export function formatNumber(n: number | null | undefined, opts: Intl.NumberFormatOptions = {}): string {
  if (n === null || n === undefined || Number.isNaN(n)) return "—";
  return new Intl.NumberFormat("en-US", { maximumFractionDigits: 0, ...opts }).format(n);
}

export function formatCompact(n: number | null | undefined): string {
  if (n === null || n === undefined) return "—";
  return new Intl.NumberFormat("en-US", { notation: "compact", maximumFractionDigits: 1 }).format(n);
}

export function formatBytes(bytes: number | null | undefined): string {
  if (bytes === null || bytes === undefined) return "—";
  if (bytes < 1024) return `${bytes} B`;
  const units = ["KB", "MB", "GB", "TB"];
  let v = bytes / 1024;
  let i = 0;
  while (v >= 1024 && i < units.length - 1) {
    v /= 1024;
    i++;
  }
  return `${v.toFixed(v >= 100 ? 0 : v >= 10 ? 1 : 2)} ${units[i]}`;
}

export function formatMs(ms: number | null | undefined): string {
  if (ms === null || ms === undefined) return "—";
  if (ms < 1000) return `${Math.round(ms)} ms`;
  return `${(ms / 1000).toFixed(2)} s`;
}

export function formatUsd(n: number | null | undefined, precise = false): string {
  if (n === null || n === undefined) return "—";
  if (n === 0) return "$0.00";
  if (precise || Math.abs(n) < 0.01) return `$${n.toFixed(n < 0.001 ? 6 : 4)}`;
  return new Intl.NumberFormat("en-US", { style: "currency", currency: "USD" }).format(n);
}

export function formatPercent(n: number | null | undefined, digits = 1): string {
  if (n === null || n === undefined || Number.isNaN(n)) return "—";
  return `${n.toFixed(digits)}%`;
}

export function formatDate(d: Date | string | null | undefined, opts: Intl.DateTimeFormatOptions = {}): string {
  if (!d) return "—";
  const date = typeof d === "string" ? new Date(d) : d;
  return new Intl.DateTimeFormat("en-US", { dateStyle: "medium", timeStyle: "short", ...opts }).format(date);
}

export function formatDateOnly(d: Date | string | null | undefined): string {
  if (!d) return "—";
  const date = typeof d === "string" ? new Date(d) : d;
  return new Intl.DateTimeFormat("en-US", { dateStyle: "medium" }).format(date);
}

export function timeAgo(d: Date | string | null | undefined): string {
  if (!d) return "never";
  const date = typeof d === "string" ? new Date(d) : d;
  const diff = Date.now() - date.getTime();
  const s = Math.round(diff / 1000);
  if (s < 5) return "just now";
  if (s < 60) return `${s}s ago`;
  const m = Math.round(s / 60);
  if (m < 60) return `${m}m ago`;
  const h = Math.round(m / 60);
  if (h < 24) return `${h}h ago`;
  const days = Math.round(h / 24);
  if (days < 30) return `${days}d ago`;
  return formatDateOnly(date);
}

export function truncate(s: string, n = 48): string {
  return s.length > n ? `${s.slice(0, n - 1)}…` : s;
}

export function titleCase(s: string): string {
  return s.replace(/[_-]/g, " ").replace(/\b\w/g, (c) => c.toUpperCase());
}