// src/lib/lexical-headings.ts
import { slugify } from './slugify'

export type Heading = { id: string; text: string; level: number; children: Heading[] }

type Node = { type: string; tag?: string; children?: Node[]; text?: string }

function textOf(node: { children?: Node[] }): string {
  return (node.children ?? []).map((c) => c.text ?? '').join('')
}

export function anchorFor(node: { children?: Node[] }): string {
  return slugify(textOf(node))
}

export function extractHeadingsFromLexical(value: { root: { children: Node[] } }): Heading[] {
  const flat: Heading[] = []
  for (const node of value.root.children) {
    if (node.type !== 'heading' || !node.tag) continue
    const level = Number(node.tag.replace('h', ''))
    if (level < 2 || level > 6) continue
    const text = textOf(node)
    flat.push({ id: slugify(text), text, level, children: [] })
  }
  // build nesting
  const root: Heading[] = []
  for (const h of flat) {
    let inserted = false
    for (let i = root.length - 1; i >= 0; i--) {
      if (root[i].level < h.level) {
        let cursor = root[i]
        while (cursor.children.length && cursor.children[cursor.children.length - 1].level < h.level) {
          cursor = cursor.children[cursor.children.length - 1]
        }
        cursor.children.push(h)
        inserted = true
        break
      }
    }
    if (!inserted) root.push(h)
  }
  return root
}