/**
 * Fixed-window rate limiter, keyed by principal (falls back to client IP).
 *
 * In-memory and per-instance: the effective global limit is `limit × #instances`. For a hard global
 * cap, back this with a shared store (Redis); for protecting one instance from a hot caller this is
 * enough. `limit <= 0` disables it.
 */
export interface RateDecision {
    allowed: boolean;
    retryAfterSec: number;
    remaining: number;
}
/** [ref] 批1:限额的**值换代**入参(六实现类同一形)。语义定案([ref] §5):窗口内计数**不清零**,
 *  新限额即时用于比较 —— 调小 = 窗内立刻更严(可能当场 429,符合运营意图),调大 = 立刻放宽。 */
export interface RateLimits {
    /** 每窗请求上限;`<= 0` = **关断哨兵**(恒放行、不记账、SQL 腿不起刷新环)。 */
    rateLimitPerMin: number;
}
/** The surface the HTTP layer uses — satisfied by the in-memory {@link RateLimiter} (single replica)
 *  and the cross-replica {@link import("../plugins/tidb-rate-limiter.js").TiDBRateLimiter}. */
export interface RateGate {
    check(key: string): RateDecision;
    sweep(now?: number): void;
    /** [ref]:值换代座位。**接口级**声明(不是各类自选):新实现漏掉它 = 编译红,而不是热更新在那条腿上静默失效。 */
    setLimits(next: RateLimits): void;
}
export declare class RateLimiter implements RateGate {
    private readonly windowMs;
    private readonly windows;
    /** 🔴 不再 `readonly`:限额是**比较参数**,不是窗表状态 —— 换代只动它,窗内已计的数一个不动(§5)。 */
    private limit;
    constructor(limit: number, windowMs?: number);
    check(key: string): RateDecision;
    setLimits(next: RateLimits): void;
    /** Drop expired windows (call periodically). */
    sweep(now?: number): void;
}
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