'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