--- /dev/null
+'use strict';
+// based on https://github.com/bestiejs/punycode.js/blob/master/punycode.js
+var maxInt = 2147483647; // aka. 0x7FFFFFFF or 2^31-1
+var base = 36;
+var tMin = 1;
+var tMax = 26;
+var skew = 38;
+var damp = 700;
+var initialBias = 72;
+var initialN = 128; // 0x80
+var delimiter = '-'; // '\x2D'
+var regexNonASCII = /[^\0-\u007E]/; // non-ASCII chars
+var regexSeparators = /[.\u3002\uFF0E\uFF61]/g; // RFC 3490 separators
+var OVERFLOW_ERROR = 'Overflow: input needs wider integers to process';
+var baseMinusTMin = base - tMin;
+var floor = Math.floor;
+var stringFromCharCode = String.fromCharCode;
+
+/**
+ * Creates an array containing the numeric code points of each Unicode
+ * character in the string. While JavaScript uses UCS-2 internally,
+ * this function will convert a pair of surrogate halves (each of which
+ * UCS-2 exposes as separate characters) into a single code point,
+ * matching UTF-16.
+ */
+var ucs2decode = function (string) {
+ var output = [];
+ var counter = 0;
+ var length = string.length;
+ while (counter < length) {
+ var value = string.charCodeAt(counter++);
+ if (value >= 0xD800 && value <= 0xDBFF && counter < length) {
+ // It's a high surrogate, and there is a next character.
+ var extra = string.charCodeAt(counter++);
+ if ((extra & 0xFC00) == 0xDC00) { // Low surrogate.
+ output.push(((value & 0x3FF) << 10) + (extra & 0x3FF) + 0x10000);
+ } else {
+ // It's an unmatched surrogate; only append this code unit, in case the
+ // next code unit is the high surrogate of a surrogate pair.
+ output.push(value);
+ counter--;
+ }
+ } else {
+ output.push(value);
+ }
+ }
+ return output;
+};
+
+/**
+ * Converts a digit/integer into a basic code point.
+ */
+var digitToBasic = function (digit) {
+ // 0..25 map to ASCII a..z or A..Z
+ // 26..35 map to ASCII 0..9
+ return digit + 22 + 75 * (digit < 26);
+};
+
+/**
+ * Bias adaptation function as per section 3.4 of RFC 3492.
+ * https://tools.ietf.org/html/rfc3492#section-3.4
+ */
+var adapt = function (delta, numPoints, firstTime) {
+ var k = 0;
+ delta = firstTime ? floor(delta / damp) : delta >> 1;
+ delta += floor(delta / numPoints);
+ for (; delta > baseMinusTMin * tMax >> 1; k += base) {
+ delta = floor(delta / baseMinusTMin);
+ }
+ return floor(k + (baseMinusTMin + 1) * delta / (delta + skew));
+};
+
+/**
+ * Converts a string of Unicode symbols (e.g. a domain name label) to a
+ * Punycode string of ASCII-only symbols.
+ */
+// eslint-disable-next-line max-statements
+var encode = function (input) {
+ var output = [];
+
+ // Convert the input in UCS-2 to an array of Unicode code points.
+ input = ucs2decode(input);
+
+ // Cache the length.
+ var inputLength = input.length;
+
+ // Initialize the state.
+ var n = initialN;
+ var delta = 0;
+ var bias = initialBias;
+ var i, currentValue;
+
+ // Handle the basic code points.
+ for (i = 0; i < input.length; i++) {
+ currentValue = input[i];
+ if (currentValue < 0x80) {
+ output.push(stringFromCharCode(currentValue));
+ }
+ }
+
+ var basicLength = output.length; // number of basic code points.
+ var handledCPCount = basicLength; // number of code points that have been handled;
+
+ // Finish the basic string with a delimiter unless it's empty.
+ if (basicLength) {
+ output.push(delimiter);
+ }
+
+ // Main encoding loop:
+ while (handledCPCount < inputLength) {
+ // All non-basic code points < n have been handled already. Find the next larger one:
+ var m = maxInt;
+ for (i = 0; i < input.length; i++) {
+ currentValue = input[i];
+ if (currentValue >= n && currentValue < m) {
+ m = currentValue;
+ }
+ }
+
+ // Increase `delta` enough to advance the decoder's <n,i> state to <m,0>, but guard against overflow.
+ var handledCPCountPlusOne = handledCPCount + 1;
+ if (m - n > floor((maxInt - delta) / handledCPCountPlusOne)) {
+ throw RangeError(OVERFLOW_ERROR);
+ }
+
+ delta += (m - n) * handledCPCountPlusOne;
+ n = m;
+
+ for (i = 0; i < input.length; i++) {
+ currentValue = input[i];
+ if (currentValue < n && ++delta > maxInt) {
+ throw RangeError(OVERFLOW_ERROR);
+ }
+ if (currentValue == n) {
+ // Represent delta as a generalized variable-length integer.
+ var q = delta;
+ for (var k = base; /* no condition */; k += base) {
+ var t = k <= bias ? tMin : (k >= bias + tMax ? tMax : k - bias);
+ if (q < t) break;
+ var qMinusT = q - t;
+ var baseMinusT = base - t;
+ output.push(stringFromCharCode(digitToBasic(t + qMinusT % baseMinusT)));
+ q = floor(qMinusT / baseMinusT);
+ }
+
+ output.push(stringFromCharCode(digitToBasic(q)));
+ bias = adapt(delta, handledCPCountPlusOne, handledCPCount == basicLength);
+ delta = 0;
+ ++handledCPCount;
+ }
+ }
+
+ ++delta;
+ ++n;
+ }
+ return output.join('');
+};
+
+module.exports = function (input) {
+ var encoded = [];
+ var labels = input.toLowerCase().replace(regexSeparators, '\u002E').split('.');
+ var i, label;
+ for (i = 0; i < labels.length; i++) {
+ label = labels[i];
+ encoded.push(regexNonASCII.test(label) ? 'xn--' + encode(label) : label);
+ }
+ return encoded.join('.');
+};