/**
 * Hybrid Re-Ranker using Reciprocal Rank Fusion (RRF)
 * Combines vector search results with FTS5 results for better ranking
 */
/**
 * Configuration for hybrid re-ranking
 */
export interface RerankConfig {
    /** RRF constant k - higher values reduce the impact of rank differences (default: 60) */
    rrfK: number;
    /** Weight for vector search results (0-1, default: 0.7) */
    vectorWeight: number;
    /** Weight for FTS results (0-1, default: 0.3) */
    ftsWeight: number;
    /** Whether re-ranking is enabled */
    enabled: boolean;
}
export declare const DEFAULT_RERANK_CONFIG: RerankConfig;
/**
 * Generic result with ID and score
 */
export interface RankableResult {
    id: number | string;
    score: number;
}
/**
 * Re-ranked result with combined score
 */
export interface RerankResult {
    id: number | string;
    combinedScore: number;
    vectorRank: number | null;
    ftsRank: number | null;
    vectorScore: number | null;
    ftsScore: number | null;
}
/**
 * Hybrid Re-Ranker class
 */
export declare class HybridReranker {
    private config;
    constructor(config?: Partial<RerankConfig>);
    /**
     * Get current configuration
     */
    getConfig(): RerankConfig;
    /**
     * Calculate RRF score for a given rank
     * Formula: 1 / (k + rank)
     */
    private calculateRrfScore;
    /**
     * Re-rank results using Reciprocal Rank Fusion
     * Combines vector search and FTS results for better overall ranking
     *
     * @param vectorResults - Results from vector/semantic search (sorted by similarity)
     * @param ftsResults - Results from full-text search (sorted by relevance)
     * @param limit - Maximum results to return
     */
    rerank(vectorResults: RankableResult[], ftsResults: RankableResult[], limit: number): RerankResult[];
    /**
     * Re-rank with boosting for results that appear in both sources
     * Results in both vector and FTS get an extra boost
     *
     * @param vectorResults - Results from vector/semantic search
     * @param ftsResults - Results from full-text search
     * @param limit - Maximum results to return
     * @param overlapBoost - Extra score multiplier for overlapping results (default: 1.2)
     */
    rerankWithOverlapBoost(vectorResults: RankableResult[], ftsResults: RankableResult[], limit: number, overlapBoost?: number): RerankResult[];
}
/**
 * Get or create a hybrid reranker with given config
 */
export declare function getHybridReranker(config?: Partial<RerankConfig>): HybridReranker;
/**
 * Get rerank config from environment or defaults
 */
export declare function getRerankConfig(): RerankConfig;
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