import crypto from "crypto";

// Simple in-memory CAPTCHA store (in production, use Redis or database)
const captchaStore: Map<string, { code: string; createdAt: number; attempts: number }> = new Map();

const CAPTCHA_TTL = 5 * 60 * 1000; // 5 minutes
const MAX_ATTEMPTS = 5;
const CLEANUP_INTERVAL = 10 * 60 * 1000; // 10 minutes

// Cleanup old captchas periodically
setInterval(() => {
  const now = Date.now();
  for (const [key, value] of captchaStore.entries()) {
    if (now - value.createdAt > CAPTCHA_TTL) {
      captchaStore.delete(key);
    }
  }
}, CLEANUP_INTERVAL);

export function generateCaptcha(identifier: string): { id: string; code: string } {
  const code = Math.random().toString().slice(2, 8); // 6-digit code
  const id = crypto.randomBytes(16).toString("hex");

  captchaStore.set(id, {
    code,
    createdAt: Date.now(),
    attempts: 0,
  });

  return { id, code };
}

export interface CaptchaVerificationResult {
  success: boolean;
  error?: string;
  attemptsRemaining?: number;
}

export function verifyCaptcha(id: string, code: string): CaptchaVerificationResult {
  const captcha = captchaStore.get(id);

  if (!captcha) {
    return { success: false, error: "CAPTCHA not found or expired. Please reload and try again." };
  }

  // Check if expired
  if (Date.now() - captcha.createdAt > CAPTCHA_TTL) {
    captchaStore.delete(id);
    return { success: false, error: "CAPTCHA code has expired. Please request a new one." };
  }

  // Check attempts
  if (captcha.attempts >= MAX_ATTEMPTS) {
    captchaStore.delete(id);
    return { success: false, error: "Too many incorrect attempts. Please request a new CAPTCHA code." };
  }

  // Verify code
  if (captcha.code === code) {
    captchaStore.delete(id);
    return { success: true };
  }

  // Increment attempts
  captcha.attempts++;
  const remaining = MAX_ATTEMPTS - captcha.attempts;
  return {
    success: false,
    error: `Incorrect CAPTCHA code. ${remaining} attempt${remaining === 1 ? "" : "s"} remaining.`,
    attemptsRemaining: remaining,
  };
}

export function getMaxAttempts(): number {
  return MAX_ATTEMPTS;
}