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'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