/**
 * Stateless scoring primitives for the solution matcher.
 *
 * Extracted from solution-matcher.ts — these are pure functions with no
 * filesystem or module-level state dependencies.
 */
/** High-frequency tags that should be weighted lower */
export declare const COMMON_TAGS: Set<string>;
/** Apply IDF-like weight: common tags get reduced weight */
export declare function tagWeight(tag: string): number;
/**
 * Compute the Dice coefficient between two strings using character bigrams.
 *
 * Dice = 2 * |intersection| / (|A| + |B|)
 *
 * Both strings are lowercased and whitespace-stripped before bigram generation.
 * Returns 0 for empty strings or single-character strings (no bigrams possible).
 * Returns 1.0 for identical non-trivial strings.
 *
 * This is used as a lightweight fuzzy matching signal for borderline cases
 * where the TF-IDF tag intersection produces a low score but the query and
 * solution tags are character-similar (e.g., "database" vs "데이터베이스"
 * won't match, but "database" vs "databse" will get a high score).
 */
export declare function bigramSimilarity(a: string, b: string): number;
/**
 * Simplified BM25 score for a single query-document pair.
 * Uses tag overlap with term frequency normalization.
 * k1=1.2, b=0.75 (standard BM25 parameters).
 */
export declare function bm25Score(queryTags: string[], docTags: string[], avgDocLength: number): number;