import type { DeepPartial } from "@rotorsoft/act-patch";
/**
 * Base constraint for state objects managed by the broadcast system.
 * Apps extend this with their own domain state shape.
 */
export type BroadcastState = Record<string, unknown> & {
    /** Event store stream version — set by the broadcast layer from snap.event.version */
    _v: number;
};
/**
 * SSE message: version-keyed domain patches.
 * Keys are stringified version numbers, values are domain patches (deep partials).
 * Multi-event commits produce multiple version-keyed entries.
 *
 * The optional `_overlay` marker flags a version-neutral update (presence,
 * computed-field refresh) emitted by {@link BroadcastChannel.overlay} — a
 * single entry keyed at the *current* version. It tells `applyPatchMessage`
 * to merge the entry on top of the client's caught-up state instead of
 * rejecting it as stale (a same-version patch WITHOUT the marker stays
 * stale). Ordinary version-bumping patches from `publish()` omit it.
 *
 * `_resync` carries no versions at all. The server emits it when it cannot
 * construct a patch — today, when `overlay()` finds the stream's baseline
 * evicted from the LRU. A client that receives one always reports `behind`
 * and refetches. Without it the server had nothing to say in that case, so
 * live subscribers silently stopped receiving presence updates and had no
 * way to notice (#1423).
 */
export type PatchMessage<S extends BroadcastState = BroadcastState> = Record<number, DeepPartial<S>> & {
    readonly _overlay?: true;
    readonly _resync?: true;
};
/**
 * Subscriber callback — receives version-keyed patch messages.
 */
export type Subscriber<S extends BroadcastState = BroadcastState> = (msg: PatchMessage<S>) => void;
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