import type { CurrencyCode } from '@rareindex/shared';

/** Display formatting shared by server and client components (no Node-only imports). */

export function fmtMoney(amount: number | null | undefined, currency: CurrencyCode | string = 'USD', opts: { compact?: boolean; digits?: number } = {}): string {
  if (amount === null || amount === undefined || !Number.isFinite(amount)) return '—';
  const zero = currency === 'JPY' || currency === 'KRW';
  const digits = opts.digits ?? (zero ? 0 : Math.abs(amount) >= 1000 ? 0 : 2);
  try {
    return new Intl.NumberFormat('en-US', { style: 'currency', currency, notation: opts.compact ? 'compact' : 'standard', maximumFractionDigits: digits, minimumFractionDigits: opts.compact ? 0 : digits }).format(amount);
  } catch {
    return `${amount.toFixed(digits)} ${currency}`;
  }
}

export function fmtPct(value: number | null | undefined, digits = 2, signed = true): string {
  if (value === null || value === undefined || !Number.isFinite(value)) return '—';
  const sign = signed && value > 0 ? '+' : '';
  return `${sign}${(value * 100).toFixed(digits)}%`;
}

export function fmtNum(value: number | null | undefined, opts: { compact?: boolean; digits?: number } = {}): string {
  if (value === null || value === undefined || !Number.isFinite(value)) return '—';
  return new Intl.NumberFormat('en-US', { notation: opts.compact ? 'compact' : 'standard', maximumFractionDigits: opts.digits ?? (opts.compact ? 1 : 0) }).format(value);
}

export function fmtDate(d: Date | string | null | undefined, opts: { month?: 'short' | 'long' | 'numeric'; year?: boolean; time?: boolean } = {}): string {
  if (!d) return '—';
  const date = typeof d === 'string' ? new Date(d.length === 10 ? `${d}T00:00:00Z` : d) : d;
  if (Number.isNaN(date.getTime())) return '—';
  return new Intl.DateTimeFormat('en-US', { month: opts.month ?? 'short', day: 'numeric', year: opts.year === false ? undefined : 'numeric', ...(opts.time ? { hour: 'numeric', minute: '2-digit' } : {}), timeZone: 'UTC' }).format(date);
}

export function fmtRelative(d: Date | string | null | undefined): string {
  if (!d) return '—';
  const date = typeof d === 'string' ? new Date(d) : d;
  const diff = Date.now() - date.getTime();
  const abs = Math.abs(diff);
  const rtf = new Intl.RelativeTimeFormat('en', { numeric: 'auto' });
  const units: Array<[number, Intl.RelativeTimeFormatUnit]> = [
    [60_000, 'second'],
    [3_600_000, 'minute'],
    [86_400_000, 'hour'],
    [604_800_000, 'day'],
    [2_629_800_000, 'week'],
    [31_557_600_000, 'month'],
    [Infinity, 'year'],
  ];
  let prevMs = 1;
  for (const [ms, unit] of units) {
    if (abs < ms) return rtf.format(Math.round(-diff / prevMs), unit);
    prevMs = ms;
  }
  return fmtDate(date);
}

export function deltaClass(value: number | null | undefined): string {
  if (value === null || value === undefined || !Number.isFinite(value) || Math.abs(value) < 0.00005) return 'text-flat';
  return value > 0 ? 'text-gain' : 'text-loss';
}

export function confidenceLabel(c: number | null | undefined): 'High' | 'Medium' | 'Low' | 'Insufficient' {
  if (c === null || c === undefined) return 'Insufficient';
  if (c >= 0.75) return 'High';
  if (c >= 0.5) return 'Medium';
  if (c > 0) return 'Low';
  return 'Insufficient';
}

export function scoreLabel(s: number | null | undefined): string {
  if (s === null || s === undefined) return 'n/a';
  if (s >= 80) return 'Very high';
  if (s >= 60) return 'High';
  if (s >= 40) return 'Moderate';
  if (s >= 20) return 'Low';
  return 'Very low';
}

export function cn(...parts: Array<string | false | null | undefined>): string {
  return parts.filter(Boolean).join(' ');
}