct + r_id_remap_data->skipped_indirect,
         r_id_remap_data->skipped_direct,
         r_id_remap_data->skipped_indirect);
#endif
}

/**
 * Replace all references in given Main to \a old_id by \a new_id
 * (if \a new_id is NULL, it unlinks \a old_id).
 */
void BKE_libblock_remap_locked(Main *bmain, void *old_idv, void *new_idv, const short remap_flags)
{
  IDRemap id_remap_data;
  ID *old_id = old_idv;
  ID *new_id = new_idv;
  int skipped_direct, skipped_refcounted;

  BLI_assert(old_id != NULL);
  BLI_assert((new_id == NULL) || GS(old_id->name) == GS(new_id->name));
  BLI_assert(old_id != new_id);

  libblock_remap_data(bmain, NULL, old_id, new_id, remap_flags, &id_remap_data);

  if (free_notifier_reference_cb) {
    free_notifier_reference_cb(old_id);
  }

  /* We assume editors do not hold references to their IDs... This is false in some cases
   * (Image is especially tricky here),
   * editors' code is to handle refcount (id->us) itself then. */
  if (remap_editor_id_reference_cb) {
    remap_editor_id_reference_cb(old_id, new_id);
  }

  skipped_direct = id_remap_data.skipped_direct;
  skipped_refcounted = id_remap_data.skipped_refcounted;

  if ((remap_flags & ID_REMAP_SKIP_USER_CLEAR) == 0) {
    /* If old_id was used by some ugly 'user_one' stuff (like Image or Clip editors...), and user
     * count has actually been incremented for that, we have to decrease once more its user
     * count... unless we had to skip some 'user_one' cases. */
    if ((old_id->tag & LIB_TAG_EXTRAUSER_SET) &&
        !(id_remap_data.status & ID_REMAP_IS_USER_ONE_SKIPPED)) {
      id_us_clear_real(old_id);
    }
  }

  if (old_id->us - skipped_refcounted < 0) {
    CLOG_ERROR(&LOG,
               "Error in remapping process from '%s' (%p) to '%s' (%p): "
               "wrong user count in old ID after process (summing up to %d)",
               old_id->name,
               old_id,
               new_id ? new_id->name : "<NULL>",
               new_id,
               old_id->us - skipped_refcounted);
    BLI_assert(0);
  }

  if (skipped_direct == 0) {
    /* old_id is assumed to not be used directly anymore... */
    if (old_id->lib && (old_id->tag & LIB_TAG_EXTERN)) {
      old_id->tag &= ~LIB_TAG_EXTERN;
      old_id->tag |= LIB_TAG_INDIRECT;
    }
  }

  /* Some after-process updates.
   * This is a bit ugly, but cannot see a way to avoid it.
   * Maybe we should do a per-ID callback for this instead? */
  switch (GS(old_id->name)) {
    case ID_OB:
      libblock_remap_data_postprocess_object_update(bmain, (Object *)old_id, (Object *)new_id);
      break;
    case ID_GR:
      libblock_remap_data_postprocess_collection_update(
          bmain, NULL, (Collection *)old_id, (Collection *)new_id);
      break;
    case ID_ME:
    case ID_CU:
    case ID_MB:
    case ID_HA:
    case ID_PT:
    case ID_VO:
      if (new_id) { /* Only affects us in case obdata was relinked (changed). */
        for (Object *ob = bmain->objects.first; ob; ob = ob->id.next) {
          libblock_remap_data_postprocess_obdata_relink(bmain, ob, new_id);
        }
      }
      break;
    default:
      break;
  }

  /* Node trees may virtually use any kind of data-block... */
  /* XXX Yuck!!!! nodetree update can do pretty much any thing when talking about py nodes,
   *     including creating new data-blocks (see T50385), so we need to unlock main here. :(
   *     Why can't we have re-entrent locks? */
  BKE_main_unlock(bmain);
  libblock_remap_data_postprocess_nodetree_update(bmain, new_id);
  BKE_main_lock(bmain);

  /* Full rebuild of DEG! */
  DEG_relations_tag_update(bmain);
}

void BKE_libblock_remap(Main *bmain, void *old_idv, void *new_idv, const short remap_flags)
{
  BKE_main_lock(bmain);

  BKE_libblock_remap_locked(bmain, old_idv, new_idv, remap_flags);

  BKE_main_unlock(bmain);
}

/**
 * Unlink given \a id from given \a bmain
 * (does not touch to indirect, i.e. library, usages of the ID).
 *
 * \param do_flag_never_null: If true, all IDs using \a idv in a 'non-NULL' way are flagged by
 * #LIB_TAG_DOIT flag (quite obviously, 'non-NULL' usages can never be unlinked by this function).
 */
void BKE_libblock_unlink(Main *bmain,
                         void *idv,
                         const bool do_flag_never_null,
                         const bool do_skip_indirect)
{
  const short remap_flags = (do_skip_indirect ? ID_REMAP_SKIP_INDIRECT_USAGE : 0) |
                            (do_flag_never_null ? ID_REMAP_FLAG_NEVER_NULL_USAGE : 0);

  BKE_main_lock(bmain);

  BKE_libblock_remap_locked(bmain, idv, NULL, remap_flags);

  BKE_main_unlock(bmain);
}

/**
 * Similar to libblock_remap, but only affects IDs used by given \a idv ID.
 *
 * \param old_idv: Unlike BKE_libblock_remap, can be NULL,
 * in which case all ID usages by given \a idv will be cleared.
 * \param us_min_never_null: If \a true and new_id is NULL,
 * 'NEVER_NULL' ID usages keep their old id, but this one still gets its user count decremented
 * (needed when given \a idv is going to be deleted right after being unlinked).
 */
/* Should be able to replace all _relink() funcs (constraints, rigidbody, etc.) ? */
/* XXX Arg! Naming... :(
 *     _relink? avoids confusion with _remap, but is confusing with _unlink
 *     _remap_used_ids?
 *     _remap_datablocks?
 *     BKE_id_remap maybe?
 *     ... sigh
 */
void BKE_libblock_relink_ex(
    Main *bmain, void *idv, void *old_idv, void *new_idv, const short remap_flags)
{
  ID *id = idv;
  ID *old_id = old_idv;
  ID *new_id = new_idv;

  /* No need to lock here, we are only affecting given ID, not bmain database. */

  BLI_assert(id);
  if (old_id) {
    BLI_assert((new_id == NULL) || GS(old_id->name) == GS(new_id->name));
    BLI_assert(old_id != new_id);
  }
  else {
    BLI_assert(new_id == NULL);
  }

  libblock_remap_data(bmain, id, old_id, new_id, remap_flags, NULL);

  /* Some after-process updates.
   * This is a bit ugly, but cannot see a way to avoid it.
   * Maybe we should do a per-ID callback for this instead?
   */
  switch (GS(id->name)) {
    case ID_SCE:
    case ID_GR: {
      /* Note: here we know which collection we have affected, so at lest for NULL children
       * detection we can only process that one.
       * This is also a required fix in case `id` would not be in Main anymore, which can happen
       * e.g. when called from `id_delete`. */
      Collection *owner_collection = (GS(id->name) == ID_GR) ? (Collection *)id :
                                                               ((Scene *)id)->master_collection;
      if (old_id) {
        switch (GS(old_id->name)) {
          case ID_OB:
            libblock_remap_data_postprocess_object_update(
                bmain, (Object *)old_id, (Object *)new_id);
            break;
          case ID_GR:
            libblock_remap_data_postprocess_collection_update(
                bmain, owner_collection, (Collection *)old_id, (Collection *)new_id);
            break;
          default:
            break;
        }
      }
      else {
        /* No choice but to check whole objects/collections. */
        libblock_remap_data_postprocess_collection_update(bmain, owner_collection, NULL, NULL);
        libblock_remap_data_postprocess_object_update(bmain, NULL, NULL);
      }
      break;
    }
    case ID_OB:
      if (new_id) { /* Only affects us in case obdata was relinked (changed). */
        libblock_remap_data_postprocess_obdata_relink(bmain, (Object *)id, new_id);
      }
      break;
    default:
      break;
  }

  DEG_relations_tag_update(bmain);
}

static int id_relink_to_newid_looper(LibraryIDLinkCallbackData *cb_data)
{
  const int cb_flag = cb_data->cb_flag;
  if (cb_flag & IDWALK_CB_EMBEDDED) {
    return IDWALK_RET_NOP;
  }

  ID **id_pointer = cb_data->id_pointer;
  ID *id = *id_pointer;
  if (id) {
    /* See: NEW_ID macro */
    if (id->newid) {
      BKE_library_update_ID_link_user(id->newid, id, cb_flag);
      id = id->newid;
      *id_pointer = id;
    }
    if (id->tag & LIB_TAG_NEW) {
      id->tag &= ~LIB_TAG_NEW;
      BKE_libblock_relink_to_newid(id);
    }
  }
  return IDWALK_RET_NOP;
}

/**
 * Similar to #libblock_relink_ex,
 * but is remapping IDs to their newid value if non-NULL, in given \a id.
 *
 * Very specific usage, not sure we'll keep it on the long run,
 * currently only used in Object/Collection duplication code...
 */
void BKE_libblock_relink_to_newid(ID *id)
{
  if (ID_IS_LINKED(id)) {
    return;
  }

  BKE_library_foreach_ID_link(NULL, id, id_relink_to_newid_looper, NULL, 0);
}
