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

/**
 * Utility for merging tailwind classes safely.
 */
export function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs));
}

/**
 * Formats a number as a currency string.
 */
export function formatCurrency(value: number, decimals: number = 2) {
  return new Intl.NumberFormat("en-US", {
    style: "currency",
    currency: "USD",
    minimumFractionDigits: decimals,
    maximumFractionDigits: decimals,
  }).format(value);
}

/**
 * Formats a percentage from midpoint.
 */
export function formatPercent(value: number) {
  return (value * 100).toFixed(1) + "%";
}

/**
 * Converts Fahrenheit to Celsius.
 */
export function fToC(f: number) {
  return ((f - 32) * 5) / 9;
}

/**
 * Formats a date/time string to HH:MM:SS.
 */
export function formatTime(date: Date | string) {
  const d = typeof date === "string" ? new Date(date) : date;
  if (isNaN(d.getTime())) return String(date);
  return d.toLocaleTimeString("zh-CN", {
    hour12: false,
    hour: "2-digit",
    minute: "2-digit",
    second: "2-digit",
  });
}