enum FontWeight {
  100,
  200,
  300,
  400,
  500,
  600,
  700,
  800,
  900,
}

enum FontStyle {
  italic,
}

/// A class that enables the dynamic loading of fonts at runtime.
///
/// The [FontLoader] class provides a builder pattern, where the caller builds
/// up the assets that make up a font family, then calls [load] to load the
/// entire font family into a running Flutter application.
class FontLoader {
  /// Creates a new [FontLoader] that will load font assets for the specified
  /// [family].
  ///
  /// The font family will not be available for use until [load] has been
  /// called.
  FontLoader(this.family);

  /// The font family being loaded.
  ///
  /// The family groups a series of related font assets, each of which defines
  /// how to render a specific [FontWeight] and [FontStyle] within the family.
  final String family;

  /// Registers a font asset to be loaded by this font loader.
  ///
  /// The [bytes] argument specifies the actual font asset bytes. Currently,
  /// only TrueType (TTF) fonts are supported.
  ///
  /// The optional [weight] and [style] arguments specify the [FontWeight]
  /// and [FontStyle] to which the asset corresponds, respectively. If they
  /// are unspecified, it signals that this is the default font asset for the
  /// font [family].
  ///
  /// If a font has already been added to this loader that corresponds to the
  /// specified [weight] and [style], a [StateError] will be thrown.
  void addFont(
    Uint8List bytes, {
    FontWeight weight,
    FontStyle style,
  });

  /// Loads this font loader's font [family] and all of its associated assets
  /// into the Flutter engine, making the font available to the current
  /// application.
  ///
  /// This method should only be called once per font loader. Attempts to
  /// load fonts from the same loader more than once will cause a [StateError]
  /// to be thrown.
  Future<void> load();
}