import type { ParsedLocation } from "@tanstack/react-router";

export type NavDirection = "forward" | "back" | "none";

const tabRank = (pathname: string): number | null => {
  if (pathname === "/") return 0;
  if (pathname.startsWith("/stats")) return 1;
  if (pathname.startsWith("/tournaments")) return 2;
  if (pathname.startsWith("/profile") || pathname.startsWith("/settings")) return 3;
  if (pathname.startsWith("/admin")) return 4;
  return null;
};

const depth = (pathname: string) => pathname.split("/").filter(Boolean).length;

// Keep in sync with route loaders that set header.collapsed
const headerHidden = (pathname: string) => {
  const segs = pathname.split("/").filter(Boolean);
  return segs.length === 2 && ["profile", "teams", "tournaments"].includes(segs[0]);
};

export function headerChange(
  from: ParsedLocation | undefined,
  to: ParsedLocation
): "exit" | "enter" | "none" {
  if (!from) return "none";
  const fromHidden = headerHidden(from.pathname);
  const toHidden = headerHidden(to.pathname);
  if (fromHidden === toHidden) return "none";
  return toHidden ? "exit" : "enter";
}

export function navDirection(
  from: ParsedLocation | undefined,
  to: ParsedLocation
): NavDirection {
  if (!from || from.pathname === to.pathname) return "none";

  const fromRank = tabRank(from.pathname);
  const toRank = tabRank(to.pathname);
  if (fromRank !== null && toRank !== null && fromRank !== toRank) {
    return toRank > fromRank ? "forward" : "back";
  }

  const fromIndex = from.state.__TSR_index;
  const toIndex = to.state.__TSR_index;
  if (Number.isFinite(fromIndex) && Number.isFinite(toIndex) && fromIndex !== toIndex) {
    return toIndex > fromIndex ? "forward" : "back";
  }

  return depth(to.pathname) >= depth(from.pathname) ? "forward" : "back";
}