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

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

export function formatBytes(bytes: number, decimals = 1): string {
  if (!Number.isFinite(bytes) || bytes <= 0) return "0 B";
  const k = 1024;
  const sizes = ["B", "KB", "MB", "GB", "TB"];
  const i = Math.min(Math.floor(Math.log(bytes) / Math.log(k)), sizes.length - 1);
  return `${(bytes / Math.pow(k, i)).toFixed(decimals)} ${sizes[i]}`;
}

export function formatRelativeDate(date: Date | string): string {
  const d = typeof date === "string" ? new Date(date) : date;
  const now = new Date();
  const diff = now.getTime() - d.getTime();
  const startOfToday = new Date(now.getFullYear(), now.getMonth(), now.getDate()).getTime();
  const startOfDate = new Date(d.getFullYear(), d.getMonth(), d.getDate()).getTime();
  const dayDiff = Math.round((startOfToday - startOfDate) / (1000 * 60 * 60 * 24));

  if (dayDiff === 0) return "Today";
  if (dayDiff === 1) return "Yesterday";
  if (dayDiff < 7) return "Previous 7 days";
  if (dayDiff < 30) return "Previous 30 days";
  if (dayDiff < 365) return d.toLocaleDateString(undefined, { month: "long", year: "numeric" });
  return d.getFullYear().toString();
}

export function groupChatsByDate<T extends { updatedAt: Date | string }>(
  chats: T[],
): Record<string, T[]> {
  const groups: Record<string, T[]> = {};
  for (const chat of chats) {
    const key = formatRelativeDate(chat.updatedAt);
    if (!groups[key]) groups[key] = [];
    groups[key].push(chat);
  }
  return groups;
}

export const GROUP_ORDER = [
  "Today",
  "Yesterday",
  "Previous 7 days",
  "Previous 30 days",
];