import { ConnectionOptions, OpenSessionRequest } from './IDBSQLClient';
import ISessionBackend from './ISessionBackend';
/**
 * Top-level backend dispatch handle. One instance per `DBSQLClient`,
 * chosen at `connect()` time based on the `useKernel` flag and never
 * re-selected per-call.
 */
export default interface IBackend {
    /**
     * Establish backend-level state before any session is opened. Implementations
     * consume `options` to build backend-specific connection parameters (e.g. the
     * kernel backend derives napi-binding `KernelNativeConnectionOptions` from the auth
     * + host fields here). Transport-layer connection providers are owned by
     * `DBSQLClient` (via `IClientContext`) and exposed to backends through
     * constructor injection.
     */
    connect(options: ConnectionOptions): Promise<void>;
    /**
     * Open a session. Returned `ISessionBackend` is owned by the caller
     * and torn down via its own `close()`.
     */
    openSession(request: OpenSessionRequest): Promise<ISessionBackend>;
    /**
     * Backend-level teardown. Transport-layer cleanup (connection provider,
     * thrift client, auth provider) is owned by `DBSQLClient` and runs
     * after this returns. Implementations release backend-internal resources
     * here, and MUST be safe to call on a partially-initialized backend
     * (i.e. after a failed `connect()`).
     */
    close(): Promise<void>;
}