(() => {
  const ipv4Placeholder = "203.0.113.10";
  const ipv6Placeholder = "2001:db8::10";
  const needsIpv4 = () => (
    document.body.textContent.includes(ipv4Placeholder)
    || document.querySelector(`[data-copy*="${ipv4Placeholder}"]`)
  );
  const needsIpv6 = () => (
    document.body.textContent.includes(ipv6Placeholder)
    || document.querySelector(`[data-copy*="${ipv6Placeholder}"]`)
  );

  const fetchIp = async (url) => {
    try {
      const response = await fetch(url, { cache: "no-store", mode: "cors" });
      if (!response.ok) return "";
      const payload = await response.json();
      return typeof payload.ip === "string" ? payload.ip : "";
    } catch (_) {
      return "";
    }
  };

  const replaceInTextNodes = (search, replacement) => {
    const walker = document.createTreeWalker(document.body, NodeFilter.SHOW_TEXT);
    const nodes = [];
    while (walker.nextNode()) {
      if (walker.currentNode.nodeValue.includes(search)) nodes.push(walker.currentNode);
    }
    nodes.forEach((node) => {
      node.nodeValue = node.nodeValue.split(search).join(replacement);
    });
  };

  const replaceInCopyValues = (search, replacement) => {
    document.querySelectorAll("[data-copy]").forEach((element) => {
      const value = element.dataset.copy || "";
      if (value.includes(search)) element.dataset.copy = value.split(search).join(replacement);
    });
  };

  const replaceEverywhere = (search, replacement) => {
    if (!replacement || replacement === search) return;
    replaceInTextNodes(search, replacement);
    replaceInCopyValues(search, replacement);
  };

  const updateCopyCommand = (button, ipv6Command) => {
    const value = button.dataset.copy || "";
    if (!value || value.includes("?myipv6=")) return;
    const lines = value.split("\n");
    const output = [];
    let inserted = false;
    lines.forEach((line) => {
      output.push(line);
      if (!inserted && line.includes("/api/v1/router/update/") && line.includes("?myip=")) {
        output.push(ipv6Command);
        inserted = true;
      }
    });
    if (inserted) button.dataset.copy = output.join("\n");
  };

  const insertIpv6Examples = (ip) => {
    if (!ip) return;
    document.querySelectorAll(".terminal-card.manual-code").forEach((card) => {
      if (card.textContent.includes("?myipv6=")) return;
      const lines = [...card.querySelectorAll("code")];
      const ipv4Line = lines.find((line) => (
        line.textContent.includes("/api/v1/router/update/")
        && line.textContent.includes("?myip=")
      ));
      if (!ipv4Line) return;
      const base = ipv4Line.textContent.split("?myip=", 1)[0].replace(/'$/, "");
      const ipv6Command = `${base}?myipv6=${ip}'`;
      const code = document.createElement("code");
      code.textContent = ipv6Command;
      ipv4Line.after(code);
      const copyButton = card.querySelector("[data-copy]");
      if (copyButton) updateCopyCommand(copyButton, ipv6Command);
    });
  };

  document.addEventListener("DOMContentLoaded", async () => {
    const tasks = [];
    if (needsIpv4()) {
      tasks.push(fetchIp("https://api4.ipify.org?format=json").then((ip) => {
        replaceEverywhere(ipv4Placeholder, ip);
      }));
    }
    if (needsIpv6()) {
      tasks.push(fetchIp("https://api6.ipify.org?format=json").then((ip) => {
        replaceEverywhere(ipv6Placeholder, ip);
        insertIpv6Examples(ip);
      }));
    }
    await Promise.allSettled(tasks);
  });
})();