/*
 * 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.
 *
 * The Original Code is Copyright (C) 2007 Blender Foundation.
 * All rights reserved.
 */

/** \file
 * \ingroup wm
 *
 * Functions for dealing with append/link operators and helpers.
 */

#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <float.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>

#include "MEM_guardedalloc.h"

#include "DNA_ID.h"
#include "DNA_scene_types.h"
#include "DNA_screen_types.h"
#include "DNA_windowmanager_types.h"

#include "BLI_bitmap.h"
#include "BLI_blenlib.h"
#include "BLI_ghash.h"
#include "BLI_linklist.h"
#include "BLI_math.h"
#include "BLI_memarena.h"
#include "BLI_utildefines.h"

#include "BLO_readfile.h"

#include "BKE_context.h"
#include "BKE_global.h"
#include "BKE_layer.h"
#include "BKE_lib_id.h"
#include "BKE_lib_remap.h"
#include "BKE_main.h"
#include "BKE_report.h"

#include "BKE_idtype.h"

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

#include "IMB_colormanagement.h"

#include "ED_datafiles.h"
#include "ED_screen.h"

#include "RNA_access.h"
#include "RNA_define.h"

#include "WM_api.h"
#include "WM_types.h"

#include "wm_files.h"

/* -------------------------------------------------------------------- */
/** \name Link/Append Operator
 * \{ */

static bool wm_link_append_poll(bContext *C)
{
  if (WM_operator_winactive(C)) {
    /* linking changes active object which is pretty useful in general,
     * but which totally confuses edit mode (i.e. it becoming not so obvious
     * to leave from edit mode and invalid tools in toolbar might be displayed)
     * so disable link/append when in edit mode (sergey) */
    if (CTX_data_edit_object(C)) {
      return 0;
    }

    return 1;
  }

  return 0;
}

static int wm_link_append_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(event))
{
  if (!RNA_struct_property_is_set(op->ptr, "filepath")) {
    if (G.lib[0] != '\0') {
      RNA_string_set(op->ptr, "filepath", G.lib);
    }
    else if (G.relbase_valid) {
      char path[FILE_MAX];
      BLI_strncpy(path, BKE_main_blendfile_path_from_global(), sizeof(path));
      BLI_parent_dir(path);
      RNA_string_set(op->ptr, "filepath", path);
    }
  }

  WM_event_add_fileselect(C, op);
  return OPERATOR_RUNNING_MODAL;
}

static short wm_link_append_flag(wmOperator *op)
{
  PropertyRNA *prop;
  short flag = 0;

  if (RNA_boolean_get(op->ptr, "autoselect")) {
    flag |= FILE_AUTOSELECT;
  }
  if (RNA_boolean_get(op->ptr, "active_collection")) {
    flag |= FILE_ACTIVE_COLLECTION;
  }
  if ((prop = RNA_struct_find_property(op->ptr, "relative_path")) &&
      RNA_property_boolean_get(op->ptr, prop)) {
    flag |= FILE_RELPATH;
  }
  if (RNA_boolean_get(op->ptr, "link")) {
    flag |= FILE_LINK;
  }
  if (RNA_boolean_get(op->ptr, "instance_collections")) {
    flag |= FILE_GROUP_INSTANCE;
  }

  return flag;
}

typedef struct WMLinkAppendDataItem {
  char *name;
  BLI_bitmap
      *libraries; /* All libs (from WMLinkAppendData.libraries) to try to load this ID from. */
  short idcode;

  ID *new_id;
  void *customdata;
} WMLinkAppendDataItem;

typedef struct WMLinkAppendData {
  LinkNodePair libraries;
  LinkNodePair items;
  int num_libraries;
  int num_items;
  /** Combines #eFileSel_Params_Flag from DNA_space_types.h and
   * BLO_LibLinkFlags from BLO_readfile.h */
  int flag;

  /* Internal 'private' data */
  MemArena *memarena;
} WMLinkAppendData;

static WMLinkAppendData *wm_link_append_data_new(const int flag)
{
  MemArena *ma = BLI_memarena_new(BLI_MEMARENA_STD_BUFSIZE, __func__);
  WMLinkAppendData *lapp_data = BLI_memarena_calloc(ma, sizeof(*lapp_data));

  lapp_data->flag = flag;
  lapp_data->memarena = ma;

  return lapp_data;
}

static void wm_link_append_data_free(WMLinkAppendData *lapp_data)
{
  BLI_memarena_free(lapp_data->memarena);
}

/* WARNING! *Never* call wm_link_append_data_library_add() after having added some items! */

static void wm_link_append_data_library_add(WMLinkAppendData *lapp_data, const char *libname)
{
  size_t len = strlen(libname) + 1;
  char *libpath = BLI_memarena_alloc(lapp_data->memarena, len);

  BLI_strncpy(libpath, libname, len);
  BLI_linklist_append_arena(&lapp_data->libraries, libpath, lapp_data->memarena);
  lapp_data->num_libraries++;
}

static WMLinkAppendDataItem *wm_link_append_data_item_add(WMLinkAppendData *lapp_data,
                                                          const char *idname,
                                                          const short idcode,
                                                          void *customdata)
{
  WMLinkAppendDataItem *item = BLI_memarena_alloc(lapp_data->memarena, sizeof(*item));
  size_t len = strlen(idname) + 1;

  item->name = BLI_memarena_alloc(lapp_data->memarena, len);
  BLI_strncpy(item->name, idname, len);
  item->idcode = idcode;
  item->libraries = BLI_BITMAP_NEW_MEMARENA(lapp_data->memarena, lapp_data->num_libraries);

  item->new_id = NULL;
  item->customdata = customdata;

  BLI_linklist_append_arena(&lapp_data->items, item, lapp_data->memarena);
  lapp_data->num_items++;

  return item;
}

static void wm_link_do(WMLinkAppendData *lapp_data,
                       ReportList *reports,
                       Main *bmain,
                       Scene *scene,
                       ViewLayer *view_layer,
                       const View3D *v3d)
{
  Main *mainl;
  BlendHandle *bh;
  Library *lib;

  const int flag = lapp_data->flag;

  LinkNode *liblink, *itemlink;
  int lib_idx, item_idx;

  BLI_assert(lapp_data->num_items && lapp_data->num_libraries);

  for (lib_idx = 0, liblink = lapp_data->libraries.list; liblink;
       lib_idx++, liblink = liblink->next) {
    char *libname = liblink->link;

    if (STREQ(libname, BLO_EMBEDDED_STARTUP_BLEND)) {
      bh = BLO_blendhandle_from_memory(datatoc_startup_blend, datatoc_startup_blend_size);
    }
    else {
      bh = BLO_blendhandle_from_file(libname, reports);
    }

    if (bh == NULL) {
      /* Unlikely since we just browsed it, but possible
       * Error reports will have been made by BLO_blendhandle_from_file() */
      continue;
    }

    /* here appending/linking starts */
    mainl = BLO_library_link_begin(bmain, &bh, libname);
    lib = mainl->curlib;
    BLI_assert(lib);
    UNUSED_VARS_NDEBUG(lib);

    if (mainl->versionfile < 250) {
      BKE_reportf(reports,
                  RPT_WARNING,
                  "Linking or appending from a very old .blend file format (%d.%d), no animation "
                  "conversion will "
                  "be done! You may want to re-save your lib file with current Blender",
                  mainl->versionfile,
                  mainl->subversionfile);
    }

    /* For each lib file, we try to link all items belonging to that lib,
     * and tag those successful to not try to load them again with the other libs. */
    for (item_idx = 0, itemlink = lapp_data->items.list; itemlink;
         item_idx++, itemlink = itemlink->next) {
      WMLinkAppendDataItem *item = itemlink->link;
      ID *new_id;

      if (!BLI_BITMAP_TEST(item->libraries, lib_idx)) {
        continue;
      }

      new_id = BLO_library_link_named_part_ex(mainl, &bh, item->idcode, item->name, flag);

      if (new_id) {
        /* If the link is successful, clear item's libs 'todo' flags.
         * This avoids trying to link same item with other libraries to come. */
        BLI_bitmap_set_all(item->libraries, false, lapp_data->num_libraries);
        item->new_id = new_id;
      }
    }

    BLO_library_link_end(mainl, &bh, flag, bmain, scene, view_layer, v3d);
    BLO_blendhandle_close(bh);
  }
}

/**
 * Check if an item defined by \a name and \a group can be appended/linked.
 *
 * \param reports: Optionally report an error when an item can't be appended/linked.
 */
static bool wm_link_append_item_poll(ReportList *reports,
                                     const char *path,
                                     const char *group,
                                     const char *name,
                                     const bool do_append)
{
  short idcode;

  if (!group || !name) {
    printf("skipping %s\n", path);
    return false;
  }

  idcode = BKE_idtype_idcode_from_name(group);

  /* XXX For now, we do a nasty exception for workspace, forbid linking them.
   *     Not nice, ultimately should be solved! */
  if (!BKE_idtype_idcode_is_linkable(idcode) && (do_append || idcode != ID_WS)) {
    if (reports) {
      if (do_append) {
        BKE_reportf(reports,
                    RPT_ERROR_INVALID_INPUT,
                    "Can't append data-block '%s' of type '%s'",
                    name,
                    group);
      }
      else {
        BKE_reportf(reports,
                    RPT_ERROR_INVALID_INPUT,
                    "Can't link data-block '%s' of type '%s'",
                    name,
                    group);
      }
    }
    return false;
  }

  return true;
}

static int wm_link_append_exec(bContext *C, wmOperator *op)
{
  Main *bmain = CTX_data_main(C);
  Scene *scene = CTX_data_scene(C);
  ViewLayer *view_layer = CTX_data_view_layer(C);
  PropertyRNA *prop;
  WMLinkAppendData *lapp_data;
  char path[FILE_MAX_LIBEXTRA], root[FILE_MAXDIR], libname[FILE_MAX_LIBEXTRA], relname[FILE_MAX];
  char *group, *name;
  int totfiles = 0;

  RNA_string_get(op->ptr, "filename", relname);
  RNA_string_get(op->ptr, "directory", root);

  BLI_join_dirfile(path, sizeof(path), root, relname);

  /* test if we have a valid data */
  if (!BLO_library_path_explode(path, libname, &group, &name)) {
    BKE_reportf(op->reports, RPT_ERROR, "'%s': not a library", path);
    return OPERATOR_CANCELLED;
  }
  else if (!group) {
    BKE_reportf(op->reports, RPT_ERROR, "'%s': nothing indicated", path);
    return OPERATOR_CANCELLED;
  }
  else if (BLI_path_cmp(BKE_main_blendfile_path(bmain), libname) == 0) {
    BKE_reportf(op->reports, RPT_ERROR, "'%s': cannot use current file as library", path);
    return OPERATOR_CANCELLED;
  }

  /* check if something is indicated for append/link */
  prop = RNA_struct_find_property(op->ptr, "files");
  if (prop) {
    totfiles = RNA_property_collection_length(op->ptr, prop);
    if (totfiles == 0) {
      if (!name) {
        BKE_reportf(op->reports, RPT_ERROR, "'%s': nothing indicated", path);
        return OPERATOR_CANCELLED;
      }
    }
  }
  else if (!name) {
    BKE_reportf(op->reports, RPT_ERROR, "'%s': nothing indicated", path);
    return OPERATOR_CANCELLED;
  }

  short flag = wm_link_append_flag(op);
  const bool do_append = (flag & FILE_LINK) == 0;

  /* sanity checks for flag */
  if (scene && scene->id.lib) {
    BKE_reportf(op->reports,
                RPT_WARNING,
                "Scene '%s' is linked, instantiation of objects & groups is disabled",
                scene->id.name + 2);
    flag &= ~FILE_GROUP_INSTANCE;
    scene = NULL;
  }

  /* We need to add nothing from BLO_LibLinkFlags to flag here. */

  /* from here down, no error returns */

  if (view_layer && RNA_boolean_get(op->ptr, "autoselect")) {
    BKE_view_layer_base_deselect_all(view_layer);
  }

  /* tag everything, all untagged data can be made local
   * its also generally useful to know what is new
   *
   * take extra care BKE_main_id_flag_all(bmain, LIB_TAG_PRE_EXISTING, false) is called after! */
  BKE_main_id_tag_all(bmain, LIB_TAG_PRE_EXISTING, true);

  /* We define our working data...
   * Note that here, each item 'uses' one library, and only one. */
  lapp_data = wm_link_append_data_new(flag);
  if (totfiles != 0) {
    GHash *libraries = BLI_ghash_new(BLI_ghashutil_strhash_p, BLI_ghashutil_strcmp, __func__);
    int lib_idx = 0;

    RNA_BEGIN (op->ptr, itemptr, "files") {
      RNA_string_get(&itemptr, "name", relname);

      BLI_join_dirfile(path, sizeof(path), root, relname);

      if (BLO_library_path_explode(path, libname, &group, &name)) {
        if (!wm_link_append_item_poll(NULL, path, group, name, do_append)) {
          continue;
        }

        if (!BLI_ghash_haskey(libraries, libname)) {
          BLI_ghash_insert(libraries, BLI_strdup(libname), POINTER_FROM_INT(lib_idx));
          lib_idx++;
          wm_link_append_data_library_add(lapp_data, libname);
        }
      }
    }
    RNA_END;

    RNA_BEGIN (op->ptr, itemptr, "files") {
      RNA_string_get(&itemptr, "name", relname);

      BLI_join_dirfile(path, sizeof(path), root, relname);

      if (BLO_library_path_explode(path, libname, &group, &name)) {
        WMLinkAppendDataItem *item;

        if (!wm_link_append_item_poll(op->reports, path, group, name, do_append)) {
          continue;
        }

        lib_idx = POINTER_AS_INT(BLI_ghash_lookup(libraries, libname));

        item = wm_link_append_data_item_add(
            lapp_data, name, BKE_idtype_idcode_from_name(group), NULL);
        BLI_BITMAP_ENABLE(item->libraries, lib_idx);
      }
    }
    RNA_END;

    BLI_ghash_free(libraries, MEM_freeN, NULL);
  }
  else {
    WMLinkAppendDataItem *item;

    wm_link_append_data_library_add(lapp_data, libname);
    item = wm_link_append_data_item_add(lapp_data, name, BKE_idtype_idcode_from_name(group), NULL);
    BLI_BITMAP_ENABLE(item->libraries, 0);
  }

  if (lapp_data->num_items == 0) {
    /* Early out in case there is nothing to link. */
    wm_link_append_data_free(lapp_data);
    /* Clear pre existing tag. */
    BKE_main_id_tag_all(bmain, LIB_TAG_PRE_EXISTING, false);
    return OPERATOR_CANCELLED;
  }

  /* XXX We'd need re-entrant locking on Main for this to work... */
  /* BKE_main_lock(bmain); */

  wm_link_do(lapp_data, op->reports, bmain, scene, view_layer, CTX_wm_view3d(C));

  /* BKE_main_unlock(bmain); */

  /* mark all library linked objects to be updated */
  BKE_main_lib_objects_recalc_all(bmain);
  IMB_colormanagement_check_file_config(bmain);

  /* append, rather than linking */
  if (do_append) {
    const bool set_fake = RNA_boolean_get(op->ptr, "set_fake");
    const bool use_recursive = RNA_boolean_get(op->ptr, "use_recursive");

    if (use_recursive) {
      BKE_library_make_local(bmain, NULL, NULL, true, set_fake);
    }
    else {
      LinkNode *itemlink;
      GSet *done_libraries = BLI_gset_new_ex(
          BLI_ghashutil_ptrhash, BLI_ghashutil_ptrcmp, __func__, lapp_data->num_libraries);

      for (itemlink = lapp_data->items.list; itemlink; itemlink = itemlink->next) {
        ID *new_id = ((WMLinkAppendDataItem *)(itemlink->link))->new_id;

        if (new_id && !BLI_gset_haskey(done_libraries, new_id->lib)) {
          BKE_library_make_local(bmain, new_id->lib, NULL, true, set_fake);
          BLI_gset_insert(done_libraries, new_id->lib);
        }
      }

      BLI_gset_free(done_libraries, NULL);
    }
  }

  wm_link_append_data_free(lapp_data);

  /* important we unset, otherwise these object wont
   * link into other scenes from this blend file */
  BKE_main_id_tag_all(bmain, LIB_TAG_PRE_EXISTING, false);

  /* TODO(sergey): Use proper flag for tagging here. */

  /* TODO (dalai): Temporary solution!
   * Ideally we only need to tag the new objects themselves, not the scene.
   * This way we'll avoid flush of collection properties
   * to all objects and limit update to the particular object only.
   * But afraid first we need to change collection evaluation in DEG
   * according to depsgraph manifesto. */
  DEG_id_tag_update(&scene->id, 0);

  /* recreate dependency graph to include new objects */
  DEG_relations_tag_update(bmain);

  /* XXX TODO: align G.lib with other directory storage (like last opened image etc...) */
  BLI_strncpy(G.lib, root, FILE_MAX);

  WM_event_add_notifier(C, NC_WINDOW, NULL);

  return OPERATOR_FINISHED;
}

static void wm_link_append_properties_common(wmOperatorType *ot, bool is_link)
{
  PropertyRNA *prop;

  /* better not save _any_ settings for this operator */
  /* properties */
  prop = RNA_def_boolean(
      ot->srna, "link", is_link, "Link", "Link the objects or data-blocks rather than appending");
  RNA_def_property_flag(prop, PROP_SKIP_SAVE | PROP_HIDDEN);
  prop = RNA_def_boolean(ot->srna, "autoselect", true, "Select", "Select new objects");
  RNA_def_property_flag(prop, PROP_SKIP_SAVE);
  prop = RNA_def_boolean(ot->srna,
                         "active_collection",
                         true,
                         "Active Collection",
                         "Put new objects on the active collection");
  RNA_def_property_flag(prop, PROP_SKIP_SAVE);
  prop = RNA_def_boolean(
      ot->srna,
      "instance_collections",
      is_link,
      "Instance Collections",
      "Create instances for collections, rather than adding them directly to the scene");
  RNA_def_property_flag(prop, PROP_SKIP_SAVE);
}

void WM_OT_link(wmOperatorType *ot)
{
  ot->name = "Link";
  ot->idname = "WM_OT_link";
  ot->description = "Link from a Library .blend file";

  ot->invoke = wm_link_append_invoke;
  ot->exec = wm_link_append_exec;
  ot->poll = wm_link_append_poll;

  ot->flag |= OPTYPE_UNDO;

  WM_operator_properties_filesel(ot,
                                 FILE_TYPE_FOLDER | FILE_TYPE_BLENDER | FILE_TYPE_BLENDERLIB,
                                 FILE_LOADLIB,
                                 FILE_OPENFILE,
                                 WM_FILESEL_FILEPATH | WM_FILESEL_DIRECTORY | WM_FILESEL_FILENAME |
                                     WM_FILESEL_RELPATH | WM_FILESEL_FILES | WM_FILESEL_SHOW_PROPS,
                                 FILE_DEFAULTDISPLAY,
                                 FILE_SORT_ALPHA);

  wm_link_append_properties_common(ot, true);
}

void WM_OT_append(wmOperatorType *ot)
{
  ot->name = "Append";
  ot->idname = "WM_OT_append";
  ot->description = "Append from a Library .blend file";

  ot->invoke = wm_link_append_invoke;
  ot->exec = wm_link_append_exec;
  ot->poll = wm_link_append_poll;

  ot->flag |= OPTYPE_UNDO;

  WM_operator_properties_filesel(ot,
                                 FILE_TYPE_FOLDER | FILE_TYPE_BLENDER | FILE_TYPE_BLENDERLIB,
                                 FILE_LOADLIB,
                                 FILE_OPENFILE,
                                 WM_FILESEL_FILEPATH | WM_FILESEL_DIRECTORY | WM_FILESEL_FILENAME |
                                     WM_FILESEL_FILES | WM_FILESEL_SHOW_PROPS,
                                 FILE_DEFAULTDISPLAY,
                                 FILE_SORT_ALPHA);

  wm_link_append_properties_common(ot, false);
  RNA_def_boolean(ot->srna,
                  "set_fake",
                  false,
                  "Fake User",
                  "Set Fake User for appended items (except Objects and Groups)");
  RNA_def_boolean(
      ot->srna,
      "use_recursive",
      true,
      "Localize All",
      "Localize all appended data, including those indirectly linked from other libraries");
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Append Single Data-Block & Return it
 *
 * Used for appending workspace from startup files.
 * \{ */

ID *WM_file_append_datablock(Main *bmain,
                             Scene *scene,
                             ViewLayer *view_layer,
                             View3D *v3d,
                             const char *filepath,
                             const short id_code,
                             const char *id_name)
{
  /* Tag everything so we can make local only the new datablock. */
  BKE_main_id_tag_all(bmain, LIB_TAG_PRE_EXISTING, true);

  /* Define working data, with just the one item we want to append. */
  WMLinkAppendData *lapp_data = wm_link_append_data_new(0);

  wm_link_append_data_library_add(lapp_data, filepath);
  WMLinkAppendDataItem *item = wm_link_append_data_item_add(lapp_data, id_name, id_code, NULL);
  BLI_BITMAP_ENABLE(item->libraries, 0);

  /* Link datablock. */
  wm_link_do(lapp_data, NULL, bmain, scene, view_layer, v3d);

  /* Get linked datablock and free working data. */
  ID *id = item->new_id;
  wm_link_append_data_free(lapp_data);

  /* Make datablock local. */
  BKE_library_make_local(bmain, NULL, NULL, true, false);

  /* Clear pre existing tag. */
  BKE_main_id_tag_all(bmain, LIB_TAG_PRE_EXISTING, false);

  return id;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Library Relocate Operator & Library Reload API
 * \{ */

static int wm_lib_relocate_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(event))
{
  Library *lib;
  char lib_name[MAX_NAME];

  RNA_string_get(op->ptr, "library", lib_name);
  lib = (Library *)BKE_libblock_find_name(CTX_data_main(C), ID_LI, lib_name);

  if (lib) {
    if (lib->parent) {
      BKE_reportf(op->reports,
                  RPT_ERROR_INVALID_INPUT,
                  "Cannot relocate indirectly linked library '%s'",
                  lib->filepath);
      return OPERATOR_CANCELLED;
    }
    RNA_string_set(op->ptr, "filepath", lib->filepath);

    WM_event_add_fileselect(C, op);

    return OPERATOR_RUNNING_MODAL;
  }

  return OPERATOR_CANCELLED;
}

static void lib_relocate_do(Main *bmain,
                            Library *library,
                            WMLinkAppendData *lapp_data,
                            ReportList *reports,
                            const bool do_reload)
{
  ListBase *lbarray[MAX_LIBARRAY];
  int lba_idx;

  LinkNode *itemlink;
  int item_idx;

  /* Remove all IDs to be reloaded from Main. */
  lba_idx = set_listbasepointers(bmain, lbarray);
  while (lba_idx--) {
    ID *id = lbarray[lba_idx]->first;
    const short idcode = id ? GS(id->name) : 0;

    if (!id || !BKE_idtype_idcode_is_linkable(idcode)) {
      /* No need to reload non-linkable datatypes,
       * those will get relinked with their 'users ID'. */
      continue;
    }

    for (; id; id = id->next) {
      if (id->lib == library) {
        WMLinkAppendDataItem *item;

        /* We remove it from current Main, and add it to items to link... */
        /* Note that non-linkable IDs (like e.g. shapekeys) are also explicitly linked here... */
        BLI_remlink(lbarray[lba_idx], id);
        item = wm_link_append_data_item_add(lapp_data, id->name + 2, idcode, id);
        BLI_bitmap_set_all(item->libraries, true, lapp_data->num_libraries);

#ifdef PRINT_DEBUG
        printf("\tdatablock to seek for: %s\n", id->name);
#endif
      }
    }
  }

  if (lapp_data->num_items == 0) {
    /* Early out in case there is nothing to do. */
    return;
  }

  BKE_main_id_tag_all(bmain, LIB_TAG_PRE_EXISTING, true);

  /* We do not want any instantiation here! */
  wm_link_do(lapp_data, reports, bmain, NULL, NULL, NULL);

  BKE_main_lock(bmain);

  /* We add back old id to bmain.
   * We need to do this in a first, separated loop, otherwise some of those may not be handled by
   * ID remapping, which means they would still reference old data to be deleted... */
  for (item_idx = 0, itemlink = lapp_data->items.list; itemlink;
       item_idx++, itemlink = itemlink->next) {
    WMLinkAppendDataItem *item = itemlink->link;
    ID *old_id = item->customdata;

    BLI_assert(old_id);
    BLI_addtail(which_libbase(bmain, GS(old_id->name)), old_id);
  }

  /* Note that in reload case, we also want to replace indirect usages. */
  const short remap_flags = ID_REMAP_SKIP_NEVER_NULL_USAGE |
                            ID_REMAP_NO_INDIRECT_PROXY_DATA_USAGE |
                            (do_reload ? 0 : ID_REMAP_SKIP_INDIRECT_USAGE);
  for (item_idx = 0, itemlink = lapp_data->items.list; itemlink;
       item_idx++, itemlink = itemlink->next) {
    WMLinkAppendDataItem *item = itemlink->link;
    ID *old_id = item->customdata;
    ID *new_id = item->new_id;

    BLI_assert(old_id);
    if (do_reload) {
      /* Since we asked for placeholders in case of missing IDs,
       * we expect to always get a valid one. */
      BLI_assert(new_id);
    }
    if (new_id) {
#ifdef PRINT_DEBUG
      printf("before remap of %s, old_id users: %d, new_id users: %d\n",
             old_id->name,
             old_id->us,
             new_id->us);
#endif
      BKE_libblock_remap_locked(bmain, old_id, new_id, remap_flags);

      if (old_id->flag & LIB_FAKEUSER) {
        id_fake_user_clear(old_id);
        id_fake_user_set(new_id);
      }

#ifdef PRINT_DEBUG
      printf("after remap of %s, old_id users: %d, new_id users: %d\n",
             old_id->name,
             old_id->us,
             new_id->us);
#endif

      /* In some cases, new_id might become direct link, remove parent of library in this case. */
      if (new_id->lib->parent && (new_id->tag & LIB_TAG_INDIRECT) == 0) {
        if (do_reload) {
          BLI_assert(0); /* Should not happen in 'pure' reload case... */
        }
        new_id->lib->parent = NULL;
      }
    }

    if (old_id->us > 0 && new_id && old_id->lib == new_id->lib) {
      /* Note that this *should* not happen - but better be safe than sorry in this area,
       * at least until we are 100% sure this cannot ever happen.
       * Also, we can safely assume names were unique so far,
       * so just replacing '.' by '~' should work,
       * but this does not totally rules out the possibility of name collision. */
      size_t len = strlen(old_id->name);
      size_t dot_pos;
      bool has_num = false;

      for (dot_pos = len; dot_pos--;) {
        char c = old_id->name[dot_pos];
        if (c == '.') {
          break;
        }
        else if (c < '0' || c > '9') {
          has_num = false;
          break;
        }
        has_num = true;
      }

      if (has_num) {
        old_id->name[dot_pos] = '~';
      }
      else {
        len = MIN2(len, MAX_ID_NAME - 7);
        BLI_strncpy(&old_id->name[len], "~000", 7);
      }

      id_sort_by_name(which_libbase(bmain, GS(old_id->name)), old_id, NULL);

      BKE_reportf(
          reports,
          RPT_WARNING,
          "Lib Reload: Replacing all references to old data-block '%s' by reloaded one failed, "
          "old one (%d remaining users) had to be kept and was renamed to '%s'",
          new_id->name,
          old_id->us,
          old_id->name);
    }
  }

  BKE_main_unlock(bmain);

  for (item_idx = 0, itemlink = lapp_data->items.list; itemlink;
       item_idx++, itemlink = itemlink->next) {
    WMLinkAppendDataItem *item = itemlink->link;
    ID *old_id = item->customdata;

    if (old_id->us == 0) {
      BKE_id_free(bmain, old_id);
    }
  }

  /* Some datablocks can get reloaded/replaced 'silently' because they are not linkable
   * (shape keys e.g.), so we need another loop here to clear old ones if possible. */
  lba_idx = set_listbasepointers(bmain, lbarray);
  while (lba_idx--) {
    ID *id, *id_next;
    for (id = lbarray[lba_idx]->first; id; id = id_next) {
      id_next = id->next;
      /* XXX That check may be a bit to generic/permissive? */
      if (id->lib && (id->flag & LIB_TAG_PRE_EXISTING) && id->us == 0) {
        BKE_id_free(bmain, id);
      }
    }
  }

  /* Get rid of no more used libraries... */
  BKE_main_id_tag_idcode(bmain, ID_LI, LIB_TAG_DOIT, true);
  lba_idx = set_listbasepointers(bmain, lbarray);
  while (lba_idx--) {
    ID *id;
    for (id = lbarray[lba_idx]->first; id; id = id->next) {
      if (id->lib) {
        id->lib->id.tag &= ~LIB_TAG_DOIT;
      }
    }
  }
  Library *lib, *lib_next;
  for (lib = which_libbase(bmain, ID_LI)->first; lib; lib = lib_next) {
    lib_next = lib->id.next;
    if (lib->id.tag & LIB_TAG_DOIT) {
      id_us_clear_real(&lib->id);
      if (lib->id.us == 0) {
        BKE_id_free(bmain, (ID *)lib);
      }
    }
  }

  BKE_main_lib_objects_recalc_all(bmain);
  IMB_colormanagement_check_file_config(bmain);

  /* important we unset, otherwise these object wont
   * link into other scenes from this blend file */
  BKE_main_id_tag_all(bmain, LIB_TAG_PRE_EXISTING, false);

  /* recreate dependency graph to include new objects */
  DEG_relations_tag_update(bmain);
}

void WM_lib_reload(Library *lib, bContext *C, ReportList *reports)
{
  if (!BLO_has_bfile_extension(lib->filepath)) {
    BKE_reportf(reports, RPT_ERROR, "'%s' is not a valid library filepath", lib->filepath);
    return;
  }

  if (!BLI_exists(lib->filepath)) {
    BKE_reportf(reports,
                RPT_ERROR,
                "Trying to reload library '%s' from invalid path '%s'",
                lib->id.name,
                lib->filepath);
    return;
  }

  WMLinkAppendData *lapp_data = wm_link_append_data_new(BLO_LIBLINK_USE_PLACEHOLDERS |
                                                        BLO_LIBLINK_FORCE_INDIRECT);

  wm_link_append_data_library_add(lapp_data, lib->filepath);

  lib_relocate_do(CTX_data_main(C), lib, lapp_data, reports, true);

  wm_link_append_data_free(lapp_data);

  WM_event_add_notifier(C, NC_WINDOW, NULL);
}

static int wm_lib_relocate_exec_do(bContext *C, wmOperator *op, bool do_reload)
{
  Library *lib;
  char lib_name[MAX_NAME];

  RNA_string_get(op->ptr, "library", lib_name);
  lib = (Library *)BKE_libblock_find_name(CTX_data_main(C), ID_LI, lib_name);

  if (lib) {
    Main *bmain = CTX_data_main(C);
    PropertyRNA *prop;
    WMLinkAppendData *lapp_data;

    char path[FILE_MAX], root[FILE_MAXDIR], libname[FILE_MAX], relname[FILE_MAX];
    short flag = 0;

    if (RNA_boolean_get(op->ptr, "relative_path")) {
      flag |= FILE_RELPATH;
    }

    if (lib->parent && !do_reload) {
      BKE_reportf(op->reports,
                  RPT_ERROR_INVALID_INPUT,
                  "Cannot relocate indirectly linked library '%s'",
                  lib->filepath);
      return OPERATOR_CANCELLED;
    }

    RNA_string_get(op->ptr, "directory", root);
    RNA_string_get(op->ptr, "filename", libname);

    if (!BLO_has_bfile_extension(libname)) {
      BKE_report(op->reports, RPT_ERROR, "Not a library");
      return OPERATOR_CANCELLED;
    }

    BLI_join_dirfile(path, sizeof(path), root, libname);

    if (!BLI_exists(path)) {
      BKE_reportf(op->reports,
                  RPT_ERROR_INVALID_INPUT,
                  "Trying to reload or relocate library '%s' to invalid path '%s'",
                  lib->id.name,
                  path);
      return OPERATOR_CANCELLED;
    }

    if (BLI_path_cmp(lib->filepath, path) == 0) {
#ifdef PRINT_DEBUG
      printf("We are supposed to reload '%s' lib (%d)...\n", lib->filepath, lib->id.us);
#endif

      do_reload = true;

      lapp_data = wm_link_append_data_new(flag);
      wm_link_append_data_library_add(lapp_data, path);
    }
    else {
      int totfiles = 0;

#ifdef PRINT_DEBUG
      printf("We are supposed to relocate '%s' lib to new '%s' one...\n", lib->filepath, libname);
#endif

      /* Check if something is indicated for relocate. */
      prop = RNA_struct_find_property(op->ptr, "files");
      if (prop) {
        totfiles = RNA_property_collection_length(op->ptr, prop);
        if (totfiles == 0) {
          if (!libname[0]) {
            BKE_report(op->reports, RPT_ERROR, "Nothing indicated");
            return OPERATOR_CANCELLED;
          }
        }
      }

      lapp_data = wm_link_append_data_new(flag);

      if (totfiles) {
        RNA_BEGIN (op->ptr, itemptr, "files") {
          RNA_string_get(&itemptr, "name", relname);

          BLI_join_dirfile(path, sizeof(path), root, relname);

          if (BLI_path_cmp(path, lib->filepath) == 0 || !BLO_has_bfile_extension(relname)) {
            continue;
          }

#ifdef PRINT_DEBUG
          printf("\t candidate new lib to reload datablocks from: %s\n", path);
#endif
          wm_link_append_data_library_add(lapp_data, path);
        }
        RNA_END;
      }
      else {
#ifdef PRINT_DEBUG
        printf("\t candidate new lib to reload datablocks from: %s\n", path);
#endif
        wm_link_append_data_library_add(lapp_data, path);
      }
    }

    if (do_reload) {
      lapp_data->flag |= BLO_LIBLINK_USE_PLACEHOLDERS | BLO_LIBLINK_FORCE_INDIRECT;
    }

    lib_relocate_do(bmain, lib, lapp_data, op->reports, do_reload);

    wm_link_append_data_free(lapp_data);

    /* XXX TODO: align G.lib with other directory storage (like last opened image etc...) */
    BLI_strncpy(G.lib, root, FILE_MAX);

    WM_event_add_notifier(C, NC_WINDOW, NULL);

    return OPERATOR_FINISHED;
  }

  return OPERATOR_CANCELLED;
}

static int wm_lib_relocate_exec(bContext *C, wmOperator *op)
{
  return wm_lib_relocate_exec_do(C, op, false);
}

void WM_OT_lib_relocate(wmOperatorType *ot)
{
  PropertyRNA *prop;

  ot->name = "Relocate Library";
  ot->idname = "WM_OT_lib_relocate";
  ot->description = "Relocate the given library to one or several others";

  ot->invoke = wm_lib_relocate_invoke;
  ot->exec = wm_lib_relocate_exec;

  ot->flag |= OPTYPE_UNDO;

  prop = RNA_def_string(ot->srna, "library", NULL, MAX_NAME, "Library", "Library to relocate");
  RNA_def_property_flag(prop, PROP_HIDDEN);

  WM_operator_properties_filesel(ot,
                                 FILE_TYPE_FOLDER | FILE_TYPE_BLENDER,
                                 FILE_BLENDER,
                                 FILE_OPENFILE,
                                 WM_FILESEL_FILEPATH | WM_FILESEL_DIRECTORY | WM_FILESEL_FILENAME |
                                     WM_FILESEL_FILES | WM_FILESEL_RELPATH,
                                 FILE_DEFAULTDISPLAY,
                                 FILE_SORT_ALPHA);
}

static int wm_lib_reload_exec(bContext *C, wmOperator *op)
{
  return wm_lib_relocate_exec_do(C, op, true);
}

void WM_OT_lib_reload(wmOperatorType *ot)
{
  PropertyRNA *prop;

  ot->name = "Reload Library";
  ot->idname = "WM_OT_lib_reload";
  ot->description = "Reload the given library";

  ot->exec = wm_lib_reload_exec;

  ot->flag |= OPTYPE_UNDO;

  prop = RNA_def_string(ot->srna, "library", NULL, MAX_NAME, "Library", "Library to reload");
  RNA_def_property_flag(prop, PROP_HIDDEN);

  WM_operator_properties_filesel(ot,
                                 FILE_TYPE_FOLDER | FILE_TYPE_BLENDER,
                                 FILE_BLENDER,
                                 FILE_OPENFILE,
                                 WM_FILESEL_FILEPATH | WM_FILESEL_DIRECTORY | WM_FILESEL_FILENAME |
                                     WM_FILESEL_RELPATH,
                                 FILE_DEFAULTDISPLAY,
                                 FILE_SORT_ALPHA);
}

/** \} */