import Foundation

// 🤖 The Mac's chat Text Size preference, in points — the same seven-stop
// ladder as the web slider (TEXT_SIZES in ui.js). The default sits ONE FROM
// THE TOP: 16 is the only workable bigger size (beyond that bubbles read as
// shouting), so the room to taste lies below. One UserDefaults key that
// @AppStorage views observe; the View-menu commands, the ⌘= key monitor and
// the Settings slider all step through here so every entry point moves the
// same ladder.
enum ChatTextSize {
    static let stops: [Double] = [10, 11, 12, 13, 14, 15, 16]
    static let defaultSize: Double = 15
    static let key = "chatTextSize"

    static var current: Double {
        let v = UserDefaults.standard.double(forKey: key)
        return v > 0 ? snap(v) : defaultSize
    }

    // Nearest stop, so a value stored by a future (or hand-edited) ladder
    // still lands somewhere sane.
    static func snap(_ v: Double) -> Double {
        stops.min(by: { abs($0 - v) < abs($1 - v) }) ?? defaultSize
    }

    // @MainActor on the two WRITERS (not the pure reads/constants): UserDefaults
    // is process-global and unsafe against concurrent writes from two threads, so
    // every writer must stay on the main actor. All callers already do (View-menu
    // commands, the ⌘= key monitor); this makes that a compiler-enforced guarantee
    // rather than call-site discipline.
    @MainActor static func bump(_ direction: Int) {
        guard let i = stops.firstIndex(of: current) else { return }
        let j = min(max(i + direction, 0), stops.count - 1)
        UserDefaults.standard.set(stops[j], forKey: key)
    }

    @MainActor static func reset() {
        UserDefaults.standard.set(defaultSize, forKey: key)
    }
}