// 删除标题里面没用的内容
const pickTextNode = (el: HTMLElement) => {
  const fragment = document.createDocumentFragment();

  while (el.firstChild) {
    // 检查当前子节点是否是文本节点
    if (el.firstChild.nodeType === Node.TEXT_NODE) {
      // 如果是文本节点，将其移动到 DocumentFragment 中
      fragment.appendChild(el.firstChild);
    }
    else {
      el.removeChild(el.firstChild);
    }
  }

  return fragment.textContent;
}

// 删除里面的属性
const removeAttributes = (el: HTMLElement) => {
  const attrs = el.attributes;

  Array.from(attrs).forEach((attr) => {
    el.removeAttribute(attr.name);
  });
}

// 格式化 HTML 内容
export const formatHTML = (html: string, extraFormatter?: (doc: Document) => void) => {
  const nextDocument = document.implementation.createHTMLDocument();

  nextDocument.documentElement.innerHTML = html;

  // 删除标题内无效元素
  const titleEl = nextDocument.querySelectorAll("h2, h3, h4, h5, h6") as NodeListOf<HTMLElement>;
  titleEl.forEach((el) => {
    // 遍历并移除所有属性
    removeAttributes(el);

    el.innerHTML = pickTextNode(el);
  });

  // 优化 p 标签
  const paraEl = nextDocument.querySelectorAll("p") as NodeListOf<HTMLElement>;
  paraEl.forEach((el) => {
    // 删除空的 p 标签
    if (!el.innerHTML.trim()) {
      el.remove();
    }

    // 遍历并移除所有属性
    removeAttributes(el);

    // 删除 p 里面的 span 替换成普通 Text，应该没用的
    const spanEl = el.querySelectorAll("span");
    spanEl.forEach((el) => {
      el.parentNode.replaceChild(document.createTextNode(el.innerText), el);
    });
  });

  // 删除 figure 标签
  const figureEl = nextDocument.querySelectorAll("figure") as NodeListOf<HTMLElement>;
  figureEl.forEach((el) => {
    const img = el.querySelector("img");

    if (img) {
      el.innerHTML = "";
      el.appendChild(img);
    }
  });

  // 删除 style 标签
  const stylesEl = nextDocument.querySelectorAll("style");
  stylesEl.forEach((el) => {
    el.remove();
  });

  // 提取 pre 下面的内容
  const preEl = nextDocument.querySelectorAll("pre");
  preEl.forEach((el) => {
    removeAttributes(el);

    // hljs / prism
    const codeEl = el.querySelector("code") as HTMLElement;

    if (codeEl) {
      const nextCodeEl = document.createElement("code");
      nextCodeEl.innerText = codeEl.innerText;

      el.innerHTML = null;
      el.appendChild(nextCodeEl);
    }
  });

  if (extraFormatter) {
    extraFormatter(nextDocument);
  }

  return nextDocument.documentElement.innerHTML;
}