export type RegistrationEvent = {
  id: string; user_id: string; event: string; actor: string; note: string;
  applicant_message: string; mail_status: string; created_at: string;
  policy_changes?: string[];
}

const eventLabels: Record<string, string> = {
  approve: 'Account approved', reject: 'Registration rejected', reopen: 'Registration reopened for review',
  note: 'Internal note added', registration_observed: 'Registration recorded',
  verification_link_confirmed: 'Email address verified', verification_admin_override: 'Email marked verified by an administrator',
  verification_resend_requested: 'Verification email requested', verification_resend_failed: 'Verification email could not be sent',
  access_policy_changed: 'Access settings updated',
}
const legacyPolicyLabels: Record<string, string> = {
  enabled: 'Account access check', enableForRegistration: 'WordPress registration check',
  enableForWooCommerceRegistration: 'WooCommerce registration check', verificationMode: 'Verification method',
  skipRoles: 'Roles exempt from verification', registrationFormMode: 'Registration form handling',
}
const mailLabels: Record<string, string> = {
  queued: 'Notification email queued', sending: 'Notification email is being sent',
  accepted: 'Notification email submitted for sending. Delivery is not confirmed.',
  failed: 'Notification email could not be sent', skipped: 'Notification email was not sent',
}

function validTimezone(timezone: string) {
  if (/^[+-](?:0\d|1[0-4]):[0-5]\d$/.test(timezone)) return timezone
  try { new Intl.DateTimeFormat(undefined, { timeZone: timezone || 'UTC' }); return timezone || 'UTC' }
  catch { return 'UTC' }
}

export function activityTimezoneLabel(timezone: string) {
  const zone = validTimezone(timezone)
  return /^[+-]/.test(zone) ? /[1-9]/.test(zone) ? `UTC${zone}` : 'UTC' : zone
}

export function formatActivityDate(value: string, timezone = 'UTC') {
  const iso = value.replace(' ', 'T')
  const date = new Date(/(?:Z|[+-]\d{2}:\d{2})$/i.test(iso) ? iso : `${iso}Z`)
  if (Number.isNaN(date.getTime())) return 'Date unavailable'
  const zone = validTimezone(timezone)
  // WordPress can return a fixed offset instead of an IANA name. Support it
  // without relying on newer browsers accepting offsets in Intl.timeZone.
  const offset = zone.match(/^([+-])(\d{2}):(\d{2})$/)
  if (offset) date.setUTCMinutes(date.getUTCMinutes() + (offset[1] === '+' ? 1 : -1) * (Number(offset[2]) * 60 + Number(offset[3])))
  return date.toLocaleString(undefined, { timeZone: offset ? 'UTC' : zone, dateStyle: 'medium', timeStyle: 'short' })
}

export function policyChanges(item: RegistrationEvent) {
  if (item.event !== 'access_policy_changed') return []
  if (Array.isArray(item.policy_changes)) return item.policy_changes.filter(change => typeof change === 'string' && change.trim())
  // Backward compatible with an older Pro provider: never expose option keys.
  const keys = item.note.split(',').map(key => key.trim())
  return keys.every(key => legacyPolicyLabels[key])
    ? keys.map(key => `${legacyPolicyLabels[key]} changed`)
    : ['Account access settings changed.']
}

export function ActivityHistory({ items, timezone }: { items: RegistrationEvent[]; timezone: string }) {
  if (!items.length) return <p className="py-4 text-sm text-muted-foreground">No activity yet. New registrations, account decisions and access setting changes will appear here.</p>
  return <ol className="divide-y">{items.map(item => {
    const changes = policyChanges(item)
    return <li key={item.id} className="space-y-2 py-5 first:pt-0 last:pb-0">
      <div className="flex flex-wrap items-baseline justify-between gap-x-6 gap-y-1">
        <p className="text-sm font-medium">{eventLabels[item.event] || 'Registration activity recorded'}</p>
        <time dateTime={item.created_at.replace(' ', 'T')} className="text-xs tabular-nums text-muted-foreground">{formatActivityDate(item.created_at, timezone)}</time>
      </div>
      <p className="break-words text-xs text-muted-foreground">By {item.actor || 'System'}{Number(item.user_id) > 0 && ` · Account #${item.user_id}`}</p>
      {changes.length > 0 && <ul className="space-y-1 text-sm text-muted-foreground">{changes.map((change, index) => <li key={index} className="break-words">{change}</li>)}</ul>}
      {item.note && item.event !== 'access_policy_changed' && <p className="whitespace-pre-wrap break-words text-sm"><span className="font-medium">Internal note: </span>{item.note}</p>}
      {item.applicant_message && <p className="whitespace-pre-wrap break-words text-sm"><span className="font-medium">Message to applicant: </span>{item.applicant_message}</p>}
      {item.mail_status && item.mail_status !== 'none' && <p className="text-xs text-muted-foreground">{mailLabels[item.mail_status] || 'Notification email status unavailable'}</p>}
    </li>
  })}</ol>
}