index.js

'use strict';

/**
 * Module dependencies.
 */

const debug = require('debug')('superagent');
const formidable = require('formidable');
const FormData = require('form-data');
const Response = require('./response');
const parse = require('url').parse;
const format = require('url').format;
const resolve = require('url').resolve;
let methods = require('methods');
const Stream = require('stream');
const utils = require('../utils');
const unzip = require('./unzip').unzip;
const extend = require('extend');
const mime = require('mime');
const https = require('https');
const http = require('http');
const fs = require('fs');
const qs = require('qs');
const zlib = require('zlib');
const util = require('util');
const pkg = require('../../package.json');
const RequestBase = require('../request-base');
const CookieJar = require('cookiejar');

function request(method, url) {
  // callback
  if ('function' == typeof url) {
    return new exports.Request('GET', method).end(url);
  }

  // url first
  if (1 == arguments.length) {
    return new exports.Request('GET', method);
  }

  return new exports.Request(method, url);
}
exports = module.exports = request;

/**
 * Expose `Request`.
 */

exports.Request = Request;

/**
 * Expose the agent function
 */

exports.agent = require('./agent');

/**
 * Noop.
 */

function noop(){};

/**
 * Expose `Response`.
 */

exports.Response = Response;

/**
 * Define "form" mime type.
 */

mime.define({
  'application/x-www-form-urlencoded': ['form', 'urlencoded', 'form-data']
}, true);

/**
 * Protocol map.
 */

exports.protocols = {
  'http:': http,
  'https:': https,
};

/**
 * Default serialization map.
 *
 *     superagent.serialize['application/xml'] = function(obj){
 *       return 'generated xml here';
 *     };
 *
 */

exports.serialize = {
  'application/x-www-form-urlencoded': qs.stringify,
  'application/json': JSON.stringify,
};

/**
 * Default parsers.
 *
 *     superagent.parse['application/xml'] = function(res, fn){
 *       fn(null, res);
 *     };
 *
 */

exports.parse = require('./parsers');

/**
 * Initialize internal header tracking properties on a request instance.
 *
 * @param {Object} req the instance
 * @api private
 */
function _initHeaders(req) {
  const ua = `node-superagent/${pkg.version}`;
  req._header = { // coerces header names to lowercase
    'user-agent': ua
  };
  req.header = { // preserves header name case
    'User-Agent': ua
  };
}

/**
 * Initialize a new `Request` with the given `method` and `url`.
 *
 * @param {String} method
 * @param {String|Object} url
 * @api public
 */

function Request(method, url) {
  Stream.call(this);
  if ('string' != typeof url) url = format(url);
  this._agent = false;
  this._formData = null;
  this.method = method;
  this.url = url;
  _initHeaders(this);
  this.writable = true;
  this._redirects = 0;
  this.redirects(method === 'HEAD' ? 0 : 5);
  this.cookies = '';
  this.qs = {};
  this._query = [];
  this.qsRaw = this._query; // Unused, for backwards compatibility only
  this._redirectList = [];
  this._streamRequest = false;
  this.once('end', this.clearTimeout.bind(this));
}

/**
 * Inherit from `Stream` (which inherits from `EventEmitter`).
 * Mixin `RequestBase`.
 */
util.inherits(Request, Stream);
RequestBase(Request.prototype);

/**
 * Queue the given `file` as an attachment to the specified `field`,
 * with optional `options` (or filename).
 *
 * ``` js
 * request.post('http://localhost/upload')
 *   .attach('field', Buffer.from('<b>Hello world</b>'), 'hello.html')
 *   .end(callback);
 * ```
 *
 * A filename may also be used:
 *
 * ``` js
 * request.post('http://localhost/upload')
 *   .attach('files', 'image.jpg')
 *   .end(callback);
 * ```
 *
 * @param {String} field
 * @param {String|fs.ReadStream|Buffer} file
 * @param {String|Object} options
 * @return {Request} for chaining
 * @api public
 */

Request.prototype.attach = function(field, file, options){
  if (file) {
    if (this._data) {
      throw Error("superagent can't mix .send() and .attach()");
    }

    let o = options || {};
    if ('string' == typeof options) {
      o = { filename: options };
    }

    if ('string' == typeof file) {
      if (!o.filename) o.filename = file;
      debug('creating `fs.ReadStream` instance for file: %s', file);
      file = fs.createReadStream(file);
    } else if (!o.filename && file.path) {
      o.filename = file.path;
    }

    this._getFormData().append(field, file, o);
  }
  return this;
};

Request.prototype._getFormData = function() {
  if (!this._formData) {
    this._formData = new FormData();
    this._formData.on('error', err => {
      this.emit('error', err);
      this.abort();
    });
  }
  return this._formData;
};

/**
 * Gets/sets the `Agent` to use for this HTTP request. The default (if this
 * function is not called) is to opt out of connection pooling (`agent: false`).
 *
 * @param {http.Agent} agent
 * @return {http.Agent}
 * @api public
 */

Request.prototype.agent = function(agent){
  if (!arguments.length) return this._agent;
  this._agent = agent;
  return this;
};

/**
 * Set _Content-Type_ response header passed through `mime.lookup()`.
 *
 * Examples:
 *
 *      request.post('/')
 *        .type('xml')
 *        .send(xmlstring)
 *        .end(callback);
 *
 *      request.post('/')
 *        .type('json')
 *        .send(jsonstring)
 *        .end(callback);
 *
 *      request.post('/')
 *        .type('application/json')
 *        .send(jsonstring)
 *        .end(callback);
 *
 * @param {String} type
 * @return {Request} for chaining
 * @api public
 */

Request.prototype.type = function(type) {
  return this.set(
    'Content-Type',
    ~type.indexOf('/') ? type : mime.lookup(type)
  );
};

/**
 * Set _Accept_ response header passed through `mime.lookup()`.
 *
 * Examples:
 *
 *      superagent.types.json = 'application/json';
 *
 *      request.get('/agent')
 *        .accept('json')
 *        .end(callback);
 *
 *      request.get('/agent')
 *        .accept('application/json')
 *        .end(callback);
 *
 * @param {String} accept
 * @return {Request} for chaining
 * @api public
 */

Request.prototype.accept = function(type){
  return this.set('Accept', ~type.indexOf('/')
    ? type
    : mime.lookup(type));
};

/**
 * Add query-string `val`.
 *
 * Examples:
 *
 *   request.get('/shoes')
 *     .query('size=10')
 *     .query({ color: 'blue' })
 *
 * @param {Object|String} val
 * @return {Request} for chaining
 * @api public
 */

Request.prototype.query = function(val){
  if ('string' == typeof val) {
    this._query.push(val);
  } else {
    extend(this.qs, val);
  }
  return this;
};

/**
 * Write raw `data` / `encoding` to the socket.
 *
 * @param {Buffer|String} data
 * @param {String} encoding
 * @return {Boolean}
 * @api public
 */

Request.prototype.write = function(data, encoding){
  const req = this.request();
  if (!this._streamRequest) {
    this._streamRequest = true;
  }
  return req.write(data, encoding);
};

/**
 * Pipe the request body to `stream`.
 *
 * @param {Stream} stream
 * @param {Object} options
 * @return {Stream}
 * @api public
 */

Request.prototype.pipe = function(stream, options){
  this.piped = true; // HACK...
  this.buffer(false);
  this.end();
  return this._pipeContinue(stream, options);
};

Request.prototype._pipeContinue = function(stream, options){
  this.req.once('response', res => {
    // redirect
    const redirect = isRedirect(res.statusCode);
    if (redirect && this._redirects++ != this._maxRedirects) {
      return this._redirect(res)._pipeContinue(stream, options);
    }

    this.res = res;
    this._emitResponse();
    if (this._aborted) return;

    if (this._shouldUnzip(res)) {
      const unzipObj = zlib.createUnzip();
      unzipObj.on('error', err => {
        if (err && err.code === 'Z_BUF_ERROR') { // unexpected end of file is ignored by browsers and curl
          stream.emit('end');
          return;
        }
        stream.emit('error', err);
      });
      res.pipe(unzipObj).pipe(stream, options);
    } else {
      res.pipe(stream, options);
    }
    res.once('end', () => {
      this.emit('end');
    });
  });
  return stream;
};

/**
 * Enable / disable buffering.
 *
 * @return {Boolean} [val]
 * @return {Request} for chaining
 * @api public
 */

Request.prototype.buffer = function(val){
  this._buffer = (false !== val);
  return this;
};

/**
 * Redirect to `url
 *
 * @param {IncomingMessage} res
 * @return {Request} for chaining
 * @api private
 */

Request.prototype._redirect = function(res){
  let url = res.headers.location;
  if (!url) {
    return this.callback(new Error('No location header for redirect'), res);
  }

  debug('redirect %s -> %s', this.url, url);

  // location
  url = resolve(this.url, url);

  // ensure the response is being consumed
  // this is required for Node v0.10+
  res.resume();

  let headers = this.req._headers;

  const changesOrigin = parse(url).host !== parse(this.url).host;

  // implementation of 302 following defacto standard
  if (res.statusCode == 301 || res.statusCode == 302){
    // strip Content-* related fields
    // in case of POST etc
    headers = utils.cleanHeader(this.req._headers, changesOrigin);

    // force GET
    this.method = 'HEAD' == this.method
      ? 'HEAD'
      : 'GET';

    // clear data
    this._data = null;
  }
  // 303 is always GET
  if (res.statusCode == 303) {
    // strip Content-* related fields
    // in case of POST etc
    headers = utils.cleanHeader(this.req._headers, changesOrigin);

    // force method
    this.method = 'GET';

    // clear data
    this._data = null;
  }
  // 307 preserves method
  // 308 preserves method
  delete headers.host;

  delete this.req;
  delete this._formData;

  // remove all add header except User-Agent
  _initHeaders(this);

  // redirect
  this._endCalled = false;
  this.url = url;
  this.qs = {};
  this._query.length = 0;
  this.set(headers);
  this.emit('redirect', res);
  this._redirectList.push(this.url);
  this.end(this._callback);
  return this;
};

/**
 * Set Authorization field value with `user` and `pass`.
 *
 * Examples:
 *
 *   .auth('tobi', 'learnboost')
 *   .auth('tobi:learnboost')
 *   .auth('tobi')
 *   .auth(accessToken, { type: 'bearer' })
 *
 * @param {String} user
 * @param {String} [pass]
 * @param {Object} [options] options with authorization type 'basic' or 'bearer' ('basic' is default)
 * @return {Request} for chaining
 * @api public
 */

Request.prototype.auth = function(user, pass, options){
  if (1 === arguments.length) pass = '';
  if (typeof pass === 'object' && pass !== null) { // pass is optional and can be replaced with options
    options = pass;
    pass = '';
  }
  if (!options) {
    options = { type: 'basic' };
  }

  var encoder = function(string) {
    return new Buffer(string).toString('base64');
  };

  return this._auth(user, pass, options, encoder);
};

/**
 * Set the certificate authority option for https request.
 *
 * @param {Buffer | Array} cert
 * @return {Request} for chaining
 * @api public
 */

Request.prototype.ca = function(cert){
  this._ca = cert;
  return this;
};

/**
 * Set the client certificate key option for https request.
 *
 * @param {Buffer | String} cert
 * @return {Request} for chaining
 * @api public
 */

Request.prototype.key = function(cert){
  this._key = cert;
  return this;
};

/**
 * Set the key, certificate, and CA certs of the client in PFX or PKCS12 format.
 *
 * @param {Buffer | String} cert
 * @return {Request} for chaining
 * @api public
 */

Request.prototype.pfx = function(cert) {
  if (typeof cert === 'object' && !Buffer.isBuffer(cert)) {
    this._pfx = cert.pfx;
    this._passphrase = cert.passphrase;
  } else {
    this._pfx = cert;
  }
  return this;
};

/**
 * Set the client certificate option for https request.
 *
 * @param {Buffer | String} cert
 * @return {Request} for chaining
 * @api public
 */

Request.prototype.cert = function(cert){
  this._cert = cert;
  return this;
};

/**
 * Return an http[s] request.
 *
 * @return {OutgoingMessage}
 * @api private
 */

Request.prototype.request = function(){
  if (this.req) return this.req;

  const options = {};

  try {
    const query = qs.stringify(this.qs, {
      indices: false,
      strictNullHandling: true,
    });
    if (query) {
      this.qs = {};
      this._query.push(query);
    }
    this._finalizeQueryString();
  } catch (e) {
    return this.emit('error', e);
  }

  let url = this.url;
  const retries = this._retries;

  // default to http://
  if (0 != url.indexOf('http')) url = `http://${url}`;
  url = parse(url);

  // support unix sockets
  if (/^https?\+unix:/.test(url.protocol) === true) {
    // get the protocol
    url.protocol = `${url.protocol.split('+')[0]}:`;

    // get the socket, path
    const unixParts = url.path.match(/^([^/]+)(.+)$/);
    options.socketPath = unixParts[1].replace(/%2F/g, '/');
    url.path = unixParts[2];
  }

  // options
  options.method = this.method;
  options.port = url.port;
  options.path = url.path;
  options.host = url.hostname;
  options.ca = this._ca;
  options.key = this._key;
  options.pfx = this._pfx;
  options.cert = this._cert;
  options.passphrase = this._passphrase;
  options.agent = this._agent;

  // initiate request
  const mod = exports.protocols[url.protocol];

  // request
  const req = (this.req = mod.request(options));

  // set tcp no delay
  req.setNoDelay(true);

  if ('HEAD' != options.method) {
    req.setHeader('Accept-Encoding', 'gzip, deflate');
  }
  this.protocol = url.protocol;
  this.host = url.host;

  // expose events
  req.once('drain', () => { this.emit('drain'); });

  req.once('error', err => {
    // flag abortion here for out timeouts
    // because node will emit a faux-error "socket hang up"
    // when request is aborted before a connection is made
    if (this._aborted) return;
    // if not the same, we are in the **old** (cancelled) request,
    // so need to continue (same as for above)
    if (this._retries !== retries) return;
    // if we've received a response then we don't want to let
    // an error in the request blow up the response
    if (this.response) return;
    this.callback(err);
  });

  // auth
  if (url.auth) {
    const auth = url.auth.split(':');
    this.auth(auth[0], auth[1]);
  }
  if (this.username && this.password) {
    this.auth(this.username, this.password);
  }
  for (const key in this.header) {
    if (this.header.hasOwnProperty(key))
      req.setHeader(key, this.header[key]);
  }

  // add cookies
  if (this.cookies) {
    if(this.header.hasOwnProperty('cookie')) {
      // merge
      const tmpJar = new CookieJar.CookieJar();
      tmpJar.setCookies(this.header.cookie.split(';'));
      tmpJar.setCookies(this.cookies.split(';'));
      req.setHeader('Cookie',tmpJar.getCookies(CookieJar.CookieAccessInfo.All).toValueString());
    } else {
      req.setHeader('Cookie', this.cookies);
    }
  }

  return req;
};

/**
 * Invoke the callback with `err` and `res`
 * and handle arity check.
 *
 * @param {Error} err
 * @param {Response} res
 * @api private
 */

Request.prototype.callback = function(err, res){
  if (this._shouldRetry(err, res)) {
    return this._retry();
  }

  // Avoid the error which is emitted from 'socket hang up' to cause the fn undefined error on JS runtime.
  const fn = this._callback || noop;
  this.clearTimeout();
  if (this.called) return console.warn('superagent: double callback bug');
  this.called = true;

  if (!err) {
    try {
      if (!this._isResponseOK(res)) {
        let msg = 'Unsuccessful HTTP response';
        if (res) {
          msg = http.STATUS_CODES[res.status] || msg;
        }
        err = new Error(msg);
        err.status = res ? res.status : undefined;
      }
    } catch (new_err) {
      err = new_err;
    }
  }
  // It's important that the callback is called outside try/catch
  // to avoid double callback
  if (!err) {
    return fn(null, res);
  }

  err.response = res;
  if (this._maxRetries) err.retries = this._retries - 1;

  // only emit error event if there is a listener
  // otherwise we assume the callback to `.end()` will get the error
  if (err && this.listeners('error').length > 0) {
    this.emit('error', err);
  }

  fn(err, res);
};

/**
 * Check if `obj` is a host object,
 *
 * @param {Object} obj
 * @return {Boolean}
 * @api private
 */
Request.prototype._isHost = function _isHost(obj) {
  return Buffer.isBuffer(obj) || obj instanceof Stream || obj instanceof FormData;
}

/**
 * Initiate request, invoking callback `fn(err, res)`
 * with an instanceof `Response`.
 *
 * @param {Function} fn
 * @return {Request} for chaining
 * @api public
 */

Request.prototype._emitResponse = function(body, files) {
  const response = new Response(this);
  this.response = response;
  response.redirects = this._redirectList;
  if (undefined !== body) {
    response.body = body;
  }
  response.files = files;
  this.emit('response', response);
  return response;
};

Request.prototype.end = function(fn) {
  this.request();
  debug('%s %s', this.method, this.url);

  if (this._endCalled) {
    console.warn(
      'Warning: .end() was called twice. This is not supported in superagent'
    );
  }
  this._endCalled = true;

  // store callback
  this._callback = fn || noop;

  return this._end();
};

Request.prototype._end = function() {
  let data = this._data;
  const req = this.req;
  let buffer = this._buffer;
  const method = this.method;

  this._setTimeouts();

  // body
  if ('HEAD' != method && !req._headerSent) {
    // serialize stuff
    if ('string' != typeof data) {
      let contentType = req.getHeader('Content-Type');
      // Parse out just the content type from the header (ignore the charset)
      if (contentType) contentType = contentType.split(';')[0];
      let serialize = exports.serialize[contentType];
      if (!serialize && isJSON(contentType)) {
        serialize = exports.serialize['application/json'];
      }
      if (serialize) data = serialize(data);
    }

    // content-length
    if (data && !req.getHeader('Content-Length')) {
      req.setHeader('Content-Length', Buffer.isBuffer(data) ? data.length : Buffer.byteLength(data));
    }
  }

  // response
  req.once('response', res => {
    debug('%s %s -> %s', this.method, this.url, res.statusCode);

    if (this._responseTimeoutTimer) {
      clearTimeout(this._responseTimeoutTimer);
    }

    if (this.piped) {
      return;
    }

    const max = this._maxRedirects;
    const mime = utils.type(res.headers['content-type'] || '') || 'text/plain';
    const type = mime.split('/')[0];
    const multipart = 'multipart' == type;
    const redirect = isRedirect(res.statusCode);
    let parser = this._parser;
    const responseType = this._responseType;

    this.res = res;

    // redirect
    if (redirect && this._redirects++ != max) {
      return this._redirect(res);
    }

    if ('HEAD' == this.method) {
      this.emit('end');
      this.callback(null, this._emitResponse());
      return;
    }

    // zlib support
    if (this._shouldUnzip(res)) {
      unzip(req, res);
    }

    if (!parser) {
      if (responseType) {
        parser = exports.parse.image; // It's actually a generic Buffer
        buffer = true;
      } else if (multipart) {
        const form = new formidable.IncomingForm();
        parser = form.parse.bind(form);
        buffer = true;
      } else if (isImageOrVideo(mime)) {
        parser = exports.parse.image;
        buffer = true; // For backwards-compatibility buffering default is ad-hoc MIME-dependent
      } else if (exports.parse[mime]) {
        parser = exports.parse[mime];
      } else if ('text' == type) {
        parser = exports.parse.text;
        buffer = (buffer !== false);

        // everyone wants their own white-labeled json
      } else if (isJSON(mime)) {
        parser = exports.parse['application/json'];
        buffer = (buffer !== false);
      } else if (buffer) {
        parser = exports.parse.text;
      }
    }

    // by default only buffer text/*, json and messed up thing from hell
    if ((undefined === buffer && isText(mime)) || isJSON(mime)) {
      buffer = true;
    }

    let parserHandlesEnd = false;
    if (buffer) {
      // Protectiona against zip bombs and other nuisance
      let responseBytesLeft = this._maxResponseSize || 200000000;
      res.on('data', buf => {
        responseBytesLeft -= buf.byteLength || buf.length;
        if (responseBytesLeft < 0) {
          // This will propagate through error event
          const err = Error("Maximum response size reached");
          err.code = "ETOOLARGE";
          // Parsers aren't required to observe error event,
          // so would incorrectly report success
          parserHandlesEnd = false;
          // Will emit error event
          res.destroy(err);
        }
      });
    }

    if (parser) {
      try {
        // Unbuffered parsers are supposed to emit response early,
        // which is weird BTW, because response.body won't be there.
        parserHandlesEnd = buffer;

        parser(res, (err, obj, files) => {
          if (this.timedout) {
            // Timeout has already handled all callbacks
            return;
          }

          // Intentional (non-timeout) abort is supposed to preserve partial response,
          // even if it doesn't parse.
          if (err && !this._aborted) {
            return this.callback(err);
          }

          if (parserHandlesEnd) {
            this.emit('end');
            this.callback(null, this._emitResponse(obj, files));
          }
        });
      } catch (err) {
        this.callback(err);
        return;
      }
    }

    this.res = res;

    // unbuffered
    if (!buffer) {
      debug('unbuffered %s %s', this.method, this.url);
      this.callback(null, this._emitResponse());
      if (multipart) return; // allow multipart to handle end event
      res.once('end', () => {
        debug('end %s %s', this.method, this.url);
        this.emit('end');
      });
      return;
    }

    // terminating events
    res.once('error', err => {
      parserHandlesEnd = false;
      this.callback(err, null);
    });
    if (!parserHandlesEnd)
      res.once('end', () => {
        debug('end %s %s', this.method, this.url);
        // TODO: unless buffering emit earlier to stream
        this.emit('end');
        this.callback(null, this._emitResponse());
      });
  });

  this.emit('request', this);

  const getProgressMonitor = () => {
    const lengthComputable = true;
    const total = req.getHeader('Content-Length');
    let loaded = 0;

    const progress = new Stream.Transform();
    progress._transform = (chunk, encoding, cb) => {
      loaded += chunk.length;
      this.emit('progress', {
        direction: 'upload',
        lengthComputable,
        loaded,
        total,
      });
      cb(null, chunk);
    };
    return progress;
  };

  const bufferToChunks = (buffer) => {
    const chunkSize = 16 * 1024; // default highWaterMark value
    const chunking = new Stream.Readable();
    const totalLength = buffer.length;
    const remainder = totalLength % chunkSize;
    const cutoff = totalLength - remainder;

    for (let i = 0; i < cutoff; i += chunkSize) {
      const chunk = buffer.slice(i, i + chunkSize);
      chunking.push(chunk);
    }

    if (remainder > 0) {
      const remainderBuffer = buffer.slice(-remainder);
      chunking.push(remainderBuffer);
    }

    chunking.push(null); // no more data

    return chunking;
  }

  // if a FormData instance got created, then we send that as the request body
  const formData = this._formData;
  if (formData) {

    // set headers
    const headers = formData.getHeaders();
    for (const i in headers) {
      debug('setting FormData header: "%s: %s"', i, headers[i]);
      req.setHeader(i, headers[i]);
    }

    // attempt to get "Content-Length" header
    formData.getLength((err, length) => {
      // TODO: Add chunked encoding when no length (if err)

      debug('got FormData Content-Length: %s', length);
      if ('number' == typeof length) {
        req.setHeader('Content-Length', length);
      }
      
      formData.pipe(getProgressMonitor()).pipe(req);
    });
  } else if (Buffer.isBuffer(data)) {
    bufferToChunks(data).pipe(getProgressMonitor()).pipe(req);
  } else {
    req.end(data);
  }

  return this;
};

/**
 * Check whether response has a non-0-sized gzip-encoded body
 */
Request.prototype._shouldUnzip = res => {
  if (res.statusCode === 204 || res.statusCode === 304) {
    // These aren't supposed to have any body
    return false;
  }

  // header content is a string, and distinction between 0 and no information is crucial
  if ('0' === res.headers['content-length']) {
    // We know that the body is empty (unfortunately, this check does not cover chunked encoding)
    return false;
  }

  // console.log(res);
  return /^\s*(?:deflate|gzip)\s*$/.test(res.headers['content-encoding']);
};

// generate HTTP verb methods
if (methods.indexOf('del') == -1) {
  // create a copy so we don't cause conflicts with
  // other packages using the methods package and
  // npm 3.x
  methods = methods.slice(0);
  methods.push('del');
}
methods.forEach(method => {
  const name = method;
  method = 'del' == method ? 'delete' : method;

  method = method.toUpperCase();
  request[name] = (url, data, fn) => {
    const req = request(method, url);
    if ('function' == typeof data) (fn = data), (data = null);
    if (data) {
      if (method === 'GET' || method === 'HEAD') {
        req.query(data);
      } else {
        req.send(data);
      }
    }
    fn && req.end(fn);
    return req;
  };
});

/**
 * Check if `mime` is text and should be buffered.
 *
 * @param {String} mime
 * @return {Boolean}
 * @api public
 */

function isText(mime) {
  const parts = mime.split('/');
  const type = parts[0];
  const subtype = parts[1];

  return 'text' == type || 'x-www-form-urlencoded' == subtype;
}

function isImageOrVideo(mime) {
  const type = mime.split('/')[0];

  return 'image' == type || 'video' == type;
}

/**
 * Check if `mime` is json or has +json structured syntax suffix.
 *
 * @param {String} mime
 * @return {Boolean}
 * @api private
 */

function isJSON(mime) {
  // should match /json or +json
  // but not /json-seq
  return /[\/+]json($|[^-\w])/.test(mime);
}

/**
 * Check if we should follow the redirect `code`.
 *
 * @param {Number} code
 * @return {Boolean}
 * @api private
 */

function isRedirect(code) {
  return ~[301, 302, 303, 305, 307, 308].indexOf(code);
}