index.js

'use strict'

module.exports = parse

var dot = '.'.charCodeAt(0)
var hash = '#'.charCodeAt(0)

/* Parse a simple CSS selector into a HAST node. */
function parse(selector, defaultTagName) {
  var value = selector || ''
  var name = defaultTagName || 'div'
  var props = {}
  var index = -1
  var length = value.length
  var className
  var type
  var code
  var subvalue
  var lastIndex

  while (++index <= length) {
    code = value.charCodeAt(index)

    if (!code || code === dot || code === hash) {
      subvalue = value.slice(lastIndex, index)

      if (subvalue) {
        if (type === dot) {
          if (className) {
            className.push(subvalue)
          } else {
            className = [subvalue]
            props.className = className
          }
        } else if (type === hash) {
          props.id = subvalue
        } else {
          name = subvalue
        }
      }

      lastIndex = index + 1
      type = code
    }
  }

  return {
    type: 'element',
    tagName: name,
    properties: props,
    children: []
  }
}