import { defineHastPlugin } from "satteri"

/**
 * 在标题末尾追加一个 # 锚点链接（替代 rehype-autolink-headings）。
 *
 * 依赖 satteriHeadingIdsPlugin() 先生成 id，所以本插件必须排在它之后。
 *
 * 目标输出（与 unified 时期逐字一致）：
 *   <h3 id="slug">标题<a class="anchor" href="#slug"><span class="anchor-icon" data-pagefind-ignore="">#</span></a></h3>
 */

const HEADING_TAGS = ["h1", "h2", "h3", "h4", "h5", "h6"]

/** @param {any} node */
const hasAnchor = (node) => {
  if (!Array.isArray(node.children)) return false
  return node.children.some(
    (child) =>
      child?.type === "element" &&
      child.tagName === "a" &&
      Array.isArray(child.properties?.className) &&
      child.properties.className.includes("anchor"),
  )
}

export const autolinkHeadings = defineHastPlugin({
  name: "autolink-headings",
  element: {
    filter: HEADING_TAGS,
    visit(node, ctx) {
      const id = node.properties?.id
      if (typeof id !== "string" || id.length === 0) return
      if (hasAnchor(node)) return

      // 脚注区那个视觉隐藏的 "脚注" 标题不需要 # 锚点
      let parent = ctx.parent(node)
      while (parent) {
        if (parent.type === "element" && parent.properties?.["data-footnotes"] !== undefined) {
          return
        }
        parent = ctx.parent(parent)
      }

      ctx.appendChild(node, {
        type: "element",
        tagName: "a",
        properties: { className: ["anchor"], href: `#${id}` },
        children: [
          {
            type: "element",
            tagName: "span",
            properties: { className: ["anchor-icon"], "data-pagefind-ignore": "" },
            children: [{ type: "text", value: "#" }],
          },
        ],
      })
    },
  },
})