text: // Copyright Joyent, Inc. and other Node contributors.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a
  // copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to permit
  // persons to whom the Software is furnished to do so, subject to the
  // following conditions:
  //
  // The above copyright notice and this permission notice shall be included
  // in all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
  // NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  // USE OR OTHER DEALINGS IN THE SOFTWARE.
  
  var punycode = require('punycode');
  var util = require('util');
  
  exports.parse = urlParse;
  exports.resolve = urlResolve;
  exports.resolveObject = urlResolveObject;
  exports.format = urlFormat;
  
  exports.Url = Url;
  
  function Url() {
    this.protocol = null;
    this.slashes = null;
    this.auth = null;
    this.host = null;
    this.port = null;
    this.hostname = null;
    this.hash = null;
    this.search = null;
    this.query = null;
    this.pathname = null;
    this.path = null;
    this.href = null;
  }
  
  // Reference: RFC 3986, RFC 1808, RFC 2396
  
  // define these here so at least they only have to be
  // compiled once on the first module load.
  var protocolPattern = /^([a-z0-9.+-]+:)/i,
      portPattern = /:[0-9]*$/,
  
      // Special case for a simple path URL
      simplePathPattern = /^(\/\/?(?!\/)[^\?\s]*)(\?[^\s]*)?$/,
  
      // RFC 2396: characters reserved for delimiting URLs.
      // We actually just auto-escape these.
      delims = ['<', '>', '"', '`', ' ', '\r', '\n', '\t'],
  
      // RFC 2396: characters not allowed for various reasons.
      unwise = ['{', '}', '|', '\\', '^', '`'].concat(delims),
  
      // Allowed by RFCs, but cause of XSS attacks.  Always escape these.
      autoEscape = ['\''].concat(unwise),
      // Characters that are never ever allowed in a hostname.
      // Note that any invalid chars are also handled, but these
      // are the ones that are *expected* to be seen, so we fast-path
      // them.
      nonHostChars = ['%', '/', '?', ';', '#'].concat(autoEscape),
      hostEndingChars = ['/', '?', '#'],
      hostnameMaxLen = 255,
      hostnamePartPattern = /^[a-z0-9A-Z_-]{0,63}$/,
      hostnamePartStart = /^([a-z0-9A-Z_-]{0,63})(.*)$/,
      // protocols that can allow "unsafe" and "unwise" chars.
      unsafeProtocol = {
        'javascript': true,
        'javascript:': true
      },
      // protocols that never have a hostname.
      hostlessProtocol = {
        'javascript': true,
        'javascript:': true
      },
      // protocols that always contain a // bit.
      slashedProtocol = {
        'http': true,
        'https': true,
        'ftp': true,
        'gopher': true,
        'file': true,
        'http:': true,
        'https:': true,
        'ftp:': true,
        'gopher:': true,
        'file:': true
      },
      querystring = require('querystring');
  
  function urlParse(url, parseQueryString, slashesDenoteHost) {
    if (url && util.isObject(url) && url instanceof Url) return url;
  
    var u = new Url;
    u.parse(url, parseQueryString, slashesDenoteHost);
    return u;
  }
  
  Url.prototype.parse = function(url, parseQueryString, slashesDenoteHost) {
    if (!util.isString(url)) {
      throw new TypeError("Parameter 'url' must be a string, not " + typeof url);
    }
  
    // Copy chrome, IE, opera backslash-handling behavior.
    // See: https://code.google.com/p/chromium/issues/detail?id=25916
    var hashSplit = url.split('#');
    hashSplit[0] = hashSplit[0].replace(/\\/g, '/');
    url = hashSplit.join('#');
  
    var rest = url;
  
    // trim before proceeding.
    // This is to support parse stuff like "  http://foo.com  \n"
    rest = rest.trim();
  
    if (!slashesDenoteHost && hashSplit.length === 1) {
      // Try fast path regexp
      var simplePath = simplePathPattern.exec(rest);
      if (simplePath) {
        this.path = rest;
        this.href = rest;
        this.pathname = simplePath[1];
        if (simplePath[2]) {
          this.search = simplePath[2];
          if (parseQueryString) {
            this.query = querystring.parse(this.search.substr(1));
          } else {
            this.query = this.search.substr(1);
          }
        }
        return this;
      }
    }
  
    var proto = protocolPattern.exec(rest);
    if (proto) {
      proto = proto[0];
      var lowerProto = proto.toLowerCase();
      this.protocol = lowerProto;
      rest = rest.substr(proto.length);
    }
  
    // figure out if it's got a host
    // user@server is *always* interpreted as a hostname, and url
    // resolution will treat //foo/bar as host=foo,path=bar because that's
    // how the browser resolves relative URLs.
    if (slashesDenoteHost || proto || rest.match(/^\/\/[^@\/]+@[^@\/]+/)) {
      var slashes = rest.substr(0, 2) === '//';
      if (slashes && !(proto && hostlessProtocol[proto])) {
        rest = rest.substr(2);
        this.slashes = true;
      }
    }
  
    if (!hostlessProtocol[proto] &&
        (slashes || (proto && !slashedProtocol[proto]))) {
  
      // there's a hostname.
      // the first instance of /, ?, ;, or # ends the host.
      //
      // If there is an @ in the hostname, then non-host chars *are* allowed
      // to the left of the last @ sign, unless some host-ending character
      // comes *before* the @-sign.
      // URLs are obnoxious.
      //
      // ex:
      // http://a@b@c/ => user:a@b host:c
      // http://a@b?@c => user:a host:c path:/?@c
  
      // v0.12 TODO(isaacs): This is not quite how Chrome does things.
      // Review our test case against browsers more comprehensively.
  
      // find the first instance of any hostEndingChars
      var hostEnd = -1;
      for (var i = 0; i < hostEndingChars.length; i++) {
        var hec = rest.indexOf(hostEndingChars[i]);
        if (hec !== -1 && (hostEnd === -1 || hec < hostEnd))
          hostEnd = hec;
      }
  
      // at this point, either we have an explicit point where the
      // auth portion cannot go past, or the last @ char is the decider.
      var auth, atSign;
      if (hostEnd === -1) {
        // atSign can be anywhere.
        atSign = rest.lastIndexOf('@');
      } else {
        // atSign must be in auth portion.
        // http://a@b/c@d => host:b auth:a path:/c@d
        atSign = rest.lastIndexOf('@', hostEnd);
      }
  
      // Now we have a portion which is definitely the auth.
      // Pull that off.
      if (atSign !== -1) {
        auth = rest.slice(0, atSign);
        rest = rest.slice(atSign + 1);
        this.auth = decodeURIComponent(auth);
      }
  
      // the host is the remaining to the left of the first non-host char
      hostEnd = -1;
      for (var i = 0; i < nonHostChars.length; i++) {
        var hec = rest.indexOf(nonHostChars[i]);
        if (hec !== -1 && (hostEnd === -1 || hec < hostEnd))
          hostEnd = hec;
      }
      // if we still have not hit it, then the entire thing is a host.
      if (hostEnd === -1)
        hostEnd = rest.length;
  
      this.host = rest.slice(0, hostEnd);
      rest = rest.slice(hostEnd);
  
      // pull out port.
      this.parseHost();
  
      // we've indicated that there is a hostname,
      // so even if it's empty, it has to be present.
      this.hostname = this.hostname || '';
  
      // if hostname begins with [ and ends with ]
      // assume that it's an IPv6 address.
      var ipv6Hostname = this.hostname[0] === '[' &&
          this.hostname[this.hostname.length - 1] === ']';
  
      // validate a little.
      if (!ipv6Hostname) {
        var hostparts = this.hostname.split(/\./);
        for (var i = 0, l = hostparts.length; i < l; i++) {
          var part = hostparts[i];
          if (!part) continue;
          if (!part.match(hostnamePartPattern)) {
            var newpart = '';
            for (var j = 0, k = part.length; j < k; j++) {
              if (part.charCodeAt(j) > 127) {
                // we replace non-ASCII char with a temporary placeholder
                // we need this to make sure size of hostname is not
                // broken by replacing non-ASCII by nothing
                newpart += 'x';
              } else {
                newpart += part[j];
              }
            }
            // we test again with ASCII char only
            if (!newpart.match(hostnamePartPattern)) {
              var validParts = hostparts.slice(0, i);
              var notHost = hostparts.slice(i + 1);
              var bit = part.match(hostnamePartStart);
              if (bit) {
                validParts.push(bit[1]);
                notHost.unshift(bit[2]);
              }
              if (notHost.length) {
                rest = '/' + notHost.join('.') + rest;
              }
              this.hostname = validParts.join('.');
              break;
            }
          }
        }
      }
  
      if (this.hostname.length > hostnameMaxLen) {
        this.hostname = '';
      } else {
        // hostnames are always lower case.
        this.hostname = this.hostname.toLowerCase();
      }
  
      if (!ipv6Hostname) {
        // IDNA Support: Returns a punycoded representation of "domain".
        // It only converts parts of the domain name that
        // have non-ASCII characters, i.e. it doesn't matter if
        // you call it with a domain that already is ASCII-only.
        this.hostname = punycode.toASCII(this.hostname);
      }
  
      var p = this.port ? ':' + this.port : '';
      var h = this.hostname || '';
      this.host = h + p;
      this.href += this.host;
  
      // strip [ and ] from the hostname
      // the host field still retains them, though
      if (ipv6Hostname) {
        this.hostname = this.hostname.substr(1, this.hostname.length - 2);
        if (rest[0] !== '/') {
          rest = '/' + rest;
        }
      }
    }
  
    // now rest is set to the post-host stuff.
    // chop off any delim chars.
    if (!unsafeProtocol[lowerProto]) {
  
      // First, make 100% sure that any "autoEscape" chars get
      // escaped, even if encodeURIComponent doesn't think they
      // need to be.
      for (var i = 0, l = autoEscape.length; i < l; i++) {
        var ae = autoEscape[i];
        var esc = encodeURIComponent(ae);
        if (esc === ae) {
          esc = escape(ae);
        }
        rest = rest.split(ae).join(esc);
      }
    }
  
  
    // chop off from the tail first.
    var hash = rest.indexOf('#');
    if (hash !== -1) {
      // got a fragment string.
      this.hash = rest.substr(hash);
      rest = rest.slice(0, hash);
    }
    var qm = rest.indexOf('?');
    if (qm !== -1) {
      this.search = rest.substr(qm);
      this.query = rest.substr(qm + 1);
      if (parseQueryString) {
        this.query = querystring.parse(this.query);
      }
      rest = rest.slice(0, qm);
    } else if (parseQueryString) {
      // no query string, but parseQueryString still requested
      this.search = '';
      this.query = {};
    }
    if (rest) this.pathname = rest;
    if (slashedProtocol[lowerProto] &&
        this.hostname && !this.pathname) {
      this.pathname = '/';
    }
  
    // to support http.request
    if (this.pathname || this.search) {
      var p = this.pathname || '';
      var s = this.search || '';
      this.path = p + s;
    }
  
    // finally, reconstruct the href based on what has been validated.
    this.href = this.format();
    return this;
  };
  
  // format a parsed object into a url string
  function urlFormat(obj) {
    // ensure it's an object, and not a string url.
    // If it's an obj, this is a no-op.
    // this way, you can call url_format() on strings
    // to clean up potentially wonky urls.
    if (util.isString(obj)) obj = urlParse(obj);
    if (!(obj instanceof Url)) return Url.prototype.format.call(obj);
    return obj.format();
  }
  
  Url.prototype.format = function() {
    var auth = this.auth || '';
    if (auth) {
      auth = encodeURIComponent(auth);
      auth = auth.replace(/%3A/i, ':');
      auth += '@';
    }
  
    var protocol = this.protocol || '',
        pathname = this.pathname || '',
        hash = this.hash || '',
        host = false,
        query = '';
  
    if (this.host) {
      host = auth + this.host;
    } else if (this.hostname) {
      host = auth + (this.hostname.indexOf(':') === -1 ?
          this.hostname :
          '[' + this.hostname + ']');
      if (this.port) {
        host += ':' + this.port;
      }
    }
  
    if (this.query &&
        util.isObject(this.query) &&
        Object.keys(this.query).length) {
      query = querystring.stringify(this.query);
    }
  
    var search = this.search || (query && ('?' + query)) || '';
  
    if (protocol && protocol.substr(-1) !== ':') protocol += ':';
  
    // only the slashedProtocols get the //.  Not mailto:, xmpp:, etc.
    // unless they had them to begin with.
    if (this.slashes ||
        (!protocol || slashedProtocol[protocol]) && host !== false) {
      host = '//' + (host || '');
      if (pathname && pathname.charAt(0) !== '/') pathname = '/' + pathname;
    } else if (!host) {
      host = '';
    }
  
    if (hash && hash.charAt(0) !== '#') hash = '#' + hash;
    if (search && search.charAt(0) !== '?') search = '?' + search;
  
    pathname = pathname.replace(/[?#]/g, function(match) {
      return encodeURIComponent(match);
    });
    search = search.replace('#', '%23');
  
    return protocol + host + pathname + search + hash;
  };
  
  function urlResolve(source, relative) {
    return urlParse(source, false, true).resolve(relative);
  }
  
  Url.prototype.resolve = function(relative) {
    return this.resolveObject(urlParse(relative, false, true)).format();
  };
  
  function urlResolveObject(source, relative) {
    if (!source) return relative;
    return urlParse(source, false, true).resolveObject(relative);
  }
  
  Url.prototype.resolveObject = function(relative) {
    if (util.isString(relative)) {
      var rel = new Url();
      rel.parse(relative, false, true);
      relative = rel;
    }
  
    var result = new Url();
    var tkeys = Object.keys(this);
    for (var tk = 0; tk < tkeys.length; tk++) {
      var tkey = tkeys[tk];
      result[tkey] = this[tkey];
    }
  
    // hash is always overridden, no matter what.
    // even href="" will remove it.
    result.hash = relative.hash;
  
    // if the relative url is empty, then there's nothing left to do here.
    if (relative.href === '') {
      result.href = result.format();
      return result;
    }
  
    // hrefs like //foo/bar always cut to the protocol.
    if (relative.slashes && !relative.protocol) {
      // take everything except the protocol from relative
      var rkeys = Object.keys(relative);
      for (var rk = 0; rk < rkeys.length; rk++) {
        var rkey = rkeys[rk];
        if (rkey !== 'protocol')
          result[rkey] = relative[rkey];
      }
  
      // urlParse appends trailing / to urls like http://www.example.com
      if (slashedProtocol[result.protocol] &&
          result.hostname && !result.pathname) {
        result.path = result.pathname = '/';
      }
  
      result.href = result.format();
      return result;
    }
  
    if (relative.protocol && relative.protocol !== result.protocol) {
      // if it's a known url protocol, then changing
      // the protocol does weird things
      // first, if it's not file:, then we MUST have a host,
      // and if there was a path
      // to begin with, then we MUST have a path.
      // if it is file:, then the host is dropped,
      // because that's known to be hostless.
      // anything else is assumed to be absolute.
      if (!slashedProtocol[relative.protocol]) {
        var keys = Object.keys(relative);
        for (var v = 0; v < keys.length; v++) {
          var k = keys[v];
          result[k] = relative[k];
        }
        result.href = result.format();
        return result;
      }
  
      result.protocol = relative.protocol;
      if (!relative.host && !hostlessProtocol[relative.protocol]) {
        var relPath = (relative.pathname || '').split('/');
        while (relPath.length && !(relative.host = relPath.shift()));
        if (!relative.host) relative.host = '';
        if (!relative.hostname) relative.hostname = '';
        if (relPath[0] !== '') relPath.unshift('');
        if (relPath.length < 2) relPath.unshift('');
        result.pathname = relPath.join('/');
      } else {
        result.pathname = relative.pathname;
      }
      result.search = relative.search;
      result.query = relative.query;
      result.host = relative.host || '';
      result.auth = relative.auth;
      result.hostname = relative.hostname || relative.host;
      result.port = relative.port;
      // to support http.request
      if (result.pathname || result.search) {
        var p = result.pathname || '';
        var s = result.search || '';
        result.path = p + s;
      }
      result.slashes = result.slashes || relative.slashes;
      result.href = result.format();
      return result;
    }
  
    var isSourceAbs = (result.pathname && result.pathname.charAt(0) === '/'),
        isRelAbs = (
            relative.host ||
            relative.pathname && relative.pathname.charAt(0) === '/'
        ),
        mustEndAbs = (isRelAbs || isSourceAbs ||
                      (result.host && relative.pathname)),
        removeAllDots = mustEndAbs,
        srcPath = result.pathname && result.pathname.split('/') || [],
        relPath = relative.pathname && relative.pathname.split('/') || [],
        psychotic = result.protocol && !slashedProtocol[result.protocol];
  
    // if the url is a non-slashed url, then relative
    // links like ../.. should be able
    // to crawl up to the hostname, as well.  This is strange.
    // result.protocol has already been set by now.
    // Later on, put the first path part into the host field.
    if (psychotic) {
      result.hostname = '';
      result.port = null;
      if (result.host) {
        if (srcPath[0] === '') srcPath[0] = result.host;
        else srcPath.unshift(result.host);
      }
      result.host = '';
      if (relative.protocol) {
        relative.hostname = null;
        relative.port = null;
        if (relative.host) {
          if (relPath[0] === '') relPath[0] = relative.host;
          else relPath.unshift(relative.host);
        }
        relative.host = null;
      }
      mustEndAbs = mustEndAbs && (relPath[0] === '' || srcPath[0] === '');
    }
  
    if (isRelAbs) {
      // it's absolute.
      result.host = (relative.host || relative.host === '') ?
                    relative.host : result.host;
      result.hostname = (relative.hostname || relative.hostname === '') ?
                        relative.hostname : result.hostname;
      result.search = relative.search;
      result.query = relative.query;
      srcPath = relPath;
      // fall through to the dot-handling below.
    } else if (relPath.length) {
      // it's relative
      // throw away the existing file, and take the new path instead.
      if (!srcPath) srcPath = [];
      srcPath.pop();
      srcPath = srcPath.concat(relPath);
      result.search = relative.search;
      result.query = relative.query;
    } else if (!util.isNullOrUndefined(relative.search)) {
      // just pull out the search.
      // like href='?foo'.
      // Put this after the other two cases because it simplifies the booleans
      if (psychotic) {
        result.hostname = result.host = srcPath.shift();
        // occasionally the auth can get stuck only in host
        // this especially happens in cases like
        // url.resolveObject('mailto:local1@domain1', 'local2@domain2')
        var authInHost = result.host && result.host.indexOf('@') > 0 ?
                         result.host.split('@') : false;
        if (authInHost) {
          result.auth = authInHost.shift();
          result.host = result.hostname = authInHost.shift();
        }
      }
      result.search = relative.search;
      result.query = relative.query;
      // to support http.request
      if (!util.isNull(result.pathname) || !util.isNull(result.search)) {
        result.path = (result.pathname ? result.pathname : '') +
                      (result.search ? result.search : '');
      }
      result.href = result.format();
      return result;
    }
  
    if (!srcPath.length) {
      // no path at all.  easy.
      // we've already handled the other stuff above.
      result.pathname = null;
      //to support http.request
      if (result.search) {
        result.path = '/' + result.search;
      } else {
        result.path = null;
      }
      result.href = result.format();
      return result;
    }
  
    // if a url ENDs in . or .., then it must get a trailing slash.
    // however, if it ends in anything else non-slashy,
    // then it must NOT get a trailing slash.
    var last = srcPath.slice(-1)[0];
    var hasTrailingSlash = (
        (result.host || relative.host) && (last === '.' || last === '..') ||
        last === '');
  
    // strip single dots, resolve double dots to parent dir
    // if the path tries to go above the root, `up` ends up > 0
    var up = 0;
    for (var i = srcPath.length; i >= 0; i--) {
      last = srcPath[i];
      if (last === '.') {
        srcPath.splice(i, 1);
      } else if (last === '..') {
        srcPath.splice(i, 1);
        up++;
      } else if (up) {
        srcPath.splice(i, 1);
        up--;
      }
    }
  
    // if the path is allowed to go above the root, restore leading ..s
    if (!mustEndAbs && !removeAllDots) {
      for (; up--; up) {
        srcPath.unshift('..');
      }
    }
  
    if (mustEndAbs && srcPath[0] !== '' &&
        (!srcPath[0] || srcPath[0].charAt(0) !== '/')) {
      srcPath.unshift('');
    }
  
    if (hasTrailingSlash && (srcPath.join('/').substr(-1) !== '/')) {
      srcPath.push('');
    }
  
    var isAbsolute = srcPath[0] === '' ||
        (srcPath[0] && srcPath[0].charAt(0) === '/');
  
    // put the host back
    if (psychotic) {
      result.hostname = result.host = isAbsolute ? '' :
                                      srcPath.length ? srcPath.shift() : '';
      // occasionally the auth can get stuck only in host
      // this especially happens in cases like
      // url.resolveObject('mailto:local1@domain1', 'local2@domain2')
      var authInHost = result.host && result.host.indexOf('@') > 0 ?
                       result.host.split('@') : false;
      if (authInHost) {
        result.auth = authInHost.shift();
        result.host = result.hostname = authInHost.shift();
      }
    }
  
    mustEndAbs = mustEndAbs || (result.host && srcPath.length);
  
    if (mustEndAbs && !isAbsolute) {
      srcPath.unshift('');
    }
  
    if (!srcPath.length) {
      result.pathname = null;
      result.path = null;
    } else {
      result.pathname = srcPath.join('/');
    }
  
    // to support request.http
    if (!util.isNull(result.pathname) || !util.isNull(result.search)) {
      result.path = (result.pathname ? result.pathname : '') +
                    (result.search ? result.search : '');
    }
    result.auth = relative.auth || result.auth;
    result.slashes = result.slashes || relative.slashes;
    result.href = result.format();
    return result;
  };
  
  Url.prototype.parseHost = function() {
    var host = this.host;
    var port = portPattern.exec(host);
    if (port) {
      port = port[0];
      if (port !== ':') {
        this.port = port.substr(1);
      }
      host = host.substr(0, host.length - port.length);
    }
    if (host) this.hostname = host;
  };
  