/** Formatting helpers — bytes, thin-space grouped numbers, ISO UTC timestamps. */

const THIN = " "; // narrow no-break space

export function fmtInt(n: number | null | undefined): string {
  if (n === null || n === undefined || Number.isNaN(Number(n))) return "—";
  const v = Math.round(Number(n));
  const neg = v < 0;
  const s = Math.abs(v).toString();
  const parts: string[] = [];
  for (let i = s.length; i > 0; i -= 3) parts.unshift(s.slice(Math.max(0, i - 3), i));
  return (neg ? "-" : "") + parts.join(THIN);
}

export function fmtNum(n: number | null | undefined, digits = 2): string {
  if (n === null || n === undefined || Number.isNaN(Number(n))) return "—";
  const v = Number(n);
  if (Number.isInteger(v) && digits === 0) return fmtInt(v);
  const [i, f] = v.toFixed(digits).split(".");
  return fmtInt(Number(i)) + (f ? "." + f : "");
}

/** Compact 1 284 / 12.9K / 4.2M / 1.3B */
export function fmtCompact(n: number | null | undefined): string {
  if (n === null || n === undefined || Number.isNaN(Number(n))) return "—";
  const v = Number(n);
  const a = Math.abs(v);
  if (a < 10_000) return fmtInt(v);
  if (a < 1e6) return (v / 1e3).toFixed(1).replace(/\.0$/, "") + "K";
  if (a < 1e9) return (v / 1e6).toFixed(1).replace(/\.0$/, "") + "M";
  if (a < 1e12) return (v / 1e9).toFixed(2).replace(/\.?0+$/, "") + "B";
  return (v / 1e12).toFixed(2).replace(/\.?0+$/, "") + "T";
}

export function fmtBytes(b: number | null | undefined, digits = 1): string {
  if (b === null || b === undefined || Number.isNaN(Number(b))) return "—";
  const v = Number(b);
  if (v < 1e3) return `${fmtInt(v)} B`;
  if (v < 1e6) return `${(v / 1e3).toFixed(digits)} kB`;
  if (v < 1e9) return `${(v / 1e6).toFixed(digits)} MB`;
  if (v < 1e12) return `${(v / 1e9).toFixed(digits)} GB`;
  return `${(v / 1e12).toFixed(digits)} TB`;
}

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

export function fmtPct(x: number | null | undefined, digits = 1): string {
  if (x === null || x === undefined || Number.isNaN(Number(x))) return "—";
  return `${(Number(x) * 100).toFixed(digits)} %`;
}

const pad = (n: number) => String(n).padStart(2, "0");

/** ISO UTC → `YYYY-MM-DD HH:mm:ssZ` */
export function fmtTs(iso: string | null | undefined): string {
  if (!iso) return "—";
  const d = new Date(iso);
  if (Number.isNaN(d.getTime())) return String(iso);
  return `${d.getUTCFullYear()}-${pad(d.getUTCMonth() + 1)}-${pad(d.getUTCDate())} ${pad(d.getUTCHours())}:${pad(d.getUTCMinutes())}:${pad(d.getUTCSeconds())}Z`;
}

/** Short time-of-day `HH:mm` (UTC) */
export function fmtTime(iso: string | null | undefined): string {
  if (!iso) return "—";
  const d = new Date(iso);
  if (Number.isNaN(d.getTime())) return String(iso);
  return `${pad(d.getUTCHours())}:${pad(d.getUTCMinutes())}`;
}

export function fmtDate(iso: string | null | undefined): string {
  if (!iso) return "—";
  return String(iso).slice(0, 10);
}

export function fmtRelative(iso: string | null | undefined): string {
  if (!iso) return "—";
  const d = new Date(iso).getTime();
  if (Number.isNaN(d)) return String(iso);
  const s = Math.round((Date.now() - d) / 1000);
  const abs = Math.abs(s);
  const suffix = s >= 0 ? "ago" : "from now";
  if (abs < 60) return `${abs} s ${suffix}`;
  if (abs < 3600) return `${Math.round(abs / 60)} min ${suffix}`;
  if (abs < 86400) return `${(abs / 3600).toFixed(1)} h ${suffix}`;
  return `${Math.round(abs / 86400)} d ${suffix}`;
}

export function fmtDuration(startIso: string | null | undefined, endIso: string | null | undefined): string {
  if (!startIso) return "—";
  const a = new Date(startIso).getTime();
  const b = endIso ? new Date(endIso).getTime() : Date.now();
  const s = Math.max(0, Math.round((b - a) / 1000));
  if (s < 60) return `${s} s`;
  if (s < 3600) return `${Math.floor(s / 60)} min ${s % 60} s`;
  return `${(s / 3600).toFixed(1)} h`;
}

export function isoDate(d: Date): string {
  return `${d.getUTCFullYear()}-${pad(d.getUTCMonth() + 1)}-${pad(d.getUTCDate())}`;
}

export function daysAgo(n: number): string {
  const d = new Date();
  d.setUTCDate(d.getUTCDate() - n);
  return isoDate(d);
}

export function today(): string {
  return isoDate(new Date());
}

/** datetime-local value (local tz) for `now` */
export function nowLocalInput(): string {
  const d = new Date();
  const off = d.getTimezoneOffset();
  const local = new Date(d.getTime() - off * 60_000);
  return local.toISOString().slice(0, 16);
}

export function toCsv(columns: string[], rows: Record<string, unknown>[]): string {
  const esc = (v: unknown) => {
    if (v === null || v === undefined) return "";
    const s = typeof v === "object" ? JSON.stringify(v) : String(v);
    return /[",\n\r]/.test(s) ? `"${s.replace(/"/g, '""')}"` : s;
  };
  const lines = [columns.map(esc).join(",")];
  for (const r of rows) lines.push(columns.map((c) => esc(r[c])).join(","));
  return lines.join("\n");
}

export function downloadText(filename: string, text: string, mime = "text/csv;charset=utf-8") {
  const blob = new Blob([text], { type: mime });
  const url = URL.createObjectURL(blob);
  const a = document.createElement("a");
  a.href = url;
  a.download = filename;
  document.body.appendChild(a);
  a.click();
  a.remove();
  setTimeout(() => URL.revokeObjectURL(url), 1000);
}

export function splitList(text: string): string[] {
  return Array.from(new Set(text.split(/[\s,;]+/).map((s) => s.trim().toUpperCase()).filter(Boolean)));
}