"use client";

import { useEffect, useRef } from "react";

const DEFAULT_TEXT =
  "Engenharia de software para sistemas que precisam operar de verdade.";

const MAX_DPR = 1.5;
const ASSEMBLE_MS = 2000;
const REPEL_RADIUS_PX = 80;
const MIN_PARTICLES = 1200;
const MAX_PARTICLES = 2500;
const OFFSCREEN_POINTER = -100000;

type Particle = {
  sx: number;
  sy: number;
  tx: number;
  ty: number;
  ox: number;
  oy: number;
  delay: number;
  color: string;
  size: number;
  phase: number;
  speed: number;
  amp: number;
};

type TrackingCapableContext = CanvasRenderingContext2D & {
  letterSpacing?: string;
};

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;
}

function wrapLines(
  ctx: CanvasRenderingContext2D,
  text: string,
  maxWidth: number,
) {
  const lines: string[] = [];
  let current = "";
  for (const word of text.split(" ")) {
    const candidate = current ? `${current} ${word}` : word;
    if (!current || ctx.measureText(candidate).width <= maxWidth) {
      current = candidate;
    } else {
      lines.push(current);
      current = word;
    }
  }
  if (current) lines.push(current);
  return lines;
}

export function ParticleBuildText({ text = DEFAULT_TEXT }: { text?: string }) {
  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 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;

    // next/font gera nome de família com hash: resolver pela classe font-display real
    const probe = document.createElement("span");
    probe.className = "font-display";
    probe.style.position = "absolute";
    probe.style.opacity = "0";
    document.body.appendChild(probe);
    const fontFamily = getComputedStyle(probe).fontFamily || "sans-serif";
    document.body.removeChild(probe);

    const fontsReady =
      typeof document.fonts === "undefined"
        ? Promise.resolve()
        : document.fonts.ready;

    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 offscreen = document.createElement("canvas");
      offscreen.width = canvas.width;
      offscreen.height = canvas.height;
      const offCtx = offscreen.getContext("2d");
      if (!offCtx) return;
      // Backing store é device-pixel: escala p/ que coordenadas CSS preencham o painel inteiro
      offCtx.scale(dpr, dpr);

      const maxWidth = width * 0.92;
      let fontSize = Math.min(height * 0.22, width / 7);
      let lines: string[] = [];
      while (fontSize >= 12) {
        offCtx.font = `800 ${fontSize}px ${fontFamily}`;
        const trackingCtx = offCtx as TrackingCapableContext;
        if (trackingCtx.letterSpacing !== undefined) {
          trackingCtx.letterSpacing = "-0.04em";
        }
        lines = wrapLines(offCtx, text, maxWidth);
        if (lines.length * fontSize * 0.98 <= height * 0.8) break;
        fontSize *= 0.94;
      }
      fontSize = Math.max(fontSize, 12);

      const lineHeight = fontSize * 0.98;
      const startY = (height - lines.length * lineHeight) / 2 + fontSize * 0.74;
      offCtx.fillStyle = "#ffffff";
      offCtx.textBaseline = "alphabetic";
      lines.forEach((line, index) => {
        const lineWidth = offCtx.measureText(line).width;
        offCtx.fillText(
          line,
          (width - lineWidth) / 2,
          startY + index * lineHeight,
        );
      });

      const pixels = offCtx.getImageData(
        0,
        0,
        offscreen.width,
        offscreen.height,
      ).data;
      const targets: Array<[number, number]> = [];
      const stride = 3;
      for (let py = 0; py < offscreen.height; py += stride) {
        for (let px = 0; px < offscreen.width; px += stride) {
          if (pixels[(py * offscreen.width + px) * 4 + 3] > 128) {
            targets.push([px, py]);
          }
        }
      }
      if (targets.length === 0) return;

      const desired = Math.round(
        Math.min(
          MAX_PARTICLES,
          Math.max(MIN_PARTICLES, (width * height) / 180),
        ),
      );

      particles = Array.from({ length: desired }, () => {
        const target = targets[Math.floor(Math.random() * targets.length)];
        const useSlash = Math.random() < 0.72;
        const rgb = useSlash ? slashRgb : paperRgb;
        const alpha = useSlash
          ? 0.28 + Math.random() * 0.22
          : 0.25 + Math.random() * 0.15;
        return {
          tx: target[0],
          ty: target[1],
          sx: hasAssembled
            ? target[0]
            : (Math.random() * 1.3 - 0.15) * canvas.width,
          sy: hasAssembled
            ? target[1]
            : (Math.random() * 1.3 - 0.15) * canvas.height,
          ox: 0,
          oy: 0,
          delay: Math.random() * 0.35,
          color: `rgba(${rgb[0]},${rgb[1]},${rgb[2]},${alpha.toFixed(2)})`,
          size: (Math.random() < 0.85 ? 1 : 2) * dpr,
          phase: Math.random() * Math.PI * 2,
          speed: 0.0005 + Math.random() * 0.0007,
          amp: (0.6 + Math.random()) * dpr,
        };
      });
    };

    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;

        const driftX =
          Math.sin(elapsed * particle.speed + particle.phase) *
          particle.amp *
          progress;
        const driftY =
          Math.cos(elapsed * particle.speed * 0.9 + particle.phase) *
          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;

        ctx.fillStyle = particle.color;
        ctx.fillRect(
          baseX + driftX + particle.ox,
          baseY + driftY + particle.oy,
          particle.size,
          particle.size,
        );
      }

      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.color;
        ctx.fillRect(particle.tx, particle.ty, particle.size, particle.size);
      }
    };

    const tick = (now: number) => {
      elapsed += Math.min(now - lastTime, 50);
      lastTime = now;
      render();
    };

    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);
      }
    };

    const scheduleResample = () => {
      window.clearTimeout(resampleTimer);
      resampleTimer = window.setTimeout(() => {
        sample();
        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
      fontsReady.then(() => {
        if (cancelled) return;
        hasAssembled = true;
        sample();
        drawStaticFrame();
      });

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

    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);

    fontsReady.then(() => {
      if (cancelled) return;
      sample();
      syncLoop();
    });

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

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