/**
 * Multi-tab coordination: primary/secondary election (Web Locks)
 * + presence heartbeat (BroadcastChannel). Browser-only; opt-in; no-op
 * when the APIs are absent. The lock/channel interfaces are hub-local
 * (structurally compatible with @noy-db/by-peer + @noy-db/by-tabs, but
 * not imported — those packages depend on hub).
 */
export type TabRole = 'primary' | 'secondary' | 'unknown';
export interface TabPresence {
    readonly tabId: string;
    readonly lastSeen: number;
    readonly role: TabRole;
}
export type Unsubscribe = () => void;
/** Structural subset of the Web Locks API / by-peer's MinimalLockManager. */
export interface TabLockManager {
    request<T>(name: string, options: {
        mode?: 'exclusive' | 'shared';
        signal?: AbortSignal;
    }, callback: (lock: unknown) => Promise<T>): Promise<T>;
}
/** Structural subset of by-peer's PeerChannel / a BroadcastChannel wrapper. */
export interface TabChannel {
    send(payload: string): void;
    on(event: 'message', listener: (payload: string) => void): Unsubscribe;
    on(event: 'close', listener: () => void): Unsubscribe;
    close(): void;
    readonly isOpen: boolean;
}
export interface TabCoordinationOptions {
    readonly lockManager?: TabLockManager;
    readonly channel?: TabChannel;
    readonly tabId?: string;
    readonly lockName?: string;
    readonly heartbeatMs?: number;
    readonly staleMs?: number;
    readonly now?: () => number;
    /**
     * Close the channel on `dispose()`. Set this only for a channel the
     * coordinator owns (e.g. the one `defaultChannel()` created); leave it
     * false for a caller-injected channel so the coordinator never closes a
     * channel it didn't create. Default: false.
     */
    readonly closeChannelOnDispose?: boolean;
    /**
     * Also propagate committed writes to other tabs. Default true:
     * when tab coordination is enabled and a channel is available, a write in
     * one tab refreshes that document in every other tab. Set false to opt out.
     */
    readonly propagateWrites?: boolean;
    /**
     * Channel for write propagation — distinct from the presence
     * channel. Default: an inline BroadcastChannel on `noydb:tab-writes`.
     */
    readonly writeChannel?: TabChannel;
}
export declare class TabCoordinator {
    #private;
    readonly tabId: string;
    role: TabRole;
    constructor(opts?: TabCoordinationOptions);
    start(): void;
    activeTabs(): TabPresence[];
    onTabRoleChange(fn: (r: TabRole) => void): Unsubscribe;
    onActiveTabsChange(fn: (t: TabPresence[]) => void): Unsubscribe;
    dispose(): void;
    /** @internal test seam — broadcast one heartbeat now. */
    _beat(): void;
}
/** Browser default lock manager (navigator.locks) or undefined. */
export declare function defaultLockManager(): TabLockManager | undefined;
/** Browser default channel: an inline BroadcastChannel wrapper, or undefined. */
export declare function defaultChannel(name?: string): TabChannel | undefined;