blender-archive/source/blender/editors/asset/intern/asset_indexer.cc

/* SPDX-License-Identifier: GPL-2.0-or-later */

/** \file
 * \ingroup edasset
 */

#include <ctime>
#include <fstream>
#include <iomanip>
#include <optional>

#include "ED_asset_indexer.h"

#include "DNA_asset_types.h"
#include "DNA_userdef_types.h"

#include "BLI_fileops.h"
#include "BLI_hash.hh"
#include "BLI_linklist.h"
#include "BLI_path_util.h"
#include "BLI_serialize.hh"
#include "BLI_set.hh"
#include "BLI_string_ref.hh"
#include "BLI_uuid.h"

#include "AS_asset_catalog.hh"
#include "BKE_appdir.h"
#include "BKE_asset.h"
#include "BKE_idprop.hh"

#include "CLG_log.h"

static CLG_LogRef LOG = {"ed.asset"};

namespace blender::ed::asset::index {

using namespace blender::asset_system;
using namespace blender::io::serialize;
using namespace blender::bke::idprop;

/**
 * \brief Indexer for asset libraries.
 *
 * Indexes are stored per input file. Each index can contain zero to multiple asset entries.
 * The indexes are grouped together per asset library. They are stored in
 * #BKE_appdir_folder_caches +
 * /asset-library-indices/<asset-library-hash>/<asset-index-hash>_<asset_file>.index.json.
 *
 * The structure of an index file is
 * \code
 * {
 *   "version": <file version number>,
 *   "entries": [{
 *     "name": "<asset name>",
 *     "catalog_id": "<catalog_id>",
 *     "catalog_name": "<catalog_name>",
 *     "description": "<description>",
 *     "author": "<author>",
 *     "tags": ["<tag>"],
 *     "properties": [..]
 *   }]
 * }
 * \endcode
 *
 * NOTE: entries, author, description, tags and properties are optional attributes.
 *
 * NOTE: File browser uses name and idcode separate. Inside the index they are joined together like
 * #ID.name.
 * NOTE: File browser group name isn't stored in the index as it is a translatable name.
 */
constexpr StringRef ATTRIBUTE_VERSION("version");
constexpr StringRef ATTRIBUTE_ENTRIES("entries");
constexpr StringRef ATTRIBUTE_ENTRIES_NAME("name");
constexpr StringRef ATTRIBUTE_ENTRIES_CATALOG_ID("catalog_id");
constexpr StringRef ATTRIBUTE_ENTRIES_CATALOG_NAME("catalog_name");
constexpr StringRef ATTRIBUTE_ENTRIES_DESCRIPTION("description");
constexpr StringRef ATTRIBUTE_ENTRIES_AUTHOR("author");
constexpr StringRef ATTRIBUTE_ENTRIES_TAGS("tags");
constexpr StringRef ATTRIBUTE_ENTRIES_PROPERTIES("properties");

/** Abstract class for #BlendFile and #AssetIndexFile. */
class AbstractFile {
 public:
  virtual ~AbstractFile() = default;

  virtual const char *get_file_path() const = 0;

  bool exists() const
  {
    return BLI_exists(get_file_path());
  }

  size_t get_file_size() const
  {
    return BLI_file_size(get_file_path());
  }
};

/**
 * \brief Reference to a blend file that can be indexed.
 */
class BlendFile : public AbstractFile {
  StringRefNull file_path_;

 public:
  BlendFile(StringRefNull file_path) : file_path_(file_path)
  {
  }

  uint64_t hash() const
  {
    DefaultHash<StringRefNull> hasher;
    return hasher(file_path_);
  }

  std::string get_filename() const
  {
    char filename[FILE_MAX];
    BLI_split_file_part(get_file_path(), filename, sizeof(filename));
    return std::string(filename);
  }

  const char *get_file_path() const override
  {
    return file_path_.c_str();
  }
};

/**
 * \brief Single entry inside a #AssetIndexFile for reading.
 */
struct AssetEntryReader {
 private:
  /**
   * \brief Lookup table containing the elements of the entry.
   */
  DictionaryValue::Lookup lookup;

  StringRefNull get_name_with_idcode() const
  {
    return lookup.lookup(ATTRIBUTE_ENTRIES_NAME)->as_string_value()->value();
  }

 public:
  AssetEntryReader(const DictionaryValue &entry) : lookup(entry.create_lookup())
  {
  }

  ID_Type get_idcode() const
  {
    const StringRefNull name_with_idcode = get_name_with_idcode();
    return GS(name_with_idcode.c_str());
  }

  StringRef get_name() const
  {
    const StringRefNull name_with_idcode = get_name_with_idcode();
    return name_with_idcode.substr(2);
  }

  bool has_description() const
  {
    return lookup.contains(ATTRIBUTE_ENTRIES_DESCRIPTION);
  }

  StringRefNull get_description() const
  {
    return lookup.lookup(ATTRIBUTE_ENTRIES_DESCRIPTION)->as_string_value()->value();
  }

  bool has_author() const
  {
    return lookup.contains(ATTRIBUTE_ENTRIES_AUTHOR);
  }

  StringRefNull get_author() const
  {
    return lookup.lookup(ATTRIBUTE_ENTRIES_AUTHOR)->as_string_value()->value();
  }

  StringRefNull get_catalog_name() const
  {
    return lookup.lookup(ATTRIBUTE_ENTRIES_CATALOG_NAME)->as_string_value()->value();
  }

  CatalogID get_catalog_id() const
  {
    const std::string &catalog_id =
        lookup.lookup(ATTRIBUTE_ENTRIES_CATALOG_ID)->as_string_value()->value();
    CatalogID catalog_uuid(catalog_id);
    return catalog_uuid;
  }

  void add_tags_to_meta_data(AssetMetaData *asset_data) const
  {
    const DictionaryValue::LookupValue *value_ptr = lookup.lookup_ptr(ATTRIBUTE_ENTRIES_TAGS);
    if (value_ptr == nullptr) {
      return;
    }

    const ArrayValue *array_value = (*value_ptr)->as_array_value();
    const ArrayValue::Items &elements = array_value->elements();
    for (const ArrayValue::Item &item : elements) {
      const StringRefNull tag_name = item->as_string_value()->value();
      BKE_asset_metadata_tag_add(asset_data, tag_name.c_str());
    }
  }

  void add_properties_to_meta_data(AssetMetaData *asset_data) const
  {
    BLI_assert(asset_data->properties == nullptr);
    const DictionaryValue::LookupValue *value_ptr = lookup.lookup_ptr(
        ATTRIBUTE_ENTRIES_PROPERTIES);
    if (value_ptr == nullptr) {
      return;
    }

    const Value &value = *(value_ptr->get());
    IDProperty *properties = convert_from_serialize_value(value);
    asset_data->properties = properties;
  }
};

struct AssetEntryWriter {
 private:
  DictionaryValue::Items &attributes;

 public:
  AssetEntryWriter(DictionaryValue &entry) : attributes(entry.elements())
  {
  }

  /**
   * \brief add id + name to the attributes.
   *
   * NOTE: id and name are encoded like #ID.name
   */
  void add_id_name(const short idcode, const StringRefNull name)
  {
    char idcode_prefix[2];
    /* Similar to `BKE_libblock_alloc`. */
    *((short *)idcode_prefix) = idcode;
    std::string name_with_idcode = std::string(idcode_prefix, sizeof(idcode_prefix)) + name;

    attributes.append_as(std::pair(ATTRIBUTE_ENTRIES_NAME, new StringValue(name_with_idcode)));
  }

  void add_catalog_id(const CatalogID &catalog_id)
  {
    char catalog_id_str[UUID_STRING_LEN];
    BLI_uuid_format(catalog_id_str, catalog_id);
    attributes.append_as(std::pair(ATTRIBUTE_ENTRIES_CATALOG_ID, new StringValue(catalog_id_str)));
  }

  void add_catalog_name(const StringRefNull catalog_name)
  {
    attributes.append_as(std::pair(ATTRIBUTE_ENTRIES_CATALOG_NAME, new StringValue(catalog_name)));
  }

  void add_description(const StringRefNull description)
  {
    attributes.append_as(std::pair(ATTRIBUTE_ENTRIES_DESCRIPTION, new StringValue(description)));
  }

  void add_author(const StringRefNull author)
  {
    attributes.append_as(std::pair(ATTRIBUTE_ENTRIES_AUTHOR, new StringValue(author)));
  }

  void add_tags(const ListBase /* AssetTag */ *asset_tags)
  {
    ArrayValue *tags = new ArrayValue();
    attributes.append_as(std::pair(ATTRIBUTE_ENTRIES_TAGS, tags));
    ArrayValue::Items &tag_items = tags->elements();

    LISTBASE_FOREACH (AssetTag *, tag, asset_tags) {
      tag_items.append_as(new StringValue(tag->name));
    }
  }

  void add_properties(const IDProperty *properties)
  {
    std::unique_ptr<Value> value = convert_to_serialize_values(properties);
    if (value == nullptr) {
      return;
    }
    attributes.append_as(std::pair(ATTRIBUTE_ENTRIES_PROPERTIES, value.release()));
  }
};

static void init_value_from_file_indexer_entry(AssetEntryWriter &result,
                                               const FileIndexerEntry *indexer_entry)
{
  const BLODataBlockInfo &datablock_info = indexer_entry->datablock_info;

  result.add_id_name(indexer_entry->idcode, datablock_info.name);

  const AssetMetaData &asset_data = *datablock_info.asset_data;
  result.add_catalog_id(asset_data.catalog_id);
  result.add_catalog_name(asset_data.catalog_simple_name);

  if (asset_data.description != nullptr) {
    result.add_description(asset_data.description);
  }
  if (asset_data.author != nullptr) {
    result.add_author(asset_data.author);
  }

  if (!BLI_listbase_is_empty(&asset_data.tags)) {
    result.add_tags(&asset_data.tags);
  }

  if (asset_data.properties != nullptr) {
    result.add_properties(asset_data.properties);
  }

  /* TODO: asset_data.IDProperties */
}

static void init_value_from_file_indexer_entries(DictionaryValue &result,
                                                 const FileIndexerEntries &indexer_entries)
{
  ArrayValue *entries = new ArrayValue();
  ArrayValue::Items &items = entries->elements();

  for (LinkNode *ln = indexer_entries.entries; ln; ln = ln->next) {
    const FileIndexerEntry *indexer_entry = static_cast<const FileIndexerEntry *>(ln->link);
    /* We also get non asset types (brushes, work-spaces), when browsing using the asset browser.
     */
    if (indexer_entry->datablock_info.asset_data == nullptr) {
      continue;
    }
    DictionaryValue *entry_value = new DictionaryValue();
    AssetEntryWriter entry(*entry_value);
    init_value_from_file_indexer_entry(entry, indexer_entry);
    items.append_as(entry_value);
  }

  /* When no entries to index, we should not store the entries attribute as this would make the
   * size bigger than the #MIN_FILE_SIZE_WITH_ENTRIES. */
  if (items.is_empty()) {
    delete entries;
    return;
  }

  DictionaryValue::Items &attributes = result.elements();
  attributes.append_as(std::pair(ATTRIBUTE_ENTRIES, entries));
}

static void init_indexer_entry_from_value(FileIndexerEntry &indexer_entry,
                                          const AssetEntryReader &entry)
{
  indexer_entry.idcode = entry.get_idcode();

  const std::string name = entry.get_name();
  BLI_strncpy(
      indexer_entry.datablock_info.name, name.c_str(), sizeof(indexer_entry.datablock_info.name));

  AssetMetaData *asset_data = BKE_asset_metadata_create();
  indexer_entry.datablock_info.asset_data = asset_data;
  indexer_entry.datablock_info.free_asset_data = true;

  if (entry.has_description()) {
    const StringRefNull description = entry.get_description();
    char *description_c_str = static_cast<char *>(MEM_mallocN(description.size() + 1, __func__));
    BLI_strncpy(description_c_str, description.c_str(), description.size() + 1);
    asset_data->description = description_c_str;
  }
  if (entry.has_author()) {
    const StringRefNull author = entry.get_author();
    char *author_c_str = static_cast<char *>(MEM_mallocN(author.size() + 1, __func__));
    BLI_strncpy(author_c_str, author.c_str(), author.size() + 1);
    asset_data->author = author_c_str;
  }

  const StringRefNull catalog_name = entry.get_catalog_name();
  BLI_strncpy(asset_data->catalog_simple_name,
              catalog_name.c_str(),
              sizeof(asset_data->catalog_simple_name));

  asset_data->catalog_id = entry.get_catalog_id();

  entry.add_tags_to_meta_data(asset_data);
  entry.add_properties_to_meta_data(asset_data);
}

static int init_indexer_entries_from_value(FileIndexerEntries &indexer_entries,
                                           const DictionaryValue &value)
{
  const DictionaryValue::Lookup attributes = value.create_lookup();
  const DictionaryValue::LookupValue *entries_value = attributes.lookup_ptr(ATTRIBUTE_ENTRIES);
  BLI_assert(entries_value != nullptr);

  if (entries_value == nullptr) {
    return 0;
  }

  int num_entries_read = 0;
  const ArrayValue::Items elements = (*entries_value)->as_array_value()->elements();
  for (ArrayValue::Item element : elements) {
    const AssetEntryReader asset_entry(*element->as_dictionary_value());

    FileIndexerEntry *entry = static_cast<FileIndexerEntry *>(
        MEM_callocN(sizeof(FileIndexerEntry), __func__));
    init_indexer_entry_from_value(*entry, asset_entry);

    BLI_linklist_prepend(&indexer_entries.entries, entry);
    num_entries_read += 1;
  }

  return num_entries_read;
}

/**
 * \brief References the asset library directory.
 *
 * The #AssetLibraryIndex instance collects file indices that are existing before the actual
 * reading/updating starts. This way, the reading/updating can tag pre-existing files as used when
 * they are still needed. Remaining ones (indices that are not tagged as used) can be removed once
 * reading finishes.
 */
struct AssetLibraryIndex {
  struct PreexistingFileIndexInfo {
    bool is_used = false;
  };

  /**
   * File indices that are existing already before reading/updating performs changes. The key is
   * the absolute path. The value can store information like if the index is known to be used.
   *
   * Note that when deleting a file index (#delete_index_file()), it's also removed from here,
   * since it doesn't exist and isn't relevant to keep track of anymore.
   */
  Map<std::string /*path*/, PreexistingFileIndexInfo> preexisting_file_indices;

  /**
   * \brief Absolute path where the indices of `library` are stored.
   *
   * \NOTE: includes trailing directory separator.
   */
  std::string indices_base_path;

  std::string library_path;

 public:
  AssetLibraryIndex(const StringRef library_path) : library_path(library_path)
  {
    init_indices_base_path();
  }

  uint64_t hash() const
  {
    DefaultHash<StringRefNull> hasher;
    return hasher(get_library_file_path());
  }

  StringRefNull get_library_file_path() const
  {
    return library_path;
  }

  /**
   * \brief Initializes #AssetLibraryIndex.indices_base_path.
   *
   * `BKE_appdir_folder_caches/asset-library-indices/<asset-library-name-hash>/`
   */
  void init_indices_base_path()
  {
    char index_path[FILE_MAX];
    BKE_appdir_folder_caches(index_path, sizeof(index_path));

    BLI_path_append(index_path, sizeof(index_path), "asset-library-indices");

    std::stringstream ss;
    ss << std::setfill('0') << std::setw(16) << std::hex << hash() << "/";
    BLI_path_append(index_path, sizeof(index_path), ss.str().c_str());

    indices_base_path = std::string(index_path);
  }

  /**
   * \return absolute path to the index file of the given `asset_file`.
   *
   * `{indices_base_path}/{asset-file_hash}_{asset-file-filename}.index.json`.
   */
  std::string index_file_path(const BlendFile &asset_file) const
  {
    std::stringstream ss;
    ss << indices_base_path;
    ss << std::setfill('0') << std::setw(16) << std::hex << asset_file.hash() << "_"
       << asset_file.get_filename() << ".index.json";
    return ss.str();
  }

  /**
   * Check for pre-existing index files to be able to track what is still used and what can be
   * removed. See #AssetLibraryIndex::preexisting_file_indices.
   */
  void collect_preexisting_file_indices()
  {
    const char *index_path = indices_base_path.c_str();
    if (!BLI_is_dir(index_path)) {
      return;
    }
    struct direntry *dir_entries = nullptr;
    const int dir_entries_num = BLI_filelist_dir_contents(index_path, &dir_entries);
    for (int i = 0; i < dir_entries_num; i++) {
      struct direntry *entry = &dir_entries[i];
      if (BLI_str_endswith(entry->relname, ".index.json")) {
        preexisting_file_indices.add_as(std::string(entry->path));
      }
    }

    BLI_filelist_free(dir_entries, dir_entries_num);
  }

  void mark_as_used(const std::string &filename)
  {
    PreexistingFileIndexInfo *preexisting = preexisting_file_indices.lookup_ptr(filename);
    if (preexisting) {
      preexisting->is_used = true;
    }
  }

  /**
   * Removes the file index from disk and #preexisting_file_indices (invalidating its iterators, so
   * don't call while iterating).
   * \return true if deletion was successful.
   */
  bool delete_file_index(const std::string &filename)
  {
    if (BLI_delete(filename.c_str(), false, false) == 0) {
      preexisting_file_indices.remove(filename);
      return true;
    }
    return false;
  }

  /**
   * A bug was creating empty index files for a while (see D16665). Remove empty index files from
   * this period, so they are regenerated.
   */
  /* Implemented further below. */
  int remove_broken_index_files();

  int remove_unused_index_files()
  {
    int num_files_deleted = 0;

    Set<StringRef> files_to_remove;

    for (auto preexisting_index : preexisting_file_indices.items()) {
      if (preexisting_index.value.is_used) {
        continue;
      }

      const std::string &file_path = preexisting_index.key;
      CLOG_INFO(&LOG, 2, "Remove unused index file [%s].", file_path.c_str());
      files_to_remove.add(preexisting_index.key);
    }

    for (StringRef file_to_remove : files_to_remove) {
      if (delete_file_index(file_to_remove)) {
        num_files_deleted++;
      }
    }

    return num_files_deleted;
  }
};

/**
 * Instance of this class represents the contents of an asset index file.
 *
 * \code
 * {
 *    "version": {version},
 *    "entries": ...
 * }
 * \endcode
 */
struct AssetIndex {
  /**
   * \brief Version to store in new index files.
   *
   * Versions are written to each index file. When reading the version is checked against
   * `CURRENT_VERSION` to make sure we can use the index. Developer should increase
   * `CURRENT_VERSION` when changes are made to the structure of the stored index.
   */
  static const int CURRENT_VERSION = 1;

  /**
   * Version number to use when version couldn't be read from an index file.
   */
  const int UNKNOWN_VERSION = -1;

  /**
   * `blender::io::serialize::Value` representing the contents of an index file.
   *
   * Value is used over #DictionaryValue as the contents of the index could be corrupted and
   * doesn't represent an object. In case corrupted files are detected the `get_version` would
   * return `UNKNOWN_VERSION`.
   */
  std::unique_ptr<Value> contents;

  /**
   * Constructor for when creating/updating an asset index file.
   * #AssetIndex.contents are filled from the given \p indexer_entries.
   */
  AssetIndex(const FileIndexerEntries &indexer_entries)
  {
    std::unique_ptr<DictionaryValue> root = std::make_unique<DictionaryValue>();
    DictionaryValue::Items &root_attributes = root->elements();
    root_attributes.append_as(std::pair(ATTRIBUTE_VERSION, new IntValue(CURRENT_VERSION)));
    init_value_from_file_indexer_entries(*root, indexer_entries);

    contents = std::move(root);
  }

  /**
   * Constructor when reading an asset index file.
   * #AssetIndex.contents are read from the given \p value.
   */
  AssetIndex(std::unique_ptr<Value> &value) : contents(std::move(value))
  {
  }

  int get_version() const
  {
    const DictionaryValue *root = contents->as_dictionary_value();
    if (root == nullptr) {
      return UNKNOWN_VERSION;
    }
    const DictionaryValue::Lookup attributes = root->create_lookup();
    const DictionaryValue::LookupValue *version_value = attributes.lookup_ptr(ATTRIBUTE_VERSION);
    if (version_value == nullptr) {
      return UNKNOWN_VERSION;
    }
    return (*version_value)->as_int_value()->value();
  }

  bool is_latest_version() const
  {
    return get_version() == CURRENT_VERSION;
  }

  /**
   * Extract the contents of this index into the given \p indexer_entries.
   *
   * \return The number of entries read from the given entries.
   */
  int extract_into(FileIndexerEntries &indexer_entries) const
  {
    const DictionaryValue *root = contents->as_dictionary_value();
    const int num_entries_read = init_indexer_entries_from_value(indexer_entries, *root);
    return num_entries_read;
  }
};

class AssetIndexFile : public AbstractFile {
 public:
  AssetLibraryIndex &library_index;
  /**
   * Asset index files with a size smaller than this attribute would be considered to not contain
   * any entries.
   */
  const size_t MIN_FILE_SIZE_WITH_ENTRIES = 32;
  std::string filename;

  AssetIndexFile(AssetLibraryIndex &library_index, StringRef index_file_path)
      : library_index(library_index), filename(index_file_path)
  {
  }

  AssetIndexFile(AssetLibraryIndex &library_index, BlendFile &asset_filename)
      : AssetIndexFile(library_index, library_index.index_file_path(asset_filename))
  {
  }

  void mark_as_used()
  {
    library_index.mark_as_used(filename);
  }

  const char *get_file_path() const override
  {
    return filename.c_str();
  }

  /**
   * Returns whether the index file is older than the given asset file.
   */
  bool is_older_than(BlendFile &asset_file) const
  {
    return BLI_file_older(get_file_path(), asset_file.get_file_path());
  }

  /**
   * Check whether the index file contains entries without opening the file.
   */
  bool constains_entries() const
  {
    const size_t file_size = get_file_size();
    return file_size >= MIN_FILE_SIZE_WITH_ENTRIES;
  }

  std::unique_ptr<AssetIndex> read_contents() const
  {
    JsonFormatter formatter;
    std::ifstream is;
    is.open(filename);
    std::unique_ptr<Value> read_data = formatter.deserialize(is);
    is.close();

    return std::make_unique<AssetIndex>(read_data);
  }

  bool ensure_parent_path_exists() const
  {
    /* `BLI_make_existing_file` only ensures parent path, otherwise than expected from the name of
     * the function. */
    return BLI_make_existing_file(get_file_path());
  }

  void write_contents(AssetIndex &content)
  {
    JsonFormatter formatter;
    if (!ensure_parent_path_exists()) {
      CLOG_ERROR(&LOG, "Index not created: couldn't create folder [%s].", get_file_path());
      return;
    }

    std::ofstream os;
    os.open(filename, std::ios::out | std::ios::trunc);
    formatter.serialize(os, *content.contents);
    os.close();
  }
};

/* TODO(Julian): remove this after a short while. Just necessary for people who've been using alpha
 * builds from a certain period. */
int AssetLibraryIndex::remove_broken_index_files()
{
  Set<StringRef> files_to_remove;

  preexisting_file_indices.foreach_item(
      [&](const std::string &index_path, const PreexistingFileIndexInfo &) {
        AssetIndexFile index_file(*this, index_path);

        /* Bug was causing empty index files, so non-empty ones can be skipped. */
        if (index_file.constains_entries()) {
          return;
        }

        /* Use the file modification time stamp to attempt to remove empty index files from a
         * certain period (when the bug was in there). Starting from a day before the bug was
         * introduced until a day after the fix should be enough to mitigate possible local time
         * zone issues. */

        std::tm tm_from{};
        tm_from.tm_year = 2022 - 1900; /* 2022 */
        tm_from.tm_mon = 11 - 1;       /* November */
        tm_from.tm_mday = 8;           /* Day before bug was introduced. */
        std::tm tm_to{};
        tm_from.tm_year = 2022 - 1900; /* 2022 */
        tm_from.tm_mon = 12 - 1;       /* December */
        tm_from.tm_mday = 3;           /* Day after fix. */
        std::time_t timestamp_from = std::mktime(&tm_from);
        std::time_t timestamp_to = std::mktime(&tm_to);
        BLI_stat_t stat = {};
        if (BLI_stat(index_file.get_file_path(), &stat) == -1) {
          return;
        }
        if (IN_RANGE(stat.st_mtime, timestamp_from, timestamp_to)) {
          CLOG_INFO(&LOG, 2, "Remove potentially broken index file [%s].", index_path.c_str());
          files_to_remove.add(index_path);
        }
      });

  int num_files_deleted = 0;
  for (StringRef files_to_remove : files_to_remove) {
    if (delete_file_index(files_to_remove)) {
      num_files_deleted++;
    }
  }

  return num_files_deleted;
}

static eFileIndexerResult read_index(const char *filename,
                                     FileIndexerEntries *entries,
                                     int *r_read_entries_len,
                                     void *user_data)
{
  AssetLibraryIndex &library_index = *static_cast<AssetLibraryIndex *>(user_data);
  BlendFile asset_file(filename);
  AssetIndexFile asset_index_file(library_index, asset_file);

  if (!asset_index_file.exists()) {
    return FILE_INDEXER_NEEDS_UPDATE;
  }

  /* Mark index as used, even when it will be recreated. When not done it would remove the index
   * when the indexing has finished (see `AssetLibraryIndex.remove_unused_index_files`), thereby
   * removing the newly created index.
   */
  asset_index_file.mark_as_used();

  if (asset_index_file.is_older_than(asset_file)) {
    CLOG_INFO(
        &LOG,
        3,
        "Asset index file [%s] needs to be refreshed as it is older than the asset file [%s].",
        asset_index_file.filename.c_str(),
        filename);
    return FILE_INDEXER_NEEDS_UPDATE;
  }

  if (!asset_index_file.constains_entries()) {
    CLOG_INFO(&LOG,
              3,
              "Asset file index is to small to contain any entries. [%s]",
              asset_index_file.filename.c_str());
    *r_read_entries_len = 0;
    return FILE_INDEXER_ENTRIES_LOADED;
  }

  std::unique_ptr<AssetIndex> contents = asset_index_file.read_contents();
  if (!contents->is_latest_version()) {
    CLOG_INFO(&LOG,
              3,
              "Asset file index is ignored; expected version %d but file is version %d [%s].",
              AssetIndex::CURRENT_VERSION,
              contents->get_version(),
              asset_index_file.filename.c_str());
    return FILE_INDEXER_NEEDS_UPDATE;
  }

  const int read_entries_len = contents->extract_into(*entries);
  CLOG_INFO(&LOG, 1, "Read %d entries from asset index for [%s].", read_entries_len, filename);
  *r_read_entries_len = read_entries_len;

  return FILE_INDEXER_ENTRIES_LOADED;
}

static void update_index(const char *filename, FileIndexerEntries *entries, void *user_data)
{
  AssetLibraryIndex &library_index = *static_cast<AssetLibraryIndex *>(user_data);
  BlendFile asset_file(filename);
  AssetIndexFile asset_index_file(library_index, asset_file);
  CLOG_INFO(&LOG,
            1,
            "Update asset index for [%s] store index in [%s].",
            asset_file.get_file_path(),
            asset_index_file.get_file_path());

  AssetIndex content(*entries);
  asset_index_file.write_contents(content);
}

static void *init_user_data(const char *root_directory, size_t root_directory_maxlen)
{
  AssetLibraryIndex *library_index = MEM_new<AssetLibraryIndex>(
      __func__, StringRef(root_directory, BLI_strnlen(root_directory, root_directory_maxlen)));
  library_index->collect_preexisting_file_indices();
  library_index->remove_broken_index_files();
  return library_index;
}

static void free_user_data(void *user_data)
{
  MEM_delete((AssetLibraryIndex *)user_data);
}

static void filelist_finished(void *user_data)
{
  AssetLibraryIndex &library_index = *static_cast<AssetLibraryIndex *>(user_data);
  const int num_indices_removed = library_index.remove_unused_index_files();
  if (num_indices_removed > 0) {
    CLOG_INFO(&LOG, 1, "Removed %d unused indices.", num_indices_removed);
  }
}

constexpr FileIndexerType asset_indexer()
{
  FileIndexerType indexer = {nullptr};
  indexer.read_index = read_index;
  indexer.update_index = update_index;
  indexer.init_user_data = init_user_data;
  indexer.free_user_data = free_user_data;
  indexer.filelist_finished = filelist_finished;
  return indexer;
}

}  // namespace blender::ed::asset::index

extern "C" {
const FileIndexerType file_indexer_asset = blender::ed::asset::index::asset_indexer();
}