/** Pure part of entity search (§294, §312): tier → match label and the final ordering. */

export type SearchType = 'cancer' | 'gene' | 'variant' | 'drug' | 'trial' | 'publication' | 'source';
export type SearchMatch = 'exact' | 'alias' | 'prefix' | 'trigram' | 'identifier';

export interface RankedHit {
  type: SearchType;
  title: string;
  /** 0 exact · 1 alias/identifier · 2 prefix · 3 trigram */
  tier: number;
  /** pg_trgm similarity (0..1), higher is better */
  score: number;
}

const IDENTIFIER_TYPES: ReadonlySet<SearchType> = new Set(['gene', 'trial', 'publication', 'variant']);

/** Tier 1 means "matched an identifier" for code-like entities and "matched an alias" for the rest. */
export function matchFromTier(tier: number, type: SearchType): SearchMatch {
  if (tier <= 0) return 'exact';
  if (tier === 1) return IDENTIFIER_TYPES.has(type) ? 'identifier' : 'alias';
  if (tier === 2) return 'prefix';
  return 'trigram';
}

/** Ordering: exact > alias/identifier > prefix > trigram, then similarity desc, then title A→Z. */
export function compareHits(a: RankedHit, b: RankedHit): number {
  if (a.tier !== b.tier) return a.tier - b.tier;
  if (a.score !== b.score) return b.score - a.score;
  return a.title.localeCompare(b.title, 'en', { sensitivity: 'base' });
}

export function sortHits<T extends RankedHit>(hits: T[]): T[] {
  return [...hits].sort(compareHits);
}