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 };