source: imaps-frontend/node_modules/clean-css/lib/reader/load-remote-resource.js

var http = require('http');
var https = require('https');
var url = require('url');

var isHttpResource = require('../utils/is-http-resource');
var isHttpsResource = require('../utils/is-https-resource');
var override = require('../utils/override');

var HTTP_PROTOCOL = 'http:';

function loadRemoteResource(uri, inlineRequest, inlineTimeout, callback) {
  var proxyProtocol = inlineRequest.protocol || inlineRequest.hostname;
  var errorHandled = false;
  var requestOptions;
  var fetch;

  requestOptions = override(
    url.parse(uri),
    inlineRequest || {}
  );

  if (inlineRequest.hostname !== undefined) {
    // overwrite as we always expect a http proxy currently
    requestOptions.protocol = inlineRequest.protocol || HTTP_PROTOCOL;
    requestOptions.path = requestOptions.href;
  }

  fetch = (proxyProtocol && !isHttpsResource(proxyProtocol)) || isHttpResource(uri)
    ? http.get
    : https.get;

  fetch(requestOptions, function(res) {
    var chunks = [];
    var movedUri;

    if (errorHandled) {
      return;
    }

    if (res.statusCode < 200 || res.statusCode > 399) {
      return callback(res.statusCode, null);
    } if (res.statusCode > 299) {
      movedUri = url.resolve(uri, res.headers.location);
      return loadRemoteResource(movedUri, inlineRequest, inlineTimeout, callback);
    }

    res.on('data', function(chunk) {
      chunks.push(chunk.toString());
    });
    res.on('end', function() {
      var body = chunks.join('');
      callback(null, body);
    });
  })
    .on('error', function(res) {
      if (errorHandled) {
        return;
      }

      errorHandled = true;
      callback(res.message, null);
    })
    .on('timeout', function() {
      if (errorHandled) {
        return;
      }

      errorHandled = true;
      callback('timeout', null);
    })
    .setTimeout(inlineTimeout);
}

module.exports = loadRemoteResource;