import type { BroadcastState, PatchMessage } from "./types.js";
/**
 * Result of applying a patch message to cached client state.
 */
export type ApplyResult<S extends BroadcastState = BroadcastState> = {
    ok: true;
    state: S;
} | {
    ok: false;
    reason: "stale" | "behind";
};
/**
 * Apply a version-keyed patch message to the client's cached state.
 *
 * ## Version logic
 *
 * - All patches older than cached → "stale" (client already ahead)
 * - Gap between cached version and first patch → "behind" (client missed versions, must resync)
 * - Contiguous from cached version → apply in order
 * - No baseline (fresh client) → the genesis patch (version 0) folds onto init
 *   state; a first patch at version ≥ 1 is "behind" (can't build from init)
 * - Overlay frame ({@link PatchMessage._overlay}) at the current version →
 *   merged on top of cached state, `_v` unchanged (presence / computed
 *   fields reach caught-up clients instead of being dropped as stale)
 *
 * ## Usage (React Query)
 *
 * ```typescript
 * onData: (msg) => {
 *   const cached = utils.get_state.get_data({ streamId });
 *   const result = applyPatchMessage(msg, cached);
 *   if (result.ok) {
 *     utils.get_state.setData({ streamId }, result.state);
 *   } else if (result.reason === "behind") {
 *     utils.get_state.invalidate({ streamId }); // trigger full refetch
 *   }
 *   // "stale" → no-op, client already has newer state
 * }
 * ```
 */
export declare function applyPatchMessage<S extends BroadcastState>(msg: PatchMessage<S>, cached: S | null | undefined): ApplyResult<S>;
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