/**
 * In-memory knowledge index construction.
 *
 * Index construction is an application-process lifecycle operation, not a
 * per-session one. A complete `KnowledgeIndexSnapshot` is built once from the
 * normalized entries and then queried by every turn.
 *
 * The lexical scorer is a compact field-aware BM25 (BM25F-style): each of the
 * five text fields is scored independently and combined with per-field
 * weights, retaining the per-field breakdown so a retrieval decision is
 * explainable in traces. No embedding model or vector store is involved.
 */
import type { IndexedKnowledgeDocument, KnowledgeFieldWeights, KnowledgeIndexSnapshot, KnowledgeLexicalMatch, NormalizedKnowledgeEntry } from "../types/index.js";
/**
 * Field-aware BM25 over the document set. Query text is scored per field and
 * the weighted per-field scores are summed. Satisfies the structural
 * `KnowledgeLexicalSearcher` type held by a snapshot.
 */
export declare class KnowledgeLexicalIndex {
    private readonly weights;
    private readonly postings;
    private readonly fieldLengths;
    private readonly fieldTokenTotals;
    private readonly avgFieldLength;
    private docCount;
    constructor(weights: KnowledgeFieldWeights);
    add(document: IndexedKnowledgeDocument): void;
    finalize(): void;
    search(queryTokens: string[], topK: number, eligibleEntryIds?: ReadonlySet<string>): KnowledgeLexicalMatch[];
}
/**
 * Build the internal search document from a normalized entry. `exactKeys`
 * carry whole-phrase identifiers (entry id and title); each
 * text field is tokenized for the field-aware scorer.
 */
export declare const buildDocument: (entry: NormalizedKnowledgeEntry) => IndexedKnowledgeDocument;
/**
 * Build the complete immutable snapshot: entry map, exact/alias/relation
 * indexes, and the field-aware lexical index.
 */
export declare const buildIndexSnapshot: (entries: NormalizedKnowledgeEntry[], weights: KnowledgeFieldWeights) => KnowledgeIndexSnapshot;