// reference: https://github.com/Oktavilla/markdown-it-table-of-contents

const defaults = {
  includeLevel: [2, 3],
  containerClass: 'table-of-contents',
  markerPattern: /^\[\[toc\]\]/im,
  listType: 'ul',
  containerHeaderHtml: '',
  containerFooterHtml: ''
}

module.exports = (md, options) => {
  options = Object.assign({}, defaults, options)
  const tocRegexp = options.markerPattern

  function toc (state, silent) {
    var token
    var match

    // Reject if the token does not start with [
    if (state.src.charCodeAt(state.pos) !== 0x5B /* [ */) {
      return false
    }
    // Don't run any pairs in validation mode
    if (silent) {
      return false
    }

    // Detect TOC markdown
    match = tocRegexp.exec(state.src)
    match = !match ? [] : match.filter(function (m) { return m })
    if (match.length < 1) {
      return false
    }

    // Build content
    token = state.push('toc_open', 'toc', 1)
    token.markup = '[[toc]]'
    token = state.push('toc_body', '', 0)
    token = state.push('toc_close', 'toc', -1)

    // Update pos so the parser can continue
    var newline = state.src.indexOf('\n')
    if (newline !== -1) {
      state.pos = state.pos + newline
    } else {
      state.pos = state.pos + state.posMax + 1
    }

    return true
  }

  md.renderer.rules.toc_open = function () {
    return vBindEscape`<TOC
      :class=${options.containerClass}
      :list-type=${options.listType}
      :include-level=${options.includeLevel}
    >`
  }

  md.renderer.rules.toc_body = function () {
    return `<template slot="header">${options.containerHeaderHtml}</template>`
      + `<template slot="footer">${options.containerFooterHtml}</template>`
  }

  md.renderer.rules.toc_close = function () {
    return `</TOC>`
  }

  // Insert TOC
  md.inline.ruler.after('emphasis', 'toc', toc)
}

/** escape double quotes in v-bind derivatives */
function vBindEscape (strs, ...args) {
  return strs.reduce((prev, curr, index) => {
    return prev + curr + (index >= args.length
      ? ''
      : `"${JSON.stringify(args[index])
        .replace(/"/g, "'")
        .replace(/([^\\])(\\\\)*\\'/g, (_, char) => char + '\\u0022')}"`)
  }, '')
}