feat: implement answer submission and scoring system for guessing game

src/server/game/answerCheck.js

@@ -0,0 +1,107 @@
+// Fuzzy matching helpers for title/artist guessing
+
+function stripDiacritics(s) {
+  return String(s).normalize('NFKD').replace(/[\u0300-\u036f]/g, '');
+}
+
+function normalizeCommon(s) {
+  return stripDiacritics(String(s))
+    .toLowerCase()
+    .replace(/\s*(?:&|and|x|×|with|vs\.?|feat\.?|featuring)\s*/g, ' ')
+    .replace(/[^\p{L}\p{N}\s]/gu, ' ')
+    .replace(/\s+/g, ' ')
+    .trim();
+}
+
+function cleanTitleNoise(raw) {
+  let s = String(raw);
+  s = s.replace(/\(([^)]*remaster[^)]*)\)/gi, '')
+       .replace(/\(([^)]*radio edit[^)]*)\)/gi, '')
+       .replace(/\(([^)]*edit[^)]*)\)/gi, '')
+       .replace(/\(([^)]*version[^)]*)\)/gi, '')
+       .replace(/\(([^)]*live[^)]*)\)/gi, '')
+       .replace(/\(([^)]*mono[^)]*|[^)]*stereo[^)]*)\)/gi, '');
+  s = s.replace(/\b(remaster(?:ed)?(?: \d{2,4})?|radio edit|single version|original mix|version|live)\b/gi, '');
+  return s;
+}
+
+function normalizeTitle(s) { return normalizeCommon(cleanTitleNoise(s)); }
+function normalizeArtist(s) { return normalizeCommon(s).replace(/\bthe\b/g, ' ').replace(/\s+/g, ' ').trim(); }
+
+function tokenize(s) { return s ? String(s).split(' ').filter(Boolean) : []; }
+function tokenSet(s) { return new Set(tokenize(s)); }
+function jaccard(a, b) {
+  const A = tokenSet(a), B = tokenSet(b);
+  if (A.size === 0 && B.size === 0) return 1;
+  let inter = 0; for (const t of A) if (B.has(t)) inter++;
+  const union = A.size + B.size - inter;
+  return union ? inter / union : 0;
+}
+
+function levenshtein(a, b) {
+  a = String(a);
+  b = String(b);
+  const m = a.length, n = b.length;
+  if (!m) return n;
+  if (!n) return m;
+  const dp = new Array(n + 1);
+  for (let j = 0; j <= n; j++) dp[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];
+      const cost = a[i - 1] === b[j - 1] ? 0 : 1;
+      dp[j] = Math.min(dp[j] + 1, dp[j - 1] + 1, prev + cost);
+      prev = temp;
+    }
+  }
+  return dp[n];
+}
+function simRatio(a, b) {
+  if (!a && !b) return 1;
+  if (!a || !b) return 0;
+  const d = levenshtein(a, b);
+  return 1 - d / Math.max(String(a).length, String(b).length);
+}
+
+export function splitArtists(raw) {
+  const unified = String(raw)
+    .replace(/\s*(?:,|&|and|x|×|with|vs\.?|feat\.?|featuring)\s*/gi, ',')
+    .replace(/,+/g, ',')
+    .replace(/(^,|,$)/g, '');
+  const parts = unified.split(',').map(normalizeArtist).filter(Boolean);
+  return Array.from(new Set(parts));
+}
+
+const TITLE_SIM_THRESHOLD = 0.86;
+const TITLE_JACCARD_THRESHOLD = 0.8;
+const ARTIST_SIM_THRESHOLD = 0.82;
+
+export function scoreTitle(guessRaw, truthRaw) {
+  const g = normalizeTitle(guessRaw);
+  const t = normalizeTitle(truthRaw);
+  const sim = simRatio(g, t);
+  const jac = jaccard(g, t);
+  const pass = sim >= TITLE_SIM_THRESHOLD || jac >= TITLE_JACCARD_THRESHOLD;
+  return { pass, sim, jac, g, t };
+}
+
+export function scoreArtist(guessRaw, truthArtistsRaw, primaryCount) {
+  const truthArtists = (truthArtistsRaw || []).map((a) => normalizeArtist(a));
+  const truthSet = new Set(truthArtists);
+  const guessArtists = splitArtists(guessRaw);
+  const matches = new Set();
+  for (const ga of guessArtists) {
+    for (const ta of truthSet) {
+      const s = simRatio(ga, ta);
+      if (s >= ARTIST_SIM_THRESHOLD) matches.add(ta);
+    }
+  }
+  const primary = truthArtists.slice(0, primaryCount || truthArtists.length);
+  const pass = primary.some((p) => matches.has(p)); // accept any one artist
+  let best = 0; for (const ga of guessArtists) { for (const ta of truthSet) best = Math.max(best, simRatio(ga, ta)); }
+  return { pass, best, matched: Array.from(matches), guessArtists, truthArtists };
+}
+
+export default { scoreTitle, scoreArtist, splitArtists };