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

/** shadcn/ui's class merger: conditional classes with Tailwind conflict resolution. */
export function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs));
}

const MONEY = new Intl.NumberFormat("en-US", {
  minimumFractionDigits: 2,
  maximumFractionDigits: 2,
});

const COMPACT = new Intl.NumberFormat("en-US", {
  notation: "compact",
  maximumFractionDigits: 1,
});

export function formatMoney(value: number | null | undefined, currency?: string | null): string {
  if (value === null || value === undefined) return "—";
  return currency ? `${currency} ${MONEY.format(value)}` : MONEY.format(value);
}

export function formatCompact(value: number): string {
  return COMPACT.format(value);
}

/** Sub-dollar figures need more precision than a currency formatter gives. */
export function formatCost(value: number): string {
  if (value === 0) return "$0.00";
  if (value < 0.01) return `$${value.toFixed(4)}`;
  return `$${value.toFixed(2)}`;
}

export function formatLatency(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 formatBytes(bytes: number): string {
  if (bytes < 1024) return `${bytes} B`;
  if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`;
  return `${(bytes / 1024 / 1024).toFixed(1)} MB`;
}

export function formatDate(value: string | null | undefined): string {
  if (!value) return "—";
  const parsed = new Date(value);
  if (Number.isNaN(parsed.getTime())) return value;
  return parsed.toLocaleDateString("en-GB", {
    day: "2-digit",
    month: "short",
    year: "numeric",
  });
}

export function formatTime(value: string | null | undefined): string {
  if (!value) return "—";
  const parsed = new Date(value);
  if (Number.isNaN(parsed.getTime())) return value;
  return parsed.toLocaleTimeString("en-GB", {
    hour: "2-digit",
    minute: "2-digit",
    second: "2-digit",
  });
}

export function relativeTime(value: string): string {
  const then = new Date(value).getTime();
  if (Number.isNaN(then)) return value;
  const seconds = Math.round((Date.now() - then) / 1000);
  if (seconds < 60) return "just now";
  if (seconds < 3600) return `${Math.floor(seconds / 60)}m ago`;
  if (seconds < 86_400) return `${Math.floor(seconds / 3600)}h ago`;
  return `${Math.floor(seconds / 86_400)}d ago`;
}

/** Turn `pipeline.extraction_succeeded` into `Extraction succeeded`. */
export function humaniseEvent(event: string): string {
  const tail = event.includes(".") ? event.slice(event.indexOf(".") + 1) : event;
  const words = tail.replace(/_/g, " ");
  return words.charAt(0).toUpperCase() + words.slice(1);
}

export function titleCase(value: string): string {
  return value.charAt(0).toUpperCase() + value.slice(1).toLowerCase();
}