/* Copy buttons and the on-page contents. Every page reads fine without this script. */
(() => {
  const body = document.body;

  // a copy pill on every code block
  const copyLabel = body.dataset.copy || "Copy";
  const copiedLabel = body.dataset.copied || "Copied";
  const copyText = async (text) => {
    try {
      await navigator.clipboard.writeText(text);
      return true;
    } catch (err) {
      const area = document.createElement("textarea");
      area.value = text;
      area.setAttribute("readonly", "");
      area.style.position = "fixed";
      area.style.opacity = "0";
      document.body.append(area);
      area.select();
      let ok = false;
      try {
        ok = document.execCommand("copy");
      } catch (e) {
        ok = false;
      }
      area.remove();
      return ok;
    }
  };
  document.querySelectorAll(".code").forEach((block) => {
    const head = block.querySelector(".code-head");
    const pre = block.querySelector("pre");
    if (!head || !pre) return;
    const button = document.createElement("button");
    button.type = "button";
    button.className = "copy";
    button.textContent = copyLabel;
    button.addEventListener("click", async () => {
      if (!(await copyText(pre.innerText.replace(/\n$/, "")))) return;
      button.textContent = copiedLabel;
      button.classList.add("done");
      clearTimeout(button.copyTimer);
      button.copyTimer = setTimeout(() => {
        button.textContent = copyLabel;
        button.classList.remove("done");
      }, 1600);
    });
    head.append(button);
  });

  // the on-page contents mark the section being read
  const links = [...document.querySelectorAll(".toc a[href^='#']")];
  if (!links.length) return;
  const byId = new Map(links.map((a) => [decodeURIComponent(a.hash.slice(1)), a]));
  const heads = [...document.querySelectorAll(".prose :is(h1, h2, h3)[id]")].filter((h) => byId.has(h.id));
  let current = null;
  let queued = false;
  const mark = () => {
    queued = false;
    const line = 120;
    let found = heads[0];
    for (const h of heads) {
      if (h.getBoundingClientRect().top <= line) found = h;
      else break;
    }
    const link = found ? byId.get(found.id) : null;
    if (link === current) return;
    if (current) current.removeAttribute("aria-current");
    current = link;
    if (current) {
      current.setAttribute("aria-current", "location");
      const toc = current.closest(".toc");
      if (toc) {
        const top = current.offsetTop - toc.scrollTop;
        if (top < 0 || top > toc.clientHeight - current.offsetHeight) {
          toc.scrollTop = current.offsetTop - toc.clientHeight / 3;
        }
      }
    }
  };
  window.addEventListener("scroll", () => {
    if (!queued) {
      queued = true;
      requestAnimationFrame(mark);
    }
  }, { passive: true });
  mark();
})();