/// The typefaces bundled with the client (spec 8.2: the reader chooses).
/// Pure data, shared by the settings page that offers them and the renderer
/// that applies them.
library;

/// One bundled family: the name used in pubspec.yaml and stored in settings,
/// the id of its display name in the locale file, and where to look when it
/// has no glyph for a character.
typedef ReaderFont = ({String family, String labelId, List<String> fallback});

/// Offered in this order: the two sans faces first, then the two serifs.
/// Adding a font is four files in assets/fonts, one `fonts` entry in
/// pubspec.yaml, one entry here, one label in the locale file, and its licence
/// beside the files.
///
/// Each face names where to look for a character it has no glyph for. Hebrew
/// comes from a bundled Hebrew face, matched to the shape of the chosen one,
/// so it never depends on what the device happens to have installed. The
/// serifs also cover Greek, Cyrillic and a wide Latin range, so each falls
/// back to the other; the sans faces are narrow and have no bundled sans to
/// turn to, so for those the platform answers, and it answers a sans with a
/// sans. Scripts nothing here covers, such as Arabic and the CJK languages,
/// always come from the platform.
const readerFonts = <ReaderFont>[
  (
    family: 'Atkinson Hyperlegible',
    labelId: 'settings-font-atkinson',
    fallback: [hebrewSans],
  ),
  (
    family: 'Luciole',
    labelId: 'settings-font-luciole',
    fallback: [hebrewSans],
  ),
  (
    family: 'Literata',
    labelId: 'settings-font-literata',
    fallback: ['Charis SIL', hebrewSerif],
  ),
  (
    family: 'Charis SIL',
    labelId: 'settings-font-charis',
    fallback: ['Literata', hebrewSerif],
  ),
];

/// Bundled to be fallen back on, never offered: the reader picks a face for
/// the Latin text they are reading, and Hebrew follows its shape.
const hebrewSans = 'Noto Sans Hebrew';
const hebrewSerif = 'Noto Serif Hebrew';

const defaultFontFamily = 'Atkinson Hyperlegible';

/// Where to look after [family], or nothing when it is not one of ours.
List<String> fallbackFor(String family) {
  for (final font in readerFonts) {
    if (font.family == family) return font.fallback;
  }
  return const [];
}