fast-sass-loader/lib/replace.js

fast sass loader for Webpack

const async = require('async')

/**
 * replace string async
 *
 * @param  {String} text        text to replace
 * @param  {RegExp} rule        RegExp
 * @param  {Function} replacer  function that return promise
 * @return {String}
 */
function replaceAsync (text, rule, replacer) {
  let matches
  const ranges = []

  rule.lastIndex = 0

  while ((matches = rule.exec(text))) {
    // eslint-disable-line
    ranges.push([rule.lastIndex - matches[0].length, rule.lastIndex, matches.slice()])
  }

  return new Promise((resolve, reject) => {
    async.mapSeries(
      ranges,
      function (range, done) {
        replacer
          .apply(
            {
              start: range[0],
              end: range[1]
            },
            range[2]
          )
          .then(
            ret => {
              done(null, ret)
            },
            err => {
              done(err)
            }
          )
      },
      function (err, results) {
        if (err) {
          reject(err)
        } else {
          resolve(replaceByRanges(text, ranges, results))
        }
      }
    )
  })
}

function replaceByRanges (text, ranges, replaces) {
  const points = [0]
  const map = {}
  const pieces = []

  ranges.forEach((range, i) => {
    points.push(range[0])
    points.push(range[1])

    map[`${range[0]}-${range[1]}`] = replaces[i] || ''
  })

  points.push(Infinity)

  while (points.length > 1) {
    const start = points.shift()
    const stop = points[0]
    const key = `${start}-${stop}`

    if (key in map) {
      pieces.push(map[key])
    } else {
      pieces.push(text.substring(start, stop))
    }
  }

  return pieces.join('')
}

module.exports = replaceAsync