/**
 * Source-metadata payload → `{ sources, refs }`.
 *
 * ONE decoder for two arrival paths: the live `GUIDE`/`SOURCES` NATS chunk and
 * the persisted row of the same name in dialog history. That is the whole point
 * of putting it here rather than in either consumer — a reloaded thread has to
 * render identically to the live turn, and two parsers is exactly how that stops
 * being true.
 *
 * Everything is validated, and anything that fails is DROPPED rather than
 * repaired: this payload is assembled from a remote MCP server's tool output,
 * so a malformed row means an upstream contract slip, and rendering a chip with
 * a blank title or a link to a non-https URL is worse than rendering nothing.
 *
 * Server-safe: no React, no browser APIs beyond `URL`.
 */
import type { ChatRef } from '../components/chat/chat-ref.types';
import type { ChatSource } from '../components/chat/types/message.types';
import type { SourcesEvent } from './events';
/**
 * A YouTube video id, from either a bare id or any of the watch/short/embed URL
 * shapes. Returns the ID, never a URL — the player takes an id.
 */
export declare function youtubeVideoId(value: unknown): string | undefined;
/**
 * Decode one source-metadata payload into its event, or `null` when there is
 * nothing usable in it.
 *
 * Returning `null` for an empty result matters: the reducer stamps this onto a
 * message, and an event carrying two empty arrays would overwrite metadata that
 * an earlier chunk of the same turn had already supplied.
 */
export declare function sourceMetadataEvent(payload: unknown): SourcesEvent | null;
/** What one assistant answer carries: its citations and its expandable refs. */
export interface SourceMetadata {
    sources?: ChatSource[];
    refs?: ChatRef[];
}
/**
 * Fold one decoded chunk into an answer's accumulated metadata.
 *
 * A single turn can call several remote tools, each returning its own metadata,
 * so this merges rather than replaces — and it is shared by the live reducer and
 * the history replay precisely because those two must agree on what a reloaded
 * answer shows.
 *
 * First writer wins per identity (`index` for a source, `type:id` for a ref),
 * the same rule the decoder applies within one payload.
 *
 * KNOWN LIMIT: citation numbers are assigned per tool result, so two tool calls
 * in one turn can both claim `[1]`. The later source is dropped rather than
 * renumbered — by then the numbers are already written into the answer text,
 * and renumbering would point `[1]` at a document the sentence is not about.
 */
export declare function mergeSourceMetadata(previous: SourceMetadata | null, event: SourcesEvent): SourceMetadata;
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