import CoreText
import SwiftUI

enum Fonts {
    nonisolated(unsafe) private static let descriptors: [String: CTFontDescriptor] = {
        let dir = Bundle.main.resourceURL!.appendingPathComponent("fonts")
        var out: [String: CTFontDescriptor] = [:]
        for name in try! FileManager.default.contentsOfDirectory(atPath: dir.path) where name.hasSuffix(".woff2") {
            let url = dir.appendingPathComponent(name)
            let found = CTFontManagerCreateFontDescriptorsFromURL(url as CFURL) as! [CTFontDescriptor]
            out[name] = found[0]
        }
        return out
    }()

    private static func file(_ subset: String, _ italic: Bool, _ weight: CGFloat) -> CTFontDescriptor {
        let d = descriptors["atkinson-hyperlegible-mono-\(subset)-wght-\(italic ? "italic" : "normal").woff2"]!
        return CTFontDescriptorCreateCopyWithVariation(d, 0x7767_6874 as CFNumber, weight)
    }

    static func ct(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> CTFont {
        let ext = file("latin-ext", italic, weight)
        let d = CTFontDescriptorCreateCopyWithAttributes(file("latin", italic, weight), [kCTFontCascadeListAttribute: [ext]] as CFDictionary)
        return CTFontCreateWithFontDescriptor(d, size, nil)
    }

    nonisolated(unsafe) private static var fonts: [String: (font: Font, ns: NSFont)] = [:]
    private static let lock = NSLock()

    private static func cached(_ size: CGFloat, _ weight: CGFloat, _ italic: Bool) -> (font: Font, ns: NSFont) {
        let key = "\(size) \(weight) \(italic)"
        lock.lock()
        defer {
            lock.unlock()
        }
        if let f = fonts[key] {
            return f
        }
        let c = ct(size, weight: weight, italic: italic)
        let f = (Font(c), c as NSFont)
        fonts[key] = f
        return f
    }

    static func font(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> Font {
        cached(size, weight, italic).font
    }

    static func ns(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> NSFont {
        cached(size, weight, italic).ns
    }
}