import { ActionSource, FindActionSourceConstraints } from "./ActionSource.js";
/**
 * Find an available free kill source subject to constraints.
 *
 * @param constraints Preexisting constraints that restrict possible sources.
 * @returns Free kill source satisfying constraints, or null.
 */
export declare function tryFindFreeKill(constraints?: FindActionSourceConstraints): ActionSource | null;
/**
 * Ensure an available free kill source subject to constraints.
 * Throws an error if no source can be found.
 *
 * @param constraints Preexisting constraints that restrict possible sources.
 * @returns Free kill source satisfying constraints.
 */
export declare function ensureFreeKill(constraints?: FindActionSourceConstraints): ActionSource;