// https://github.com/wooorm/xdm#syntax-highlighting-with-the-meta-field

import visit from 'unist-util-visit'

const re = /\b([-\w]+)(?:=(?:"([^"]*)"|'([^']*)'|([^"'\s]+)))?/g

export default (options = {}) => {
  return (tree) => {
    visit(tree, 'element', onelement)
  }

  function onelement(node) {
    let match
    if (node.tagName === 'code' && node.data && node.data.meta) {
      re.lastIndex = 0 // Reset regex.

      while ((match = re.exec(node.data.meta))) {
        const key = match[1]
        const value = match[2] || match[3] || match[4] || ''

        // Merge class/className into existing className array to avoid duplicate key warning
        if (key === 'class' || key === 'className') {
          node.properties.className = [...(node.properties.className || []), value]
        } else {
          node.properties[key] = value
        }
      }
    }
  }
}