var upperCase = require('upper-case')
var lowerCase = require('lower-case')

/**
 * Swap the case of a string. Manually iterate over every character and check
 * instead of replacing certain characters for better unicode support.
 *
 * @param  {String} str
 * @param  {String} [locale]
 * @return {String}
 */
module.exports = function (str, locale) {
  if (str == null) {
    return ''
  }

  var result = ''

  for (var i = 0; i < str.length; i++) {
    var c = str[i]
    var u = upperCase(c, locale)

    result += u === c ? lowerCase(c, locale) : u
  }

  return result
}