import { randomInt } from 'crypto'

interface CaptchaChallenge {
  answer: number
  expires: number
}

// Simple in-memory store for captcha challenges
const captchaStore = new Map<string, CaptchaChallenge>()

// Clean up expired captchas every 5 minutes
setInterval(() => {
  const now = Date.now()
  for (const [key, value] of captchaStore.entries()) {
    if (value.expires < now) {
      captchaStore.delete(key)
    }
  }
}, 5 * 60 * 1000)

function generateCaptchaId(): string {
  return `captcha_${Date.now()}_${randomInt(10000, 99999)}`
}

export interface CaptchaData {
  captchaId: string
  question: string
}

export function generateCaptcha(): CaptchaData {
  // Generate simple math problem
  const num1 = randomInt(1, 20)
  const num2 = randomInt(1, 20)
  const operations = ['+', '-', '×'] as const
  const operation = operations[randomInt(0, operations.length)]

  let answer: number
  let question: string

  switch (operation) {
    case '+':
      answer = num1 + num2
      question = `${num1} + ${num2}`
      break
    case '-':
      // Ensure positive result
      const larger = Math.max(num1, num2)
      const smaller = Math.min(num1, num2)
      answer = larger - smaller
      question = `${larger} - ${smaller}`
      break
    case '×':
      // Use smaller numbers for multiplication
      const small1 = randomInt(2, 10)
      const small2 = randomInt(2, 10)
      answer = small1 * small2
      question = `${small1} × ${small2}`
      break
  }

  const captchaId = generateCaptchaId()

  // Store captcha with 10 minute expiration
  captchaStore.set(captchaId, {
    answer,
    expires: Date.now() + 10 * 60 * 1000
  })

  return {
    captchaId,
    question
  }
}

export function verifyCaptcha(captchaId: string, answer: string | number): boolean {
  const stored = captchaStore.get(captchaId)

  if (!stored) {
    return false
  }

  if (stored.expires < Date.now()) {
    captchaStore.delete(captchaId)
    return false
  }

  const isValid = parseInt(answer.toString()) === stored.answer

  // Delete captcha after verification (one-time use)
  captchaStore.delete(captchaId)

  return isValid
}