/**
 * Format a Date for an HTML <input type="date"> value (yyyy-mm-dd, local timezone).
 * Returns "" for null/undefined.
 */
export function toDateInputValue(date: Date | string | null | undefined): string {
  if (!date) return "";
  const d = typeof date === "string" ? new Date(date) : date;
  const y = d.getFullYear();
  const m = String(d.getMonth() + 1).padStart(2, "0");
  const day = String(d.getDate()).padStart(2, "0");
  return `${y}-${m}-${day}`;
}

/**
 * Format a date as dd/mm/yyyy for display in the UI.
 * Input date inputs (type="date") still use yyyy-mm-dd — this is for rendered text only.
 */
export function formatDate(d: Date | string | null | undefined): string {
  if (!d) return "";
  return new Date(d).toLocaleDateString("en-GB"); // en-GB → dd/mm/yyyy
}

/**
 * Format a date as "DD MMM" (e.g. "04 Mar") for compact timeline labels.
 */
export function formatDateShort(d: Date | string): string {
  return new Date(d).toLocaleDateString("en-GB", { day: "2-digit", month: "short" });
}

/**
 * Format a date as "MMM YY" (e.g. "Mar 26") for timeline month headers.
 */
export function formatMonthYear(d: Date | string): string {
  return new Date(d).toLocaleDateString("en-GB", { month: "short", year: "2-digit" });
}

/**
 * Format a date in long form (e.g. "4 March 2026") for descriptive contexts.
 */
export function formatDateLong(d: Date | string): string {
  return new Date(d).toLocaleDateString("en-GB", { day: "numeric", month: "long", year: "numeric" });
}

/**
 * Format integer cents as a currency string (e.g. "1.234 €").
 * Defaults to EUR with no decimal places. Pass `fractionDigits: 2` for precise display.
 */
export function formatMoney(cents: number | null | undefined, currency = "EUR", fractionDigits = 0): string {
  const value = (cents ?? 0) / 100;
  return new Intl.NumberFormat("de-DE", {
    style: "currency",
    currency,
    minimumFractionDigits: fractionDigits,
    maximumFractionDigits: fractionDigits,
  }).format(value);
}

/**
 * Format a date as "16 Mar 2026" for compact display with year.
 */
export function formatDateMedium(d: Date | string | null | undefined): string {
  if (!d) return "";
  return new Date(d).toLocaleDateString("en-GB", { year: "numeric", month: "short", day: "numeric" });
}

/**
 * Format integer cents as a plain decimal string (e.g. "12,34").
 * Returns "-" for null/undefined.
 */
export function formatCents(cents: number | null | undefined): string {
  if (cents == null) return "-";
  return (cents / 100).toLocaleString("de-DE", { minimumFractionDigits: 2, maximumFractionDigits: 2 });
}