/**
 * Transport auto-select.
 *
 * Tiny helper that probes which transport lanes the runtime AND the platform
 * BOTH support, and returns the best one for this client/host pair.
 *
 * Preference order (best -> fallback):
 *   1. webtransport - multi-stream, lower head-of-line blocking
 *   2. websocket    - universal default
 *   3. sse          - HTTP-only fallback for restrictive networks
 *
 * The function fetches `<httpUrl>/api/info` once, intersects its
 * `transports` array with the runtime's capabilities, and returns the
 * highest-preference match. Caller then instantiates the corresponding
 * primitive (`WebTransportTransport` / WebSocket / `SseTransport`) and
 * uses it as their lane.
 *
 * @example
 * ```ts
 * import { selectTransport, WebTransportTransport, SseTransport } from '@droponair/sdk-js';
 * const lane = await selectTransport({ httpUrl: 'https://sdk.droponair.com' });
 * switch (lane) {
 *   case 'webtransport': // construct WebTransportTransport break;
 *   case 'sse':          // construct SseTransport          break;
 *   default:             // fall through to WebSocket
 * }
 * ```
 */
export type TransportLane = 'webtransport' | 'websocket' | 'sse';
export interface SelectTransportOptions {
    /** Base URL of the platform's REST API (no trailing slash). */
    httpUrl: string;
    /**
     * Override the default WT -> WS -> SSE preference order. Useful for tests
     * or when a specific lane is preferred (e.g. force `sse` first on a known
     * firewalled network).
     */
    preference?: TransportLane[];
    /** Custom fetch impl, useful for Node polyfills + test doubles. */
    fetchFn?: typeof fetch;
}
/**
 * Returns the highest-preference transport lane available on BOTH the
 * runtime and the platform. Throws if no lane is supported (extremely
 * unusual; WebSocket is the universal floor).
 */
export declare function selectTransport(options: SelectTransportOptions): Promise<TransportLane>;