/**
 * Sliding-window duplicate guard for inbound messages.
 *
 * Channel SDKs can re-deliver the same event after a reconnect (the Feishu
 * WebSocket dispatcher does this), which would otherwise queue the same user
 * message twice. Each inbound message carries a stable per-message id in
 * `replyRef`; keys are (channel, chatKey, messageId) within a recency window.
 * Messages without an id (not all channels set one) are never deduplicated.
 * @module dsh-connect/dedup
 */
export declare class InboundDedup {
    /** Re-delivery of the same id inside this window is a duplicate (default 5 min). */
    private readonly windowMs;
    /** Hard cap on remembered ids; oldest entries are dropped beyond it. */
    private readonly maxEntries;
    /** key → last-seen timestamp */
    private readonly seen;
    constructor(
    /** Re-delivery of the same id inside this window is a duplicate (default 5 min). */
    windowMs?: number, 
    /** Hard cap on remembered ids; oldest entries are dropped beyond it. */
    maxEntries?: number);
    /**
     * Record the message and report whether an identical id was already seen
     * within the window. Side-effect free for messages without an id.
     */
    isDuplicate(channel: string, chatKey: string, messageId: string | undefined, now?: number): boolean;
    /** Forget ids older than the window, then the oldest beyond the cap. */
    private prune;
}
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