export declare class FirebaseNotificationService {
    private readonly logger;
    constructor();
    sendToDevice(token: string, title: string, body: string, data?: Record<string, string>): Promise<string>;
    sendToMultipleDevices(tokens: string[], title: string, body: string, data?: Record<string, any>): Promise<{
        response: import("firebase-admin/lib/messaging/messaging-api").BatchResponse;
        failedTokens: string[];
    }>;
}