'use client';

import { useEffect, useState } from 'react';
import { startRegistration } from '@simplewebauthn/browser';

interface Passkey {
  credentialId: string;
  label: string;
  createdAt: string;
  lastUsedAt: string | null;
}

function formatDate(iso: string | null): string {
  if (!iso) return '—';
  // SQLite liefert "YYYY-MM-DD HH:MM:SS" (UTC).
  const d = new Date(iso.replace(' ', 'T') + 'Z');
  if (isNaN(d.getTime())) return '—';
  return d.toLocaleDateString('de-DE', { day: '2-digit', month: '2-digit', year: 'numeric' });
}

export default function Passkeys() {
  const [passkeys, setPasskeys] = useState<Passkey[]>([]);
  const [loading, setLoading] = useState(true);
  const [busy, setBusy] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const [label, setLabel] = useState('');

  function load() {
    return fetch('/api/passkey')
      .then((r) => (r.ok ? r.json() : Promise.reject(new Error())))
      .then((data) => setPasskeys(data.passkeys ?? []))
      .catch(() => setError('Passkeys konnten nicht geladen werden.'))
      .finally(() => setLoading(false));
  }

  useEffect(() => {
    load();
  }, []);

  async function handleRegister() {
    setError(null);
    setBusy(true);
    try {
      const optRes = await fetch('/api/passkey/register');
      if (!optRes.ok) throw new Error('Optionen konnten nicht geladen werden.');
      const optionsJSON = await optRes.json();

      const response = await startRegistration({ optionsJSON });

      const verifyRes = await fetch('/api/passkey/register', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ response, label }),
      });
      if (!verifyRes.ok) {
        const data = await verifyRes.json().catch(() => null);
        throw new Error(data?.error ?? 'Passkey konnte nicht registriert werden.');
      }
      setLabel('');
      await load();
    } catch (err) {
      if (err instanceof Error && err.name === 'NotAllowedError') {
        setError(null); // Abbruch durch Nutzer
      } else {
        setError(err instanceof Error ? err.message : 'Passkey konnte nicht registriert werden.');
      }
    } finally {
      setBusy(false);
    }
  }

  async function handleDelete(credentialId: string) {
    if (!confirm('Diesen Passkey wirklich entfernen?')) return;
    setError(null);
    try {
      const res = await fetch(`/api/passkey?id=${encodeURIComponent(credentialId)}`, {
        method: 'DELETE',
      });
      if (!res.ok) throw new Error();
      await load();
    } catch {
      setError('Passkey konnte nicht entfernt werden.');
    }
  }

  return (
    <div className="max-w-md mt-8 pt-6 border-t border-gray-200">
      <h3 className="text-sm font-semibold text-gray-900 mb-1">Passkeys</h3>
      <p className="text-xs text-gray-500 mb-3">
        Melde dich künftig per Fingerabdruck, Gesichtserkennung oder Geräte-PIN an. Das Passwort
        bleibt als Alternative bestehen.
      </p>

      {loading ? (
        <p className="text-sm text-gray-500">Lädt…</p>
      ) : passkeys.length === 0 ? (
        <p className="text-sm text-gray-500 mb-3">Noch keine Passkeys registriert.</p>
      ) : (
        <ul className="space-y-2 mb-4">
          {passkeys.map((pk) => (
            <li
              key={pk.credentialId}
              className="flex items-center justify-between gap-3 border-2 border-gray-300 rounded-lg px-3 py-2"
            >
              <div className="min-w-0">
                <div className="text-sm font-medium text-gray-900 truncate">{pk.label}</div>
                <div className="text-xs text-gray-500">
                  Erstellt {formatDate(pk.createdAt)} · Zuletzt {formatDate(pk.lastUsedAt)}
                </div>
              </div>
              <button
                onClick={() => handleDelete(pk.credentialId)}
                className="text-xs px-2 py-1 text-red-600 hover:text-red-800 shrink-0"
              >
                Entfernen
              </button>
            </li>
          ))}
        </ul>
      )}

      <div className="flex items-end gap-2">
        <div className="flex-1">
          <label className="block text-xs font-medium text-gray-700 mb-1">
            Bezeichnung (optional)
          </label>
          <input
            type="text"
            value={label}
            onChange={(e) => setLabel(e.target.value)}
            placeholder="z. B. iPhone von Birgit"
            maxLength={80}
            className="w-full px-3 py-2 border-2 border-gray-400 rounded-lg bg-white text-gray-900 text-sm focus:border-green-600 focus:outline-none"
          />
        </div>
        <button
          onClick={handleRegister}
          disabled={busy}
          className="px-4 py-2 bg-[#86C28B] hover:bg-[#6FB075] text-black font-medium rounded-lg transition-colors disabled:opacity-50 text-sm shrink-0"
        >
          {busy ? 'Läuft…' : 'Passkey hinzufügen'}
        </button>
      </div>

      {error && (
        <div className="mt-3 bg-red-50 border border-red-300 text-red-700 px-3 py-2 rounded-lg text-sm">
          {error}
        </div>
      )}
    </div>
  );
}