"use client";

import { LazyMotion, domAnimation, m } from "motion/react";
import { useEffect, useRef, useState } from "react";
import { NAV_ITEMS } from "@/content/site";
import { Logo } from "./Logo";

const LEFT = NAV_ITEMS.slice(0, 3);
const RIGHT = NAV_ITEMS.slice(3);

type NavItem = (typeof NAV_ITEMS)[number];

/**
 * Kopfzeile wie bei der Filmcamp-Referenz: Logo mittig, Abschnitte links und
 * rechts. Ueber dem Headerbild transparent mit heller Schrift, nach dem
 * Scrollen auf hellem Grund.
 */
export function SiteHeader({ logoLight, logoDark }: { logoLight: string | null; logoDark: string | null }) {
  const [active, setActive] = useState<string | null>(null);
  const [scrolled, setScrolled] = useState(false);
  const [menuOpen, setMenuOpen] = useState(false);
  const menuButton = useRef<HTMLButtonElement>(null);
  const firstLink = useRef<HTMLAnchorElement>(null);

  useEffect(() => {
    const onScroll = () => setScrolled(window.scrollY > 24);
    onScroll();
    window.addEventListener("scroll", onScroll, { passive: true });
    return () => window.removeEventListener("scroll", onScroll);
  }, []);

  // Markiert den Abschnitt, der gerade die Bildschirmmitte kreuzt.
  useEffect(() => {
    const sections = NAV_ITEMS.map((item) => document.getElementById(item.id)).filter(Boolean) as HTMLElement[];
    const observer = new IntersectionObserver(
      (entries) => {
        for (const entry of entries) if (entry.isIntersecting) setActive(entry.target.id);
      },
      { rootMargin: "-45% 0px -50% 0px" },
    );
    sections.forEach((s) => observer.observe(s));
    return () => observer.disconnect();
  }, []);

  useEffect(() => {
    if (!menuOpen) return;
    firstLink.current?.focus();
    const onKey = (e: KeyboardEvent) => {
      if (e.key === "Escape") {
        setMenuOpen(false);
        menuButton.current?.focus();
      }
    };
    document.addEventListener("keydown", onKey);
    return () => document.removeEventListener("keydown", onKey);
  }, [menuOpen]);

  const solid = scrolled || menuOpen;

  const navList = (items: readonly NavItem[], align: string) => (
    <ul className={`flex items-center gap-7 text-[0.9375rem] font-medium ${align}`}>
      {items.map((item) => (
        <li key={item.id} className="relative">
          <a href={`#${item.id}`} aria-current={active === item.id ? "location" : undefined} className="block py-2 opacity-85 transition-opacity hover:opacity-100 aria-[current]:opacity-100">
            {item.label}
          </a>
          {active === item.id && (
            <m.span layoutId="nav-indicator" className="absolute inset-x-0 -bottom-0.5 h-0.5 rounded-full bg-current" transition={{ type: "spring", stiffness: 380, damping: 34 }} />
          )}
        </li>
      ))}
    </ul>
  );

  return (
    <header
      className={`fixed inset-x-0 top-0 z-40 transition-[background-color,color,box-shadow] duration-300 ${
        solid ? "bg-plaster/95 text-ink shadow-[0_1px_0_var(--color-line)] backdrop-blur" : "on-dark bg-transparent text-paper"
      }`}
    >
      <a href="#inhalt" className="sr-only focus:not-sr-only focus:absolute focus:left-4 focus:top-3 focus:z-50 focus:bg-paper focus:px-3 focus:py-2 focus:text-ink">
        Zum Inhalt springen
      </a>
      <LazyMotion features={domAnimation}>
        <div className="container-edge grid h-[4.5rem] grid-cols-[1fr_auto_1fr] items-center gap-4">
          <div className="flex items-center">
            <button
              ref={menuButton}
              type="button"
              className="inline-flex h-11 items-center rounded-full border border-current/40 px-4 text-sm font-semibold xl:hidden"
              aria-expanded={menuOpen}
              aria-controls="mobile-menu"
              onClick={() => setMenuOpen((v) => !v)}
            >
              {menuOpen ? "Schließen" : "Menü"}
            </button>
            <nav aria-label="Abschnitte" className="hidden xl:block">
              {navList(LEFT, "justify-start")}
            </nav>
          </div>

          <a href="#top" aria-label="ARTISTA Modelcamp 2027, zum Seitenanfang" className="flex h-8 items-center text-xl md:h-10 md:text-2xl">
            <Logo src={solid ? logoDark : logoLight} />
          </a>

          <div className="flex items-center justify-end gap-7">
            <nav aria-label="Weitere Abschnitte" className="hidden xl:block">
              {navList(RIGHT, "justify-end")}
            </nav>
            <a href="#preis" className="btn btn-primary hidden min-h-10 px-5 py-2 text-sm sm:inline-flex">
              Platz sichern
            </a>
          </div>
        </div>
      </LazyMotion>
      {menuOpen && (
        <nav id="mobile-menu" aria-label="Abschnitte" className="border-t border-line bg-plaster text-ink xl:hidden">
          <ul className="container-edge py-4">
            {NAV_ITEMS.map((item, index) => (
              <li key={item.id}>
                <a
                  ref={index === 0 ? firstLink : undefined}
                  href={`#${item.id}`}
                  onClick={() => setMenuOpen(false)}
                  className="display block border-b border-line/70 py-3 text-2xl"
                >
                  {item.label}
                </a>
              </li>
            ))}
          </ul>
        </nav>
      )}
    </header>
  );
}