const crypto = require('crypto');
const env = require('../config/env');

const otpStore = new Map();

function generateOtp() {
  const minimum = 10 ** (env.otpLength - 1);
  const maximum = 10 ** env.otpLength;
  return String(minimum + crypto.randomInt(0, maximum - minimum));
}

function createOtp(targetKey) {
  const otpCode = generateOtp();
  const expiresAt = Date.now() + env.otpTtlMinutes * 60 * 1000;

  otpStore.set(targetKey, {
    otpCode,
    expiresAt,
  });

  return {
    otpCode,
    expiresAt,
  };
}

function verifyOtp(targetKey, otpCode) {
  const record = otpStore.get(targetKey);

  if (!record) {
    return false;
  }

  if (record.expiresAt < Date.now()) {
    otpStore.delete(targetKey);
    return false;
  }

  const isValid = record.otpCode === String(otpCode || '').trim();

  if (isValid) {
    otpStore.delete(targetKey);
  }

  return isValid;
}

module.exports = {
  createOtp,
  verifyOtp,
};