/**
 * Token-bucket rate limiter.
 *
 * A bucket of `capacity` tokens refills at `refillRate` tokens per second.
 * Every request consumes one token; if the bucket is empty, the request is
 * rejected. Allows *controlled burst* — an idle caller accumulates a full
 * bucket and can spend it at once, then drops to the steady rate.
 *
 * State is stored as a single JSON blob per key: `{ tokens, updatedAt }`.
 * Tokens are recomputed on read from the elapsed time — no background
 * timer needed.
 *
 * Because token accounting is more than a simple counter, this reads the
 * state, recomputes, and writes it back. When the store exposes the
 * optional atomic `compareAndSet` (the bundled memory and Redis stores
 * both do), the write is a CAS retried on contention — concurrent
 * requests can never double-spend a token. Stores without it fall back
 * to a last-writer-wins `set`, which can race under concurrency.
 *
 * @param {import('../index.js').BucketLimiterConfig} config
 * @returns {import('../index.js').Limiter}
 */
export function tokenBucket(config: import("../index.js").BucketLimiterConfig): import("../index.js").Limiter;