// UTF-8-safe Levenshtein distance with custom insertion/replacement/deletion costs.
// Iterates by Unicode code point (matches the PHP mb_levenshtein behaviour).

export function mbLevenshtein(s1, s2, costIns = 1, costRep = 1, costDel = 1) {
  const a = [...s1];
  const b = [...s2];
  const la = a.length;
  const lb = b.length;

  if (la === 0) return lb * costIns;
  if (lb === 0) return la * costDel;

  let prev = new Array(lb + 1);
  let curr = new Array(lb + 1);
  for (let j = 0; j <= lb; j++) prev[j] = j * costIns;

  for (let i = 1; i <= la; i++) {
    curr[0] = i * costDel;
    for (let j = 1; j <= lb; j++) {
      const cost = a[i - 1] === b[j - 1] ? 0 : costRep;
      const del = prev[j] + costDel;
      const ins = curr[j - 1] + costIns;
      const rep = prev[j - 1] + cost;
      curr[j] = del < ins ? (del < rep ? del : rep) : (ins < rep ? ins : rep);
    }
    [prev, curr] = [curr, prev];
  }
  return prev[lb];
}

export function mbLevenshteinRatio(s1, s2, costIns = 1, costRep = 1, costDel = 1) {
  const l1 = [...s1].length;
  const l2 = [...s2].length;
  const size = Math.max(l1, l2);
  if (!size) return 0;
  if (!s1) return l2 / size;
  if (!s2) return l1 / size;
  return 1 - mbLevenshtein(s1, s2, costIns, costRep, costDel) / size;
}

export function mbStrlen(s) {
  return [...s].length;
}

export function mbStrtolower(s) {
  return s.toLocaleLowerCase();
}