basant307/AI_Governance_Project

1(function () {2 3  'use strict';4 5  var assign = require('object-assign');6  var vary = require('vary');7 8  var defaults = {9    origin: '*',10    methods: 'GET,HEAD,PUT,PATCH,POST,DELETE',11    preflightContinue: false,12    optionsSuccessStatus: 20413  };14 15  function isString(s) {16    return typeof s === 'string' || s instanceof String;17  }18 19  function isOriginAllowed(origin, allowedOrigin) {20    if (Array.isArray(allowedOrigin)) {21      for (var i = 0; i < allowedOrigin.length; ++i) {22        if (isOriginAllowed(origin, allowedOrigin[i])) {23          return true;24        }25      }26      return false;27    } else if (isString(allowedOrigin)) {28      return origin === allowedOrigin;29    } else if (allowedOrigin instanceof RegExp) {30      return allowedOrigin.test(origin);31    } else {32      return !!allowedOrigin;33    }34  }35 36  function configureOrigin(options, req) {37    var requestOrigin = req.headers.origin,38      headers = [],39      isAllowed;40 41    if (!options.origin || options.origin === '*') {42      // allow any origin43      headers.push([{44        key: 'Access-Control-Allow-Origin',45        value: '*'46      }]);47    } else if (isString(options.origin)) {48      // fixed origin49      headers.push([{50        key: 'Access-Control-Allow-Origin',51        value: options.origin52      }]);53      headers.push([{54        key: 'Vary',55        value: 'Origin'56      }]);57    } else {58      isAllowed = isOriginAllowed(requestOrigin, options.origin);59      // reflect origin60      headers.push([{61        key: 'Access-Control-Allow-Origin',62        value: isAllowed ? requestOrigin : false63      }]);64      headers.push([{65        key: 'Vary',66        value: 'Origin'67      }]);68    }69 70    return headers;71  }72 73  function configureMethods(options) {74    var methods = options.methods;75    if (methods.join) {76      methods = options.methods.join(','); // .methods is an array, so turn it into a string77    }78    return {79      key: 'Access-Control-Allow-Methods',80      value: methods81    };82  }83 84  function configureCredentials(options) {85    if (options.credentials === true) {86      return {87        key: 'Access-Control-Allow-Credentials',88        value: 'true'89      };90    }91    return null;92  }93 94  function configureAllowedHeaders(options, req) {95    var allowedHeaders = options.allowedHeaders || options.headers;96    var headers = [];97 98    if (!allowedHeaders) {99      allowedHeaders = req.headers['access-control-request-headers']; // .headers wasn't specified, so reflect the request headers100      headers.push([{101        key: 'Vary',102        value: 'Access-Control-Request-Headers'103      }]);104    } else if (allowedHeaders.join) {105      allowedHeaders = allowedHeaders.join(','); // .headers is an array, so turn it into a string106    }107    if (allowedHeaders && allowedHeaders.length) {108      headers.push([{109        key: 'Access-Control-Allow-Headers',110        value: allowedHeaders111      }]);112    }113 114    return headers;115  }116 117  function configureExposedHeaders(options) {118    var headers = options.exposedHeaders;119    if (!headers) {120      return null;121    } else if (headers.join) {122      headers = headers.join(','); // .headers is an array, so turn it into a string123    }124    if (headers && headers.length) {125      return {126        key: 'Access-Control-Expose-Headers',127        value: headers128      };129    }130    return null;131  }132 133  function configureMaxAge(options) {134    var maxAge = (typeof options.maxAge === 'number' || options.maxAge) && options.maxAge.toString()135    if (maxAge && maxAge.length) {136      return {137        key: 'Access-Control-Max-Age',138        value: maxAge139      };140    }141    return null;142  }143 144  function applyHeaders(headers, res) {145    for (var i = 0, n = headers.length; i < n; i++) {146      var header = headers[i];147      if (header) {148        if (Array.isArray(header)) {149          applyHeaders(header, res);150        } else if (header.key === 'Vary' && header.value) {151          vary(res, header.value);152        } else if (header.value) {153          res.setHeader(header.key, header.value);154        }155      }156    }157  }158 159  function cors(options, req, res, next) {160    var headers = [],161      method = req.method && req.method.toUpperCase && req.method.toUpperCase();162 163    if (method === 'OPTIONS') {164      // preflight165      headers.push(configureOrigin(options, req));166      headers.push(configureCredentials(options, req));167      headers.push(configureMethods(options, req));168      headers.push(configureAllowedHeaders(options, req));169      headers.push(configureMaxAge(options, req));170      headers.push(configureExposedHeaders(options, req));171      applyHeaders(headers, res);172 173      if (options.preflightContinue) {174        next();175      } else {176        // Safari (and potentially other browsers) need content-length 0,177        //   for 204 or they just hang waiting for a body178        res.statusCode = options.optionsSuccessStatus;179        res.setHeader('Content-Length', '0');180        res.end();181      }182    } else {183      // actual response184      headers.push(configureOrigin(options, req));185      headers.push(configureCredentials(options, req));186      headers.push(configureExposedHeaders(options, req));187      applyHeaders(headers, res);188      next();189    }190  }191 192  function middlewareWrapper(o) {193    // if options are static (either via defaults or custom options passed in), wrap in a function194    var optionsCallback = null;195    if (typeof o === 'function') {196      optionsCallback = o;197    } else {198      optionsCallback = function (req, cb) {199        cb(null, o);200      };201    }202 203    return function corsMiddleware(req, res, next) {204      optionsCallback(req, function (err, options) {205        if (err) {206          next(err);207        } else {208          var corsOptions = assign({}, defaults, options);209          var originCallback = null;210          if (corsOptions.origin && typeof corsOptions.origin === 'function') {211            originCallback = corsOptions.origin;212          } else if (corsOptions.origin) {213            originCallback = function (origin, cb) {214              cb(null, corsOptions.origin);215            };216          }217 218          if (originCallback) {219            originCallback(req.headers.origin, function (err2, origin) {220              if (err2 || !origin) {221                next(err2);222              } else {223                corsOptions.origin = origin;224                cors(corsOptions, req, res, next);225              }226            });227          } else {228            next();229          }230        }231      });232    };233  }234 235  // can pass either an options hash, an options delegate, or nothing236  module.exports = middlewareWrapper;237 238}());239