/**
 * item-match-text — the pure text scoring behind the POS matcher.
 *
 * These three helpers used to live in `item-intel-service.ts`. They
 * moved here so that `pos-match.ts` (the shared, size-aware POS
 * matcher) and `item-intel-service.ts` (the ⓘ popover) can share one
 * implementation without importing each other.
 *
 * Pure and client-safe: no PocketBase, no AI, no DOM.
 */

import { jaccard } from "@/lib/server/order-quote-match";

/** Tokenizer tuned for item-intel fuzzy matching.
 *
 *  Differs from `order-quote-match.tokenize` in three ways that
 *  matter for catalogue fuzziness:
 *
 *    1. Keeps short numeric tokens ("50", "20L", "M20") — these
 *       carry product identity (sizes, capacities, model numbers).
 *       Dropping them made every SAE oil tie at overlap=1.0 and
 *       ruined price_list matching against the AFRIQ SKUs.
 *    2. Smaller stopword set — only tokens that are pure noise
 *       across every catalogue. No "mm" / "qty" filter because
 *       "qty" doesn't appear in our descriptions and "mm" only
 *       does so meaningfully (e.g. "M6 X 30MM" — keep it).
 *    3. Allows single-character numeric tokens ("L", "5") so
 *       compound unit strings like "20LT" or "5L" tokenise as
 *       one unit token (the regex matches the whole run, not
 *       per-character).
 */
const INTEL_STOPWORDS = new Set([
  "the", "and", "with", "for", "of", "to", "a", "an", "in", "on", "at",
  "by", "from", "as", "is", "or", "x",
]);

export function tokenizeIntel(s: string): Set<string> {
  const out = new Set<string>();
  if (!s) return out;
  for (const tok of String(s).toLowerCase().match(/[a-z0-9]+/g) || []) {
    if (INTEL_STOPWORDS.has(tok)) continue;
    out.add(tok);
  }
  return out;
}

/** Overlap coefficient: |A ∩ B| / min(|A|, |B|).
 *  Better than Jaccard for "short query against a rich candidate" —
 *  doesn't penalise extra tokens on the candidate side. Used for
 *  ranking against the price_list `search_text` blob. */
export function overlapScore(a: Set<string>, b: Set<string>): number {
  if (a.size === 0 || b.size === 0) return 0;
  let inter = 0;
  for (const t of a) if (b.has(t)) inter++;
  return inter / Math.min(a.size, b.size);
}

/** Drop stopwords + short tokens. */
const INFORMATIVE_MIN_LEN = 3;

/** Pick the top N tokens by length desc (most distinctive first). */
export function informativeTokens(s: string, max = 4): string[] {
  const toks = tokenizeIntel(s || "");
  return [...toks]
    .filter((t) => !INTEL_STOPWORDS.has(t) && t.length >= INFORMATIVE_MIN_LEN)
    .sort((a, b) => b.length - a.length)
    .slice(0, max);
}

/** Combined Jaccard + overlap score, capped at 1. */
export function combinedScore(a: Set<string>, b: Set<string>): number {
  return Math.max(jaccard(a, b), overlapScore(a, b));
}