net     = require("net")
dns     = require("dns")
url     = require("url")
Promise = require("bluebird")

module.exports = {
  byPortAndAddress: (port, address) ->
    ## https://nodejs.org/api/net.html#net_net_connect_port_host_connectlistener
    new Promise (resolve, reject) ->
      client = net.connect(port, address.address)
      client.on "connect", ->
        client.end()
        resolve(address)
      client.on "error", reject

  getAddress: (port, hostname) ->
    fn = @byPortAndAddress.bind(@, port)

    ## promisify at the very last second which enables us to
    ## modify dns lookup function (via hosts overrides)
    lookupAsync = Promise.promisify(dns.lookup, {context: dns})

    ## this does not go out to the network to figure
    ## out the addresess. in fact it respects the /etc/hosts file
    ## https://github.com/nodejs/node/blob/dbdbdd4998e163deecefbb1d34cda84f749844a4/lib/dns.js#L108
    ## https://nodejs.org/api/dns.html#dns_dns_lookup_hostname_options_callback
    lookupAsync(hostname, {all: true})
    .then (addresses) ->
      ## convert to an array if string
      [].concat(addresses).map(fn)
    .any()

  ensureUrl: (urlStr) ->
    ## takes a urlStr and verifies the hostname + port
    {hostname, protocol, port} = url.parse(urlStr)

    port ?= if protocol is "https:" then "443" else "80"

    @getAddress(port, hostname)
}