enum GenreRelationEnum : ubyte {
  based_on = 0,
  basis_for = 1,
  child = 2,
  different_from = 3,
  facet_of = 4,
  followed_by = 5,
  follows = 6,
  fusion_of = 7,
  has_facet = 8,
  has_fusion_genre = 9,
  has_part = 10,
  influenced = 11,
  influenced_by = 12,
  inspired = 13,
  inspired_by = 14,
  parent = 15,
  part_of = 16,
  same_as = 17,
}

table GenreIndex {
  // Lookup ID is the signed long carrying the unchanged XXH3-64 bits
  // of canonical UTF-8 produced by central requirements section 5.2.
  // TL;DR: fast lookup of a hash for the XXH3(Confusable(genre))
  // Must be sorted by `hash` for the `key` to work.
  id: ulong (key);
  genre_index: int32; // -> GenreList
}

table GenreRelation {
  kind: GenreRelationEnum;
  genre_index: int32; // -> GenreList
}

table GenreName {
  locale: string (required); // e.g.: `en`
  name: string (required); // e.g.: `Rock`
}

table Genre {
  /// This data is to be trusted; no runtime sanitization is required.
  /// The raw APK resource is stored uncompressed and mapped read-only by its
  /// exact asset offset/length; XXH3-64 is supplied in Binder metadata.
  /// Note: this file is never rebuilt at runtime; APK supplied version is
  /// final. Valid data is assumed and is outside of this scheme.

  /// Numeric part of a Wikidata Q-id (or a synthetic ID starting at -1).
  /// e.g.: 10334882 for Wikidata Q-id "Q10334882"
  /// Note: synthetic Qids must be stable across builds.
  /// Note: it must be sorted while building an FB for the key to work.
  /// Note: it is tempting to compact the indexes like first Qid -> 0, …
  ///       but this is going to break MediaLibrary if Wikidata remove
  ///       any genre in the future.
  id: ulong (key); // long is an overkill but lets keep it for consistency

  /// Related genres. Cycles are allowed; client must limit the depth.
  related: [GenreRelation];

  /// Names support UI display and compound-genre comparison (GP-2).
  /// For display, vtable traversal does not matter because
  /// this gets resolved only for the already selected genres (estimated ~5 max)
  /// per playlist construction.
  ///
  /// When building:
  ///
  ///   1. Group by locale name, place `en` first, sort the rest alphabetically.
  ///   2. Include the preferred name for each locale as the FIRST in the group.
  ///
  /// When playing:
  ///
  ///   IF player locale matches any existing locale:
  ///     Use the first record matching the player locale
  ///     e.g.: Player is `zh` and `zh` group is present: use first `zh` record.
  ///   ELSE IF English locale defined:
  ///     Use the English locale
  ///     e.g.: Player is `zh` and `zh` group is NOT present -> `en`.
  ///   ELSE:
  ///     Use the first available locale
  ///     e.g.: Player is `zh` and not `zh`, nor `en` is present, only `es`
  ///     and `pt` is present with `es` come first -> `es`
  names: [GenreName] (required);
}

table GenreList {
  /// Positive, monotonic bundled-resource revision. A deployed Indexer upgrades
  /// a valid genre DB when this value is greater than the deployed value.
  generation: int32;
  genres: [Genre] (required);
  indexes: [GenreIndex] (required);
}

root_type GenreList;
file_identifier "GNRE";