import { Tool } from '../../tool.js';
import { BM25SearchResult, IndexDocumentInput } from './types.js';
export interface BM25EngineOptions {
    k1?: number;
    b?: number;
    nameBoost?: number;
    titleBoost?: number;
    paramBoost?: number;
    descBoost?: number;
}
export declare class BM25Engine<T = Tool> {
    private readonly k1;
    private readonly b;
    private readonly nameBoost;
    private readonly titleBoost;
    private readonly paramBoost;
    private readonly descBoost;
    private documents;
    private df;
    private avgDocLength;
    private contentHash;
    constructor(options?: BM25EngineOptions);
    /**
     * Builds the in-memory inverted index from generic document inputs.
     * If a matching content hash is provided and index exists, indexing is skipped.
     */
    buildIndex(docs: IndexDocumentInput<T>[], hash?: string): void;
    /**
     * Helper to build index directly from Tool instances.
     */
    indexTools(tools: Tool[], hash?: string): void;
    /**
     * Searches the indexed documents using Lucene BM25 Okapi non-negative scoring.
     */
    search(query: string, limit?: number): BM25SearchResult<T>[];
    /**
     * Diagnostic statistics for debugging and NitroStudio telemetry.
     */
    getStats(): {
        docCount: number;
        avgDocLength: number;
        vocabSize: number;
        contentHash: string;
    };
}
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