(() => {
  document.addEventListener("DOMContentLoaded", () => {
    const bg = document.querySelector(".background");

    // ---- Inject realistic clouds into .background ----
    if (bg && !bg.querySelector(".cloud")) {
      const isMobile = window.matchMedia("(max-width:768px)").matches;
      if (!isMobile && !document.getElementById("cloud-fluff")) {
        const defs = document.createElementNS("http://www.w3.org/2000/svg", "svg");
        defs.setAttribute("width", "0");
        defs.setAttribute("height", "0");
        defs.setAttribute("aria-hidden", "true");
        defs.style.position = "absolute";
        defs.innerHTML =
          '<filter id="cloud-fluff" x="-150%" y="-150%" width="400%" height="400%">' +
          '<feTurbulence type="fractalNoise" baseFrequency="0.012 0.02" numOctaves="4" seed="11" result="noise"/>' +
          '<feDisplacementMap in="SourceGraphic" in2="noise" scale="120"/>' +
          "</filter>";
        document.body.appendChild(defs);
      }
      const cloudCount = isMobile ? 2 : 4;
      for (let i = 1; i <= cloudCount; i++) {
        const cloud = document.createElement("div");
        cloud.className = "cloud cloud-" + i;
        cloud.setAttribute("aria-hidden", "true");
        bg.appendChild(cloud);
      }
    }

    // ---- Grass strip along the bottom of the viewport ----
    if (!document.querySelector(".grass")) {
      const NS = "http://www.w3.org/2000/svg";
      const W = isMobile ? 1200 : 2400;
      const H = 70;
      const svg = document.createElementNS(NS, "svg");
      svg.setAttribute("class", "grass");
      svg.setAttribute("viewBox", "0 0 " + W + " " + H);
      svg.setAttribute("preserveAspectRatio", "xMidYMax slice");
      svg.setAttribute("aria-hidden", "true");

      // soft ground shading under the blades
      svg.innerHTML =
        '<defs><linearGradient id="grass-base" x1="0" y1="1" x2="0" y2="0">' +
        '<stop offset="0" stop-color="#3e7a46" stop-opacity="0.55"/>' +
        '<stop offset="1" stop-color="#3e7a46" stop-opacity="0"/>' +
        "</linearGradient></defs>" +
        '<rect x="0" y="' + (H - 16) + '" width="' + W + '" height="16" fill="url(#grass-base)"/>';

      const isMobile = window.matchMedia("(max-width: 768px)").matches;

      const layers = isMobile
  ? [
      { count: 50, hMin: 18, hMax: 32, colors: ["#4f9854"], opacity: 0.9 },
      { count: 40, hMin: 24, hMax: 42, colors: ["#63ad64"], opacity: 1 },
    ]
  : [
      { count: 190, hMin: 18, hMax: 36, colors: ["#3e7a46","#457f4b","#4a8a50"], opacity: 0.8 },
      { count: 160, hMin: 26, hMax: 52, colors: ["#4f9854","#57a05a","#63ad64","#6db36e"], opacity: 1 },
    ];

      const layerEls = [];
      layers.forEach((layer) => {
        const g = document.createElementNS(NS, "g");
        g.setAttribute("opacity", layer.opacity);
        g.style.transformBox = "fill-box";
        g.style.transformOrigin = "50% 100%";
        layerEls.push(g);
        for (let i = 0; i < layer.count; i++) {
          const x = Math.random() * W;
          const h = layer.hMin + Math.random() * (layer.hMax - layer.hMin);
          const lean = (Math.random() - 0.5) * 16;
          const w = 3 + Math.random() * 3;
          const color = layer.colors[(Math.random() * layer.colors.length) | 0];
          const blade = document.createElementNS(NS, "path");
          blade.setAttribute(
            "d",
            "M " + x + " " + H +
              " Q " + (x + lean * 0.2) + " " + (H - h * 0.6) + " " + (x + lean) + " " + (H - h) +
              " Q " + (x + lean * 0.6 + w * 0.5) + " " + (H - h * 0.55) + " " + (x + w) + " " + H + " Z"
          );
          blade.setAttribute("fill", color);
          blade.style.transformBox = "fill-box";
          blade.style.transformOrigin = "50% 100%";
          // stagger by x so a gust appears to travel across the lawn
          if (!isMobile) {
            blade.style.animation =
              "blade-sway " + (2.6 + Math.random() * 2.4).toFixed(2) + "s ease-in-out " +
              (-(x / W) * 3 - Math.random()).toFixed(2) + "s infinite alternate";
          }
          g.appendChild(blade);
        }
        svg.appendChild(g);
      });

      document.body.appendChild(svg);

      // ---- Scroll physics: scrolling down squashes the grass toward the
      // ground, scrolling up stretches it, and a damped spring makes it
      // boing back upright ----
      if (!window.matchMedia("(prefers-reduced-motion: reduce)").matches) {
        let squash = 0; // offset from natural height (scaleY = 1 + squash)
        let squashVel = 0;
        let lastY = window.scrollY;
        let raf = null;

        const settle = () => {
          squashVel -= squash * 0.06; // spring pull toward natural height
          squashVel *= 0.88;          // damping
          squash += squashVel;
          const s = Math.max(-0.3, Math.min(0.14, squash));
          layerEls.forEach((g, i) => {
            // back layer reacts less than the front for depth
            const depth = i === 0 ? 0.55 : 1;
            g.style.transform = "scaleY(" + (1 + s * depth).toFixed(4) + ")";
          });
          if (Math.abs(squash) > 0.001 || Math.abs(squashVel) > 0.001) {
            raf = requestAnimationFrame(settle);
          } else {
            layerEls.forEach((g) => (g.style.transform = ""));
            raf = null;
          }
        };

        const impulse = (v) => {
          squashVel += v;
          if (!raf) raf = requestAnimationFrame(settle);
        };

        window.addEventListener(
          "scroll",
          () => {
            const y = window.scrollY;
            // scroll down -> stretch, scroll up -> duck
            impulse(Math.max(-0.08, Math.min(0.08, (y - lastY) * 0.0015)));
            lastY = y;
          },
          { passive: true }
        );

        // wheel fallback so short pages that can't scroll still react
        window.addEventListener(
          "wheel",
          (e) => {
            if (document.documentElement.scrollHeight <= window.innerHeight + 4) {
              impulse(Math.max(-0.05, Math.min(0.05, e.deltaY * 0.0005)));
            }
          },
          { passive: true }
        );
      }
    }

    // ---- Copy buttons on <pre> ----
    document.querySelectorAll("pre").forEach((pre) => {
      if (pre.querySelector(".copy-btn")) return;
      const code = pre.querySelector("code") || pre;
      const btn = document.createElement("button");
      btn.className = "copy-btn";
      btn.textContent = "Copy";
      btn.addEventListener("click", async () => {
        try {
          await navigator.clipboard.writeText(code.innerText);
          btn.textContent = "Copied!";
          setTimeout(() => (btn.textContent = "Copy"), 1200);
        } catch {
          btn.textContent = "Error";
          setTimeout(() => (btn.textContent = "Copy"), 1200);
        }
      });
      pre.appendChild(btn);
    });

    // ---- Article-only features: sidebar + collapsible code ----
    const article = document.querySelector(".article");
    if (!article) return;

    // Collect headings for TOC
    const headings = article.querySelectorAll("h1, h2, h3");
    const codeBlocks = article.querySelectorAll("pre");

    // Determine filenames from preceding h2
    const codeFiles = [];
    codeBlocks.forEach((pre, idx) => {
      let name = null;
      let el = pre.previousElementSibling;
      while (el) {
        if (el.tagName === "H2" || el.tagName === "H3") {
          const text = el.textContent.trim();
          if (text.match(/\.\w{1,5}$/) || text.match(/\.\w{1,5}\s/)) {
            name = text.replace(/\s*\(.*\)/, "").trim();
          }
          break;
        }
        el = el.previousElementSibling;
      }
      if (!name) name = `code-block-${idx + 1}.txt`;
      codeFiles.push({ name, pre });
    });

    // Make code blocks collapsible
    codeBlocks.forEach((pre, idx) => {
      const wrapper = document.createElement("div");
      wrapper.className = "code-collapsible";

      const toggle = document.createElement("button");
      toggle.className = "code-toggle";
      const fileName = codeFiles[idx].name;
      toggle.innerHTML = `<span class="code-toggle-arrow">▶</span> <span class="code-toggle-name">${fileName}</span>`;
      toggle.setAttribute("aria-expanded", "false");

      pre.parentNode.insertBefore(wrapper, pre);
      wrapper.appendChild(toggle);
      wrapper.appendChild(pre);
      pre.classList.add("collapsed");

      toggle.addEventListener("click", () => {
        const expanded = pre.classList.toggle("collapsed");
        toggle.setAttribute("aria-expanded", !expanded);
        toggle.querySelector(".code-toggle-arrow").textContent = expanded ? "▶" : "▼";
      });
    });

    // Build sidebar
    const sidebar = document.createElement("nav");
    sidebar.className = "article-sidebar";

    // TOC section
    const tocTitle = document.createElement("div");
    tocTitle.className = "sidebar-title";
    tocTitle.textContent = "Contents";
    sidebar.appendChild(tocTitle);

    const tocList = document.createElement("ul");
    tocList.className = "sidebar-toc";

    headings.forEach((h, i) => {
      if (!h.id) h.id = "heading-" + i;
      const li = document.createElement("li");
      li.className = "toc-" + h.tagName.toLowerCase();
      const a = document.createElement("a");
      a.href = "#" + h.id;
      a.textContent = h.textContent;
      a.addEventListener("click", (e) => {
        e.preventDefault();
        h.scrollIntoView({ behavior: "smooth", block: "start" });
      });
      li.appendChild(a);
      tocList.appendChild(li);
    });
    sidebar.appendChild(tocList);

    // Files section
    if (codeFiles.length > 0) {
      const filesTitle = document.createElement("div");
      filesTitle.className = "sidebar-title";
      filesTitle.textContent = "Files";
      sidebar.appendChild(filesTitle);

      const fileList = document.createElement("ul");
      fileList.className = "sidebar-files";

      codeFiles.forEach(({ name, pre }) => {
        const li = document.createElement("li");
        const btn = document.createElement("button");
        btn.className = "sidebar-file-btn";
        btn.innerHTML = `<svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M21 15v4a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2v-4"/><polyline points="7 10 12 15 17 10"/><line x1="12" y1="15" x2="12" y2="3"/></svg> ${name}`;

        btn.addEventListener("click", () => {
          const code = pre.querySelector("code") || pre;
          const text = code.innerText;
          const blob = new Blob([text], { type: "text/plain" });
          const url = URL.createObjectURL(blob);
          const a = document.createElement("a");
          a.href = url;
          a.download = name;
          a.click();
          URL.revokeObjectURL(url);
        });

        li.appendChild(btn);
        fileList.appendChild(li);
      });
      sidebar.appendChild(fileList);
    }

    document.body.appendChild(sidebar);

    // Highlight active TOC item on scroll
    const tocLinks = tocList.querySelectorAll("a");
    const observer = new IntersectionObserver(
      (entries) => {
        entries.forEach((entry) => {
          if (entry.isIntersecting) {
            tocLinks.forEach((l) => l.classList.remove("active"));
            const link = tocList.querySelector(`a[href="#${entry.target.id}"]`);
            if (link) link.classList.add("active");
          }
        });
      },
      { rootMargin: "-80px 0px -70% 0px" }
    );
    headings.forEach((h) => observer.observe(h));
  });
})();