lernie 0.1.39

//! **`act:<op>` — the machine token a control carries so drift is catchable**
//! (yog's `docs/PARITY.md` §4).
//!
//! The operator's requirement is interaction parity between this seat and the
//! android client: *if something is interactable in one it must exist in the
//! other*, caught mechanically rather than noticed by hand. The subject is
//! exactly what crosses the §8.5 control boundary — an **op** — and the
//! authority for which ops owe a seat a control is yog's help table, published
//! through the `surface` field of the vendored corpus (`reply/help.json`).
//!
//! So a control that fires op `V` carries the literal token `act:V`, and the
//! meta-assertion in [`crate::snapshot::parity`] reads them back off the real
//! accessibility tree. **The op token is the one name that already exists
//! everywhere** — help row, envelope, corpus filename — so nothing here is a
//! translation table, and every call site spells the op by naming the verb's
//! own `word` rather than by writing a string.
//!
//! # Why it is `author_id` and not the label
//!
//! The visible label stays a human word: `send`, `nudge`, `start`. AccessKit's
//! `author_id` is defined for exactly this — *"a way for application authors to
//! identify this node for automated testing purpose"* — so it is machine
//! metadata that no screen reader announces and no operator sees. Putting the
//! token in the label instead would publish a wire spelling into the face.
//!
//! # One control may fire more than one op, so the token list is a list
//!
//! Two of this seat's controls compose a second gesture the walk can never see
//! as its own control. Start fires `prepare` and, when the engine's reply
//! lands, the frame fires `prompt` (`crate::ui::model::start`); selecting a
//! conversation causes both the `transcript` read and the `follow` lane. The
//! tokens ride the one control that begins each, space separated, which is
//! PARITY §3's rule that the ledger's unit is the op and never the widget.
//!
//! # Why the write is `cfg(test)` and why that costs nothing
//!
//! `egui::Context::accesskit_node_builder` exists only when `egui/accesskit` is
//! on, and by the standing dev-only ruling recorded in `Cargo.toml` that
//! feature is raised in `[dev-dependencies]` alone — **the released seat links
//! no accesskit and therefore publishes no accessibility tree at all**. There
//! is no node in a release build for a token to be written to, so the write is
//! compiled where the tree exists and nowhere else.
//!
//! What is NOT conditional is the **call**, and that is the point of the seam:
//! the decision about which ops a control fires is recorded at the control, in
//! the same expression that paints it, and a control added without one is a
//! control the parity gate reddens for. The alternative — a table mapping
//! labels to ops — is the translation table PARITY §4 exists to avoid, and it
//! would drift the first time a label was reworded.

/// **The reserved namespace.** A token outside it is not this ledger's, and a
/// token inside it that names no corpus op fails the assertion — the same
/// two-direction discipline the leak fixtures hold.
pub const PREFIX: &str = "act:";

/// **The `author_id` a control firing `ops` carries**, and the one spelling of
/// the format: `act:` on each op, space separated.
///
/// Space separated rather than comma, because whitespace is what
/// `str::split_whitespace` reads back with no delimiter to get wrong, and an op
/// token never contains one (`crate::verbs::Verb::word` is a wire op).
pub fn tokens(ops: &[&str]) -> String {
    ops.iter()
        .map(|op| format!("{PREFIX}{op}"))
        .collect::<Vec<_>>()
        .join(" ")
}

/// **Tag one control with every op its activation fires.**
///
/// Call it with the response the widget handed back, in the frame that painted
/// it: the node the token lands on is the one egui created for that widget in
/// this pass, so the label, bounds and actions are already on it and this adds
/// the one field nobody else writes.
pub fn tag(response: &egui::Response, ops: &[&str]) {
    #[cfg(test)]
    {
        let author = tokens(ops);
        let _ = response
            .ctx
            .accesskit_node_builder(response.id, move |node| node.set_author_id(author));
    }
    #[cfg(not(test))]
    let _ = (response, ops);
}