From 000a10b375662b09d7f998a7ee3ddb40f616ef84 Mon Sep 17 00:00:00 2001
From: "Michael Bradley, Jr" <michaelsbradleyjr@gmail.com>
Date: Sun, 15 Jul 2018 10:10:55 -0500
Subject: [PATCH] host utils

---
 lib/utils/host.js | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 lib/utils/host.js

diff --git a/lib/utils/host.js b/lib/utils/host.js
new file mode 100644
index 00000000..67588161
--- /dev/null
+++ b/lib/utils/host.js
@@ -0,0 +1,45 @@
+const isDocker = (() => {
+    let isDocker;
+
+    const hostname = require('os').hostname();
+    const pattern = new RegExp(
+        '[0-9]+\:[a-z_-]+\:\/docker\/' + hostname + '[0-9a-z]+', 'i'
+    );
+
+    try {
+        isDocker = require('child_process')
+            .execSync(
+                'cat /proc/self/cgroup',
+                {stdio: ['ignore', 'pipe', 'ignore']}
+            )
+            .toString().match(pattern) !== null;
+    } catch (e) {
+        isDocker = false;
+    }
+
+    return isDocker;
+})();
+
+const defaultHost = isDocker ? '0.0.0.0' : 'localhost';
+
+// when we're runing in Docker, we can expect (generally, in a development
+// scenario) that the user would like to connect to the service in the
+// container via the **host's** loopback address, so this helper can be used to
+// swap 0.0.0.0 for localhost in code/messages that pertain to client-side
+function canonicalHost(host) {
+    return isDocker && host === '0.0.0.0' ? 'localhost' : host;
+}
+
+function dockerHostSwap(host) {
+    return (isDocker && (host === 'localhost' || host === '127.0.0.1')) ? defaultHost : host;
+}
+
+const defaultCorsHost = canonicalHost(defaultHost);
+
+module.exports = {
+    canonicalHost,
+    defaultCorsHost,
+    defaultHost,
+    dockerHostSwap,
+    isDocker
+};