/** Levenshtein edit distance between two strings */
export function editDistance(a: string, b: string): number {
  const m = a.length, n = b.length;
  const dp: number[] = Array(n + 1).fill(0).map((_, j) => j);
  for (let i = 1; i <= m; i++) {
    let prev = dp[0];
    dp[0] = i;
    for (let j = 1; j <= n; j++) {
      const temp = dp[j];
      dp[j] = a[i - 1] === b[j - 1] ? prev : 1 + Math.min(prev, dp[j], dp[j - 1]);
      prev = temp;
    }
  }
  return dp[n];
}

/** Return a score 0–1 for how well a user matches a search query */
export function scoreUser(u: any, raw: string): number {
  const q = raw.toLowerCase().trim();
  if (!q || q.length < 2) return 0;

  const name  = (u.name  || "").toLowerCase();
  const email = (u.email || "").toLowerCase();
  const phone = (u.phoneNumber || "").replace(/\D/g, "");
  const qPhone = q.replace(/\D/g, "");

  let best = 0;

  // Exact substring matches — highest priority
  if (name.includes(q))  best = Math.max(best, 1.0);
  if (email.includes(q)) best = Math.max(best, 0.95);
  if (qPhone.length >= 3 && phone.includes(qPhone)) best = Math.max(best, 0.95);

  // Word-level starts-with (handles partial first/last name)
  const words = name.split(/\s+/);
  if (words.some((w: string) => w.startsWith(q))) best = Math.max(best, 0.85);

  // Fuzzy edit-distance against each name word
  const maxDist = q.length <= 4 ? 1 : q.length <= 7 ? 2 : 3;
  for (const w of words) {
    const slice = w.slice(0, q.length + 2); // compare against similar-length slice
    const d = editDistance(q, slice);
    if (d <= maxDist) best = Math.max(best, 0.75 - d * 0.15);
  }
  // Also fuzzy against the full name (catches "jhn smth" → "john smith")
  const nameSlice = name.slice(0, q.length + 4);
  const fullDist = editDistance(q, nameSlice);
  if (fullDist <= maxDist + 1) best = Math.max(best, 0.6 - fullDist * 0.12);

  return best;
}