import Lenis from "lenis";

const REVEAL_SELECTOR = ".fade-item:not(.revealed)";
const REVEAL_SCROLL_RATIO = 0.88;
const REVEAL_INITIAL_RATIO = 0.92;
const INITIAL_REVEAL_DELAY_MS = 150;

/**
 * Inertial scrolling plus the two scroll-driven effects that depend on it:
 * the top progress bar and the `.fade-item` reveal.
 */
export default defineNuxtPlugin((nuxtApp) => {
  const lenis = new Lenis({
    duration: 1.2,
    easing: (t: number) => Math.min(1, 1.001 - Math.pow(2, -10 * t)),
    orientation: "vertical",
    smoothWheel: true,
    wheelMultiplier: 1.05,
    touchMultiplier: 1.8,
  });

  let pending: HTMLElement[] = [];
  let progressEl: HTMLElement | null = null;

  const collect = () => {
    pending = Array.from(document.querySelectorAll<HTMLElement>(REVEAL_SELECTOR));
    progressEl = document.querySelector<HTMLElement>(".scroll-progress");
  };

  const reveal = (ratio: number) => {
    if (!pending.length) return;
    const limit = window.innerHeight * ratio;
    const hits: HTMLElement[] = [];
    pending = pending.filter((el) => {
      if (!el.isConnected) return false;
      if (el.getBoundingClientRect().top <= limit) {
        hits.push(el);
        return false;
      }
      return true;
    });
    for (const el of hits) el.classList.add("revealed");
  };

  lenis.on("scroll", (e: Lenis) => {
    if (progressEl) {
      const total = document.documentElement.scrollHeight - window.innerHeight;
      const progress = total > 0 ? e.scroll / total : 0;
      progressEl.style.transform = `scaleX(${progress})`;
    }
    reveal(REVEAL_SCROLL_RATIO);
  });

  let rafId = 0;
  const loop = (time: number) => {
    lenis.raf(time);
    rafId = requestAnimationFrame(loop);
  };
  rafId = requestAnimationFrame(loop);

  const initialReveal = () => {
    collect();
    window.setTimeout(() => {
      collect();
      reveal(REVEAL_INITIAL_RATIO);
    }, INITIAL_REVEAL_DELAY_MS);
  };

  nuxtApp.hook("app:mounted", initialReveal);
  nuxtApp.hook("page:finish", initialReveal);
  nuxtApp.vueApp.onUnmount(() => {
    cancelAnimationFrame(rafId);
    lenis.destroy();
  });

  return { provide: { lenis } };
});