/**
 * Session-watch registry — the server half of the session-level SSE subscription
 * (design: sema-internal `server/docs/SESSION-SSE-DESIGN.md`, 黑板 [ref]①/[ref]).
 *
 * One entry per watched session; N subscribers SHARE one probe loop (this is the whole point:
 * it converts web-side per-client polling into one per-replica probe). Two change channels:
 *  - fast path: `notifyLocal(sessionId, leafId)` — an append that lands on THIS replica fans out
 *    synchronously (zero latency on single-replica deployments, the common TOC/local shape);
 *  - slow path: the probe loop reads leafId through the SAME storage face the /head probe uses.
 *
 * codex 复审(1.230 一轮)后的三条硬语义:
 *  - **revision 守卫**:notifyLocal 每次推进 bump `rev`;探针起读前抓拍 rev,读回后 rev 变=结果作废
 *    (陈旧慢读不得把 B 倒退回 A——latest-wins 的机制保证,不靠时序运气)。
 *  - **replay-on-subscribe**:已有条目携带 `last` 时,新订阅者同步补发一帧(「join 与基线原子化」的
 *    registry 半场;连接层再配 lastSent 去重,乱序/重复帧对下游不可见)。
 *  - **冷启动 warm**:新条目 lastChangeAt=0(没观测到变化就不算热)——首拍一次 hotMs 快确认后即落
 *    warm 拍距,直到真观测到跳变才进热窗(codex:重连风暴下 256 会话×200ms=对存储的自造尖峰)。
 *
 * Deliberately backend-agnostic (tidb|pg|local all go through getLeafId — the seamless-local-cloud
 * invariant): no PG LISTEN/NOTIFY specialization, no shared bus. Latest-wins semantics: subscribers
 * converge on the newest leafId; intermediate hops may be dropped (content still comes from tail faces).
 */
/** [ref] 二轮复审:SSE 资源旋钮的 env 解析——有界正整数,坏形(NaN/0/负/超界)一律回缺省并可观测
 *  (坏 `SESSION_EVENTS_MAX_PROBES=foo` 若直进 Number() 会把帽谓词变恒假=无帽,拍距 NaN 进 setTimeout
 *  =0ms 紧循环打爆存储)。 */
export declare function posIntEnv(raw: string | undefined, fallback: number, max?: number): number;
export interface SessionWatchOptions {
    /** Probe interval while a change was OBSERVED within `hotWindowMs` (default 200ms). */
    hotMs?: number;
    /** Probe interval otherwise (default 2000ms). */
    warmMs?: number;
    /** How long after the last observed change the probe stays hot (default 60s). */
    hotWindowMs?: number;
    /** Cap on concurrently-probed sessions per replica (default 512). Exceeding = subscribe refused. */
    maxWatchedSessions?: number;
}
export declare class SessionWatchRegistry {
    /** 五轮复审:owner 与 leaf **同拍原子读**——探针每拍先核 owner(被删=undefined/换主=≠条目 owner
     *  ⇒ dropSession 断全部订阅者),匹配才应用 leaf。跨副本 reclaim 的披露窗从 25s 心跳收紧到
     *  ≤一个探针拍(hot 200ms/warm 2s),且旧流在新主推进**之前**先死(owner 检查先于 leaf 应用)。 */
    private readonly getHead;
    private readonly entries;
    private readonly hotMs;
    private readonly warmMs;
    private readonly hotWindowMs;
    private readonly maxWatched;
    constructor(
    /** 五轮复审:owner 与 leaf **同拍原子读**——探针每拍先核 owner(被删=undefined/换主=≠条目 owner
     *  ⇒ dropSession 断全部订阅者),匹配才应用 leaf。跨副本 reclaim 的披露窗从 25s 心跳收紧到
     *  ≤一个探针拍(hot 200ms/warm 2s),且旧流在新主推进**之前**先死(owner 检查先于 leaf 应用)。 */
    getHead: (sessionId: string) => Promise<{
        leafId: string | null | undefined;
        owner: string | null | undefined;
    }>, opts?: SessionWatchOptions);
    /** Number of sessions currently probed (observability + the cap predicate). */
    watchedCount(): number;
    /**
     * Subscribe to head changes. Returns undefined when the per-replica probe cap is reached
     * (caller answers 503 + Retry-After — the client falls back to /head polling).
     * If the shared entry already knows a head (`last`), it is REPLAYED synchronously into
     * `onHead` before returning — a subscriber joining an advanced entry can never miss the
     * newest value (connection-level dedupe absorbs any overlap with the caller's own read).
     */
    subscribe(sessionId: string, owner: string | null, onHead: (leafId: string | null) => void, onEnd?: () => void): (() => void) | undefined;
    /** [ref] 三轮复审(租户轮转围栏,同副本半场):session 删除即终结条目——通知全部订阅者(onEnd,
     *  路由据此断流)+ 停探针 + 弃缓存 head(新租户同键重订阅=全新世代,旧 replay 不可能渗入)。 */
    dropSession(sessionId: string): void;
    /** S2 fast path: an append that landed on THIS replica. Safe to call for unwatched sessions (no-op).
     *  `owner` 给了就 owner-限定(五轮复审):不符=条目属旧世代 ⇒ drop(断旧流),值不投——S2 接线时
     *  append 落点必然知道 session owner,应当传。 */
    notifyLocal(sessionId: string, leafId: string | null, owner?: string | null, leafSeq?: number): void;
    /** 立即压缩下一拍到 0ms(owner 疑云的权威核验)。探针自身 probing 串行 + 世代守卫照旧;urgent 旗
     *  保证「疑云到达时已有读在飞(其快照摄于 reclaim 前=陈旧)」也必有一次**疑云后开始**的权威读。 */
    private probeNow;
    private arm;
    private probe;
    /** 对**给定世代**应用一次推进(fan-out 恒按 rev 单调序)。 */
    private applyAdvance;
}
//# sourceMappingURL=session-watch.d.ts.map