export interface UserAgentInfo {
  browser: string | null
  operatingSystem: string | null
  device: string | null
}

const BROWSER_PATTERNS: Array<[RegExp, string]> = [
  [/Edg\//i, 'Microsoft Edge'],
  [/OPR\//i, 'Opera'],
  [/Chrome\//i, 'Chrome'],
  [/Safari\//i, 'Safari'],
  [/Firefox\//i, 'Firefox'],
  [/MSIE |Trident\//i, 'Internet Explorer']
]

const OS_PATTERNS: Array<[RegExp, string]> = [
  [/Windows NT 10\.0/i, 'Windows 10/11'],
  [/Windows NT 6\.3/i, 'Windows 8.1'],
  [/Windows NT 6\.2/i, 'Windows 8'],
  [/Windows NT 6\.1/i, 'Windows 7'],
  [/Windows/i, 'Windows'],
  [/Mac OS X ([\d_.]+)/i, 'macOS'],
  [/iPhone OS ([\d_]+)/i, 'iOS'],
  [/iPad.*CPU OS ([\d_]+)/i, 'iPadOS'],
  [/Android ([\d.]+)/i, 'Android'],
  [/Linux/i, 'Linux']
]

const DEVICE_PATTERNS: Array<[RegExp, string]> = [
  [/iPhone/i, 'iPhone'],
  [/iPad/i, 'iPad'],
  [/Android.*Mobile/i, 'Android Phone'],
  [/Android/i, 'Android Tablet'],
  [/Windows Phone/i, 'Windows Phone'],
  [/Macintosh/i, 'Mac'],
  [/Windows/i, 'Windows PC'],
  [/Linux/i, 'Linux PC']
]

export function parseUserAgent(userAgent: string | null | undefined): UserAgentInfo {
  const ua = (userAgent ?? '').trim()
  if (!ua) return { browser: null, operatingSystem: null, device: null }

  let browser: string | null = null
  for (const [regex, name] of BROWSER_PATTERNS) {
    if (regex.test(ua)) {
      browser = name
      break
    }
  }

  let operatingSystem: string | null = null
  for (const [regex, name] of OS_PATTERNS) {
    if (regex.test(ua)) {
      operatingSystem = name
      break
    }
  }

  let device: string | null = null
  for (const [regex, name] of DEVICE_PATTERNS) {
    if (regex.test(ua)) {
      device = name
      break
    }
  }

  return { browser, operatingSystem, device }
}

export type LoginMethod = 'password' | 'oauth' | 'webauthn' | 'totp_2fa' | 'email_2fa'