"use client";

import { useEffect, useId, useRef, useState, type KeyboardEvent, type MouseEvent } from "react";
import { AnimatePresence, motion, useReducedMotion } from "motion/react";

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

type MorphMenuProps = {
  items: MorphMenuItem[];
  /** Called on click. Call e.preventDefault() to stop the browser following the link. */
  onSelect?: (item: MorphMenuItem, e: MouseEvent<HTMLAnchorElement>) => void;
  /** Width of the open panel in pixels. */
  width?: number;
  /** Size of the closed button in pixels. */
  size?: number;
  /** Which side the panel grows from. */
  align?: "left" | "right";
  /** Colour of the hover marker. */
  accent?: string;
  /** Name read out by screen readers. */
  label?: string;
  /** Look of the button / panel. */
  className?: string;
};

/* MorphMenu: the round menu button itself stretches into the menu panel, and the lines turn into a cross. */
export function MorphMenu({
  items,
  onSelect,
  width = 240,
  size = 48,
  align = "right",
  accent = "#a78bfa",
  label = "Menu",
  className = "border border-white/10 bg-[#161229] text-white shadow-2xl shadow-black/50",
}: MorphMenuProps) {
  const reduce = useReducedMotion();
  const uid = useId();
  const wrap = useRef<HTMLDivElement>(null);
  const button = useRef<HTMLButtonElement>(null);
  const [open, setOpen] = useState(false);
  const spring = reduce ? { duration: 0 } : { type: "spring" as const, stiffness: 380, damping: 32 };

  // Close on a click outside.
  useEffect(() => {
    if (!open) return;
    const away = (e: PointerEvent) => {
      if (!wrap.current?.contains(e.target as Node)) setOpen(false);
    };
    document.addEventListener("pointerdown", away);
    return () => document.removeEventListener("pointerdown", away);
  }, [open]);

  const close = () => {
    setOpen(false);
    button.current?.focus();
  };

  const onKeyDown = (e: KeyboardEvent<HTMLDivElement>) => {
    if (e.key === "Escape" && open) close();
  };

  return (
    <div ref={wrap} className="relative inline-block" style={{ width: size, height: size }} onKeyDown={onKeyDown}>
      <motion.div
        initial={false}
        animate={{
          width: open ? width : size,
          height: open ? "auto" : size,
          borderRadius: open ? 20 : size / 2,
        }}
        transition={spring}
        className={`absolute top-0 z-20 overflow-hidden ${align === "right" ? "right-0" : "left-0"} ${className}`}
        style={{ minHeight: size }}
      >
        <button
          ref={button}
          type="button"
          aria-expanded={open}
          aria-controls={`${uid}-menu`}
          aria-label={open ? "Close menu" : "Open menu"}
          onClick={() => setOpen((o) => !o)}
          className={`absolute top-0 z-10 grid place-items-center rounded-full outline-none focus-visible:ring-2 focus-visible:ring-white/70 ${align === "right" ? "right-0" : "left-0"}`}
          style={{ width: size, height: size }}
        >
          <motion.span
            aria-hidden
            className="absolute h-0.5 w-5 rounded-full bg-current"
            initial={false}
            animate={open ? { y: 0, rotate: 45 } : { y: -4, rotate: 0 }}
            transition={spring}
          />
          <motion.span
            aria-hidden
            className="absolute h-0.5 w-5 rounded-full bg-current"
            initial={false}
            animate={open ? { y: 0, rotate: -45 } : { y: 4, rotate: 0 }}
            transition={spring}
          />
        </button>

        <AnimatePresence initial={false}>
          {open && (
            <motion.nav
              id={`${uid}-menu`}
              aria-label={label}
              initial={{ opacity: 0 }}
              animate={{ opacity: 1 }}
              exit={{ opacity: 0, transition: { duration: reduce ? 0 : 0.1 } }}
              transition={{ duration: reduce ? 0 : 0.2, delay: reduce ? 0 : 0.08 }}
              style={{ width, paddingTop: size }}
              className="px-3 pb-3"
            >
              <p className="px-3 pb-2 font-mono text-[11px] uppercase tracking-[0.2em] opacity-50">{label}</p>
              <ul className="grid">
                {items.map((item, i) => (
                  <motion.li
                    key={item.href}
                    initial={{ opacity: 0, y: 8 }}
                    animate={{ opacity: 1, y: 0 }}
                    transition={reduce ? { duration: 0 } : { delay: 0.1 + i * 0.04, duration: 0.3, ease: [0.22, 1, 0.36, 1] }}
                  >
                    <a
                      href={item.href}
                      onClick={(e) => {
                        onSelect?.(item, e);
                        close();
                      }}
                      className="group flex items-center gap-3 rounded-xl px-3 py-2 text-lg outline-none hover:bg-white/5 focus-visible:bg-white/5 focus-visible:ring-2 focus-visible:ring-white/70"
                    >
                      <span
                        aria-hidden
                        className="h-1.5 w-1.5 scale-0 rounded-full transition-transform duration-200 group-hover:scale-100 group-focus-visible:scale-100"
                        style={{ background: accent }}
                      />
                      <span className="-ml-[18px] transition-[margin] duration-200 group-hover:ml-0 group-focus-visible:ml-0">
                        {item.label}
                      </span>
                    </a>
                  </motion.li>
                ))}
              </ul>
            </motion.nav>
          )}
        </AnimatePresence>
      </motion.div>
    </div>
  );
}