urllib/lib/get_proxy_from_uri.js

// copy from https://github.com/request/request/blob/90cf8c743bb9fd6a4cb683a56fb7844c6b316866/lib/getProxyFromURI.js

'use strict'

function formatHostname(hostname) {
  // canonicalize the hostname, so that 'oogle.com' won't match 'google.com'
  return hostname.replace(/^\.*/, '.').toLowerCase()
}

function parseNoProxyZone(zone) {
  zone = zone.trim().toLowerCase()

  var zoneParts = zone.split(':', 2)
    , zoneHost = formatHostname(zoneParts[0])
    , zonePort = zoneParts[1]
    , hasPort = zone.indexOf(':') > -1

  return {hostname: zoneHost, port: zonePort, hasPort: hasPort}
}

function uriInNoProxy(uri, noProxy) {
  var port = uri.port || (uri.protocol === 'https:' ? '443' : '80')
    , hostname = formatHostname(uri.hostname)
    , noProxyList = noProxy.split(',')

  // iterate through the noProxyList until it finds a match.
  return noProxyList.map(parseNoProxyZone).some(function(noProxyZone) {
    var isMatchedAt = hostname.indexOf(noProxyZone.hostname)
      , hostnameMatched = (
          isMatchedAt > -1 &&
          (isMatchedAt === hostname.length - noProxyZone.hostname.length)
        )

    if (noProxyZone.hasPort) {
      return (port === noProxyZone.port) && hostnameMatched
    }

    return hostnameMatched
  })
}

function getProxyFromURI(uri) {
  // Decide the proper request proxy to use based on the request URI object and the
  // environmental variables (NO_PROXY, HTTP_PROXY, etc.)
  // respect NO_PROXY environment variables (see: http://lynx.isc.org/current/breakout/lynx_help/keystrokes/environments.html)

  var noProxy = process.env.NO_PROXY || process.env.no_proxy || ''

  // if the noProxy is a wildcard then return null

  if (noProxy === '*') {
    return null
  }

  // if the noProxy is not empty and the uri is found return null

  if (noProxy !== '' && uriInNoProxy(uri, noProxy)) {
    return null
  }

  // Check for HTTP or HTTPS Proxy in environment Else default to null

  if (uri.protocol === 'http:') {
    return process.env.HTTP_PROXY ||
           process.env.http_proxy || null
  }

  if (uri.protocol === 'https:') {
    return process.env.HTTPS_PROXY ||
           process.env.https_proxy ||
           process.env.HTTP_PROXY  ||
           process.env.http_proxy  || null
  }

  // if none of that works, return null
  // (What uri protocol are you using then?)

  return null
}

module.exports = getProxyFromURI