'use strict'

var slug = require('remark-slug')
var util = require('mdast-util-toc')

module.exports = toc

var DEFAULT_HEADING = 'toc|table[ -]of[ -]contents?'

function toc(options) {
  var settings = options || {}
  var heading = settings.heading || DEFAULT_HEADING
  var depth = settings.maxDepth || 6
  var tight = settings.tight

  this.use(slug)

  return transformer

  /* Adds an example section based on a valid example
   * JavaScript document to a `Usage` section. */
  function transformer(node) {
    var result = util(node, {
      heading: heading,
      maxDepth: depth,
      tight: tight
    })

    if (result.index === null || result.index === -1 || !result.map) {
      return
    }

    /* Replace markdown. */
    node.children = [].concat(
      node.children.slice(0, result.index),
      result.map,
      node.children.slice(result.endIndex)
    )
  }
}