document.addEventListener("DOMContentLoaded", () => {
  const canvas = document.getElementById("background");
  if (!canvas) return;
  const ctx = canvas.getContext("2d");

  // Grab config from the embedded <script>
  const configEl = document.getElementById("background-config");
  const config = configEl ? JSON.parse(configEl.textContent) : {};

  // Use config values with defaults as fallback
  const spacing    = config.spacing    ?? 24;
  const maxRadius  = config.maxRadius  ?? 8;
  const baseOffset = config.baseOffset ?? 120;
  const freq       = config.freq       ?? 0.008;
  const speed      = config.speed      ?? 0.02;

  const baseAmp    = config.baseAmp    ?? 100;
  const env1Freq   = config.envelope1Freq ?? 0.002;
  const env1Amp    = config.envelope1Amp  ?? 120;
  const env2Freq   = config.envelope2Freq ?? 0.0005;
  const env2Amp    = config.envelope2Amp  ?? 200;

  let t = parseFloat(localStorage.getItem("waveProgress")) || 0;
  let widthCss = window.innerWidth;
  let heightCss = window.innerHeight;
  let pixelRatio = window.devicePixelRatio || 1;

  function resize() {
    widthCss = window.innerWidth;
    heightCss = window.innerHeight;
    pixelRatio = window.devicePixelRatio || 1;

    canvas.width = Math.floor(widthCss * pixelRatio);
    canvas.height = Math.floor(heightCss * pixelRatio);
    canvas.style.width = widthCss + "px";
    canvas.style.height = heightCss + "px";
    ctx.setTransform(pixelRatio, 0, 0, pixelRatio, 0, 0);
  }
  window.addEventListener("resize", resize);
  resize();

  function draw() {
    const styles = getComputedStyle(document.documentElement);
    const fg = styles.getPropertyValue("--fg").trim();

    ctx.clearRect(0, 0, widthCss, heightCss);
    ctx.fillStyle = fg;

    for (let x = 0; x <= widthCss + spacing; x += spacing) {
      // envelope: controls crest variance
      const envelope =
        baseAmp
        + Math.sin(x * env1Freq + t * 0.1) * env1Amp
        + Math.sin(x * env2Freq + t * 0.05) * env2Amp;

      const waveY = heightCss - (Math.sin(x * freq + t) * envelope + baseOffset);
      // const waveY = Math.max(heightCss - 50, heightCss - (Math.sin(x * freq + t) * envelope + baseOffset));

      for (let y = heightCss; y >= 0; y -= spacing) {
        const dist = Math.max(0, y - waveY);
        const radius = Math.min(maxRadius, dist / 40);
        if (radius > 0.2) {
          ctx.beginPath();
          // ctx.arc(x + spacing / 2, y - spacing / 2, radius, 0, Math.PI * 2);
          ctx.fillRect(
            x + spacing / 2 - radius,
            y - spacing / 2 - radius,
            radius * 2,
            radius * 2
          );
          ctx.fill();
        }
      }
    }

    t += speed;
    localStorage.setItem("waveProgress", t);
    requestAnimationFrame(draw);
  }

  draw();
});