/**
 * Formatting lives here so a rupee looks the same in a KPI, an axis tick and a
 * tooltip. Locale is pinned to en-IN — this is an Indian retail product, and
 * lakh/crore grouping is what merchants read.
 *
 * Every formatter is pure and locale-explicit: relying on the runtime default
 * would make the server and client disagree and produce hydration mismatches.
 */

const NUM = new Intl.NumberFormat('en-IN');
const INR = new Intl.NumberFormat('en-IN', {
  style: 'currency',
  currency: 'INR',
  maximumFractionDigits: 0,
});

export function formatCount(v: number): string {
  return NUM.format(Math.round(v));
}

export function formatInr(v: number): string {
  return INR.format(Math.round(v));
}

/** Drops a trailing ".0" so axis ticks read ₹90k rather than ₹90.0k. */
function trim(n: number): string {
  return n.toFixed(1).replace(/\.0$/, '');
}

/** Axis-scale currency: ₹1.2L rather than ₹1,20,000. */
export function formatInrCompact(v: number): string {
  if (Math.abs(v) >= 10000000) return `₹${trim(v / 10000000)}Cr`;
  if (Math.abs(v) >= 100000) return `₹${trim(v / 100000)}L`;
  if (Math.abs(v) >= 1000) return `₹${trim(v / 1000)}k`;
  return `₹${Math.round(v)}`;
}

export function formatCompact(v: number): string {
  if (Math.abs(v) >= 10000000) return `${trim(v / 10000000)}Cr`;
  if (Math.abs(v) >= 100000) return `${trim(v / 100000)}L`;
  if (Math.abs(v) >= 1000) return `${trim(v / 1000)}k`;
  return String(Math.round(v));
}

export function formatPct(v: number, digits = 1): string {
  return `${v.toFixed(digits)}%`;
}

export function formatLyt(v: number): string {
  return `${NUM.format(Math.round(v))} LYT`;
}

/** Signed delta for the KPI change chip. */
export function formatDelta(v: number): string {
  return `${v > 0 ? '+' : ''}${v.toFixed(1)}%`;
}

/** "12 Aug" — short axis label for a yyyy-mm-dd key. */
export function formatDayLabel(iso: string | number): string {
  const d = new Date(String(iso));
  if (Number.isNaN(d.getTime())) return String(iso);
  return new Intl.DateTimeFormat('en-IN', {
    day: 'numeric',
    month: 'short',
    timeZone: 'UTC',
  }).format(d);
}

export function formatByUnit(unit: 'count' | 'inr' | 'lyt' | 'pct') {
  switch (unit) {
    case 'inr':
      return formatInr;
    case 'lyt':
      return formatLyt;
    case 'pct':
      return (v: number) => formatPct(v);
    default:
      return formatCount;
  }
}