"use client";

import { useId, useState, type MouseEvent, type RefObject } from "react";
import { motion, useMotionValueEvent, useReducedMotion, useScroll } from "motion/react";

export type FloatNavItem = { label: string; href: string };

type FloatNavProps = {
  items: FloatNavItem[];
  /** href of the active link at start. Defaults to the first item. */
  active?: string;
  /** Called on click. Call e.preventDefault() to stop the browser following the link. */
  onSelect?: (item: FloatNavItem, e: MouseEvent<HTMLAnchorElement>) => void;
  /** Slip away while scrolling down, come back on scroll up. */
  hideOnScroll?: boolean;
  /** Scrolling box to watch. Leave out to watch the page. */
  container?: RefObject<HTMLElement | null>;
  /** Colour of the sliding pill. */
  color?: string;
  /** Text colour on the pill. */
  activeText?: string;
  /** Name read out by screen readers. */
  label?: string;
  className?: string;
};

/* FloatNav: a floating pill bar. The active pill slides between links; the bar slips away on scroll down. */
export function FloatNav({
  items,
  active,
  onSelect,
  hideOnScroll = true,
  container,
  color = "#a78bfa",
  activeText = "#0b0a14",
  label = "Main",
  className = "rounded-full border border-white/10 bg-[#16132a]/80 p-1.5 text-sm text-white/70 shadow-lg shadow-black/40 backdrop-blur-md",
}: FloatNavProps) {
  const reduce = useReducedMotion();
  const id = useId();
  const [current, setCurrent] = useState(active ?? items[0]?.href);
  const [hidden, setHidden] = useState(false);
  const { scrollY } = useScroll({ container });

  useMotionValueEvent(scrollY, "change", (y) => {
    if (!hideOnScroll) return;
    const prev = scrollY.getPrevious() ?? 0;
    setHidden(y > prev && y > 80);
  });

  const spring = reduce ? { duration: 0 } : { type: "spring" as const, stiffness: 420, damping: 34 };

  return (
    <motion.nav
      aria-label={label}
      onFocus={() => setHidden(false)}
      animate={{ y: hidden ? "-160%" : "0%", opacity: hidden ? 0 : 1 }}
      transition={spring}
      className={`inline-flex ${className}`}
    >
      <ul className="flex items-center gap-1">
        {items.map((item) => {
          const on = item.href === current;
          return (
            <li key={item.href} className="relative">
              {on && (
                <motion.span
                  layoutId={`${id}-pill`}
                  aria-hidden
                  className="absolute inset-0 rounded-full"
                  style={{ background: color }}
                  transition={spring}
                />
              )}
              <a
                href={item.href}
                aria-current={on ? "page" : undefined}
                onClick={(e) => {
                  setCurrent(item.href);
                  onSelect?.(item, e);
                }}
                className="relative block whitespace-nowrap rounded-full px-4 py-2 outline-none transition-colors hover:text-white focus-visible:ring-2 focus-visible:ring-white/70"
                style={on ? { color: activeText, fontWeight: 500 } : undefined}
              >
                {item.label}
              </a>
            </li>
          );
        })}
      </ul>
    </motion.nav>
  );
}