//! How the interface is being driven — a finger, or a pointer.
//!
//! # Why this is a platform question
//!
//! It is the last `cfg(target_os)` anyone should want, and it earns its place
//! the way the rest of this crate does: the answer differs per platform, every
//! entry point needs it, and resolving it in `apps/` would mean writing it
//! twice.
//!
//! # Why it is not the layout class
//!
//! [`crate::display`] answers "how much room is there", and `dr-ui` turns that
//! into a layout class from the window's width, deliberately not from the
//! device (FR-UI-1). That was the right call and this does not revisit it: a
//! narrow desktop window still gets the compact layout, and a tablet in
//! landscape still gets the expanded one.
//!
//! This answers a different question — "what is the user pointing with" —
//! which width cannot stand in for. The two 12-inch targets DarkRoom is built
//! for are the same size and the same layout class, and one of them has no
//! hover, no modifier keys and a 44-pixel minimum target.
//!
//! # Why it is a guess, and says so
//!
//! There is no reliable runtime answer on either platform. Android devices
//! have touchscreens and can have a mouse attached; desktops have mice and can
//! have touchscreens. Reporting the *usual* case per platform and letting the
//! photographer override it is honest; probing input devices and being
//! confidently wrong is not. The override lives in
//! `dr_types::GroupNavigation`, which takes this as an input rather than
//! reading it.

/// What this build is usually driven with.
///
/// `true` on Android, `false` everywhere else. Deliberately a plain bool
/// rather than an enum: there are exactly two answers today, and the thing
/// that consumes it — [`dr_types::GroupNavigation::groups_in_rail`] — is a
/// choice between two controls.
pub const fn is_touch_first() -> bool {
    cfg!(target_os = "android")
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn the_desktop_build_is_pointer_first() {
        // Asserted rather than assumed, because the value is a `cfg!` and a
        // typo in the target name compiles to a silent `false` — which on
        // desktop is the right answer for the wrong reason and would pass
        // unnoticed until the tablet build shipped with the desktop layout.
        assert_eq!(is_touch_first(), cfg!(target_os = "android"));
        #[cfg(not(target_os = "android"))]
        assert!(!is_touch_first());
    }
}