text: 'use strict'
  var config
  var CHAR_COMMENT_REPLACEMENT = '\uFFFD' // �
  var CHAR_TOKEN_REPLACEMENT = '\u00A4'// ¤
  var CHAR_TOKEN_START = '\u00AB' // «
  var CHAR_TOKEN_END = '\u00BB' // »
  
  var REGEX_COMMENT_REPLACEMENT = new RegExp(CHAR_COMMENT_REPLACEMENT, 'ig')
  var REGEX_TOKEN_REPLACEMENT = new RegExp(CHAR_TOKEN_REPLACEMENT, 'ig')
  
  var PATTERN_NUMBER = '\\-?(\\d*?\\.\\d+|\\d+)'
  var PATTERN_NUMBER_WITH_CALC = '(calc' + CHAR_TOKEN_REPLACEMENT + ')|(' + PATTERN_NUMBER + ')(?!d\\()'
  var PATTERN_TOKEN = CHAR_TOKEN_START + '\\d+:\\d+' + CHAR_TOKEN_END // «offset:index»
  var PATTERN_TOKEN_WITH_NAME = '\\w*?' + CHAR_TOKEN_START + '\\d+:\\d+' + CHAR_TOKEN_END // «offset:index»
  
  var REGEX_COMMENT = /\/\*[^]*?\*\//igm // none-greedy
  var REGEX_DIRECTIVE = /\/\*\s*(?:!)?\s*rtl:[^]*?\*\//img
  var REGEX_ESCAPE = /[.*+?^${}()|[\]\\]/g
  var REGEX_FUNCTION = /\([^\(\)]+\)/i
  var REGEX_HEX_COLOR = /#[a-f0-9]{3,6}/ig
  var REGEX_CALC = /calc/
  var REGEX_TOKENS = new RegExp(PATTERN_TOKEN, 'ig')
  var REGEX_TOKENS_WITH_NAME = new RegExp(PATTERN_TOKEN_WITH_NAME, 'ig')
  
  var REGEX_COMPLEMENT = new RegExp(PATTERN_NUMBER_WITH_CALC, 'i')
  var REGEX_NEGATE_ALL = new RegExp(PATTERN_NUMBER_WITH_CALC, 'ig')
  var REGEX_NEGATE_ONE = new RegExp(PATTERN_NUMBER_WITH_CALC, 'i')
  
  var DEFAULT_STRING_MAP_OPTIONS = { scope: '*', ignoreCase: true }
  var TOKEN_ID = 0
  
  function compare (what, to, ignoreCase) {
    if (ignoreCase) {
      return what.toLowerCase() === to.toLowerCase()
    }
    return what === to
  }
  
  function escapeRegExp (string) {
    return string.replace(REGEX_ESCAPE, '\\$&')
  }
  
  module.exports = {
    extend: function (dest, src) {
      if (typeof dest === 'undefined' || typeof dest !== 'object') {
        dest = {}
      }
      for (var prop in src) {
        if (!dest.hasOwnProperty(prop)) {
          dest[prop] = src[prop]
        }
      }
      return dest
    },
    swap: function (value, a, b, options) {
      var expr = escapeRegExp(a) + '|' + escapeRegExp(b)
      options = options || DEFAULT_STRING_MAP_OPTIONS
      var greedy = options.hasOwnProperty('greedy') ? options.greedy : config.greedy
      if (!greedy) {
        expr = '\\b(' + expr + ')\\b'
      }
      var flags = options.ignoreCase ? 'img' : 'mg'
      return value.replace(new RegExp(expr, flags), function (m) { return compare(m, a, options.ignoreCase) ? b : a })
    },
    swapLeftRight: function (value) {
      return this.swap(value, 'left', 'right')
    },
    swapLtrRtl: function (value) {
      return this.swap(value, 'ltr', 'rtl')
    },
    applyStringMap: function (value, isUrl) {
      var result = value
      for (var x = 0; x < config.stringMap.length; x++) {
        var map = config.stringMap[x]
        var options = this.extend(map.options, DEFAULT_STRING_MAP_OPTIONS)
        if (options.scope === '*' || (isUrl && options.scope === 'url') || (!isUrl && options.scope === 'selector')) {
          if (Array.isArray(map.search) && Array.isArray(map.replace)) {
            for (var mapIndex = 0; mapIndex < map.search.length; mapIndex++) {
              result = this.swap(result, map.search[mapIndex], map.replace[mapIndex % map.search.length], options)
            }
          } else {
            result = this.swap(result, map.search, map.replace, options)
          }
          if (map.exclusive === true) {
            break
          }
        }
      }
      return result
    },
    negate: function (value) {
      var state = this.saveTokens(value)
      state.value = state.value.replace(REGEX_NEGATE_ONE, function (num) {
        return REGEX_TOKEN_REPLACEMENT.test(num) ? num.replace(REGEX_TOKEN_REPLACEMENT, function (m) { return '(-1*' + m + ')' }) : parseFloat(num, 10) * -1
      })
      return this.restoreTokens(state)
    },
    negateAll: function (value) {
      var state = this.saveTokens(value)
      state.value = state.value.replace(REGEX_NEGATE_ALL, function (num) {
        return REGEX_TOKEN_REPLACEMENT.test(num) ? num.replace(REGEX_TOKEN_REPLACEMENT, function (m) { return '(-1*' + m + ')' }) : parseFloat(num, 10) * -1
      })
      return this.restoreTokens(state)
    },
    complement: function (value) {
      var state = this.saveTokens(value)
      state.value = state.value.replace(REGEX_COMPLEMENT, function (num) {
        return REGEX_TOKEN_REPLACEMENT.test(num) ? num.replace(REGEX_TOKEN_REPLACEMENT, function (m) { return '(100% - ' + m + ')' }) : 100 - parseFloat(num, 10)
      })
      return this.restoreTokens(state)
    },
    flipLength: function (value) {
      return config.useCalc ? 'calc(100% - ' + value + ')' : value
    },
    save: function (what, who, replacement, restorer, exclude) {
      var state = {
        value: who,
        store: [],
        replacement: replacement,
        restorer: restorer
      }
      state.value = state.value.replace(what, function (c) {
        if (exclude && c.match(exclude)) {
          return c
        } else {
          state.store.push(c); return state.replacement
        }
      })
      return state
    },
    restore: function (state) {
      var index = 0
      var result = state.value.replace(state.restorer, function () {
        return state.store[index++]
      })
      state.store.length = 0
      return result
    },
    saveComments: function (value) {
      return this.save(REGEX_COMMENT, value, CHAR_COMMENT_REPLACEMENT, REGEX_COMMENT_REPLACEMENT)
    },
    restoreComments: function (state) {
      return this.restore(state)
    },
    saveTokens: function (value, excludeCalc) {
      return excludeCalc === true
        ? this.save(REGEX_TOKENS_WITH_NAME, value, CHAR_TOKEN_REPLACEMENT, REGEX_TOKEN_REPLACEMENT, REGEX_CALC)
        : this.save(REGEX_TOKENS, value, CHAR_TOKEN_REPLACEMENT, REGEX_TOKEN_REPLACEMENT)
    },
    restoreTokens: function (state) {
      return this.restore(state)
    },
    guard: function (what, who, indexed) {
      var state = {
        value: who,
        store: [],
        offset: TOKEN_ID++,
        token: CHAR_TOKEN_START + TOKEN_ID,
        indexed: indexed === true
      }
      if (state.indexed === true) {
        while (what.test(state.value)) {
          state.value = state.value.replace(what, function (m) { state.store.push(m); return state.token + ':' + state.store.length + CHAR_TOKEN_END })
        }
      } else {
        state.value = state.value.replace(what, function (m) { state.store.push(m); return state.token + CHAR_TOKEN_END })
      }
      return state
    },
    unguard: function (state, callback) {
      if (state.indexed === true) {
        var detokenizer = new RegExp('(\\w*?)' + state.token + ':(\\d+)' + CHAR_TOKEN_END, 'i')
        while (detokenizer.test(state.value)) {
          state.value = state.value.replace(detokenizer, function (match, name, index) {
            var value = state.store[index - 1]
            if (typeof callback === 'function') {
              return name + callback(value, name)
            }
            return name + value
          })
        }
        return state.value
      } else {
        return state.value.replace(new RegExp('(\\w*?)' + state.token + CHAR_TOKEN_END, 'i'), function (match, name) {
          var value = state.store.shift()
          if (typeof callback === 'function') {
            return name + callback(value, name)
          }
          return name + value
        })
      }
    },
    guardHexColors: function (value) {
      return this.guard(REGEX_HEX_COLOR, value, true)
    },
    unguardHexColors: function (state, callback) {
      return this.unguard(state, callback)
    },
    guardFunctions: function (value) {
      return this.guard(REGEX_FUNCTION, value, true)
    },
    unguardFunctions: function (state, callback) {
      return this.unguard(state, callback)
    },
    trimDirective: function (value) {
      return value.replace(REGEX_DIRECTIVE, '')
    },
    regexCache: {},
    regexDirective: function (name) {
      // /(?:\/\*(?:!)?rtl:ignore(?::)?)([^]*?)(?:\*\/)/img
      this.regexCache[name] = this.regexCache[name] || new RegExp('(?:\\/\\*\\s*(?:!)?\\s*rtl:' + (name ? escapeRegExp(name) + '(?::)?' : '') + ')([^]*?)(?:\\*\\/)', 'img')
      return this.regexCache[name]
    },
    regex: function (what, options) {
      what = what || []
      var expression = ''
      for (var x = 0; x < what.length; x++) {
        switch (what[x]) {
          case 'percent':
            expression += '|(' + PATTERN_NUMBER + '%)'
            break
          case 'length':
            expression += '|(' + PATTERN_NUMBER + ')(?:ex|ch|r?em|vh|vw|vmin|vmax|px|mm|cm|in|pt|pc)?'
            break
          case 'number':
            expression += '|(' + PATTERN_NUMBER + ')'
            break
          case 'position':
            expression += '|(left|center|right|top|bottom)'
            break
          case 'calc':
            expression += '|(calc' + PATTERN_TOKEN + ')'
            break
        }
      }
      return new RegExp(expression.slice(1), options)
    },
    isLastOfType: function (node) {
      var isLast = true
      var next = node.next()
      while (next) {
        if (next && next.type === node.type) {
          isLast = false
          break
        }
        next = next.next()
      }
      return isLast
    },
    /**
     * Simple breakable each: returning false in the callback will break the loop
     * returns false if the loop was broken, otherwise true
     */
    each: function (array, callback) {
      for (var len = 0; len < array.length; len++) {
        if (callback(array[len]) === false) {
          return false
        }
      }
      return true
    }
  }
  
  module.exports.configure = function (configuration) {
    config = configuration
    return this
  }
  