import { clsx, type ClassValue } from "clsx";
import { twMerge } from "tailwind-merge";

export function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs));
}

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 "—";
  if (n >= 1_000_000) return `${(n / 1_000_000).toFixed(n % 1_000_000 === 0 ? 0 : 1)}M`;
  if (n >= 1_000) return `${(n / 1_000).toFixed(n % 1_000 === 0 ? 0 : 0)}K`;
  return String(n);
}

export function formatTokens(n: number | null | undefined): string {
  if (n === null || n === undefined) return "—";
  if (n >= 1_000_000) return `${(n / 1_000_000).toFixed(2).replace(/\.?0+$/, "")}M`;
  if (n >= 10_000) return `${(n / 1_000).toFixed(1).replace(/\.?0+$/, "")}K`;
  return new Intl.NumberFormat("en-US").format(n);
}

export function formatUsd(n: number | null | undefined, opts: { precise?: boolean } = {}): string {
  if (n === null || n === undefined || Number.isNaN(n)) return "—";
  if (n === 0) return "$0.00";
  if (n < 0.01 || opts.precise) return `$${n.toFixed(n < 0.001 ? 5 : 4)}`;
  return `$${n.toFixed(2)}`;
}

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(ms < 10_000 ? 2 : 1)} s`;
}

export function formatRelative(date: Date | string | null | undefined): string {
  if (!date) return "—";
  const d = typeof date === "string" ? new Date(date) : date;
  const diff = Date.now() - d.getTime();
  const s = Math.round(diff / 1000);
  if (s < 45) return "just now";
  const m = Math.round(s / 60);
  if (m < 60) return `${m} min ago`;
  const h = Math.round(m / 60);
  if (h < 24) return `${h} h ago`;
  const days = Math.round(h / 24);
  if (days < 7) return `${days} d ago`;
  return d.toLocaleDateString("en-US", { month: "short", day: "numeric", year: d.getFullYear() === new Date().getFullYear() ? undefined : "numeric" });
}

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

export function sleep(ms: number, signal?: AbortSignal): Promise<void> {
  return new Promise((resolve, reject) => {
    const t = setTimeout(resolve, ms);
    signal?.addEventListener(
      "abort",
      () => {
        clearTimeout(t);
        reject(new DOMException("Aborted", "AbortError"));
      },
      { once: true },
    );
  });
}