"use client";

import { usePathname, useRouter } from "next/navigation";
import { useEffect, useRef, useState, type ReactNode } from "react";
import { gsap, EASE } from "@/lib/gsap";
import { WolfMark } from "@/components/brand/WolfMark";
import { chrome as chromeDe, type Chrome } from "@/content/chrome";
import { crossesLangRoot } from "@/lib/i18n";
import { endTransition, setTransitionPhase, subscribe } from "./transition-store";

export interface CurtainProps {
  /** The monogram (48 px). layout.tsx passes `<BrandMark/>`; falls back to `<WolfMark/>`. */
  children?: ReactNode;
  /** Texte der Hülle. Ohne Angabe die deutsche Fassung. */
  chrome?: Chrome;
}

/**
 * The page-turn sheet: fixed ivory, 1 px gold hairline on its top edge,
 * monogram + destination label centred. Note the start state lives ONLY in
 * GSAP (`yPercent`) – a CSS `translateY(100%)` would be read as the tween's
 * base `y` and added on top, which pushed the whole cover tween one viewport
 * below the fold (the reader saw a hard cut, then the sheet wiping up over the
 * new page). Slides up 0.45 s (power3.inOut),
 * pushes the route, keeps rising once the pathname changed, then resets.
 * Hard fallback: full navigation when the route has not changed after 900 ms.
 */
export function Curtain({ children, chrome = chromeDe }: CurtainProps) {
  const router = useRouter();
  const pathname = usePathname();
  const sheet = useRef<HTMLDivElement>(null);
  const phase = useRef<"idle" | "cover" | "pushed" | "reveal">("idle");
  const timer = useRef<number>(0);
  const [label, setLabel] = useState<string | null>(null);

  useEffect(() => {
    return subscribe((s) => {
      if (s.phase !== "cover" || !s.href || phase.current !== "idle") return;
      const el = sheet.current;
      if (!el) return;
      const href = s.href;
      phase.current = "cover";
      setLabel(s.label ?? chrome.curtain.fallbackLabel);
      gsap.killTweensOf(el);
      gsap.set(el, { y: 0, yPercent: 100, autoAlpha: 1, pointerEvents: "auto" });
      gsap.to(el, {
        yPercent: 0,
        duration: 0.45,
        ease: EASE.inOut,
        onComplete: () => {
          phase.current = "pushed";
          setTransitionPhase("pushed");
          /* Sprachwechsel: den Dokumentwechsel macht der Browser, nicht der Router
             (Begründung in crossesLangRoot(), src/lib/i18n.ts). Die Hülle bleibt
             liegen, bis das neue Dokument da ist – sie gehört zu diesem hier. */
          if (crossesLangRoot(pathname, href)) {
            window.location.assign(href);
            return;
          }
          router.push(href, { scroll: false });
          window.clearTimeout(timer.current);
          timer.current = window.setTimeout(() => {
            if (phase.current === "pushed") window.location.assign(href);
          }, 900);
        },
      });
    });
  }, [router, pathname, chrome.curtain.fallbackLabel]);

  // Route changed → the sheet continues upward and resets.
  useEffect(() => {
    if (phase.current !== "pushed") return;
    const el = sheet.current;
    if (!el) return;
    window.clearTimeout(timer.current);
    phase.current = "reveal";
    setTransitionPhase("reveal");
    gsap.to(el, {
      yPercent: -100,
      duration: 0.45,
      ease: EASE.inOut,
      delay: 0.05,
      onComplete: () => {
        gsap.set(el, { y: 0, yPercent: 100, autoAlpha: 0, pointerEvents: "none" });
        phase.current = "idle";
        setLabel(null);
        endTransition();
      },
    });
  }, [pathname]);

  useEffect(() => () => window.clearTimeout(timer.current), []);

  return (
    <div
      ref={sheet}
      id="curtain"
      aria-hidden="true"
      data-theme="light"
      className="pointer-events-none invisible fixed inset-0 z-[70] flex flex-col items-center justify-center gap-6 bg-ivory text-ink"
    >
      <span
        aria-hidden="true"
        className="absolute inset-x-0 top-0 h-px"
        style={{ background: "var(--gold-hairline-light)" }}
      />
      <span className="block h-12 text-ink [&_svg]:h-12 [&_svg]:w-auto">
        {children ?? <WolfMark idPrefix="curtain" className="h-12 w-auto" />}
      </span>
      <span className="min-h-[1em] font-mono text-xs tracking-[0.06em] text-gold-deep">{label}</span>
    </div>
  );
}

export default Curtain;