export type PageTitleError = 'required' | 'maxlength' | null;

export function pageTitleError(value: string | null | undefined, maxLength = 120): PageTitleError {
  const v = value ?? '';
  if (v.trim().length === 0) return 'required';
  if (v.length > maxLength) return 'maxlength';
  return null;
}

export function normalizePageTitle(value: string): string {
  return value.trim();
}

export type EventDerivedState = 'running' | 'countdown' | 'stopped' | 'unconfigured';

export function deriveEventState(start: string, end: string): EventDerivedState {
  if (!start || !end) return 'unconfigured';
  const s = Date.parse(start);
  const e = Date.parse(end);
  if (!Number.isFinite(s) || !Number.isFinite(e)) return 'unconfigured';
  const now = Date.now();
  if (now < s) return 'countdown';
  if (now >= s && now < e) return 'running';
  return 'stopped';
}

export function endAfterStartValidator(group: any): { endBeforeStart: true } | null {
  const start = group.get?.('eventStartUtc')?.value;
  const end = group.get?.('eventEndUtc')?.value;
  if (!start || !end) return null;
  const s = Date.parse(start);
  const e = Date.parse(end);
  if (Number.isFinite(s) && Number.isFinite(e) && e <= s) {
    return { endBeforeStart: true };
  }
  return null;
}

export function toDatetimeLocal(iso: string): string {
  if (!iso) return '';
  const d = new Date(iso);
  if (Number.isNaN(d.getTime())) return '';
  const pad = (n: number) => String(n).padStart(2, '0');
  return `${d.getUTCFullYear()}-${pad(d.getUTCMonth() + 1)}-${pad(d.getUTCDate())}T${pad(d.getUTCHours())}:${pad(d.getUTCMinutes())}`;
}

export function toIsoUtc(local: string): string {
  if (!local) return '';
  const d = new Date(local);
  if (Number.isNaN(d.getTime())) return local;
  return d.toISOString();
}