import type { TokenCacheHook } from '../../types/index.js';
/**
 * FCM service-account configuration. `clientEmail` and `privateKey` map 1:1
 * to the `client_email` and `private_key` fields of a Google service-account
 * JSON file (download from Firebase console). The PEM-encoded `privateKey`
 * is passed verbatim into Node's `crypto.createSign('RSA-SHA256')`.
 *
 * The wrapper holds no token state, so it signs + exchanges the OAuth access
 * token on every `.send()` / `sendMessage()` by default. A consumer who wants
 * amortization plugs in a `tokenCache: TokenCacheHook`; the wrapper memoizes
 * through the hook with key `'fcm:' + projectId + ':' + clientEmail`.
 */
export interface FcmConfig {
    projectId: string;
    /** Service-account `client_email`. */
    clientEmail: string;
    /** Service-account `private_key` — PEM-encoded RSA private key. */
    privateKey: string;
    /**
     * Optional consumer-provided token cache for the RS256 -> OAuth2
     * access-token exchange. The wrapper holds no token state — pass
     * a hook here to amortize signing cost. The cache key is exactly
     * `'fcm:' + projectId + ':' + clientEmail` (deterministic, no time-varying
     * component).
     * On vendor 401 the wrapper does NOT evict; eviction is the consumer's
     * responsibility.
     */
    tokenCache?: TokenCacheHook;
    /** Bring-your-own fetch implementation BYO-fetch contract. */
    fetch?: typeof fetch;
}