// System TrueType/OpenType font discovery.
//
// Wraps a `fontdb` database loaded with the user's installed system fonts so
// the rest of the app can (a) list available font families for the text-style
// picker and (b) borrow a face's raw bytes to extract glyph outlines (see the
// TTF glyph engine). LFF stroke fonts stay separate — this is purely the
// TrueType side of the renderer.

use std::sync::OnceLock;

struct SysFonts {
    db: fontdb::Database,
    /// Sorted, de-duplicated family names for the picker.
    families: Vec<String>,
}

static FONTS: OnceLock<SysFonts> = OnceLock::new();

fn fonts() -> &'static SysFonts {
    FONTS.get_or_init(|| {
        let mut db = fontdb::Database::new();
        db.load_system_fonts();

        let mut families: Vec<String> = db
            .faces()
            .filter_map(|face| face.families.first().map(|(name, _)| name.clone()))
            .collect();
        families.sort_by_key(|n| n.to_lowercase());
        families.dedup();

        SysFonts { db, families }
    })
}

/// All installed system font families, sorted case-insensitively, de-duped.
pub fn families() -> &'static [String] {
    &fonts().families
}

/// Resolve a family name to a concrete face id (regular weight/style).
fn face_id(family: &str) -> Option<fontdb::ID> {
    let db = &fonts().db;
    let query = fontdb::Query {
        families: &[fontdb::Family::Name(family)],
        ..Default::default()
    };
    db.query(&query)
}

/// Borrow the raw face bytes for `family` and run `f` over them. The byte slice
/// is only valid inside the closure, so callers extract everything they need
/// (e.g. flattened glyph outlines) before returning. `index` is the face index
/// within a TrueType collection. Returns `None` if the family is unknown.
pub fn with_face_data<T>(family: &str, f: impl FnOnce(&[u8], u32) -> T) -> Option<T> {
    let id = face_id(family)?;
    fonts().db.with_face_data(id, f)
}

/// Whether `family` matches an installed system font (case-insensitive via
/// fontdb's own matching).
pub fn has_family(family: &str) -> bool {
    face_id(family).is_some()
}