/**
 * NotifierImpl — concrete implementation of the Notifier interface.
 *
 * Holds a registry of named NotificationChannel instances and dispatches
 * notify() calls to the matching channels. Tracks delivery counters per
 * channel for diagnostics and health reporting.
 *
 * Thread-safe: all public methods are re-entrant. `notify()` may be called
 * concurrently for different messages; each channel's `deliver()` runs in
 * its own Promise (no serialisation).
 *
 * @module notifications
 * @public
 */
import type { NotificationChannel, NotificationMessage, NotificationResult } from './types.js';
import type { NotificationChannelStatus, Notifier, NotifierCounters } from './notifier.js';
export declare class NotifierImpl implements Notifier {
    #private;
    notify(channels: string | string[], message: NotificationMessage): Promise<NotificationResult[]>;
    registerChannel(channel: NotificationChannel): void;
    unregisterChannel(name: string): void;
    channels(): Promise<NotificationChannelStatus[]>;
    counters(): NotifierCounters;
    /**
     * Return per-channel counters for detailed diagnostics.
     * Not part of the `Notifier` interface — available on the concrete class.
     */
    perChannelCounters(): Record<string, {
        attempted: number;
        delivered: number;
        failed: number;
    }>;
}
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