import type { KV } from "@nats-io/kv";
/** One answer to one checkpoint. `value` is the program's payload; `artifact` is the digest of
 *  what the answerer actually saw, which is what makes an approval evidence rather than a claim. */
export interface CheckpointAnswerValue {
    readonly v: 1;
    readonly token: string;
    readonly answerId: string;
    /** Absent when the answer carries no payload — an approval that is only a "yes". */
    readonly value?: unknown;
    readonly artifact?: string;
    /** WHO answered, as the run's own ACL knows them — never the presenting principal, which is the
     *  driver for every answer and therefore discriminates nothing. */
    readonly by: string;
    readonly at: number;
}
/**
 * The id an answer is filed under, DERIVED rather than random.
 *
 * A resolver that wrote its record and then crashed before presenting the token has to be able to
 * retry, and a fresh random id on the retry would file a second answer and leave the first one
 * unnameable. Deriving from the answer's own content makes the retry land on the same key with the
 * same bytes; two resolvers who genuinely answer the same thing are then indistinguishable, which
 * is correct, and two who answer differently get different ids and race on the settle, which is
 * what the settle is for.
 */
export declare function checkpointAnswerId(a: {
    token: string;
    by: string;
    value?: unknown;
    artifact?: string;
}): string;
/**
 * File an answer, create-only.
 *
 * A retry of the SAME answer is not a conflict: the id is derived from the content, so an existing
 * record under this id with identical bytes is this resolver's own earlier attempt and the call
 * succeeds. Different bytes under the same id would be a digest collision, which is refused rather
 * than overwritten.
 */
export declare function recordCheckpointAnswer(kv: KV, endpoint: string, value: CheckpointAnswerValue): Promise<{
    key: string;
    created: boolean;
}>;
/** Read one answer. `undefined` = no answer was filed under this id. */
export declare function readCheckpointAnswer(kv: KV, endpoint: string, token: string, answerId: string): Promise<CheckpointAnswerValue | undefined>;
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