// Word masking and hint helpers for Skribbl mode.

function normalize(s) {
  return String(s || "")
    .trim()
    .toLowerCase()
    .replace(/\s+/g, " ");
}

function maskWord(word, revealed = new Set()) {
  // produce a mask like "_ _ _ _" preserving spaces
  return word
    .split("")
    .map((ch, i) => {
      if (ch === " ") return " ";
      if (revealed.has(i)) return ch.toLowerCase();
      return "_";
    })
    .join("");
}

function pickRevealIndex(word, revealed) {
  const candidates = [];
  for (let i = 0; i < word.length; i++) {
    if (word[i] === " ") continue;
    if (revealed.has(i)) continue;
    candidates.push(i);
  }
  if (candidates.length === 0) return null;
  return candidates[Math.floor(Math.random() * candidates.length)];
}

function isCloseGuess(guess, word) {
  const g = normalize(guess);
  const w = normalize(word);
  if (!g || !w || g === w) return false;
  if (Math.abs(g.length - w.length) > 2) return false;
  // simple Levenshtein
  const m = g.length, n = w.length;
  const dp = Array.from({ length: m + 1 }, () => new Array(n + 1).fill(0));
  for (let i = 0; i <= m; i++) dp[i][0] = i;
  for (let j = 0; j <= n; j++) dp[0][j] = j;
  for (let i = 1; i <= m; i++) {
    for (let j = 1; j <= n; j++) {
      const cost = g[i - 1] === w[j - 1] ? 0 : 1;
      dp[i][j] = Math.min(
        dp[i - 1][j] + 1,
        dp[i][j - 1] + 1,
        dp[i - 1][j - 1] + cost
      );
    }
  }
  return dp[m][n] <= 2;
}

module.exports = { normalize, maskWord, pickRevealIndex, isCloseGuess };