refactor getting mail auth

src/mail.js

@@ -26,6 +26,7 @@ exports = module.exports = {
     startMail: restartMail,
     restartMail: restartMail,
     handleCertChanged: handleCertChanged,
+    getMailAuth: getMailAuth,
 
     sendTestMail: sendTestMail,
 
@@ -55,6 +56,7 @@ var assert = require('assert'),
     constants = require('./constants.js'),
     debug = require('debug')('box:mail'),
     dns = require('./native-dns.js'),
+    docker = require('./docker.js'),
     domains = require('./domains.js'),
     eventlog = require('./eventlog.js'),
     hat = require('./hat.js'),
@@ -661,6 +663,31 @@ function configureMail(mailFqdn, mailDomain, callback) {
     });
 }
 
+function getMailAuth(callback) {
+    assert.strictEqual(typeof callback, 'function');
+
+    docker.inspect('mail', function (error, data) {
+        if (error) return callback(error);
+
+        const ip = safe.query(data, 'NetworkSettings.Networks.cloudron.IPAddress');
+        if (!ip) return callback(new BoxError(BoxError.MAIL_ERROR, 'Error querying mail server IP'));
+
+        // extract the relay token for auth
+        const env = safe.query(data, 'Config.Env', null);
+        if (!env) return callback(new BoxError(BoxError.MAIL_ERROR, 'Error getting mail env'));
+        const tmp = env.find(function (e) { return e.indexOf('CLOUDRON_RELAY_TOKEN') === 0; });
+        if (!tmp) return callback(new BoxError(BoxError.MAIL_ERROR, 'Error getting CLOUDRON_RELAY_TOKEN env var'));
+        const relayToken = tmp.slice('CLOUDRON_RELAY_TOKEN'.length + 1); // +1 for the = sign
+        if (!relayToken)  return callback(new BoxError(BoxError.MAIL_ERROR, 'Error parsing CLOUDRON_RELAY_TOKEN'));
+
+        callback(null, {
+            ip,
+            port: constants.INTERNAL_SMTP_PORT,
+            relayToken
+        });
+    });
+}
+
 function restartMail(callback) {
     assert.strictEqual(typeof callback, 'function');