"use client";

import { useEffect, useRef } from "react";

const MAX_DPR = 1.5;
const ASSEMBLE_MS = 2000;
const REPEL_RADIUS_PX = 80;
// Densidade: ~1 star por STAR_AREA_DIVISOR px² CSS, entre piso e teto absolutos
const STAR_AREA_DIVISOR = 700;
const MIN_STARS = 300;
const MAX_STARS = 850;
const OFFSCREEN_POINTER = -100000;

type Particle = {
  sx: number; // origem da assemblei (espalhada) no primeiro load
  sy: number;
  tx: number; // âncora na grade com jitter
  ty: number;
  ox: number; // deslocamento acumulado do repel do ponteiro
  oy: number;
  delay: number;
  fillStyle: string;
  baseAlpha: number;
  size: number;
  phase: number;
  speed: number;
  amp: number;
  ttl: number;
  birth: number;
};

type Rgb = [number, number, number];

const FALLBACK_SLASH: Rgb = [204, 255, 0];
const FALLBACK_PAPER: Rgb = [244, 242, 237];

function hexToRgb(hex: string): Rgb | null {
  const value = hex.trim().replace("#", "");
  const full =
    value.length === 3
      ? value
          .split("")
          .map((char) => char + char)
          .join("")
      : value;
  if (!/^[0-9a-fA-F]{6}$/.test(full)) return null;
  return [
    Number.parseInt(full.slice(0, 2), 16),
    Number.parseInt(full.slice(2, 4), 16),
    Number.parseInt(full.slice(4, 6), 16),
  ];
}

function easeOutQuint(progress: number) {
  return 1 - (1 - progress) ** 5;
}

export function HeroStarfield() {
  const containerRef = useRef<HTMLDivElement>(null);
  const canvasRef = useRef<HTMLCanvasElement>(null);

  useEffect(() => {
    const container = containerRef.current;
    const canvas = canvasRef.current;
    if (!container || !canvas) return;

    const ctx = canvas.getContext("2d");
    if (!ctx) return;

    const reducedMotion = window.matchMedia(
      "(prefers-reduced-motion: reduce)",
    ).matches;

    let rafId = 0;
    let running = false;
    let cancelled = false;
    let resampleTimer = 0;
    let sampleRetryTimer = 0;
    let sampleAttempts = 0;
    let particles: Particle[] = [];
    let hasAssembled = false;
    let elapsed = 0;
    let lastTime = 0;
    let dpr = 1;
    let intersecting = true;
    const pointer = { x: OFFSCREEN_POINTER, y: OFFSCREEN_POINTER };
    let rect = container.getBoundingClientRect();

    const rootStyles = getComputedStyle(document.documentElement);
    const slashRgb =
      hexToRgb(rootStyles.getPropertyValue("--slash")) ?? FALLBACK_SLASH;
    const paperRgb =
      hexToRgb(rootStyles.getPropertyValue("--paper")) ?? FALLBACK_PAPER;

    // Grade estratificada: uma star por célula com jitter interno → cobertura
    // uniforme do card, sem os aglomerados/vazios do random puro
    const grid = {
      cols: 1,
      rows: 1,
      cellW: canvas.width || 1,
      cellH: canvas.height || 1,
    };

    const jitteredCellPosition = (cell: number): [number, number] => {
      const cx = cell % grid.cols;
      const cy = Math.floor(cell / grid.cols);
      return [
        (cx + Math.random()) * grid.cellW,
        (cy + Math.random()) * grid.cellH,
      ];
    };

    const makeParticle = (tx: number, ty: number): Particle => {
      const useSlash = Math.random() < 0.45;
      const rgb = useSlash ? slashRgb : paperRgb;
      return {
        tx,
        ty,
        sx: hasAssembled ? tx : (Math.random() * 1.3 - 0.15) * canvas.width,
        sy: hasAssembled ? ty : (Math.random() * 1.3 - 0.15) * canvas.height,
        ox: 0,
        oy: 0,
        delay: Math.random() * 0.35,
        fillStyle: `rgb(${rgb[0]},${rgb[1]},${rgb[2]})`,
        baseAlpha: 0.5 + Math.random() * 0.45,
        size: (Math.random() < 0.72 ? 2 : 3) * dpr,
        phase: Math.random() * Math.PI * 2,
        // deriva lenta: período ~2–5s com amplitude 2,5–5,5px CSS → "levemente"
        speed: 0.0011 + Math.random() * 0.0016,
        amp: (2.5 + Math.random() * 3) * dpr,
        ttl: 4000 + Math.random() * 6000,
        // birth negativo: estagia os ciclos de vida para o spawn/death já rodar disperso no load
        birth: -Math.random() * 10000,
      };
    };

    const sample = () => {
      const width = container.clientWidth;
      const height = container.clientHeight;
      if (width < 60 || height < 60) return;

      dpr = Math.min(window.devicePixelRatio || 1, MAX_DPR);
      canvas.width = Math.round(width * dpr);
      canvas.height = Math.round(height * dpr);
      rect = container.getBoundingClientRect();

      const count = Math.round(
        Math.min(
          MAX_STARS,
          Math.max(MIN_STARS, (width * height) / STAR_AREA_DIVISOR),
        ),
      );
      // células quadradas-ish para a proporção do card
      grid.cols = Math.max(
        1,
        Math.round(Math.sqrt(count * (canvas.width / canvas.height))),
      );
      grid.rows = Math.max(1, Math.ceil(count / grid.cols));
      grid.cellW = canvas.width / grid.cols;
      grid.cellH = canvas.height / grid.rows;

      // ordem embaralhada das células: cada star ocupa uma célula distinta no spawn
      const cells = Array.from({ length: grid.cols * grid.rows }, (_, i) => i);
      for (let i = cells.length - 1; i > 0; i--) {
        const j = Math.floor(Math.random() * (i + 1));
        const tmp = cells[i];
        cells[i] = cells[j];
        cells[j] = tmp;
      }
      particles = cells.slice(0, count).map((cell) => {
        const [tx, ty] = jitteredCellPosition(cell);
        return makeParticle(tx, ty);
      });
    };

    const render = () => {
      ctx.clearRect(0, 0, canvas.width, canvas.height);

      const pointerX = (pointer.x - rect.left) * dpr;
      const pointerY = (pointer.y - rect.top) * dpr;
      const radius = REPEL_RADIUS_PX * dpr;
      const radiusSq = radius * radius;
      let allSettled = true;

      for (const particle of particles) {
        const progress = Math.min(
          Math.max(
            (elapsed - particle.delay * ASSEMBLE_MS) / (ASSEMBLE_MS * 0.75),
            0,
          ),
          1,
        );
        if (progress < 1) allSettled = false;
        const eased = easeOutQuint(progress);
        const baseX = particle.sx + (particle.tx - particle.sx) * eased;
        const baseY = particle.sy + (particle.ty - particle.sy) * eased;

        // wander Lissajous: harmônico principal + secundário em razão
        // não-inteira → trajetória contínua sem repetição óbvia
        const t = elapsed * particle.speed;
        const driftX =
          (Math.sin(t + particle.phase) +
            0.5 * Math.sin(t * 0.43 + particle.phase * 1.7)) *
          particle.amp *
          progress;
        const driftY =
          (Math.cos(t * 0.9 + particle.phase) +
            0.5 * Math.cos(t * 0.51 + particle.phase * 2.3)) *
          particle.amp *
          progress;

        const dx = baseX + driftX - pointerX;
        const dy = baseY + driftY - pointerY;
        const distSq = dx * dx + dy * dy;
        if (distSq < radiusSq) {
          const dist = Math.sqrt(distSq) || 1;
          const force = (1 - dist / radius) * 10 * dpr;
          particle.ox += (dx / dist) * force;
          particle.oy += (dy / dist) * force;
        }
        particle.ox *= 0.86;
        particle.oy *= 0.86;

        const fadeIn = Math.min(elapsed / 1200, 1);
        const twinkle = 0.6 + 0.4 * Math.sin(elapsed * 0.003 + particle.phase);
        let life = elapsed - particle.birth;
        if (life > particle.ttl) {
          // renasce em outra célula da grade → uniforme também entre ciclos
          const [tx, ty] = jitteredCellPosition(
            Math.floor(Math.random() * grid.cols * grid.rows),
          );
          particle.tx = tx;
          particle.ty = ty;
          particle.sx = tx;
          particle.sy = ty;
          particle.phase = Math.random() * Math.PI * 2;
          particle.baseAlpha = 0.5 + Math.random() * 0.45;
          particle.size = (Math.random() < 0.72 ? 2 : 3) * dpr;
          particle.ttl = 4000 + Math.random() * 6000;
          particle.birth = elapsed;
          life = 0;
        }
        // fade-in de 800ms ao nascer, fade-out nos últimos 800ms de vida
        const lifeFade = Math.min(life / 800, (particle.ttl - life) / 800, 1);

        ctx.globalAlpha = Math.min(
          1,
          particle.baseAlpha * fadeIn * twinkle * lifeFade,
        );
        ctx.fillStyle = particle.fillStyle;
        ctx.fillRect(
          baseX + driftX + particle.ox,
          baseY + driftY + particle.oy,
          particle.size,
          particle.size,
        );
      }

      ctx.globalAlpha = 1;

      if (allSettled && particles.length > 0) hasAssembled = true;
    };

    const drawStaticFrame = () => {
      ctx.clearRect(0, 0, canvas.width, canvas.height);
      for (const particle of particles) {
        ctx.fillStyle = particle.fillStyle;
        ctx.globalAlpha = particle.baseAlpha;
        ctx.fillRect(particle.tx, particle.ty, particle.size, particle.size);
      }
      ctx.globalAlpha = 1;
    };

    const tick = (now: number) => {
      if (!running) return;
      elapsed += Math.min(now - lastTime, 50);
      lastTime = now;
      render();
      rafId = window.requestAnimationFrame(tick);
    };

    const syncLoop = () => {
      const shouldRun = !reducedMotion && intersecting && !document.hidden;
      if (shouldRun && !running) {
        running = true;
        lastTime = performance.now();
        rafId = window.requestAnimationFrame(tick);
      } else if (!shouldRun && running) {
        running = false;
        window.cancelAnimationFrame(rafId);
      }
    };

    // Warm-up determinístico: corrida de layout pode deixar o container com
    // 0px no primeiro sample; re-tenta até existirem partículas
    const sampleUntilBuilt = (onBuilt?: () => void) => {
      sample();
      if (particles.length > 0 || cancelled) {
        onBuilt?.();
        return;
      }
      if (sampleAttempts++ > 50) return;
      sampleRetryTimer = window.setTimeout(
        () => sampleUntilBuilt(onBuilt),
        120,
      );
    };

    const scheduleResample = () => {
      window.clearTimeout(resampleTimer);
      resampleTimer = window.setTimeout(() => {
        sampleUntilBuilt(() => {
          if (reducedMotion) drawStaticFrame();
        });
      }, 150);
    };

    const handlePointerMove = (event: PointerEvent) => {
      pointer.x = event.clientX;
      pointer.y = event.clientY;
    };
    const handlePointerLeave = () => {
      pointer.x = OFFSCREEN_POINTER;
      pointer.y = OFFSCREEN_POINTER;
    };
    const handleScroll = () => {
      rect = container.getBoundingClientRect();
    };
    const handleVisibilityChange = () => {
      syncLoop();
    };

    const resizeObserver = new ResizeObserver(scheduleResample);
    resizeObserver.observe(container);

    if (reducedMotion) {
      // Variante estática: quadro final montado, sem rAF e sem listeners de ponteiro
      hasAssembled = true;
      sampleUntilBuilt(() => drawStaticFrame());

      return () => {
        cancelled = true;
        window.clearTimeout(resampleTimer);
        window.clearTimeout(sampleRetryTimer);
        resizeObserver.disconnect();
      };
    }

    // Start determinístico: intersecting derivado de geometry no setup (o callback do IO
    // pode chegar tarde e deixar o loop rAF morto na carga)
    const syncIntersecting = () => {
      const current = container.getBoundingClientRect();
      intersecting =
        current.bottom > 0 &&
        current.right > 0 &&
        current.top < window.innerHeight &&
        current.left < window.innerWidth;
    };
    syncIntersecting();
    sampleUntilBuilt(() => syncLoop());

    const intersectionObserver = new IntersectionObserver((entries) => {
      intersecting = entries.some((entry) => entry.isIntersecting);
      syncLoop();
    });
    intersectionObserver.observe(container);

    window.addEventListener("pointermove", handlePointerMove, {
      passive: true,
    });
    document.documentElement.addEventListener(
      "pointerleave",
      handlePointerLeave,
    );
    window.addEventListener("scroll", handleScroll, { passive: true });
    document.addEventListener("visibilitychange", handleVisibilityChange);

    return () => {
      cancelled = true;
      window.cancelAnimationFrame(rafId);
      window.clearTimeout(resampleTimer);
      window.clearTimeout(sampleRetryTimer);
      resizeObserver.disconnect();
      intersectionObserver.disconnect();
      window.removeEventListener("pointermove", handlePointerMove);
      document.documentElement.removeEventListener(
        "pointerleave",
        handlePointerLeave,
      );
      window.removeEventListener("scroll", handleScroll);
      document.removeEventListener("visibilitychange", handleVisibilityChange);
    };
  }, []);

  return (
    <div
      ref={containerRef}
      aria-hidden="true"
      className="pointer-events-none absolute inset-0"
    >
      <canvas ref={canvasRef} className="h-full w-full" />
    </div>
  );
}