---
import TableOfContentsHeading from './TableOfContentsHeading.astro'

// https://kld.dev/building-table-of-contents/
const { headings } = Astro.props
const toc = buildToc(headings)

export interface Heading {
  depth: number
  slug: string
  text: string
}

function buildToc(headings: Heading[]) {
  const toc: Heading[] = []
  const parentHeadings = new Map()
  headings.forEach((h) => {
    const heading = { ...h, subheadings: [] }
    parentHeadings.set(heading.depth, heading)
    if (heading.depth === 2) {
      toc.push(heading)
    } else {
      parentHeadings.get(heading.depth - 1).subheadings.push(heading)
    }
  })
  return toc
}
---

<details open class="rounded-lg border">
  <summary>Table of Contents</summary>
  <nav>
    <ul class="py-3">
      {toc.map((heading) => <TableOfContentsHeading heading={heading} />)}
    </ul>
  </nav>
</details>

<style>
  summary {
    @apply cursor-pointer rounded-t-lg px-3 py-1.5 font-medium transition-colors;
  }
</style>