支持 GitHub 风格的 Markdown 提示块（Alert）语法 (#344)

_plugins/auto-alert.rb

@@ -0,0 +1,45 @@
+require "nokogiri"
+
+Jekyll::Hooks.register [:pages, :documents], :post_convert do |doc|
+  next unless doc.output_ext == ".html"
+  site = doc.site
+  next unless site.data["plugins"]
+  alert_type = site.data["plugins"]["auto_alert"]
+  next unless alert_type
+
+  fragment = Nokogiri::HTML::DocumentFragment.parse(doc.content)
+  # 遍历 HTML 中的所有 blockquote 标签
+  fragment.css("blockquote").each do |item|
+    # 找出第一个子节点，用于判断是否含有 [!type] 标记
+    first_child = item.at_css("*:first-child")
+    next unless first_child
+    next unless first_child.name == "p"
+
+    text = first_child.text.downcase
+
+    # 遍历所有 alert 类型
+    alert_type.each do |type, data|
+      # 情况一：完整匹配 [!type] 形式 <p>[!NOTE]</p>
+      if text == "[!#{type}]"
+        # 将 alert 类型对应的 class 加入 blockquote
+        item['class'] = [item['class'], data["class_name"]].compact.join(" ")
+
+        # 将 <p> 替换为 <div> 并插入标题
+        first_child.name = "div"
+        first_child.inner_html = "<strong>#{data["title"]}</strong>"
+        break
+
+      # 情况二：段落以 [!type]\n 开头 <p>[!NOTE]\n\n other content</p>
+      elsif text.start_with? "[!#{type}]\n"
+        # 将 alert 类型对应的 class 加入 blockquote
+        item['class'] = [item['class'], data["class_name"]].compact.join(" ")
+        # 在原段落前插入标题 <div><strong>提示</strong></div><p>[!NOTE]\n\n other content</p>
+        first_child.add_previous_sibling "<div><strong>#{data["title"]}</strong></div>"
+        # 移除段落内容开头的 [!type]\n <div><strong>提示</strong></div><p>\n other content</p>
+        first_child.content = first_child.content.sub(/\A#{Regexp.escape("[!#{type}]\n")}/i, "")
+        break
+      end
+    end
+  end
+  doc.content = fragment.to_html
+end