import ExtendedPromise from './Promise.js';

type SuccessCallback<T, U, Scope> = (this: Scope, value: T) => U;
type ErrorCallback<Scope> = (this: Scope, error: any) => any;
/**
 * Helper to create stable code if a value can be a promise or a non async value.
 *
 * @param value value or promise
 * @param success success callback
 * @param error error callback
 * @param scope this binding for the callbacks
 * @returns always produces a promise
 * @example
 * ```ts
 * // use it as wrapper to get a promise
 * return when(thing).then((thing)=> doSomethingWithTheThing);
 * ```
 *
 * @example
 * ```ts
 * import when from "apprt-core/when";
 * // bind success and error handler from an object
 * const scope = {
 *     counter : 0,
 *     ok() {
 *         ++this.counter;
 *     },
 *     error() {
 *         --this.counter;
 *     }
 * };
 * return when(thing, scope.ok, scope.error, scope);
 * ```
 */
declare function when<Value, Result, Scope extends {}>(value?: Value | PromiseLike<Value>, success?: SuccessCallback<Value, Result, Scope>, error?: ErrorCallback<Scope>, scope?: Scope): ExtendedPromise<Result>;
/**
 * Same as the first overload, but without an error callback.
 */
declare function when<Value, Result, Scope extends {}>(value?: Value | PromiseLike<Value>, success?: SuccessCallback<Value, Result, Scope>, scope?: Scope): ExtendedPromise<Result>;

export { when as default, when };