(() => {
  if (window.__hudraPageDetector) return;

  const contentRootSelectors = [
    "#content .user_content",
    ".show-content .user_content",
    ".wiki-page-content .user_content",
    ".user_content",
    "[role='main'] .page-content",
    "[role='main'] .content"
  ];

  const titleSelectors = [
    "h1.page-title",
    "h1.wiki-page-title",
    "#content h1"
  ];

  function hasMeaningfulContent(element) {
    return Boolean(
      element?.textContent?.trim() ||
      element?.querySelector("img, video, iframe, svg, canvas, picture, table")
    );
  }

  function resolve() {
    let contentRoot = null;
    let contentRootSelector = null;

    for (const selector of contentRootSelectors) {
      const candidate = document.querySelector(selector);
      if (candidate) {
        contentRoot = candidate;
        contentRootSelector = selector;
        break;
      }
    }

    if (!contentRoot) {
      return { supported: false, reason: "NO_LESSON_CONTAINER" };
    }

    const pageTitleElement =
      contentRoot.querySelector("h1") ||
      document.querySelector(titleSelectors.join(", "));

    if (!pageTitleElement) {
      return { supported: false, reason: "NO_LESSON_TITLE" };
    }

    if (!hasMeaningfulContent(contentRoot)) {
      return { supported: false, reason: "EMPTY_LESSON" };
    }

    return {
      supported: true,
      reason: null,
      contentRoot,
      contentRootSelector,
      pageTitleElement
    };
  }

  function inspect() {
    const result = resolve();
    return {
      supported: result.supported,
      reason: result.reason,
      contentRootSelector: result.contentRootSelector || null
    };
  }

  function showNotice(message) {
    document.getElementById("hudra-page-notice")?.remove();

    const notice = document.createElement("div");
    notice.id = "hudra-page-notice";
    notice.setAttribute("role", "status");
    notice.setAttribute("aria-live", "polite");
    notice.style.cssText = [
      "position:fixed",
      "z-index:2147483647",
      "right:20px",
      "bottom:20px",
      "max-width:420px",
      "box-sizing:border-box",
      "padding:16px 48px 16px 18px",
      "border:1px solid #bac4d2",
      "border-radius:10px",
      "background:#fff",
      "color:#1f2937",
      "box-shadow:0 8px 28px rgba(15,23,42,.2)",
      "font:16px/1.4 system-ui,sans-serif"
    ].join(";");

    const text = document.createElement("span");
    text.textContent = message;
    notice.appendChild(text);

    const close = document.createElement("button");
    close.type = "button";
    close.setAttribute("aria-label", "Dismiss Hudra message");
    close.textContent = "×";
    close.style.cssText = [
      "position:absolute",
      "top:8px",
      "right:10px",
      "border:0",
      "background:transparent",
      "color:#374151",
      "font:24px/1 system-ui,sans-serif",
      "cursor:pointer"
    ].join(";");
    close.addEventListener("click", () => notice.remove());
    notice.appendChild(close);

    document.body.appendChild(notice);
    window.setTimeout(() => notice.remove(), 8000);
  }

  window.__hudraPageDetector = { inspect, resolve, showNotice };
})();