/**
 * One question, two places it can be answered, and exactly one answer.
 *
 * The terminal and the phone are both live at once. Whichever comes back first
 * decides, and the other has to be taken down — a dialog left on screen after
 * the phone answered would ask again, and a Telegram message left with three
 * live buttons invites a tap that can no longer do anything.
 *
 * Kept apart from the agent loop and from the Telegram client because the part
 * that goes wrong is the ordering, and the ordering can be tested with two
 * promises and no network.
 */
export interface RaceParticipant<T> {
    /** Resolves when this side is answered. Must never reject: a rejection here
     *  would take down a run over a failure to *ask*, which is not the same thing
     *  as a denial and must not be treated as one. */
    answer: Promise<T | null>;
    /** Take this side down because the other one won. Must be safe to call when
     *  this side never started, and must not itself answer anything. */
    withdraw: (winner: string) => void | Promise<void>;
}
/**
 * Settle a question from whichever side answers first.
 *
 * A side that resolves `null` has declined to decide — it failed to send, or it
 * was cancelled — and is not treated as a winner. When both come back null,
 * nobody answered, and the caller decides what that means. It must not mean
 * approval.
 */
export declare function raceApproval<T>(terminal: RaceParticipant<T>, remote: RaceParticipant<T> | null, describe: (answer: T) => string): Promise<{
    answer: T | null;
    from: 'terminal' | 'remote' | 'nobody';
}>;