code:
/*
 * portfinder.js: A simple tool to find an open port on the current machine.
 *
 * (C) 2011, Charlie Robbins
 *
 */

"use strict";

var fs = require('fs'),
    os = require('os'),
    net = require('net'),
    path = require('path'),
    _async = require('async'),
    debug = require('debug'),
    mkdirp = require('mkdirp').mkdirp;

var debugTestPort = debug('portfinder:testPort'),
    debugGetPort = debug('portfinder:getPort'),
    debugDefaultHosts = debug('portfinder:defaultHosts');

var internals = {};

internals.testPort = function(options, callback) {
  if (!callback) {
    callback = options;
    options = {};
  }

  options.server = options.server  || net.createServer(function () {
    //
    // Create an empty listener for the port testing server.
    //
  });

  debugTestPort("entered testPort(): trying", options.host, "port", options.port);

  function onListen () {
    debugTestPort("done w/ testPort(): OK", options.host, "port", options.port);

    options.server.removeListener('error', onError);
    options.server.close();
    callback(null, options.port);
  }

  function onError (err) {
    debugTestPort("done w/ testPort(): failed", options.host, "w/ port", options.port, "with error", err.code);

    options.server.removeListener('listening', onListen);

    if (!(err.code == 'EADDRINUSE' || err.code == 'EACCES')) {
      return callback(err);
    }

    var nextPort = exports.nextPort(options.port);

    if (nextPort > exports.highestPort) {
      return callback(new Error('No open ports available'));
    }

    internals.testPort({
      port: nextPort,
      host: options.host,
      server: options.server
    }, callback);
  }

  options.server.once('error', onError);
  options.server.once('listening', onListen);

  if (options.host) {
    options.server.listen(options.port, options.host);
  } else {
    /*
      Judgement of service without host
      example:
        express().listen(options.port)
    */
    options.server.listen(options.port);
  }
};

//
// ### @basePort {Number}
// The lowest port to begin any port search from
//
exports.basePort = 8000;

//
// ### function setBasePort (port)
// #### @port {Number} The new base port
//
exports.setBasePort = function (port) {
  exports.basePort = port;
}

//
// ### @highestPort {Number}
// Largest port number is an unsigned short 2**16 -1=65335
//
exports.highestPort = 65535;

//
// ### function setHighestPort (port)
// #### @port {Number} The new highest port
//
exports.setHighestPort = function (port) {
  exports.highestPort = port;
}

//
// ### @basePath {string}
// Default path to begin any socket search from
//
exports.basePath = '/tmp/portfinder'

//
// ### function getPort (options, callback)
// #### @options {Object} Settings to use when finding the necessary port
// #### @callback {function} Continuation to respond to when complete.
// Responds with a unbound port on the current machine.
//
exports.getPort = function (options, callback) {
  if (!callback) {
    callback = options;
    options = {};

  }

  options.port   = Number(options.port) || Number(exports.basePort);
  options.host   = options.host    || null;
  options.stopPort = Number(options.stopPort) || Number(exports.highestPort);

  if(!options.startPort) {
    options.startPort = Number(options.port);
    if(options.startPort < 0) {
      throw Error('Provided options.startPort(' + options.startPort + ') is less than 0, which are cannot be bound.');
    }
    if(options.stopPort < options.startPort) {
      throw Error('Provided options.stopPort(' + options.stopPort + 'is less than options.startPort (' + options.startPort + ')');
    }
  }

  if (options.host) {
    if (exports._defaultHosts.indexOf(options.host) !== -1) {
      exports._defaultHosts.push(options.host)
    }
  }

  var openPorts = [], currentHost;
  return _async.eachSeries(exports._defaultHosts, function(host, next) {
    debugGetPort("in eachSeries() iteration callback: host is", host);

    return internals.testPort({ host: host, port: options.port }, function(err, port) {
      if (err) {
        debugGetPort("in eachSeries() iteration callback testPort() callback", "with an err:", err.code);
        currentHost = host;
        return next(err);
      } else {
        debugGetPort("in eachSeries() iteration callback testPort() callback",
                    "with a success for port", port);
        openPorts.push(port);
        return next();
      }
    });
  }, function(err) {

    if (err) {
      debugGetPort("in eachSeries() result callback: err is", err);
      // If we get EADDRNOTAVAIL it means the host is not bindable, so remove it
      // from exports._defaultHosts and start over. For ubuntu, we use EINVAL for the same
      if (err.code === 'EADDRNOTAVAIL' || err.code === 'EINVAL') {
        if (options.host === currentHost) {
          // if bad address matches host given by user, tell them
          //
          // NOTE: We may need to one day handle `my-non-existent-host.local` if users
          // report frustration with passing in hostnames that DONT map to bindable
          // hosts, without showing them a good error.
          var msg = 'Provided host ' + options.host + ' could NOT be bound. Please provide a different host address or hostname';
          return callback(Error(msg));
        } else {
          var idx = exports._defaultHosts.indexOf(currentHost);
          exports._defaultHosts.splice(idx, 1);
          return exports.getPort(options, callback);
        }
      } else {
        // error is not accounted for, file ticket, handle special case
        return callback(err);
      }
    }

    // sort so we can compare first host to last host
    openPorts.sort(function(a, b) {
      return a - b;
    });

    debugGetPort("in eachSeries() result callback: openPorts is", openPorts);

    if (openPorts[0] === openPorts[openPorts.length-1]) {
      // if first === last, we found an open port
      if(openPorts[0] <= options.stopPort) {
        return callback(null, openPorts[0]);
      }
      else {
        var msg = 'No open ports found in between '+ options.startPort + ' and ' + options.stopPort;
        return callback(Error(msg));
      }
    } else {
      // otherwise, try again, using sorted port, aka, highest open for >= 1 host
      return exports.getPort({ port: openPorts.pop(), host: options.host, startPort: options.startPort, stopPort: options.stopPort }, callback);
    }

  });
};

//
// ### function getPortPromise (options)
// #### @options {Object} Settings to use when finding the necessary port
// Responds a promise to an unbound port on the current machine.
//
exports.getPortPromise = function (options) {
  if (typeof Promise !== 'function') {
    throw Error('Native promise support is not available in this version of node.' +
      'Please install a polyfill and assign Promise to global.Promise before calling this method');
  }
  if (!options) {
    options = {};
  }
  return new Promise(function(resolve, reject) {
    exports.getPort(options, function(err, port) {
      if (err) {
        return reject(err);
      }
      resolve(port);
    });
  });
}

//
// ### function getPorts (count, options, callback)
// #### @count {Number} The number of ports to find
// #### @options {Object} Settings to use when finding the necessary port
// #### @callback {function} Continuation to respond to when complete.
// Responds with an array of unbound ports on the current machine.
//
exports.getPorts = function (count, options, callback) {
  if (!callback) {
    callback = options;
    options = {};
  }

  var lastPort = null;
  _async.timesSeries(count, function(index, asyncCallback) {
    if (lastPort) {
      options.port = exports.nextPort(lastPort);
    }

    exports.getPort(options, function (err, port) {
      if (err) {
        asyncCallback(err);
      } else {
        lastPort = port;
        asyncCallback(null, port);
      }
    });
  }, callback);
};

//
// ### function getSocket (options, callback)
// #### @options {Object} Settings to use when finding the necessary port
// #### @callback {function} Continuation to respond to when complete.
// Responds with a unbound socket using the specified directory and base
// name on the current machine.
//
exports.getSocket = function (options, callback) {
  if (!callback) {
    callback = options;
    options = {};
  }

  options.mod  = options.mod    || parseInt(755, 8);
  options.path = options.path   || exports.basePath + '.sock';

  //
  // Tests the specified socket
  //
  function testSocket () {
    fs.stat(options.path, function (err) {
      //
      // If file we're checking doesn't exist (thus, stating it emits ENOENT),
      // we should be OK with listening on this socket.
      //
      if (err) {
        if (err.code == 'ENOENT') {
          callback(null, options.path);
        }
        else {
          callback(err);
        }
      }
      else {
        //
        // This file exists, so it isn't possible to listen on it. Lets try
        // next socket.
        //
        options.path = exports.nextSocket(options.path);
        exports.getSocket(options, callback);
      }
    });
  }

  //
  // Create the target `dir` then test connection
  // against the socket.
  //
  function createAndTestSocket (dir) {
    mkdirp(dir, options.mod, function (err) {
      if (err) {
        return callback(err);
      }

      options.exists = true;
      testSocket();
    });
  }

  //
  // Check if the parent directory of the target
  // socket path exists. If it does, test connection
  // against the socket. Otherwise, create the directory
  // then test connection.
  //
  function checkAndTestSocket () {
    var dir = path.dirname(options.path);

    fs.stat(dir, function (err, stats) {
      if (err || !stats.isDirectory()) {
        return createAndTestSocket(dir);
      }

      options.exists = true;
      testSocket();
    });
  }

  //
  // If it has been explicitly stated that the
  // target `options.path` already exists, then
  // simply test the socket.
  //
  return options.exists
    ? testSocket()
    : checkAndTestSocket();
};

//
// ### function nextPort (port)
// #### @port {Number} Port to increment from.
// Gets the next port in sequence from the
// specified `port`.
//
exports.nextPort = function (port) {
  return port + 1;
};

//
// ### function nextSocket (socketPath)
// #### @socketPath {string} Path to increment from
// Gets the next socket path in sequence from the
// specified `socketPath`.
//
exports.nextSocket = function (socketPath) {
  var dir = path.dirname(socketPath),
      name = path.basename(socketPath, '.sock'),
      match = name.match(/^([a-zA-z]+)(\d*)$/i),
      index = parseInt(match[2]),
      base = match[1];
  if (isNaN(index)) {
    index = 0;
  }

  index += 1;
  return path.join(dir, base + index + '.sock');
};

/**
 * @desc List of internal hostnames provided by your machine. A user
 *       provided hostname may also be provided when calling portfinder.getPort,
 *       which would then be added to the default hosts we lookup and return here.
 *
 * @return {array}
 *
 * Long Form Explantion:
 *
 *    - Input: (os.networkInterfaces() w/ MacOS 10.11.5+ and running a VM)
 *
 *        { lo0:
 *         [ { address: '::1',
 *             netmask: 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff',
 *             family: 'IPv6',
 *             mac: '00:00:00:00:00:00',
 *             scopeid: 0,
 *             internal: true },
 *           { address: '127.0.0.1',
 *             netmask: '255.0.0.0',
 *             family: 'IPv4',
 *             mac: '00:00:00:00:00:00',
 *             internal: true },
 *           { address: 'fe80::1',
 *             netmask: 'ffff:ffff:ffff:ffff::',
 *             family: 'IPv6',
 *             mac: '00:00:00:00:00:00',
 *             scopeid: 1,
 *             internal: true } ],
 *        en0:
 *         [ { address: 'fe80::a299:9bff:fe17:766d',
 *             netmask: 'ffff:ffff:ffff:ffff::',
 *             family: 'IPv6',
 *             mac: 'a0:99:9b:17:76:6d',
 *             scopeid: 4,
 *             internal: false },
 *           { address: '10.0.1.22',
 *             netmask: '255.255.255.0',
 *             family: 'IPv4',
 *             mac: 'a0:99:9b:17:76:6d',
 *             internal: false } ],
 *        awdl0:
 *         [ { address: 'fe80::48a8:37ff:fe34:aaef',
 *             netmask: 'ffff:ffff:ffff:ffff::',
 *             family: 'IPv6',
 *             mac: '4a:a8:37:34:aa:ef',
 *             scopeid: 8,
 *             internal: false } ],
 *        vnic0:
 *         [ { address: '10.211.55.2',
 *             netmask: '255.255.255.0',
 *             family: 'IPv4',
 *             mac: '00:1c:42:00:00:08',
 *             internal: false } ],
 *        vnic1:
 *         [ { address: '10.37.129.2',
 *             netmask: '255.255.255.0',
 *             family: 'IPv4',
 *             mac: '00:1c:42:00:00:09',
 *             internal: false } ] }
 *
 *    - Output:
 *
 *         [
 *          '0.0.0.0',
 *          '::1',
 *          '127.0.0.1',
 *          'fe80::1',
 *          '10.0.1.22',
 *          'fe80::48a8:37ff:fe34:aaef',
 *          '10.211.55.2',
 *          '10.37.129.2'
 *         ]
 *
 *     Note we export this so we can use it in our tests, otherwise this API is private
 */
exports._defaultHosts = (function() {
  var interfaces = {};
  try{
    interfaces = os.networkInterfaces();
  }
  catch(e) {
    // As of October 2016, Windows Subsystem for Linux (WSL) does not support
    // the os.networkInterfaces() call and throws instead. For this platform,
    // assume 0.0.0.0 as the only address
    //
    // - https://github.com/Microsoft/BashOnWindows/issues/468
    //
    // - Workaround is a mix of good work from the community:
    //   - https://github.com/http-party/node-portfinder/commit/8d7e30a648ff5034186551fa8a6652669dec2f2f
    //   - https://github.com/yarnpkg/yarn/pull/772/files
    if (e.syscall === 'uv_interface_addresses') {
      // swallow error because we're just going to use defaults
      // documented @ https://github.com/nodejs/node/blob/4b65a65e75f48ff447cabd5500ce115fb5ad4c57/doc/api/net.md#L231
    } else {
      throw e;
    }
  }

  var interfaceNames = Object.keys(interfaces),
      hiddenButImportantHost = '0.0.0.0', // !important - dont remove, hence the naming :)
      results = [hiddenButImportantHost];
  for (var i = 0; i < interfaceNames.length; i++) {
    var _interface = interfaces[interfaceNames[i]];
    for (var j = 0; j < _interface.length; j++) {
      var curr = _interface[j];
      results.push(curr.address);
    }
  }

  // add null value, For createServer function, do not use host.
  results.push(null);

  debugDefaultHosts("exports._defaultHosts is: %o", results);

  return results;
}());


code:
3.1.0 / 2017-09-26
==================

  * Add `DEBUG_HIDE_DATE` env var (#486)
  * Remove ReDoS regexp in %o formatter (#504)
  * Remove "component" from package.json
  * Remove `component.json`
  * Ignore package-lock.json
  * Examples: fix colors printout
  * Fix: browser detection
  * Fix: spelling mistake (#496, @EdwardBetts)

3.0.1 / 2017-08-24
==================

  * Fix: Disable colors in Edge and Internet Explorer (#489)

3.0.0 / 2017-08-08
==================

  * Breaking: Remove DEBUG_FD (#406)
  * Breaking: Use `Date#toISOString()` instead to `Date#toUTCString()` when output is not a TTY (#418)
  * Breaking: Make millisecond timer namespace specific and allow 'always enabled' output (#408)
  * Addition: document `enabled` flag (#465)
  * Addition: add 256 colors mode (#481)
  * Addition: `enabled()` updates existing debug instances, add `destroy()` function (#440)
  * Update: component: update "ms" to v2.0.0
  * Update: separate the Node and Browser tests in Travis-CI
  * Update: refactor Readme, fixed documentation, added "Namespace Colors" section, redid screenshots
  * Update: separate Node.js and web browser examples for organization
  * Update: update "browserify" to v14.4.0
  * Fix: fix Readme typo (#473)

2.6.9 / 2017-09-22
==================

  * remove ReDoS regexp in %o formatter (#504)

2.6.8 / 2017-05-18
==================

  * Fix: Check for undefined on browser globals (#462, @marbemac)

2.6.7 / 2017-05-16
==================

  * Fix: Update ms to 2.0.0 to fix regular expression denial of service vulnerability (#458, @hubdotcom)
  * Fix: Inline extend function in node implementation (#452, @dougwilson)
  * Docs: Fix typo (#455, @msasad)

2.6.5 / 2017-04-27
==================

  * Fix: null reference check on window.documentElement.style.WebkitAppearance (#447, @thebigredgeek)
  * Misc: clean up browser reference checks (#447, @thebigredgeek)
  * Misc: add npm-debug.log to .gitignore (@thebigredgeek)

2.6.4 / 2017-04-20
==================

  * Fix: bug that would occur if process.env.DEBUG is a non-string value. (#444, @LucianBuzzo)
  * Chore: ignore bower.json in npm installations. (#437, @joaovieira)
  * Misc: update "ms" to v0.7.3 (@tootallnate)

2.6.3 / 2017-03-13
==================

  * Fix: Electron reference to `process.env.DEBUG` (#431, @paulcbetts)
  * Docs: Changelog fix (@thebigredgeek)

2.6.2 / 2017-03-10
==================

  * Fix: DEBUG_MAX_ARRAY_LENGTH (#420, @slavaGanzin)
  * Docs: Add backers and sponsors from Open Collective (#422, @piamancini)
  * Docs: Add Slackin invite badge (@tootallnate)

2.6.1 / 2017-02-10
==================

  * Fix: Module's `export default` syntax fix for IE8 `Expected identifier` error
  * Fix: Whitelist DEBUG_FD for values 1 and 2 only (#415, @pi0)
  * Fix: IE8 "Expected identifier" error (#414, @vgoma)
  * Fix: Namespaces would not disable once enabled (#409, @musikov)

2.6.0 / 2016-12-28
==================

  * Fix: added better null pointer checks for browser useColors (@thebigredgeek)
  * Improvement: removed explicit `window.debug` export (#404, @tootallnate)
  * Improvement: deprecated `DEBUG_FD` environment variable (#405, @tootallnate)

2.5.2 / 2016-12-25
==================

  * Fix: reference error on window within webworkers (#393, @KlausTrainer)
  * Docs: fixed README typo (#391, @lurch)
  * Docs: added notice about v3 api discussion (@thebigredgeek)

2.5.1 / 2016-12-20
==================

  * Fix: babel-core compatibility

2.5.0 / 2016-12-20
==================

  * Fix: wrong reference in bower file (@thebigredgeek)
  * Fix: webworker compatibility (@thebigredgeek)
  * Fix: output formatting issue (#388, @kribblo)
  * Fix: babel-loader compatibility (#383, @escwald)
  * Misc: removed built asset from repo and publications (@thebigredgeek)
  * Misc: moved source files to /src (#378, @yamikuronue)
  * Test: added karma integration and replaced babel with browserify for browser tests (#378, @yamikuronue)
  * Test: coveralls integration (#378, @yamikuronue)
  * Docs: simplified language in the opening paragraph (#373, @yamikuronue)

2.4.5 / 2016-12-17
==================

  * Fix: `navigator` undefined in Rhino (#376, @jochenberger)
  * Fix: custom log function (#379, @hsiliev)
  * Improvement: bit of cleanup + linting fixes (@thebigredgeek)
  * Improvement: rm non-maintainted `dist/` dir (#375, @freewil)
  * Docs: simplified language in the opening paragraph. (#373, @yamikuronue)

2.4.4 / 2016-12-14
==================

  * Fix: work around debug being loaded in preload scripts for electron (#368, @paulcbetts)

2.4.3 / 2016-12-14
==================

  * Fix: navigation.userAgent error for react native (#364, @escwald)

2.4.2 / 2016-12-14
==================

  * Fix: browser colors (#367, @tootallnate)
  * Misc: travis ci integration (@thebigredgeek)
  * Misc: added linting and testing boilerplate with sanity check (@thebigredgeek)

2.4.1 / 2016-12-13
==================

  * Fix: typo that broke the package (#356)

2.4.0 / 2016-12-13
==================

  * Fix: bower.json references unbuilt src entry point (#342, @justmatt)
  * Fix: revert "handle regex special characters" (@tootallnate)
  * Feature: configurable util.inspect()`options for NodeJS (#327, @tootallnate)
  * Feature: %O`(big O) pretty-prints objects (#322, @tootallnate)
  * Improvement: allow colors in workers (#335, @botverse)
  * Improvement: use same color for same namespace. (#338, @lchenay)

2.3.3 / 2016-11-09
==================

  * Fix: Catch `JSON.stringify()` errors (#195, Jovan Alleyne)
  * Fix: Returning `localStorage` saved values (#331, Levi Thomason)
  * Improvement: Don't create an empty object when no `process` (Nathan Rajlich)

2.3.2 / 2016-11-09
==================

  * Fix: be super-safe in index.js as well (@TooTallNate)
  * Fix: should check whether process exists (Tom Newby)

2.3.1 / 2016-11-09
==================

  * Fix: Added electron compatibility (#324, @paulcbetts)
  * Improvement: Added performance optimizations (@tootallnate)
  * Readme: Corrected PowerShell environment variable example (#252, @gimre)
  * Misc: Removed yarn lock file from source control (#321, @fengmk2)

2.3.0 / 2016-11-07
==================

  * Fix: Consistent placement of ms diff at end of output (#215, @gorangajic)
  * Fix: Escaping of regex special characters in namespace strings (#250, @zacronos)
  * Fix: Fixed bug causing crash on react-native (#282, @vkarpov15)
  * Feature: Enabled ES6+ compatible import via default export (#212 @bucaran)
  * Feature: Added %O formatter to reflect Chrome's console.log capability (#279, @oncletom)
  * Package: Update "ms" to 0.7.2 (#315, @DevSide)
  * Package: removed superfluous version property from bower.json (#207 @kkirsche)
  * Readme: fix USE_COLORS to DEBUG_COLORS
  * Readme: Doc fixes for format string sugar (#269, @mlucool)
  * Readme: Updated docs for DEBUG_FD and DEBUG_COLORS environment variables (#232, @mattlyons0)
  * Readme: doc fixes for PowerShell (#271 #243, @exoticknight @unreadable)
  * Readme: better docs for browser support (#224, @matthewmueller)
  * Tooling: Added yarn integration for development (#317, @thebigredgeek)
  * Misc: Renamed History.md to CHANGELOG.md (@thebigredgeek)
  * Misc: Added license file (#226 #274, @CantemoInternal @sdaitzman)
  * Misc: Updated contributors (@thebigredgeek)

2.2.0 / 2015-05-09
==================

  * package: update "ms" to v0.7.1 (#202, @dougwilson)
  * README: add logging to file example (#193, @DanielOchoa)
  * README: fixed a typo (#191, @amir-s)
  * browser: expose `storage` (#190, @stephenmathieson)
  * Makefile: add a `distclean` target (#189, @stephenmathieson)

2.1.3 / 2015-03-13
==================

  * Updated stdout/stderr example (#186)
  * Updated example/stdout.js to match debug current behaviour
  * Renamed example/stderr.js to stdout.js
  * Update Readme.md (#184)
  * replace high intensity foreground color for bold (#182, #183)

2.1.2 / 2015-03-01
==================

  * dist: recompile
  * update "ms" to v0.7.0
  * package: update "browserify" to v9.0.3
  * component: fix "ms.js" repo location
  * changed bower package name
  * updated documentation about using debug in a browser
  * fix: security error on safari (#167, #168, @yields)

2.1.1 / 2014-12-29
==================

  * browser: use `typeof` to check for `console` existence
  * browser: check for `console.log` truthiness (fix IE 8/9)
  * browser: add support for Chrome apps
  * Readme: added Windows usage remarks
  * Add `bower.json` to properly support bower install

2.1.0 / 2014-10-15
==================

  * node: implement `DEBUG_FD` env variable support
  * package: update "browserify" to v6.1.0
  * package: add "license" field to package.json (#135, @panuhorsmalahti)

2.0.0 / 2014-09-01
==================

  * package: update "browserify" to v5.11.0
  * node: use stderr rather than stdout for logging (#29, @stephenmathieson)

1.0.4 / 2014-07-15
==================

  * dist: recompile
  * example: remove `console.info()` log usage
  * example: add "Content-Type" UTF-8 header to browser example
  * browser: place %c marker after the space character
  * browser: reset the "content" color via `color: inherit`
  * browser: add colors support for Firefox >= v31
  * debug: prefer an instance `log()` function over the global one (#119)
  * Readme: update documentation about styled console logs for FF v31 (#116, @wryk)

1.0.3 / 2014-07-09
==================

  * Add support for multiple wildcards in namespaces (#122, @seegno)
  * browser: fix lint

1.0.2 / 2014-06-10
==================

  * browser: update color palette (#113, @gscottolson)
  * common: make console logging function configurable (#108, @timoxley)
  * node: fix %o colors on old node <= 0.8.x
  * Makefile: find node path using shell/which (#109, @timoxley)

1.0.1 / 2014-06-06
==================

  * browser: use `removeItem()` to clear localStorage
  * browser, node: don't set DEBUG if namespaces is undefined (#107, @leedm777)
  * package: add "contributors" section
  * node: fix comment typo
  * README: list authors

1.0.0 / 2014-06-04
==================

  * make ms diff be global, not be scope
  * debug: ignore empty strings in enable()
  * node: make DEBUG_COLORS able to disable coloring
  * *: export the `colors` array
  * npmignore: don't publish the `dist` dir
  * Makefile: refactor to use browserify
  * package: add "browserify" as a dev dependency
  * Readme: add Web Inspector Colors section
  * node: reset terminal color for the debug content
  * node: map "%o" to `util.inspect()`
  * browser: map "%j" to `JSON.stringify()`
  * debug: add custom "formatters"
  * debug: use "ms" module for humanizing the diff
  * Readme: add "bash" syntax highlighting
  * browser: add Firebug color support
  * browser: add colors for WebKit browsers
  * node: apply log to `console`
  * rewrite: abstract common logic for Node & browsers
  * add .jshintrc file

0.8.1 / 2014-04-14
==================

  * package: re-add the "component" section

0.8.0 / 2014-03-30
==================

  * add `enable()` method for nodejs. Closes #27
  * change from stderr to stdout
  * remove unnecessary index.js file

0.7.4 / 2013-11-13
==================

  * remove "browserify" key from package.json (fixes something in browserify)

0.7.3 / 2013-10-30
==================

  * fix: catch localStorage security error when cookies are blocked (Chrome)
  * add debug(err) support. Closes #46
  * add .browser prop to package.json. Closes #42

0.7.2 / 2013-02-06
==================

  * fix package.json
  * fix: Mobile Safari (private mode) is broken with debug
  * fix: Use unicode to send escape character to shell instead of octal to work with strict mode javascript

0.7.1 / 2013-02-05
==================

  * add repository URL to package.json
  * add DEBUG_COLORED to force colored output
  * add browserify support
  * fix component. Closes #24

0.7.0 / 2012-05-04
==================

  * Added .component to package.json
  * Added debug.component.js build

0.6.0 / 2012-03-16
==================

  * Added support for "-" prefix in DEBUG [Vinay Pulim]
  * Added `.enabled` flag to the node version [TooTallNate]

0.5.0 / 2012-02-02
==================

  * Added: humanize diffs. Closes #8
  * Added `debug.disable()` to the CS variant
  * Removed padding. Closes #10
  * Fixed: persist client-side variant again. Closes #9

0.4.0 / 2012-02-01
==================

  * Added browser variant support for older browsers [TooTallNate]
  * Added `debug.enable('project:*')` to browser variant [TooTallNate]
  * Added padding to diff (moved it to the right)

0.3.0 / 2012-01-26
==================

  * Added millisecond diff when isatty, otherwise UTC string

0.2.0 / 2012-01-22
==================

  * Added wildcard support

0.1.0 / 2011-12-02
==================

  * Added: remove colors unless stderr isatty [TooTallNate]

0.0.1 / 2010-01-03
==================

  * Initial release

license: mit


code:
# debug
[![Build Status](https://travis-ci.org/visionmedia/debug.svg?branch=master)](https://travis-ci.org/visionmedia/debug)  [![Coverage Status](https://coveralls.io/repos/github/visionmedia/debug/badge.svg?branch=master)](https://coveralls.io/github/visionmedia/debug?branch=master)  [![Slack](https://visionmedia-community-slackin.now.sh/badge.svg)](https://visionmedia-community-slackin.now.sh/) [![OpenCollective](https://opencollective.com/debug/backers/badge.svg)](#backers)
[![OpenCollective](https://opencollective.com/debug/sponsors/badge.svg)](#sponsors)

A tiny JavaScript debugging utility modelled after Node.js core's debugging
technique. Works in Node.js and web browsers.

## Installation

```bash
$ npm install debug
```

## Usage

`debug` exposes a function; simply pass this function the name of your module, and it will return a decorated version of `console.error` for you to pass debug statements to. This will allow you to toggle the debug output for different parts of your module as well as the module as a whole.

Example [_app.js_](./examples/node/app.js):

```js
var debug = require('debug')('http')
  , http = require('http')
  , name = 'My App';

// fake app

debug('booting %o', name);

http.createServer(function(req, res){
  debug(req.method + ' ' + req.url);
  res.end('hello\n');
}).listen(3000, function(){
  debug('listening');
});

// fake worker of some kind

require('./worker');
```

Example [_worker.js_](./examples/node/worker.js):

```js
var a = require('debug')('worker:a')
  , b = require('debug')('worker:b');

function work() {
  a('doing lots of uninteresting work');
  setTimeout(work, Math.random() * 1000);
}

work();

function workb() {
  b('doing some work');
  setTimeout(workb, Math.random() * 2000);
}

workb();
```

The `DEBUG` environment variable is then used to enable these based on space or
comma-delimited names.

Here are some examples:

#### Windows command prompt notes

##### CMD

On Windows the environment variable is set using the `set` command.

```cmd
set DEBUG=*,-not_this
```

Example:

```cmd
set DEBUG=* & node app.js
```

##### PowerShell (VS Code default)

PowerShell uses different syntax to set environment variables.

```cmd
$env:DEBUG = "*,-not_this"
```

Example:

```cmd
$env:DEBUG='app';node app.js
```

Then, run the program to be debugged as usual.

npm script example:
```js
  "windowsDebug": "@powershell -Command $env:DEBUG='*';node app.js",
```

## Namespace Colors

Every debug instance has a color generated for it based on its namespace name.
This helps when visually parsing the debug output to identify which debug instance
a debug line belongs to.

#### Node.js

In Node.js, colors are enabled when stderr is a TTY. You also _should_ install
the [`supports-color`](https://npmjs.org/supports-color) module alongside debug,
otherwise debug will only use a small handful of basic colors.

#### Web Browser

Colors are also enabled on "Web Inspectors" that understand the `%c` formatting
option. These are WebKit web inspectors, Firefox ([since version
31](https://hacks.mozilla.org/2014/05/editable-box-model-multiple-selection-sublime-text-keys-much-more-firefox-developer-tools-episode-31/))
and the Firebug plugin for Firefox (any version).

## Millisecond diff

When actively developing an application it can be useful to see when the time spent between one `debug()` call and the next. Suppose for example you invoke `debug()` before requesting a resource, and after as well, the "+NNNms" will show you how much time was spent between calls.

When stdout is not a TTY, `Date#toISOString()` is used, making it more useful for logging the debug information as shown below:

## Conventions

If you're using this in one or more of your libraries, you _should_ use the name of your library so that developers may toggle debugging as desired without guessing names. If you have more than one debuggers you _should_ prefix them with your library name and use ":" to separate features. For example "bodyParser" from Connect would then be "connect:bodyParser".  If you append a "*" to the end of your name, it will always be enabled regardless of the setting of the DEBUG environment variable.  You can then use it for normal output as well as debug output.

## Wildcards

The `*` character may be used as a wildcard. Suppose for example your library has
debuggers named "connect:bodyParser", "connect:compress", "connect:session",
instead of listing all three with
`DEBUG=connect:bodyParser,connect:compress,connect:session`, you may simply do
`DEBUG=connect:*`, or to run everything using this module simply use `DEBUG=*`.

You can also exclude specific debuggers by prefixing them with a "-" character.
For example, `DEBUG=*,-connect:*` would include all debuggers except those
starting with "connect:".

## Environment Variables

When running through Node.js, you can set a few environment variables that will
change the behavior of the debug logging:

| Name      | Purpose                                         |
|-----------|-------------------------------------------------|
| `DEBUG`   | Enables/disables specific debugging namespaces. |
| `DEBUG_HIDE_DATE` | Hide date from debug output (non-TTY).  |
| `DEBUG_COLORS`| Whether or not to use colors in the debug output. |
| `DEBUG_DEPTH` | Object inspection depth.                    |
| `DEBUG_SHOW_HIDDEN` | Shows hidden properties on inspected objects. |

__Note:__ The environment variables beginning with `DEBUG_` end up being
converted into an Options object that gets used with `%o`/`%O` formatters.
See the Node.js documentation for
[`util.inspect()`](https://nodejs.org/api/util.html#util_util_inspect_object_options)
for the complete list.

## Formatters

Debug uses [printf-style](https://wikipedia.org/wiki/Printf_format_string) formatting.
Below are the officially supported formatters:

| Formatter | Representation |
|-----------|----------------|
| `%O`      | Pretty-print an Object on multiple lines. |
| `%o`      | Pretty-print an Object all on a single line. |
| `%s`      | String. |
| `%d`      | Number (both integer and float). |
| `%j`      | JSON. Replaced with the string '[Circular]' if the argument contains circular references. |
| `%%`      | Single percent sign ('%'). This does not consume an argument. |

### Custom formatters

You can add custom formatters by extending the `debug.formatters` object.
For example, if you wanted to add support for rendering a Buffer as hex with
`%h`, you could do something like:

```js
const createDebug = require('debug')
createDebug.formatters.h = (v) => {
  return v.toString('hex')
}

// …elsewhere
const debug = createDebug('foo')
debug('this is hex: %h', new Buffer('hello world'))
//   foo this is hex: 68656c6c6f20776f726c6421 +0ms
```

## Browser Support

You can build a browser-ready script using [browserify](https://github.com/substack/node-browserify),
or just use the [browserify-as-a-service](https://wzrd.in/) [build](https://wzrd.in/standalone/debug@latest),
if you don't want to build it yourself.

Debug's enable state is currently persisted by `localStorage`.
Consider the situation shown below where you have `worker:a` and `worker:b`,
and wish to debug both. You can enable this using `localStorage.debug`:

```js
localStorage.debug = 'worker:*'
```

And then refresh the page.

```js
a = debug('worker:a');
b = debug('worker:b');

setInterval(function(){
  a('doing some work');
}, 1000);

setInterval(function(){
  b('doing some work');
}, 1200);
```

## Output streams

  By default `debug` will log to stderr, however this can be configured per-namespace by overriding the `log` method:

Example [_stdout.js_](./examples/node/stdout.js):

```js
var debug = require('debug');
var error = debug('app:error');

// by default stderr is used
error('goes to stderr!');

var log = debug('app:log');
// set this namespace to log via console.log
log.log = console.log.bind(console); // don't forget to bind to console!
log('goes to stdout');
error('still goes to stderr!');

// set all output to go via console.info
// overrides all per-namespace log settings
debug.log = console.info.bind(console);
error('now goes to stdout via console.info');
log('still goes to stdout, but via console.info now');
```

## Extend
You can simply extend debugger
```js
const log = require('debug')('auth');

//creates new debug instance with extended namespace
const logSign = log.extend('sign');
const logLogin = log.extend('login');

log('hello'); // auth hello
logSign('hello'); //auth:sign hello
logLogin('hello'); //auth:login hello
```

## Set dynamically

You can also enable debug dynamically by calling the `enable()` method :

```js
let debug = require('debug');

console.log(1, debug.enabled('test'));

debug.enable('test');
console.log(2, debug.enabled('test'));

debug.disable();
console.log(3, debug.enabled('test'));

```

print :
```
1 false
2 true
3 false
```

Usage :
`enable(namespaces)`
`namespaces` can include modes separated by a colon and wildcards.

Note that calling `enable()` completely overrides previously set DEBUG variable :

```
$ DEBUG=foo node -e 'var dbg = require("debug"); dbg.enable("bar"); console.log(dbg.enabled("foo"))'
=> false
```

## Checking whether a debug target is enabled

After you've created a debug instance, you can determine whether or not it is
enabled by checking the `enabled` property:

```javascript
const debug = require('debug')('http');

if (debug.enabled) {
  // do stuff...
}
```

You can also manually toggle this property to force the debug instance to be
enabled or disabled.

## Authors

 - TJ Holowaychuk
 - Nathan Rajlich
 - Andrew Rhyne

## Backers

Support us with a monthly donation and help us continue our activities. [[Become a backer](https://opencollective.com/debug#backer)]

## Sponsors

Become a sponsor and get your logo on our README on Github with a link to your site. [[Become a sponsor](https://opencollective.com/debug#sponsor)]

## License

(The MIT License)

Copyright (c) 2014-2017 TJ Holowaychuk <tj@vision-media.ca>

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.


code: module.exports = require('./src/node');


debug

type: git

description: small debugging utility

keywords: debug log debugger

author: TJ Holowaychuk <tj@vision-media.ca>

contributors: Nathan Rajlich <nathan@tootallnate.net> (http://n8.io)

license: MIT


code:
"use strict";

function _typeof(obj) { if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") { _typeof = function _typeof(obj) { return typeof obj; }; } else { _typeof = function _typeof(obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; }; } return _typeof(obj); }

/* eslint-env browser */

/**
 * This is the web browser implementation of `debug()`.
 */
exports.log = log;
exports.formatArgs = formatArgs;
exports.save = save;
exports.load = load;
exports.useColors = useColors;
exports.storage = localstorage();
/**
 * Colors.
 */

exports.colors = ['#0000CC', '#0000FF', '#0033CC', '#0033FF', '#0066CC', '#0066FF', '#0099CC', '#0099FF', '#00CC00', '#00CC33', '#00CC66', '#00CC99', '#00CCCC', '#00CCFF', '#3300CC', '#3300FF', '#3333CC', '#3333FF', '#3366CC', '#3366FF', '#3399CC', '#3399FF', '#33CC00', '#33CC33', '#33CC66', '#33CC99', '#33CCCC', '#33CCFF', '#6600CC', '#6600FF', '#6633CC', '#6633FF', '#66CC00', '#66CC33', '#9900CC', '#9900FF', '#9933CC', '#9933FF', '#99CC00', '#99CC33', '#CC0000', '#CC0033', '#CC0066', '#CC0099', '#CC00CC', '#CC00FF', '#CC3300', '#CC3333', '#CC3366', '#CC3399', '#CC33CC', '#CC33FF', '#CC6600', '#CC6633', '#CC9900', '#CC9933', '#CCCC00', '#CCCC33', '#FF0000', '#FF0033', '#FF0066', '#FF0099', '#FF00CC', '#FF00FF', '#FF3300', '#FF3333', '#FF3366', '#FF3399', '#FF33CC', '#FF33FF', '#FF6600', '#FF6633', '#FF9900', '#FF9933', '#FFCC00', '#FFCC33'];
/**
 * Currently only WebKit-based Web Inspectors, Firefox >= v31,
 * and the Firebug extension (any Firefox version) are known
 * to support "%c" CSS customizations.
 *
 * TODO: add a `localStorage` variable to explicitly enable/disable colors
 */
// eslint-disable-next-line complexity

function useColors() {
  // NB: In an Electron preload script, document will be defined but not fully
  // initialized. Since we know we're in Chrome, we'll just detect this case
  // explicitly
  if (typeof window !== 'undefined' && window.process && (window.process.type === 'renderer' || window.process.__nwjs)) {
    return true;
  } // Internet Explorer and Edge do not support colors.

  if (typeof navigator !== 'undefined' && navigator.userAgent && navigator.userAgent.toLowerCase().match(/(edge|trident)\/(\d+)/)) {
    return false;
  } // Is webkit? http://stackoverflow.com/a/16459606/376773
  // document is undefined in react-native: https://github.com/facebook/react-native/pull/1632

  return typeof document !== 'undefined' && document.documentElement && document.documentElement.style && document.documentElement.style.WebkitAppearance || // Is firebug? http://stackoverflow.com/a/398120/376773
  typeof window !== 'undefined' && window.console && (window.console.firebug || window.console.exception && window.console.table) || // Is firefox >= v31?
  // https://developer.mozilla.org/en-US/docs/Tools/Web_Console#Styling_messages
  typeof navigator !== 'undefined' && navigator.userAgent && navigator.userAgent.toLowerCase().match(/firefox\/(\d+)/) && parseInt(RegExp.$1, 10) >= 31 || // Double check webkit in userAgent just in case we are in a worker
  typeof navigator !== 'undefined' && navigator.userAgent && navigator.userAgent.toLowerCase().match(/applewebkit\/(\d+)/);
}
/**
 * Colorize log arguments if enabled.
 *
 * @api public
 */

function formatArgs(args) {
  args[0] = (this.useColors ? '%c' : '') + this.namespace + (this.useColors ? ' %c' : ' ') + args[0] + (this.useColors ? '%c ' : ' ') + '+' + module.exports.humanize(this.diff);

  if (!this.useColors) {
    return;
  }

  var c = 'color: ' + this.color;
  args.splice(1, 0, c, 'color: inherit'); // The final "%c" is somewhat tricky, because there could be other
  // arguments passed either before or after the %c, so we need to
  // figure out the correct index to insert the CSS into

  var index = 0;
  var lastC = 0;
  args[0].replace(/%[a-zA-Z%]/g, function (match) {
    if (match === '%%') {
      return;
    }

    index++;

    if (match === '%c') {
      // We only are interested in the *last* %c
      // (the user may have provided their own)
      lastC = index;
    }
  });
  args.splice(lastC, 0, c);
}
/**
 * Invokes `console.log()` when available.
 * No-op when `console.log` is not a "function".
 *
 * @api public
 */

function log() {
  var _console;

  // This hackery is required for IE8/9, where
  // the `console.log` function doesn't have 'apply'
  return (typeof console === "undefined" ? "undefined" : _typeof(console)) === 'object' && console.log && (_console = console).log.apply(_console, arguments);
}
/**
 * Save `namespaces`.
 *
 * @param {String} namespaces
 * @api private
 */

function save(namespaces) {
  try {
    if (namespaces) {
      exports.storage.setItem('debug', namespaces);
    } else {
      exports.storage.removeItem('debug');
    }
  } catch (error) {// Swallow
    // XXX (@Qix-) should we be logging these?
  }
}
/**
 * Load `namespaces`.
 *
 * @return {String} returns the previously persisted debug modes
 * @api private
 */

function load() {
  var r;

  try {
    r = exports.storage.getItem('debug');
  } catch (error) {} // Swallow
  // XXX (@Qix-) should we be logging these?
  // If debug isn't set in LS, and we're in Electron, try to load $DEBUG

  if (!r && typeof process !== 'undefined' && 'env' in process) {
    r = process.env.DEBUG;
  }

  return r;
}
/**
 * Localstorage attempts to return the localstorage.
 *
 * This is necessary because safari throws
 * when a user disables cookies/localstorage
 * and you attempt to access it.
 *
 * @return {LocalStorage}
 * @api private
 */

function localstorage() {
  try {
    // TVMLKit (Apple TV JS Runtime) does not have a window object, just localStorage in the global context
    // The Browser also has localStorage in the global context.
    return localStorage;
  } catch (error) {// Swallow
    // XXX (@Qix-) should we be logging these?
  }
}

module.exports = require('./common')(exports);
var formatters = module.exports.formatters;
/**
 * Map %j to `JSON.stringify()`, since no Web Inspectors do that by default.
 */

formatters.j = function (v) {
  try {
    return JSON.stringify(v);
  } catch (error) {
    return '[UnexpectedJSONParseError]: ' + error.message;
  }
};


code:
"use strict";

/**
 * This is the common logic for both the Node.js and web browser
 * implementations of `debug()`.
 */
function setup(env) {
  createDebug.debug = createDebug;
  createDebug.default = createDebug;
  createDebug.coerce = coerce;
  createDebug.disable = disable;
  createDebug.enable = enable;
  createDebug.enabled = enabled;
  createDebug.humanize = require('ms');
  Object.keys(env).forEach(function (key) {
    createDebug[key] = env[key];
  });
  /**
  * Active `debug` instances.
  */

  createDebug.instances = [];
  /**
  * The currently active debug mode names, and names to skip.
  */

  createDebug.names = [];
  createDebug.skips = [];
  /**
  * Map of special "%n" handling functions, for the debug "format" argument.
  *
  * Valid key names are a single, lower or upper-case letter, i.e. "n" and "N".
  */

  createDebug.formatters = {};
  /**
  * Selects a color for a debug namespace
  * @param {String} namespace The namespace string for the for the debug instance to be colored
  * @return {Number|String} An ANSI color code for the given namespace
  * @api private
  */

  function selectColor(namespace) {
    var hash = 0;

    for (var i = 0; i < namespace.length; i++) {
      hash = (hash << 5) - hash + namespace.charCodeAt(i);
      hash |= 0; // Convert to 32bit integer
    }

    return createDebug.colors[Math.abs(hash) % createDebug.colors.length];
  }

  createDebug.selectColor = selectColor;
  /**
  * Create a debugger with the given `namespace`.
  *
  * @param {String} namespace
  * @return {Function}
  * @api public
  */

  function createDebug(namespace) {
    var prevTime;

    function debug() {
      // Disabled?
      if (!debug.enabled) {
        return;
      }

      for (var _len = arguments.length, args = new Array(_len), _key = 0; _key < _len; _key++) {
        args[_key] = arguments[_key];
      }

      var self = debug; // Set `diff` timestamp

      var curr = Number(new Date());
      var ms = curr - (prevTime || curr);
      self.diff = ms;
      self.prev = prevTime;
      self.curr = curr;
      prevTime = curr;
      args[0] = createDebug.coerce(args[0]);

      if (typeof args[0] !== 'string') {
        // Anything else let's inspect with %O
        args.unshift('%O');
      } // Apply any `formatters` transformations

      var index = 0;
      args[0] = args[0].replace(/%([a-zA-Z%])/g, function (match, format) {
        // If we encounter an escaped % then don't increase the array index
        if (match === '%%') {
          return match;
        }

        index++;
        var formatter = createDebug.formatters[format];

        if (typeof formatter === 'function') {
          var val = args[index];
          match = formatter.call(self, val); // Now we need to remove `args[index]` since it's inlined in the `format`

          args.splice(index, 1);
          index--;
        }

        return match;
      }); // Apply env-specific formatting (colors, etc.)

      createDebug.formatArgs.call(self, args);
      var logFn = self.log || createDebug.log;
      logFn.apply(self, args);
    }

    debug.namespace = namespace;
    debug.enabled = createDebug.enabled(namespace);
    debug.useColors = createDebug.useColors();
    debug.color = selectColor(namespace);
    debug.destroy = destroy;
    debug.extend = extend; // Debug.formatArgs = formatArgs;
    // debug.rawLog = rawLog;
    // env-specific initialization logic for debug instances

    if (typeof createDebug.init === 'function') {
      createDebug.init(debug);
    }

    createDebug.instances.push(debug);
    return debug;
  }

  function destroy() {
    var index = createDebug.instances.indexOf(this);

    if (index !== -1) {
      createDebug.instances.splice(index, 1);
      return true;
    }

    return false;
  }

  function extend(namespace, delimiter) {
    return createDebug(this.namespace + (typeof delimiter === 'undefined' ? ':' : delimiter) + namespace);
  }
  /**
  * Enables a debug mode by namespaces. This can include modes
  * separated by a colon and wildcards.
  *
  * @param {String} namespaces
  * @api public
  */

  function enable(namespaces) {
    createDebug.save(namespaces);
    createDebug.names = [];
    createDebug.skips = [];
    var i;
    var split = (typeof namespaces === 'string' ? namespaces : '').split(/[\s,]+/);
    var len = split.length;

    for (i = 0; i < len; i++) {
      if (!split[i]) {
        // ignore empty strings
        continue;
      }

      namespaces = split[i].replace(/\*/g, '.*?');

      if (namespaces[0] === '-') {
        createDebug.skips.push(new RegExp('^' + namespaces.substr(1) + '$'));
      } else {
        createDebug.names.push(new RegExp('^' + namespaces + '$'));
      }
    }

    for (i = 0; i < createDebug.instances.length; i++) {
      var instance = createDebug.instances[i];
      instance.enabled = createDebug.enabled(instance.namespace);
    }
  }
  /**
  * Disable debug output.
  *
  * @api public
  */

  function disable() {
    createDebug.enable('');
  }
  /**
  * Returns true if the given mode name is enabled, false otherwise.
  *
  * @param {String} name
  * @return {Boolean}
  * @api public
  */

  function enabled(name) {
    if (name[name.length - 1] === '*') {
      return true;
    }

    var i;
    var len;

    for (i = 0, len = createDebug.skips.length; i < len; i++) {
      if (createDebug.skips[i].test(name)) {
        return false;
      }
    }

    for (i = 0, len = createDebug.names.length; i < len; i++) {
      if (createDebug.names[i].test(name)) {
        return true;
      }
    }

    return false;
  }
  /**
  * Coerce `val`.
  *
  * @param {Mixed} val
  * @return {Mixed}
  * @api private
  */

  function coerce(val) {
    if (val instanceof Error) {
      return val.stack || val.message;
    }

    return val;
  }

  createDebug.enable(createDebug.load());
  return createDebug;
}

module.exports = setup;


code:
"use strict";

/**
 * Detect Electron renderer / nwjs process, which is node, but we should
 * treat as a browser.
 */
if (typeof process === 'undefined' || process.type === 'renderer' || process.browser === true || process.__nwjs) {
  module.exports = require('./browser.js');
} else {
  module.exports = require('./node.js');
}


code:
"use strict";

/**
 * Module dependencies.
 */
var tty = require('tty');

var util = require('util');
/**
 * This is the Node.js implementation of `debug()`.
 */

exports.init = init;
exports.log = log;
exports.formatArgs = formatArgs;
exports.save = save;
exports.load = load;
exports.useColors = useColors;
/**
 * Colors.
 */

exports.colors = [6, 2, 3, 4, 5, 1];

try {
  // Optional dependency (as in, doesn't need to be installed, NOT like optionalDependencies in package.json)
  // eslint-disable-next-line import/no-extraneous-dependencies
  var supportsColor = require('supports-color');

  if (supportsColor && (supportsColor.stderr || supportsColor).level >= 2) {
    exports.colors = [20, 21, 26, 27, 32, 33, 38, 39, 40, 41, 42, 43, 44, 45, 56, 57, 62, 63, 68, 69, 74, 75, 76, 77, 78, 79, 80, 81, 92, 93, 98, 99, 112, 113, 128, 129, 134, 135, 148, 149, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 178, 179, 184, 185, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 214, 215, 220, 221];
  }
} catch (error) {} // Swallow - we only care if `supports-color` is available; it doesn't have to be.

/**
 * Build up the default `inspectOpts` object from the environment variables.
 *
 *   $ DEBUG_COLORS=no DEBUG_DEPTH=10 DEBUG_SHOW_HIDDEN=enabled node script.js
 */

exports.inspectOpts = Object.keys(process.env).filter(function (key) {
  return /^debug_/i.test(key);
}).reduce(function (obj, key) {
  // Camel-case
  var prop = key.substring(6).toLowerCase().replace(/_([a-z])/g, function (_, k) {
    return k.toUpperCase();
  }); // Coerce string value into JS value

  var val = process.env[key];

  if (/^(yes|on|true|enabled)$/i.test(val)) {
    val = true;
  } else if (/^(no|off|false|disabled)$/i.test(val)) {
    val = false;
  } else if (val === 'null') {
    val = null;
  } else {
    val = Number(val);
  }

  obj[prop] = val;
  return obj;
}, {});
/**
 * Is stdout a TTY? Colored output is enabled when `true`.
 */

function useColors() {
  return 'colors' in exports.inspectOpts ? Boolean(exports.inspectOpts.colors) : tty.isatty(process.stderr.fd);
}
/**
 * Adds ANSI color escape codes if enabled.
 *
 * @api public
 */

function formatArgs(args) {
  var name = this.namespace,
      useColors = this.useColors;

  if (useColors) {
    var c = this.color;
    var colorCode = "\x1B[3" + (c < 8 ? c : '8;5;' + c);
    var prefix = "  ".concat(colorCode, ";1m").concat(name, " \x1B[0m");
    args[0] = prefix + args[0].split('\n').join('\n' + prefix);
    args.push(colorCode + 'm+' + module.exports.humanize(this.diff) + "\x1B[0m");
  } else {
    args[0] = getDate() + name + ' ' + args[0];
  }
}

function getDate() {
  if (exports.inspectOpts.hideDate) {
    return '';
  }

  return new Date().toISOString() + ' ';
}
/**
 * Invokes `util.format()` with the specified arguments and writes to stderr.
 */

function log() {
  return process.stderr.write(util.format.apply(util, arguments) + '\n');
}
/**
 * Save `namespaces`.
 *
 * @param {String} namespaces
 * @api private
 */

function save(namespaces) {
  if (namespaces) {
    process.env.DEBUG = namespaces;
  } else {
    // If you set a process.env field to null or undefined, it gets cast to the
    // string 'null' or 'undefined'. Just delete instead.
    delete process.env.DEBUG;
  }
}
/**
 * Load `namespaces`.
 *
 * @return {String} returns the previously persisted debug modes
 * @api private
 */

function load() {
  return process.env.DEBUG;
}
/**
 * Init logic for `debug` instances.
 *
 * Create a new `inspectOpts` object in case `useColors` is set
 * differently for a particular `debug` instance.
 */

function init(debug) {
  debug.inspectOpts = {};
  var keys = Object.keys(exports.inspectOpts);

  for (var i = 0; i < keys.length; i++) {
    debug.inspectOpts[keys[i]] = exports.inspectOpts[keys[i]];
  }
}

module.exports = require('./common')(exports);
var formatters = module.exports.formatters;
/**
 * Map %o to `util.inspect()`, all on a single line.
 */

formatters.o = function (v) {
  this.inspectOpts.colors = this.useColors;
  return util.inspect(v, this.inspectOpts)
    .split('\n')
    .map(function (str) { return str.trim(); })
    .join(' ');
};
/**
 * Map %O to `util.inspect()`, allowing multiple lines if needed.
 */

formatters.O = function (v) {
  this.inspectOpts.colors = this.useColors;
  return util.inspect(v, this.inspectOpts);
};


portfinder

description: A simple tool to find an open port on the current machine

keywords: http ports utilities

test: vows test/*-test.js --spec


code:
# PostCSS Calc [<img src="https://postcss.github.io/postcss/logo.svg" alt="PostCSS" width="90" height="90" align="right">][PostCSS]

[![NPM Version][npm-img]][npm-url]
[![Support Chat][git-img]][git-url]

[PostCSS Calc] lets you reduce `calc()` references whenever it's possible.
When multiple units are mixed together in the same expression, the `calc()`
statement is left as is, to fallback to the [W3C calc() implementation].

## Installation

```bash
npm install postcss-calc
```

## Usage

```js
// dependencies
var fs = require("fs")
var postcss = require("postcss")
var calc = require("postcss-calc")

// css to be processed
var css = fs.readFileSync("input.css", "utf8")

// process css
var output = postcss()
  .use(calc())
  .process(css)
  .css
```

Using this `input.css`:

```css
h1 {
  font-size: calc(16px * 2);
  height: calc(100px - 2em);
  width: calc(2*var(--base-width));
  margin-bottom: calc(16px * 1.5);
}
```

you will get:

```css
h1 {
  font-size: 32px;
  height: calc(100px - 2em);
  width: calc(2*var(--base-width));
  margin-bottom: 24px
}
```
Checkout [tests] for more examples.

### Options

#### `precision` (default: `5`)

Allow you to define the precision for decimal numbers.

```js
var out = postcss()
  .use(calc({precision: 10}))
  .process(css)
  .css
```

#### `preserve` (default: `false`)

Allow you to preserve calc() usage in output so browsers will handle decimal
precision themselves.

```js
var out = postcss()
  .use(calc({preserve: true}))
  .process(css)
  .css
```

#### `warnWhenCannotResolve` (default: `false`)

Adds warnings when calc() are not reduced to a single value.

```js
var out = postcss()
  .use(calc({warnWhenCannotResolve: true}))
  .process(css)
  .css
```

#### `mediaQueries` (default: `false`)

Allows calc() usage as part of media query declarations.

```js
var out = postcss()
  .use(calc({mediaQueries: true}))
  .process(css)
  .css
```

#### `selectors` (default: `false`)

Allows calc() usage as part of selectors.

```js
var out = postcss()
  .use(calc({selectors: true}))
  .process(css)
  .css
```

Example:

```css
div[data-size="calc(3*3)"] {
  width: 100px;
}
```

---

## Related PostCSS plugins
To replace the value of CSS custom properties at build time, try [PostCSS Custom Properties].

## Contributing

Work on a branch, install dev-dependencies, respect coding style & run tests
before submitting a bug fix or a feature.

```bash
git clone git@github.com:postcss/postcss-calc.git
git checkout -b patch-1
npm install
npm test
```

## [Changelog](CHANGELOG.md)

## [License](LICENSE)

[git-img]: https://img.shields.io/badge/support-chat-blue.svg
[git-url]: https://gitter.im/postcss/postcss
[npm-img]: https://img.shields.io/npm/v/postcss-calc.svg
[npm-url]: https://www.npmjs.com/package/postcss-calc

[PostCSS]: https://github.com/postcss
[PostCSS Calc]: https://github.com/postcss/postcss-calc
[PostCSS Custom Properties]: https://github.com/postcss/postcss-custom-properties
[tests]: src/__tests__/index.js
[W3C calc() implementation]: https://www.w3.org/TR/css3-values/#calc-notation


code:
'use strict';
const { test } = require('uvu');
const assert = require('uvu/assert');
const postcss = require('postcss');

const reduceCalc = require('../index.js');

const postcssOpts = { from: undefined };

function testValue(fixture, expected, opts = {}) {
  fixture = `foo{bar:${fixture}}`;
  expected = `foo{bar:${expected}}`;

  return async () => {
    const result = await postcss(reduceCalc(opts)).process(
      fixture,
      postcssOpts
    );
    assert.is(result.css, expected);
  };
}

function testCss(fixture, expected, opts = {}) {
  return async () => {
    const result = await postcss(reduceCalc(opts)).process(
      fixture,
      postcssOpts
    );
    assert.is(result.css, expected);
  };
}

function testThrows(fixture, expected, warning, opts = {}) {
  fixture = `foo{bar:${fixture}}`;
  expected = `foo{bar:${expected}}`;

  return async () => {
    const result = await postcss(reduceCalc(opts)).process(
      fixture,
      postcssOpts
    );
    const warnings = result.warnings();
    assert.is(result.css, expected);
    assert.is(warnings[0].text, warning);
  };
}

test('should reduce simple calc (1)', testValue('calc(1px + 1px)', '2px'));

test(
  'should reduce simple calc (2)',
  testValue('calc(1px + 1px);baz:calc(2px+3px)', '2px;baz:5px')
);

test('should reduce simple calc (3)', testValue('calc(1rem * 1.5)', '1.5rem'));

test('should reduce simple calc (4)', testValue('calc(3em - 1em)', '2em'));

test('should reduce simple calc (5', testValue('calc(2ex / 2)', '1ex'));

test(
  'should reduce simple calc (6)',
  testValue('calc(50px - (20px - 30px))', '60px')
);

test(
  'should reduce simple calc (7)',
  testValue('calc(100px - (100px - 100%))', '100%')
);

test(
  'should reduce simple calc (8)',
  testValue('calc(100px + (100px - 100%))', 'calc(200px - 100%)')
);

test(
  'should reduce additions and subtractions (1)',
  testValue('calc(100% - 10px + 20px)', 'calc(100% + 10px)')
);

test(
  'should reduce additions and subtractions (2)',
  testValue('calc(100% + 10px - 20px)', 'calc(100% - 10px)')
);

test(
  'should reduce additions and subtractions (3)',
  testValue('calc(1px - (2em + 3%))', 'calc(1px - 2em - 3%)')
);

test(
  'should reduce additions and subtractions (4)',
  testValue('calc((100vw - 50em) / 2)', 'calc(50vw - 25em)')
);

test(
  'should reduce additions and subtractions (5)',
  testValue('calc(10px - (100vw - 50em) / 2)', 'calc(10px - 50vw + 25em)')
);

test(
  'should reduce additions and subtractions (6)',
  testValue('calc(1px - (2em + 4vh + 3%))', 'calc(1px - 2em - 4vh - 3%)')
);

test(
  'should reduce additions and subtractions (7)',
  testValue(
    'calc(0px - (24px - (var(--a) - var(--b)) / 2 + var(--c)))',
    'calc(-24px + (var(--a) - var(--b))/2 - var(--c))'
  )
);

test(
  'should reduce additions and subtractions (8)',
  testValue('calc(1px + (2em + (3vh + 4px)))', 'calc(5px + 2em + 3vh)')
);

test(
  'should reduce additions and subtractions (9)',
  testValue('calc(1px - (2em + 4px - 6vh) / 2)', 'calc(-1px - 1em + 3vh)')
);

test(
  'should reduce multiplication',
  testValue('calc(((var(--a) + 4px) * 2) * 2)', 'calc((var(--a) + 4px)*2*2)')
);

test(
  'should reduce multiplication before reducing additions',
  testValue(
    'calc(((var(--a) + 4px) * 2) * 2 + 4px)',
    'calc((var(--a) + 4px)*2*2 + 4px)'
  )
);

test(
  'should reduce division',
  testValue('calc(((var(--a) + 4px) / 2) / 2)', 'calc((var(--a) + 4px)/2/2)')
);

test(
  'should reduce division before reducing additions',
  testValue(
    'calc(((var(--a) + 4px) / 2) / 2 + 4px)',
    'calc((var(--a) + 4px)/2/2 + 4px)'
  )
);

test(
  'should ignore value surrounding calc function (1)',
  testValue('a calc(1px + 1px)', 'a 2px')
);

test(
  'should ignore value surrounding calc function (2)',
  testValue('calc(1px + 1px) a', '2px a')
);

test(
  'should ignore value surrounding calc function (3)',
  testValue('a calc(1px + 1px) b', 'a 2px b')
);

test(
  'should ignore value surrounding calc function (4)',
  testValue('a calc(1px + 1px) b calc(1em + 2em) c', 'a 2px b 3em c')
);

test(
  'should reduce nested calc',
  testValue('calc(100% - calc(50% + 25px))', 'calc(50% - 25px)')
);

test(
  'should reduce vendor-prefixed nested calc',
  testValue(
    '-webkit-calc(100% - -webkit-calc(50% + 25px))',
    '-webkit-calc(50% - 25px)'
  )
);

test('should reduce uppercase calc (1)', testValue('CALC(1px + 1px)', '2px'));

test(
  'should reduce uppercase calc (2)',
  testValue('CALC(1px + CALC(2px / 2))', '2px')
);

test(
  'should reduce uppercase calc (3)',
  testValue('-WEBKIT-CALC(1px + 1px)', '2px')
);

test(
  'should reduce uppercase calc (4)',
  testValue('-WEBKIT-CALC(1px + -WEBKIT-CALC(2px / 2))', '2px')
);

test(
  'should ignore calc with css variables (1)',
  testValue('calc(var(--mouseX) * 1px)', 'calc(var(--mouseX)*1px)')
);

test(
  'should ignore calc with css variables (2)',
  testValue(
    'calc(10px - (100px * var(--mouseX)))',
    'calc(10px - 100px*var(--mouseX))'
  )
);

test(
  'should ignore calc with css variables (3)',
  testValue(
    'calc(10px - (100px + var(--mouseX)))',
    'calc(-90px - var(--mouseX))'
  )
);

test(
  'should ignore calc with css variables (4)',
  testValue(
    'calc(10px - (100px / var(--mouseX)))',
    'calc(10px - 100px/var(--mouseX))'
  )
);

test(
  'should ignore calc with css variables (5)',
  testValue(
    'calc(10px - (100px - var(--mouseX)))',
    'calc(-90px + var(--mouseX))'
  )
);

test(
  'should ignore calc with css variables (6)',
  testValue('calc(var(--popupHeight) / 2)', 'calc(var(--popupHeight)/2)')
);

test(
  'should ignore calc with css variables (7)',
  testValue(
    'calc(var(--popupHeight) / 2 + var(--popupWidth) / 2)',
    'calc(var(--popupHeight)/2 + var(--popupWidth)/2)'
  )
);

test(
  'should reduce calc with newline characters',
  testValue('calc(\n1rem \n* 2 \n* 1.5)', '3rem')
);

test(
  'should preserve calc with incompatible units',
  testValue('calc(100% + 1px)', 'calc(100% + 1px)')
);

test(
  'should parse fractions without leading zero',
  testValue('calc(2rem - .14285em)', 'calc(2rem - 0.14285em)')
);

test('should handle precision correctly (1)', testValue('calc(1/100)', '0.01'));

test(
  'should handle precision correctly (2)',
  testValue('calc(5/1000000)', '0.00001')
);

test(
  'should handle precision correctly (3)',
  testValue('calc(5/1000000)', '0.000005', { precision: 6 })
);

test(
  'should reduce browser-prefixed calc (1)',
  testValue('-webkit-calc(1px + 1px)', '2px')
);

test(
  'should reduce browser-prefixed calc (2)',
  testValue('-moz-calc(1px + 1px)', '2px')
);

test(
  'should discard zero values (#2) (1)',
  testValue('calc(100vw / 2 - 6px + 0px)', 'calc(50vw - 6px)')
);

test(
  'should discard zero values (#2) (2)',
  testValue('calc(500px - 0px)', '500px')
);

test(
  'should not perform addition on unitless values (#3)',
  testValue('calc(1px + 1)', 'calc(1px + 1)')
);

test(
  'should reduce consecutive substractions (#24) (1)',
  testValue('calc(100% - 120px - 60px)', 'calc(100% - 180px)')
);

test(
  'should reduce consecutive substractions (#24) (2)',
  testValue('calc(100% - 10px - 20px)', 'calc(100% - 30px)')
);

test(
  'should reduce mixed units of time (postcss-calc#33)',
  testValue('calc(1s - 50ms)', '0.95s')
);

test(
  'should correctly reduce calc with mixed units (cssnano#211)',
  testValue('calc(99.99% * 1/1 - 0rem)', '99.99%')
);

test(
  'should apply optimization (cssnano#320)',
  testValue('calc(50% + (5em + 5%))', 'calc(55% + 5em)')
);

test(
  'should reduce substraction from zero',
  testValue('calc( 0 - 10px)', '-10px')
);

test(
  'should reduce subtracted expression from zero',
  testValue('calc( 0 - calc(1px + 1em) )', 'calc(-1px - 1em)')
);

test(
  'should reduce substracted expression from zero (1)',
  testValue('calc( 0 - (100vw - 10px) / 2 )', 'calc(-50vw + 5px)')
);

test(
  'should reduce substracted expression from zero (2)',
  testValue('calc( 0px - (100vw - 10px))', 'calc(10px - 100vw)')
);

test(
  'should reduce substracted expression from zero (3)',
  testValue('calc( 0px - (100vw - 10px) * 2 )', 'calc(20px - 200vw)')
);

test(
  'should reduce substracted expression from zero (4)',
  testValue('calc( 0px - (100vw + 10px))', 'calc(-10px - 100vw)')
);

test(
  'should reduce substracted expression from zero (css-variable)',
  testValue(
    'calc( 0px - (var(--foo, 4px) / 2))',
    'calc(0px - var(--foo, 4px)/2)'
  )
);

test(
  'should reduce nested expression',
  testValue('calc( (1em - calc( 10px + 1em)) / 2)', '-5px')
);

test(
  'should skip constant function',
  testValue(
    'calc(constant(safe-area-inset-left))',
    'calc(constant(safe-area-inset-left))'
  )
);

test(
  'should skip env function',
  testValue(
    'calc(env(safe-area-inset-left))',
    'calc(env(safe-area-inset-left))'
  )
);

test(
  'should skip env function (#1)',
  testValue(
    'calc(env(safe-area-inset-left, 50px 20px))',
    'calc(env(safe-area-inset-left, 50px 20px))'
  )
);

test(
  'should skip unknown function',
  testValue(
    'calc(unknown(safe-area-inset-left))',
    'calc(unknown(safe-area-inset-left))'
  )
);

test(
  'should preserve the original declaration when `preserve` option is set to true',
  testCss('foo{bar:calc(1rem * 1.5)}', 'foo{bar:1.5rem;bar:calc(1rem * 1.5)}', {
    preserve: true,
  })
);

test(
  'should not yield warnings when nothing is wrong',
  testValue('calc(500px - 0px)', '500px', { warnWhenCannotResolve: true })
);

test(
  'should warn when calc expression cannot be reduced to a single value',
  testValue('calc(100% + 1px)', 'calc(100% + 1px)', {
    warnWhenCannotResolve: true,
  })
);

test(
  'should reduce mixed units of time (#33)',
  testValue('calc(1s - 50ms)', '0.95s')
);

test(
  'should not parse variables as calc expressions (#35)',
  testCss(
    'foo:nth-child(2n + $var-calc){}',
    'foo:nth-child(2n + $var-calc){}',
    { selectors: true }
  )
);

test(
  'should apply algebraic reduction (cssnano#319)',
  testValue('calc((100px - 1em) + (-50px + 1em))', '50px')
);

test(
  'should discard zero values (reduce-css-calc#2) (1)',
  testValue('calc(100vw / 2 - 6px + 0px)', 'calc(50vw - 6px)')
);

test(
  'should discard zero values (reduce-css-calc#2) (2)',
  testValue('calc(500px - 0px)', '500px')
);

test(
  'should not perform addition on unitless values (reduce-css-calc#3)',
  testValue('calc(1px + 1)', 'calc(1px + 1)')
);

test(
  'should return the same and not thrown an exception for attribute selectors without a value',
  testCss('button[disabled]{}', 'button[disabled]{}', { selectors: true })
);

test(
  'should ignore reducing custom property',
  testCss(
    ':root { --foo: calc(var(--bar) / 8); }',
    ':root { --foo: calc(var(--bar)/8); }'
  )
);

test(
  'should ignore media queries',
  testCss(
    '@media (min-width:calc(10px+10px)){}',
    '@media (min-width:calc(10px+10px)){}'
  )
);

test(
  'should reduce calc in media queries when `mediaQueries` option is set to true',
  testCss('@media (min-width:calc(10px+10px)){}', '@media (min-width:20px){}', {
    mediaQueries: true,
  })
);

test(
  'should ignore selectors (1)',
  testCss('div[data-size="calc(3*3)"]{}', 'div[data-size="calc(3*3)"]{}')
);

test(
  'should ignore selectors (2)',
  testCss('div:nth-child(2n + calc(3*3)){}', 'div:nth-child(2n + calc(3*3)){}')
);

test(
  'should reduce calc in selectors when `selectors` option is set to true (1)',
  testCss('div[data-size="calc(3*3)"]{}', 'div[data-size="9"]{}', {
    selectors: true,
  })
);

test(
  'should reduce calc in selectors when `selectors` option is set to true (2)',
  testCss('div:nth-child(2n + calc(3*3)){}', 'div:nth-child(2n + 9){}', {
    selectors: true,
  })
);

test(
  'should not reduce 100% to 1 (reduce-css-calc#44)',
  testCss(
    '.@supports (width:calc(100% - constant(safe-area-inset-left))){.a{width:calc(100% - constant(safe-area-inset-left))}}',
    '.@supports (width:calc(100% - constant(safe-area-inset-left))){.a{width:calc(100% - constant(safe-area-inset-left))}}'
  )
);

test(
  'should not break css variables that have "calc" in their names',
  testCss(
    'a{transform: translateY(calc(-100% - var(--tooltip-calculated-offset)))}',
    'a{transform: translateY(calc(-100% - var(--tooltip-calculated-offset)))}'
  )
);

test(
  'should handle complex calculations (reduce-css-calc#45) (1)',
  testValue(
    'calc(100% + (2 * 100px) - ((75.37% - 63.5px) - 900px))',
    'calc(24.63% + 1163.5px)'
  )
);

test(
  'should handle complex calculations (reduce-css-calc#45) (2)',
  testValue(
    'calc(((((100% + (2 * 30px) + 63.5px) / 0.7537) - (100vw - 60px)) / 2) + 30px)',
    'calc(66.33939% + 141.92915px - 50vw)'
  )
);

test(
  'should handle advanced arithmetic (1)',
  testValue(
    'calc(((75.37% - 63.5px) - 900px) + (2 * 100px))',
    'calc(75.37% - 763.5px)'
  )
);

test(
  'should handle advanced arithmetic (2)',
  testValue(
    'calc((900px - (10% - 63.5px)) + (2 * 100px))',
    'calc(1163.5px - 10%)'
  )
);

test(
  'should handle nested calc statements (reduce-css-calc#49)',
  testValue('calc(calc(2.25rem + 2px) - 1px * 2)', '2.25rem')
);

test(
  'should throw an exception when attempting to divide by zero',
  testThrows('calc(500px/0)', 'calc(500px/0)', 'Cannot divide by zero')
);

test(
  'should throw an exception when attempting to divide by unit (#1)',
  testThrows(
    'calc(500px/2px)',
    'calc(500px/2px)',
    'Cannot divide by "px", number expected'
  )
);

test(
  'nested var (reduce-css-calc#50)',
  testValue(
    'calc(var(--xxx, var(--yyy)) / 2)',
    'calc(var(--xxx, var(--yyy))/2)'
  )
);

test(
  'should not throw an exception when unknow function exist in calc',
  testValue(
    'calc(unknown(#fff) - other-unknown(200px))',
    'calc(unknown(#fff) - other-unknown(200px))'
  )
);

test(
  'should not throw an exception when unknow function exist in calc (#1)',
  testValue(
    'calc(unknown(#fff) * other-unknown(200px))',
    'calc(unknown(#fff)*other-unknown(200px))'
  )
);

test(
  'should not strip calc with single CSS custom variable',
  testValue('calc(var(--foo))', 'calc(var(--foo))')
);

test(
  'should strip unnecessary calc with single CSS custom variable',
  testValue('calc(calc(var(--foo)))', 'calc(var(--foo))')
);

test(
  'should not strip calc with single CSS custom variables and value',
  testValue('calc(var(--foo) + 10px)', 'calc(var(--foo) + 10px)')
);

test('should reduce calc (uppercase)', testValue('CALC(1PX + 1PX)', '2PX'));

test(
  'should reduce calc (uppercase) (#1)',
  testValue('CALC(VAR(--foo) + VAR(--bar))', 'CALC(VAR(--foo) + VAR(--bar))')
);

test(
  'should reduce calc (uppercase) (#2)',
  testValue('CALC( (1EM - CALC( 10PX + 1EM)) / 2)', '-5PX')
);

test(
  'should handle nested calc function (#1)',
  testValue(
    'calc(calc(var(--foo) + var(--bar)) + var(--baz))',
    'calc(var(--foo) + var(--bar) + var(--baz))'
  )
);

test(
  'should handle nested calc function (#2)',
  testValue(
    'calc(var(--foo) + calc(var(--bar) + var(--baz)))',
    'calc(var(--foo) + var(--bar) + var(--baz))'
  )
);

test(
  'should handle nested calc function (#3)',
  testValue(
    'calc(calc(var(--foo) - var(--bar)) - var(--baz))',
    'calc(var(--foo) - var(--bar) - var(--baz))'
  )
);

test(
  'should handle nested calc function (#4)',
  testValue(
    'calc(var(--foo) - calc(var(--bar) - var(--baz)))',
    'calc(var(--foo) - var(--bar) + var(--baz))'
  )
);

test(
  'should handle nested calc function (#5)',
  testValue(
    'calc(calc(var(--foo) + var(--bar)) - var(--baz))',
    'calc(var(--foo) + var(--bar) - var(--baz))'
  )
);

test(
  'should handle nested calc function (#6)',
  testValue(
    'calc(var(--foo) + calc(var(--bar) - var(--baz)))',
    'calc(var(--foo) + var(--bar) - var(--baz))'
  )
);

test(
  'should handle nested calc function (#7)',
  testValue(
    'calc(calc(var(--foo) - var(--bar)) + var(--baz))',
    'calc(var(--foo) - var(--bar) + var(--baz))'
  )
);

test(
  'should handle nested calc function (#8)',
  testValue(
    'calc(var(--foo) - calc(var(--bar) + var(--baz)))',
    'calc(var(--foo) - var(--bar) - var(--baz))'
  )
);

test(
  'should handle nested calc function (#9)',
  testValue(
    'calc(calc(var(--foo) + var(--bar)) * var(--baz))',
    'calc((var(--foo) + var(--bar))*var(--baz))'
  )
);

test(
  'should handle nested calc function (#10)',
  testValue(
    'calc(var(--foo) * calc(var(--bar) + var(--baz)))',
    'calc(var(--foo)*(var(--bar) + var(--baz)))'
  )
);

test(
  'should handle nested calc function (#11)',
  testValue(
    'calc(calc(var(--foo) + var(--bar)) / var(--baz))',
    'calc((var(--foo) + var(--bar))/var(--baz))'
  )
);

test(
  'should handle nested calc function (#12)',
  testValue(
    'calc(var(--foo) / calc(var(--bar) + var(--baz)))',
    'calc(var(--foo)/(var(--bar) + var(--baz)))'
  )
);

test(
  'should handle nested calc function (#13)',
  testValue(
    'calc(100vh - 5rem - calc(10rem + 100px))',
    'calc(100vh - 15rem - 100px)'
  )
);

test(
  'should handle nested calc function (#14)',
  testValue('calc(100% - calc(10px + 2vw))', 'calc(100% - 10px - 2vw)')
);

test(
  'should handle nested calc function (#15)',
  testValue('calc(100% - calc(10px - 2vw))', 'calc(100% - 10px + 2vw)')
);

test(
  'should preserve division precedence',
  testValue(
    'calc(100%/(var(--aspect-ratio)))',
    'calc(100%/(var(--aspect-ratio)))'
  )
);

test(
  'should preserve division precedence (2)',
  testValue(
    `calc(
        (var(--fluid-screen) - ((var(--fluid-min-width) / 16) * 1rem)) /
        ((var(--fluid-max-width) / 16) - (var(--fluid-min-width) / 16))
    )`,
    'calc((var(--fluid-screen) - ((var(--fluid-min-width)/16)*1rem))/(var(--fluid-max-width)/16 - var(--fluid-min-width)/16))'
  )
);

test(
  'should preserve division precedence (3)',
  testValue('calc(1/(10/var(--dot-size)))', 'calc(1/(10/var(--dot-size)))')
);

test(
  'should correctly preserve parentheses',
  testValue(
    'calc(1/((var(--a) - var(--b))/16))',
    'calc(1/(var(--a) - var(--b))/16)'
  )
);

test('precision for calc', testValue('calc(100% / 3 * 3)', '100%'));

test(
  'precision for nested calc',
  testValue('calc(calc(100% / 3) * 3)', '100%')
);

test('plus sign', testValue('calc(+100px + +100px)', '200px'));

test('plus sign (#1)', testValue('calc(+100px - +100px)', '0px'));

test('plus sign (#2)', testValue('calc(200px * +1)', '200px'));

test('plus sign (#3)', testValue('calc(200px / +1)', '200px'));

test('minus sign', testValue('calc(-100px + -100px)', '-200px'));

test('minus sign (#2)', testValue('calc(-100px - -100px)', '0px'));

test('minus sign (#3)', testValue('calc(200px * -1)', '-200px'));

test('minus sign (#4)', testValue('calc(200px / -1)', '-200px'));

test('whitespace', testValue('calc( 100px + 100px )', '200px'));

test('whitespace (#1)', testValue('calc(\t100px\t+\t100px\t)', '200px'));

test('whitespace (#2)', testValue('calc(\n100px\n+\n100px\n)', '200px'));

test(
  'whitespace (#4)',
  testValue('calc(\r\n100px\r\n+\r\n100px\r\n)', '200px')
);

test(
  'comments',
  testValue('calc(/*test*/100px/*test*/ + /*test*/100px/*test*/)', '200px')
);

test(
  'comments (#1)',
  testValue('calc(/*test*/100px/*test*/*/*test*/2/*test*/)', '200px')
);

test(
  'comments nested',
  testValue(
    'calc(/*test*/100px + calc(/*test*/100px/*test*/ + /*test*/100px/*test*/))',
    '300px'
  )
);

test('exponent composed', testValue('calc(1.1e+1px + 1.1e+1px)', '22px'));

test('exponent composed (#1)', testValue('calc(10e+1px + 10e+1px)', '200px'));

test(
  'exponent composed (#2)',
  testValue('calc(1.1e+10px + 1.1e+10px)', '22000000000px')
);

test('exponent composed (#3)', testValue('calc(9e+1 * 1px)', '90px'));

test('exponent composed (#4)', testValue('calc(9e+1% + 10%)', '100%'));

test(
  'exponent composed (uppercase)',
  testValue('calc(1.1E+1px + 1.1E+1px)', '22px')
);

test('convert units', testValue('calc(1cm + 1px)', '1.02646cm'));

test('convert units (#1)', testValue('calc(1px + 1cm)', '38.79528px'));

test('convert units (#2)', testValue('calc(10Q + 10Q)', '20Q'));

test('convert units (#3)', testValue('calc(100.9q + 10px)', '111.48333q'));

test('convert units (#4)', testValue('calc(10px + 100.9q)', '105.33858px'));

test('convert units (#5)', testValue('calc(10cm + 1px)', '10.02646cm'));

test('convert units (#6)', testValue('calc(10mm + 1px)', '10.26458mm'));

test('convert units (#7)', testValue('calc(10px + 1q)', '10.94488px'));

test('convert units (#8)', testValue('calc(10cm + 1q)', '10.025cm'));

test('convert units (#9)', testValue('calc(10mm + 1q)', '10.25mm'));

test('convert units (#10)', testValue('calc(10in + 1q)', '10.00984in'));

test('convert units (#11)', testValue('calc(10pt + 1q)', '10.70866pt'));

test('convert units (#12)', testValue('calc(10pc + 1q)', '10.05906pc'));

test('convert units (#13)', testValue('calc(1q + 10px)', '11.58333q'));

test('convert units (#14)', testValue('calc(1q + 10cm)', '401q'));

test('convert units (#15)', testValue('calc(1q + 10mm)', '41q'));

test('convert units (#16)', testValue('calc(1q + 10in)', '1017q'));

test('convert units (#17)', testValue('calc(1q + 10pt)', '15.11111q'));

test('convert units (#18)', testValue('calc(1q + 10pc)', '170.33333q'));

test(
  'unknown units',
  testValue('calc(1unknown + 2unknown)', 'calc(1unknown + 2unknown)')
);

test(
  'unknown units with known',
  testValue('calc(1unknown + 2px)', 'calc(1unknown + 2px)')
);

test(
  'unknown units with known (#1)',
  testValue('calc(1px + 2unknown)', 'calc(1px + 2unknown)')
);

test(
  'error with parsing',
  testThrows(
    'calc(10pc + unknown)',
    'calc(10pc + unknown)',
    'Lexical error on line 1: Unrecognized text.\n\n  Erroneous area:\n1: 10pc + unknown\n^.........^'
  )
);

test.run();


code:
'use strict';
const transform = require('./lib/transform.js');

/**
 * @typedef {{precision?: number | false,
 *          preserve?: boolean,
 *          warnWhenCannotResolve?: boolean,
 *          mediaQueries?: boolean,
 *          selectors?: boolean}} PostCssCalcOptions
 */
/**
 * @type {import('postcss').PluginCreator<PostCssCalcOptions>}
 * @param {PostCssCalcOptions} opts
 * @return {import('postcss').Plugin}
 */
function pluginCreator(opts) {
  const options = Object.assign(
    {
      precision: 5,
      preserve: false,
      warnWhenCannotResolve: false,
      mediaQueries: false,
      selectors: false,
    },
    opts
  );

  return {
    postcssPlugin: 'postcss-calc',
    OnceExit(css, { result }) {
      css.walk((node) => {
        const { type } = node;
        if (type === 'decl') {
          transform(node, 'value', options, result);
        }

        if (type === 'atrule' && options.mediaQueries) {
          transform(node, 'params', options, result);
        }

        if (type === 'rule' && options.selectors) {
          transform(node, 'selector', options, result);
        }
      });
    },
  };
}

pluginCreator.postcss = true;

module.exports = pluginCreator;


code:
'use strict';
const convertUnit = require('./convertUnit.js');

/**
 * @param {import('../parser').CalcNode} node
 * @return {node is import('../parser').ValueExpression}
 */
function isValueType(node) {
  switch (node.type) {
    case 'LengthValue':
    case 'AngleValue':
    case 'TimeValue':
    case 'FrequencyValue':
    case 'ResolutionValue':
    case 'EmValue':
    case 'ExValue':
    case 'ChValue':
    case 'RemValue':
    case 'VhValue':
    case 'VwValue':
    case 'VminValue':
    case 'VmaxValue':
    case 'PercentageValue':
    case 'Number':
      return true;
  }
  return false;
}

/** @param {'-'|'+'} operator */
function flip(operator) {
  return operator === '+' ? '-' : '+';
}

/**
 * @param {string} operator
 * @returns {operator is '+'|'-'}
 */
function isAddSubOperator(operator) {
  return operator === '+' || operator === '-';
}

/**
 * @typedef {{preOperator: '+'|'-', node: import('../parser').CalcNode}} Collectible
 */

/**
 * @param {'+'|'-'} preOperator
 * @param {import('../parser').CalcNode} node
 * @param {Collectible[]} collected
 * @param {number} precision
 */
function collectAddSubItems(preOperator, node, collected, precision) {
  if (!isAddSubOperator(preOperator)) {
    throw new Error(`invalid operator ${preOperator}`);
  }
  if (isValueType(node)) {
    const itemIndex = collected.findIndex((x) => x.node.type === node.type);
    if (itemIndex >= 0) {
      if (node.value === 0) {
        return;
      }
      // can cast because of the criterion used to find itemIndex
      const otherValueNode = /** @type import('../parser').ValueExpression*/ (
        collected[itemIndex].node
      );
      const { left: reducedNode, right: current } = convertNodesUnits(
        otherValueNode,
        node,
        precision
      );

      if (collected[itemIndex].preOperator === '-') {
        collected[itemIndex].preOperator = '+';
        reducedNode.value *= -1;
      }
      if (preOperator === '+') {
        reducedNode.value += current.value;
      } else {
        reducedNode.value -= current.value;
      }
      // make sure reducedNode.value >= 0
      if (reducedNode.value >= 0) {
        collected[itemIndex] = { node: reducedNode, preOperator: '+' };
      } else {
        reducedNode.value *= -1;
        collected[itemIndex] = { node: reducedNode, preOperator: '-' };
      }
    } else {
      // make sure node.value >= 0
      if (node.value >= 0) {
        collected.push({ node, preOperator });
      } else {
        node.value *= -1;
        collected.push({ node, preOperator: flip(preOperator) });
      }
    }
  } else if (node.type === 'MathExpression') {
    if (isAddSubOperator(node.operator)) {
      collectAddSubItems(preOperator, node.left, collected, precision);
      const collectRightOperator =
        preOperator === '-' ? flip(node.operator) : node.operator;
      collectAddSubItems(
        collectRightOperator,
        node.right,
        collected,
        precision
      );
    } else {
      // * or /
      const reducedNode = reduce(node, precision);
      // prevent infinite recursive call
      if (
        reducedNode.type !== 'MathExpression' ||
        isAddSubOperator(reducedNode.operator)
      ) {
        collectAddSubItems(preOperator, reducedNode, collected, precision);
      } else {
        collected.push({ node: reducedNode, preOperator });
      }
    }
  } else if (node.type === 'ParenthesizedExpression') {
    collectAddSubItems(preOperator, node.content, collected, precision);
  } else {
    collected.push({ node, preOperator });
  }
}

/**
 * @param {import('../parser').CalcNode} node
 * @param {number} precision
 */
function reduceAddSubExpression(node, precision) {
  /** @type Collectible[] */
  const collected = [];
  collectAddSubItems('+', node, collected, precision);

  const withoutZeroItem = collected.filter(
    (item) => !(isValueType(item.node) && item.node.value === 0)
  );
  const firstNonZeroItem = withoutZeroItem[0]; // could be undefined

  // prevent producing "calc(-var(--a))" or "calc()"
  // which is invalid css
  if (
    !firstNonZeroItem ||
    (firstNonZeroItem.preOperator === '-' &&
      !isValueType(firstNonZeroItem.node))
  ) {
    const firstZeroItem = collected.find(
      (item) => isValueType(item.node) && item.node.value === 0
    );
    if (firstZeroItem) {
      withoutZeroItem.unshift(firstZeroItem);
    }
  }

  // make sure the preOperator of the first item is +
  if (
    withoutZeroItem[0].preOperator === '-' &&
    isValueType(withoutZeroItem[0].node)
  ) {
    withoutZeroItem[0].node.value *= -1;
    withoutZeroItem[0].preOperator = '+';
  }

  let root = withoutZeroItem[0].node;
  for (let i = 1; i < withoutZeroItem.length; i++) {
    root = {
      type: 'MathExpression',
      operator: withoutZeroItem[i].preOperator,
      left: root,
      right: withoutZeroItem[i].node,
    };
  }

  return root;
}
/**
 * @param {import('../parser').MathExpression} node
 */
function reduceDivisionExpression(node) {
  if (!isValueType(node.right)) {
    return node;
  }

  if (node.right.type !== 'Number') {
    throw new Error(`Cannot divide by "${node.right.unit}", number expected`);
  }

  return applyNumberDivision(node.left, node.right.value);
}

/**
 * apply (expr) / number
 *
 * @param {import('../parser').CalcNode} node
 * @param {number} divisor
 * @return {import('../parser').CalcNode}
 */
function applyNumberDivision(node, divisor) {
  if (divisor === 0) {
    throw new Error('Cannot divide by zero');
  }
  if (isValueType(node)) {
    node.value /= divisor;
    return node;
  }
  if (node.type === 'MathExpression' && isAddSubOperator(node.operator)) {
    // turn (a + b) / num into a/num + b/num
    // is good for further reduction
    // checkout the test case
    // "should reduce division before reducing additions"
    return {
      type: 'MathExpression',
      operator: node.operator,
      left: applyNumberDivision(node.left, divisor),
      right: applyNumberDivision(node.right, divisor),
    };
  }
  // it is impossible to reduce it into a single value
  // .e.g the node contains css variable
  // so we just preserve the division and let browser do it
  return {
    type: 'MathExpression',
    operator: '/',
    left: node,
    right: {
      type: 'Number',
      value: divisor,
    },
  };
}
/**
 * @param {import('../parser').MathExpression} node
 */
function reduceMultiplicationExpression(node) {
  // (expr) * number
  if (node.right.type === 'Number') {
    return applyNumberMultiplication(node.left, node.right.value);
  }
  // number * (expr)
  if (node.left.type === 'Number') {
    return applyNumberMultiplication(node.right, node.left.value);
  }
  return node;
}

/**
 * apply (expr) * number
 * @param {number} multiplier
 * @param {import('../parser').CalcNode} node
 * @return {import('../parser').CalcNode}
 */
function applyNumberMultiplication(node, multiplier) {
  if (isValueType(node)) {
    node.value *= multiplier;
    return node;
  }
  if (node.type === 'MathExpression' && isAddSubOperator(node.operator)) {
    // turn (a + b) * num into a*num + b*num
    // is good for further reduction
    // checkout the test case
    // "should reduce multiplication before reducing additions"
    return {
      type: 'MathExpression',
      operator: node.operator,
      left: applyNumberMultiplication(node.left, multiplier),
      right: applyNumberMultiplication(node.right, multiplier),
    };
  }
  // it is impossible to reduce it into a single value
  // .e.g the node contains css variable
  // so we just preserve the division and let browser do it
  return {
    type: 'MathExpression',
    operator: '*',
    left: node,
    right: {
      type: 'Number',
      value: multiplier,
    },
  };
}

/**
 * @param {import('../parser').ValueExpression} left
 * @param {import('../parser').ValueExpression} right
 * @param {number} precision
 */
function convertNodesUnits(left, right, precision) {
  switch (left.type) {
    case 'LengthValue':
    case 'AngleValue':
    case 'TimeValue':
    case 'FrequencyValue':
    case 'ResolutionValue':
      if (right.type === left.type && right.unit && left.unit) {
        const converted = convertUnit(
          right.value,
          right.unit,
          left.unit,
          precision
        );

        right = {
          type: left.type,
          value: converted,
          unit: left.unit,
        };
      }

      return { left, right };
    default:
      return { left, right };
  }
}

/**
 * @param {import('../parser').ParenthesizedExpression} node
 */
function includesNoCssProperties(node) {
  return (
    node.content.type !== 'Function' &&
    (node.content.type !== 'MathExpression' ||
      (node.content.right.type !== 'Function' &&
        node.content.left.type !== 'Function'))
  );
}
/**
 * @param {import('../parser').CalcNode} node
 * @param {number} precision
 * @return {import('../parser').CalcNode}
 */
function reduce(node, precision) {
  if (node.type === 'MathExpression') {
    if (isAddSubOperator(node.operator)) {
      // reduceAddSubExpression will call reduce recursively
      return reduceAddSubExpression(node, precision);
    }
    node.left = reduce(node.left, precision);
    node.right = reduce(node.right, precision);
    switch (node.operator) {
      case '/':
        return reduceDivisionExpression(node);
      case '*':
        return reduceMultiplicationExpression(node);
    }

    return node;
  }

  if (node.type === 'ParenthesizedExpression') {
    if (includesNoCssProperties(node)) {
      return reduce(node.content, precision);
    }
  }

  return node;
}

module.exports = reduce;


code:
'use strict';
const order = {
  '*': 0,
  '/': 0,
  '+': 1,
  '-': 1,
};

/**
 * @param {number} value
 * @param {number | false} prec
 */
function round(value, prec) {
  if (prec !== false) {
    const precision = Math.pow(10, prec);
    return Math.round(value * precision) / precision;
  }
  return value;
}

/**
 * @param {number | false} prec
 * @param {import('../parser').CalcNode} node
 *
 * @return {string}
 */
function stringify(node, prec) {
  switch (node.type) {
    case 'MathExpression': {
      const { left, right, operator: op } = node;
      let str = '';
      if (left.type === 'MathExpression' && order[op] < order[left.operator]) {
        str += `(${stringify(left, prec)})`;
      } else {
        str += stringify(left, prec);
      }

      str += order[op] ? ` ${node.operator} ` : node.operator;

      if (
        right.type === 'MathExpression' &&
        order[op] < order[right.operator]
      ) {
        str += `(${stringify(right, prec)})`;
      } else {
        str += stringify(right, prec);
      }

      return str;
    }
    case 'Number':
      return round(node.value, prec).toString();
    case 'Function':
      return node.value.toString();
    case 'ParenthesizedExpression':
      return `(${stringify(node.content, prec)})`;
    default:
      return round(node.value, prec) + node.unit;
  }
}

/**
 * @param {string} calc
 * @param {import('../parser').CalcNode} node
 * @param {string} originalValue
 * @param {{precision: number | false, warnWhenCannotResolve: boolean}} options
 * @param {import("postcss").Result} result
 * @param {import("postcss").ChildNode} item
 *
 * @returns {string}
 */
module.exports = function (calc, node, originalValue, options, result, item) {
  let str = stringify(node, options.precision);

  const shouldPrintCalc =
    node.type === 'MathExpression' || node.type === 'Function';

  if (shouldPrintCalc) {
    // if calc expression couldn't be resolved to a single value, re-wrap it as
    // a calc()
    str = `${calc}(${str})`;

    // if the warnWhenCannotResolve option is on, inform the user that the calc
    // expression could not be resolved to a single value
    if (options.warnWhenCannotResolve) {
      result.warn('Could not reduce expression: ' + originalValue, {
        plugin: 'postcss-calc',
        node: item,
      });
    }
  }
  return str;
};


code:
'use strict';
const selectorParser = require('postcss-selector-parser');
const valueParser = require('postcss-value-parser');

const { parser } = require('../parser.js');

const reducer = require('./reducer.js');
const stringifier = require('./stringifier.js');

const MATCH_CALC = /((?:-(moz|webkit)-)?calc)/i;

/**
 * @param {string} value
 * @param {{precision: number, warnWhenCannotResolve: boolean}} options
 * @param {import("postcss").Result} result
 * @param {import("postcss").ChildNode} item
 */
function transformValue(value, options, result, item) {
  return valueParser(value)
    .walk((node) => {
      // skip anything which isn't a calc() function
      if (node.type !== 'function' || !MATCH_CALC.test(node.value)) {
        return;
      }

      // stringify calc expression and produce an AST
      const contents = valueParser.stringify(node.nodes);
      const ast = parser.parse(contents);

      // reduce AST to its simplest form, that is, either to a single value
      // or a simplified calc expression
      const reducedAst = reducer(ast, options.precision);

      // stringify AST and write it back
      /** @type {valueParser.Node} */ (node).type = 'word';
      node.value = stringifier(
        node.value,
        reducedAst,
        value,
        options,
        result,
        item
      );

      return false;
    })
    .toString();
}
/**
 * @param {import("postcss-selector-parser").Selectors} value
 * @param {{precision: number, warnWhenCannotResolve: boolean}} options
 * @param {import("postcss").Result} result
 * @param {import("postcss").ChildNode} item
 */
function transformSelector(value, options, result, item) {
  return selectorParser((selectors) => {
    selectors.walk((node) => {
      // attribute value
      // e.g. the "calc(3*3)" part of "div[data-size="calc(3*3)"]"
      if (node.type === 'attribute' && node.value) {
        node.setValue(transformValue(node.value, options, result, item));
      }

      // tag value
      // e.g. the "calc(3*3)" part of "div:nth-child(2n + calc(3*3))"
      if (node.type === 'tag') {
        node.value = transformValue(node.value, options, result, item);
      }

      return;
    });
  }).processSync(value);
}

/**
 * @param {any} node
 * @param {{precision: number, preserve: boolean, warnWhenCannotResolve: boolean}} options
 * @param {'value'|'params'|'selector'} property
 * @param {import("postcss").Result} result
 */
module.exports = (node, property, options, result) => {
  let value = node[property];

  try {
    value =
      property === 'selector'
        ? transformSelector(node[property], options, result, node)
        : transformValue(node[property], options, result, node);
  } catch (error) {
    if (error instanceof Error) {
      result.warn(error.message, { node });
    } else {
      result.warn('Error', { node });
    }
    return;
  }

  // if the preserve option is enabled and the value has changed, write the
  // transformed value into a cloned node which is inserted before the current
  // node, preserving the original value. Otherwise, overwrite the original
  // value.
  if (options.preserve && node[property] !== value) {
    const clone = node.clone();
    clone[property] = value;
    node.parent.insertBefore(node, clone);
  } else {
    node[property] = value;
  }
};


code:
export interface MathExpression {
  type: 'MathExpression';
  right: CalcNode;
  left: CalcNode;
  operator: '*' | '+' | '-' | '/';
}

export interface ParenthesizedExpression {
  type: 'ParenthesizedExpression';
  content: CalcNode;
}

export interface DimensionExpression {
  type:
    | 'LengthValue'
    | 'AngleValue'
    | 'TimeValue'
    | 'FrequencyValue'
    | 'PercentageValue'
    | 'ResolutionValue'
    | 'EmValue'
    | 'ExValue'
    | 'ChValue'
    | 'RemValue'
    | 'VhValue'
    | 'VwValue'
    | 'VminValue'
    | 'VmaxValue';
  value: number;
  unit: string;
}

export interface NumberExpression {
  type: 'Number';
  value: number;
}

export interface FunctionExpression {
  type: 'Function';
  value: string;
}

export type ValueExpression = DimensionExpression | NumberExpression;

export type CalcNode = MathExpression | ValueExpression | FunctionExpression | ParenthesizedExpression;

export interface Parser {
  parse: (arg: string) => CalcNode;
}

export const parser: Parser;