feat: MC Report System - MySQL + Express + Vanilla JS SPA

backend/captcha.js

@@ -0,0 +1,40 @@
+const crypto = require('crypto');
+const { getDb } = require('./db');
+
+function generate() {
+  const db = getDb();
+  db.prepare("DELETE FROM captchas WHERE datetime(created_at) < datetime('now','localtime','-5 minutes')").run();
+
+  const id = crypto.randomUUID();
+  const ops = ['+', '-', '\u00d7'];
+  const op = ops[Math.floor(Math.random() * ops.length)];
+  let a, b, answer;
+
+  if (op === '\u00d7') {
+    a = Math.floor(Math.random() * 9) + 1;
+    b = Math.floor(Math.random() * 9) + 1;
+  } else {
+    a = Math.floor(Math.random() * 20) + 1;
+    b = Math.floor(Math.random() * 10) + 1;
+    if (op === '-' && a < b) [a, b] = [b, a];
+  }
+
+  if (op === '+') answer = a + b;
+  else if (op === '-') answer = a - b;
+  else answer = a * b;
+
+  const question = `${a} ${op} ${b} = ?`;
+  db.prepare('INSERT INTO captchas(id, question, answer) VALUES (?,?,?)').run(id, question, String(answer));
+
+  return { id, question };
+}
+
+function verify(id, answer) {
+  const db = getDb();
+  const row = db.prepare("SELECT * FROM captchas WHERE id = ? AND datetime(created_at) > datetime('now','localtime','-5 minutes')").get(id);
+  if (!row) return false;
+  db.prepare('DELETE FROM captchas WHERE id = ?').run(id);
+  return String(answer).trim() === row.answer;
+}
+
+module.exports = { generate, verify };