/**
 * A typed publish/subscribe hook used to assemble SDK events.
 *
 * Multiple callbacks can be registered. When `trigger` is called, each callback receives the same
 * `params` and may return:
 * - A `Result` value — merged with the other callbacks' results via `combine`.
 * - `SKIPPED` — this callback contributes nothing; processing continues.
 * - `DISCARDED` — the entire event is dropped; no further callbacks are invoked.
 *
 * @typeParam Params - The input passed to every registered callback.
 * @typeParam Result - The type of the assembled output value.
 */
export interface Hook<Params, Result> {
    /** Registers a callback and returns a handle to unregister it. */
    register(this: void, callback: (params: Params) => Result | DISCARDED | SKIPPED): {
        unregister: () => void;
    };
    /**
     * Invokes all registered callbacks with `params` and deep-merges their results.
     * Returns `DISCARDED` if any callback discards the event, or `undefined` if no callback
     * returns a result.
     */
    trigger(this: void, params: Params): Result | DISCARDED | undefined;
}
/**
 * Creates a new `Hook` instance with no registered callbacks.
 *
 * @typeParam Params - The input type passed to registered callbacks.
 * @typeParam Result - The return type that callbacks contribute to.
 */
export declare function createHook<Params, Result>(): Hook<Params, Result>;
/** Sentinel returned by a hook callback to discard the entire event (no further callbacks are invoked). */
export declare const DISCARDED = "DISCARDED";
/** Sentinel returned by a hook callback to opt out of contributing a result (other callbacks still run). */
export declare const SKIPPED = "SKIPPED";
export type DISCARDED = typeof DISCARDED;
export type SKIPPED = typeof SKIPPED;