export type SnapshotFn = (current: unknown, prev: unknown) => unknown;
/**
 * Register a custom snapshot function for instances of a class.
 * The function receives the current value, the previous snapshot (or undefined),
 * and the recursive `snapshot` function for snapshotting nested values.
 *
 * Subclasses inherit the handler automatically via prototype lookup, so
 * registering once on a base class applies to all descendants. A descendant
 * can override by registering its own handler.
 *
 * Return `prev` when nothing has changed to preserve reference stability.
 *
 * @example
 * ```ts
 * registerCustomSnapshot(MyEntity, (current, prev, snapshot) => {
 *   const name = snapshot(current.name, prev?.name);
 *   const age = current.age;
 *   if (prev && name === prev.name && age === prev.age) return prev;
 *   return { name, age };
 * });
 * ```
 */
export declare const registerCustomSnapshot: <T extends object>(ctor: new (...args: any[]) => T, snapshotFn: (current: T, prev: T | undefined, snapshot: SnapshotFn) => T) => void;
/**
 * Recursively snapshot a value with structural sharing.
 *
 * - Plain objects and arrays are deep-cloned; unchanged subtrees keep the same reference.
 * - ReactivePromise instances are read (establishing deps) and flattened to a plain object.
 * - Class instances are returned as-is unless a custom handler is registered
 *   for the class or any of its ancestors via `registerCustomSnapshot`.
 * - Primitives are returned directly.
 */
export declare function snapshot(currentValue: unknown, prevValue: unknown): unknown;
//# sourceMappingURL=snapshot.d.ts.map