/**
 * Nuxt Content v3 (minimark) AST 工具函数
 * 集中管理 body AST 的文本提取、标题提取、slugify 等操作
 */

// --- 文本提取 ---

const SKIP_TAGS = new Set(['style', 'script', 'pre', 'code', 'head', 'meta', 'link'])

export function extractTextFromAst(node: any): string {
  if (!node) return ''
  if (typeof node === 'string') return node
  if (Array.isArray(node)) {
    const tag = typeof node[0] === 'string' ? node[0] : ''
    if (SKIP_TAGS.has(tag)) return ''
    const start = typeof node[1] === 'object' && !Array.isArray(node[1]) && node[1] !== null ? 2 : 1
    return node.slice(start).map(extractTextFromAst).join('')
  }
  if (typeof node === 'object') {
    if (typeof node.value === 'string') return node.value
    if (node.children) return extractTextFromAst(node.children)
    if (node.value) return extractTextFromAst(node.value)
  }
  return ''
}

// --- 标题提取 ---

export interface Heading {
  id: string
  text: string
  level: number
}

function extractTextFromNode(node: any): string {
  if (!node) return ''
  if (typeof node === 'string') return node
  if (Array.isArray(node)) return node.map(extractTextFromNode).join('')
  if (typeof node === 'object') {
    if (typeof node.value === 'string') return node.value
    if (node.children) return extractTextFromNode(node.children)
  }
  return ''
}

export function extractHeadings(node: any, list: Heading[] = []): Heading[] {
  if (!node) return list
  if (Array.isArray(node)) {
    if (typeof node[0] === 'string' && /^h[1-6]$/.test(node[0])) {
      const level = Number(node[0].charAt(1))
      const props = typeof node[1] === 'object' && !Array.isArray(node[1]) ? node[1] : {}
      const childStart = typeof node[1] === 'object' && !Array.isArray(node[1]) ? 2 : 1
      const text = node.slice(childStart).map(extractTextFromNode).join('').trim()
      if (text) {
        list.push({ id: props.id || slugify(text), text, level })
      }
    }
    for (const child of node) {
      if (Array.isArray(child) || (typeof child === 'object' && child !== null)) {
        extractHeadings(child, list)
      }
    }
    return list
  }
  if (typeof node === 'object') {
    const tag = node.tag || node.type
    if (tag && /^h[1-6]$/.test(tag)) {
      const level = Number(tag.charAt(1))
      const text = extractTextFromNode(node).trim()
      if (text) {
        list.push({ id: node.props?.id || slugify(text), text, level })
      }
    }
    if (node.children) extractHeadings(node.children, list)
    if (node.value) extractHeadings(node.value, list)
    if (node.body) extractHeadings(node.body, list)
  }
  return list
}

// --- slugify ---

export function slugify(text: string): string {
  return text
    .trim()
    .toLowerCase()
    .replace(/[\s　]+/g, '-')
    .replace(/[^\p{L}\p{N}\-]/gu, '')
    .replace(/-+/g, '-')
    .replace(/^-|-$/g, '') || 'section'
}

// --- 去重（给 heading id 加后缀）---

export function deduplicateIds(list: Heading[]): Heading[] {
  const seen = new Map<string, number>()
  for (const h of list) {
    if (seen.has(h.id)) {
      const n = (seen.get(h.id) || 1) + 1
      seen.set(h.id, n)
      h.id = `${h.id}-${n}`
    } else {
      seen.set(h.id, 1)
    }
  }
  return list
}

// --- 从 body 提取所有标题（去重后）---

export function getHeadingsFromBody(body: Record<string, any> | null | undefined): Heading[] {
  if (!body) return []
  const list: Heading[] = []
  extractHeadings(body.value || body, list)
  return deduplicateIds(list)
}