"use client";

import dynamic from "next/dynamic";
import { useCallback, useEffect, useRef, useState } from "react";
import type { HeroFieldSceneProps } from "./HeroFieldScene";

const Scene = dynamic<HeroFieldSceneProps>(() => import("./HeroFieldScene"), {
  ssr: false,
});

function supportsWebGL2() {
  if (typeof window.WebGL2RenderingContext === "undefined") return false;
  try {
    const context = document.createElement("canvas").getContext("webgl2");
    context?.getExtension("WEBGL_lose_context")?.loseContext();
    return context !== null;
  } catch {
    return false;
  }
}

/**
 * Fundo do hero: liga a rolagem do hero à variável CSS --hero-p (0 no topo, 1 no fim do mergulho)
 * e monta a cena WebGL só quando a página fica ociosa, com WebGL2 e sem preferência por movimento reduzido.
 */
export default function HeroField() {
  const rootRef = useRef<HTMLDivElement>(null);
  const progressRef = useRef(0);
  const [mount, setMount] = useState(false);
  const [visible, setVisible] = useState(false);
  const [ready, setReady] = useState(false);
  const [failed, setFailed] = useState(false);
  // fim do mergulho: a cena já está no escuro e o hero se dissolve; parar o desenho poupa a GPU para o notebook
  const [done, setDone] = useState(false);

  useEffect(() => {
    const section = rootRef.current?.closest<HTMLElement>(".hero");
    if (!section) return;
    let frame = 0;
    const update = () => {
      frame = 0;
      const rect = section.getBoundingClientRect();
      const span = Math.max(rect.height - window.innerHeight, window.innerHeight * 0.8);
      const p = Math.min(1, Math.max(0, -rect.top / span));
      progressRef.current = p;
      section.style.setProperty("--hero-p", p.toFixed(4));
      setDone(p >= 0.999);
    };
    const queue = () => {
      if (!frame) frame = requestAnimationFrame(update);
    };
    update();
    window.addEventListener("scroll", queue, { passive: true });
    window.addEventListener("resize", queue);

    let intersecting = false;
    const sync = () => setVisible(intersecting && !document.hidden);
    const observer = new IntersectionObserver(([entry]) => {
      intersecting = entry.isIntersecting;
      sync();
    });
    observer.observe(section);
    document.addEventListener("visibilitychange", sync);
    return () => {
      cancelAnimationFrame(frame);
      window.removeEventListener("scroll", queue);
      window.removeEventListener("resize", queue);
      observer.disconnect();
      document.removeEventListener("visibilitychange", sync);
    };
  }, []);

  useEffect(() => {
    if (window.matchMedia("(prefers-reduced-motion: reduce)").matches) return;
    if (!supportsWebGL2()) return;
    // Título, botões e hidratação vêm primeiro; o Three.js entra quando o navegador fica ocioso.
    if (typeof window.requestIdleCallback === "function") {
      const id = window.requestIdleCallback(() => setMount(true), { timeout: 2500 });
      return () => window.cancelIdleCallback(id);
    }
    const id = setTimeout(() => setMount(true), 1200);
    return () => clearTimeout(id);
  }, []);

  const handleReady = useCallback(() => setReady(true), []);
  const handleError = useCallback(() => setFailed(true), []);

  return (
    <div
      ref={rootRef}
      aria-hidden="true"
      className="hero-field"
      data-ready={ready && !failed ? "" : undefined}
    >
      {mount && !failed && (
        <Scene
          progressRef={progressRef}
          visible={visible && !done}
          onReady={handleReady}
          onError={handleError}
        />
      )}
    </div>
  );
}