import { parse } from 'parse5'

const attribute = (node, name) => node.attrs?.find((item) => item.name === name)?.value

export const htmlFacts = (html) => {
  const facts = {
    ids: [], hrefs: [], languages: [],
    hasViewport: false, hasHeadingElement: false, isDraft: false,
  }
  const visit = (node) => {
    if (node.tagName) {
      const id = attribute(node, 'id')
      if (id !== undefined) facts.ids.push(id)
      const href = attribute(node, 'href')
      if (href !== undefined) facts.hrefs.push(href)
      for (const className of (attribute(node, 'class') ?? '').split(/\s+/)) {
        if (className.startsWith('language-')) facts.languages.push(className.slice('language-'.length))
      }
      if (node.tagName === 'heading') facts.hasHeadingElement = true
      if (node.tagName === 'meta') {
        const name = attribute(node, 'name')?.toLowerCase()
        if (name === 'viewport') facts.hasViewport = true
        if (name === 'robots' && /(?:^|[,\s])noindex(?:$|[,\s])/i.test(attribute(node, 'content') ?? '')) facts.isDraft = true
      }
    }
    for (const child of node.childNodes ?? []) visit(child)
    if (node.content) visit(node.content)
  }
  visit(parse(html))
  return facts
}