import crypto from 'node:crypto'

export function normalizeEmail(email: string) {
  return email.trim().toLowerCase()
}

export function isValidEmail(email: string) {
  const e = normalizeEmail(email)
  return /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(e)
}

export function isStrongPassword(password: string) {
  if (password.length < 8) return false
  const hasLetter = /[a-zA-Z]/.test(password)
  const hasNumber = /\d/.test(password)
  return hasLetter && hasNumber
}

export async function hashPassword(password: string) {
  const salt = crypto.randomBytes(16)
  const key = await new Promise<Buffer>((resolve, reject) => {
    crypto.scrypt(password, salt, 64, { N: 16384, r: 8, p: 1 }, (err, derivedKey) => {
      if (err) reject(err)
      else resolve(derivedKey as Buffer)
    })
  })
  return `scrypt$${salt.toString('hex')}$${key.toString('hex')}`
}

export async function verifyPassword(password: string, stored: string) {
  const parts = stored.split('$')
  if (parts.length !== 3 || parts[0] !== 'scrypt') return false
  const salt = Buffer.from(parts[1], 'hex')
  const expected = Buffer.from(parts[2], 'hex')

  const key = await new Promise<Buffer>((resolve, reject) => {
    crypto.scrypt(password, salt, 64, { N: 16384, r: 8, p: 1 }, (err, derivedKey) => {
      if (err) reject(err)
      else resolve(derivedKey as Buffer)
    })
  })

  if (key.length !== expected.length) return false
  return crypto.timingSafeEqual(key, expected)
}

export function hashBackupCode(code: string, saltHex?: string) {
  const salt = saltHex ? Buffer.from(saltHex, 'hex') : crypto.randomBytes(16)
  const h = crypto.createHash('sha256').update(salt).update(code).digest('hex')
  return `sha256$${salt.toString('hex')}$${h}`
}

export function verifyBackupCode(code: string, stored: string) {
  const parts = stored.split('$')
  if (parts.length !== 3 || parts[0] !== 'sha256') return false
  const saltHex = parts[1]
  const expected = parts[2]
  const actual = hashBackupCode(code, saltHex).split('$')[2]
  return crypto.timingSafeEqual(Buffer.from(actual), Buffer.from(expected))
}

export function generateBackupCodes(count: number) {
  const codes: string[] = []
  for (let i = 0; i < count; i++) {
    const raw = crypto.randomBytes(5).toString('hex').slice(0, 10).toUpperCase()
    codes.push(`${raw.slice(0, 5)}-${raw.slice(5)}`)
  }
  return codes
}