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

export function fmtGB(n?: number | null, digits = 1): string {
  if (n == null || isNaN(n)) return "—";
  return `${n.toFixed(digits)} GB`;
}

export function fmtParams(n?: number | null): string {
  if (!n) return "—";
  if (n >= 1e12) return `${(n / 1e12).toFixed(1)}T`;
  if (n >= 1e9) return `${(n / 1e9).toFixed(n >= 1e10 ? 0 : 1)}B`;
  if (n >= 1e6) return `${(n / 1e6).toFixed(0)}M`;
  return String(n);
}

export function fmtCtx(n?: number | null): string {
  if (!n) return "—";
  if (n >= 1024) return `${Math.round(n / 1024)}K`;
  return String(n);
}

export function fmtMs(n?: number | null): string {
  if (n == null || isNaN(n)) return "—";
  if (n >= 60000) return `${(n / 60000).toFixed(1)} min`;
  if (n >= 1000) return `${(n / 1000).toFixed(n >= 10000 ? 0 : 1)} s`;
  return `${Math.round(n)} ms`;
}

export function fmtNum(n?: number | null, digits = 0): string {
  if (n == null || isNaN(n)) return "—";
  return n.toLocaleString("en-US", { maximumFractionDigits: digits, minimumFractionDigits: digits });
}

export function fmtDate(ts?: number | string | null): string {
  if (!ts) return "—";
  const d = typeof ts === "number" ? new Date(ts * 1000) : new Date(ts);
  if (isNaN(d.getTime())) return "—";
  return d.toLocaleString("en-CA", { dateStyle: "medium", timeStyle: "short" });
}

export function fmtAgo(ts?: number | null): string {
  if (!ts) return "never";
  const s = Math.max(0, Date.now() / 1000 - ts);
  if (s < 60) return `${Math.round(s)}s ago`;
  if (s < 3600) return `${Math.round(s / 60)} min ago`;
  if (s < 86400) return `${Math.round(s / 3600)} h ago`;
  return `${Math.round(s / 86400)} d ago`;
}

export function fmtDuration(s?: number | null): string {
  if (s == null) return "—";
  const d = Math.floor(s / 86400);
  const h = Math.floor((s % 86400) / 3600);
  const m = Math.floor((s % 3600) / 60);
  if (d) return `${d}d ${h}h`;
  if (h) return `${h}h ${m}m`;
  return `${m}m ${Math.floor(s % 60)}s`;
}

export function fmtSpeed(bps?: number | null): string {
  if (!bps) return "—";
  return `${fmtBytes(bps)}/s`;
}