/**
 * @license
 * Copyright 2025 Steven Roussey <sroussey@gmail.com>
 * SPDX-License-Identifier: Apache-2.0
 */
export interface PollingManagerOptions {
    readonly defaultIntervalMs?: number;
}
export type ChangeCallback<T> = (change: T) => void;
export type StateFetcher<Item, Key> = () => Promise<Map<Key, Item>>;
export type ItemComparator<Item> = (a: Item, b: Item) => boolean;
export interface ChangePayloadFactory<Item, ChangePayload> {
    readonly insert: (item: Item) => ChangePayload;
    readonly update: (oldItem: Item, newItem: Item) => ChangePayload;
    readonly delete: (item: Item) => ChangePayload;
}
export interface PollingSubscriptionOptions {
    readonly intervalMs?: number;
}
/**
 * Consolidates polling subscribers into one polling loop per interval tier so
 * many subscriptions don't each spin up their own setInterval.
 */
export declare class PollingSubscriptionManager<Item, Key, ChangePayload> {
    private readonly intervals;
    private lastKnownState;
    private initialized;
    /** Guards against poll/init race while the first state fetch is in flight. */
    private initializing;
    private readonly fetchState;
    private readonly compareItems;
    private readonly payloadFactory;
    private readonly defaultIntervalMs;
    constructor(fetchState: StateFetcher<Item, Key>, compareItems: ItemComparator<Item>, payloadFactory: ChangePayloadFactory<Item, ChangePayload>, options?: PollingManagerOptions);
    subscribe(callback: ChangeCallback<ChangePayload>, options?: PollingSubscriptionOptions): () => void;
    private initAndPoll;
    private pollForNewSubscriber;
    private poll;
    get subscriptionCount(): number;
    get hasSubscriptions(): boolean;
    destroy(): void;
}
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