import type { SankeyLayoutLink, SankeyLayoutModel, SankeyLayoutNode } from '../types/sankey-internal.js';
/**
 * Id lookups for a single layout. `linksBySource` maps `sourceId` → `targetId`
 * → the links between that pair. That array holds a single link in the normal
 * case; it holds more only for parallel links (multiple links between the same
 * node pair), which are rare. Resolving one of those by its `linkIndex` with a
 * short `find` reads more simply than a third nested map and, given the array
 * is almost always length one, is effectively just as fast.
 */
export interface SankeyLayoutIndex {
    nodesById: Map<string, SankeyLayoutNode>;
    linksBySource: Map<string, Map<string, SankeyLayoutLink[]>>;
}
/**
 * Seeds the cache with an index that `generateSankeyLayout` collected during
 * d3-sankey's own single pass over the graph, so the resolvers stay `O(1)`
 * without `buildIndex` ever re-scanning the nodes and links.
 */
export declare function primeLayoutIndex(layout: SankeyLayoutModel, index: SankeyLayoutIndex): void;
/**
 * Resolves a node by id against the current layout in `O(1)`, or `undefined`
 * when the id is absent (e.g. after a data change dropped it).
 */
export declare function resolveLayoutNode(layout: SankeyLayoutModel, nodeId: string): SankeyLayoutNode | undefined;
/**
 * Resolves a link by its source/target ids and per-layout link index against
 * the current layout, together with both resolved endpoint nodes. Returns
 * `undefined` when the link is absent or either endpoint is unresolved. The
 * `linkIndex` discriminant picks the right link when parallel links share the
 * same source and target ids; with the usual single link per pair it simply
 * matches that one.
 */
export declare function resolveLayoutLink(layout: SankeyLayoutModel, sourceId: string, targetId: string, linkIndex: number): {
    link: SankeyLayoutLink;
    source: SankeyLayoutNode;
    target: SankeyLayoutNode;
} | undefined;
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