From efb1f089b049969e49f2e121b7fe1dc0dca63412 Mon Sep 17 00:00:00 2001
From: Gajus Kuizinas <gajus@gajus.com>
Date: Sun, 1 Oct 2017 10:25:37 +0100
Subject: [PATCH] feat: add augment CLI program

---
 README.md                   |  4 ++-
 package.json                |  1 +
 src/bin/commands/augment.js | 66 +++++++++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+), 1 deletion(-)
 create mode 100644 src/bin/commands/augment.js

diff --git a/README.md b/README.md
index 1c5d818..73f6358 100644
--- a/README.md
+++ b/README.md
@@ -354,9 +354,11 @@ Roarr does not have reserved context property names. However, I encourage use of
 |Context property name|Use case|
 |---|---|
 |`application`|Name of the application (do not use in code intended for distribution; see `package` property instead).|
-|`package`|Name of the package.|
+|`hostname`|Machine hostname. See `roarr augment --append-hostname` option.|
+|`instanceId`|Unique instance ID. Used to distinguish log source in high-concurrency environments. See `roarr augment --append-instance-id` option.|
 |`logLevel`|Human-readable name of the log-level, e.g. "error". See [API](#api) for build-in loggers with a pre-set log-level.|
 |`namespace`|Namespace within a package, e.g. function name. Treat the same way that you would construct namespaces when using the [`debug`](https://github.com/visionmedia/debug) package.|
+|`package`|Name of the package.|
 
 ### Using Roarr in an application
 
diff --git a/package.json b/package.json
index c618ae1..5bb64a4 100644
--- a/package.json
+++ b/package.json
@@ -17,6 +17,7 @@
     "prettyjson": "^1.2.1",
     "split2": "^2.2.0",
     "sprintf-js": "^1.1.1",
+    "ulid": "^1.0.0",
     "yargs": "^9.0.1"
   },
   "description": "JSON logger for Node.js.",
diff --git a/src/bin/commands/augment.js b/src/bin/commands/augment.js
new file mode 100644
index 0000000..a70aab5
--- /dev/null
+++ b/src/bin/commands/augment.js
@@ -0,0 +1,66 @@
+// @flow
+
+import os from 'os';
+import split from 'split2';
+import ulid from 'ulid';
+import {
+  isRoarrLine
+} from './utilities';
+
+export const command = 'augment';
+export const desc = 'Augments Roarr logs with additional information.';
+
+type LogFormatterConfigurationType = {|
+  +appendHostname: boolean,
+  +appendInstanceId: boolean
+|};
+
+const createLogFormatter = (configuration: LogFormatterConfigurationType) => {
+  let instanceId;
+
+  if (configuration.appendInstanceId) {
+    instanceId = ulid();
+  }
+
+  const stream = split((line) => {
+    if (!isRoarrLine(line)) {
+      return '';
+    }
+
+    const message = JSON.parse(line);
+
+    if (configuration.appendHostname) {
+      message.context.hostname = os.hostname();
+    }
+
+    if (configuration.appendInstanceId) {
+      message.context.instanceId = instanceId;
+    }
+
+    return JSON.stringify(message) + '\n';
+  });
+
+  return stream;
+};
+
+// eslint-disable-next-line flowtype/no-weak-types
+export const builder = (yargs: Object) => {
+  return yargs
+    .options({
+      'append-hostname-id': {
+        default: false,
+        type: 'boolean'
+      },
+      'append-instance-id': {
+        default: false,
+        type: 'boolean'
+      }
+    });
+};
+
+// eslint-disable-next-line flowtype/no-weak-types
+export const handler = (argv: Object) => {
+  process.stdin
+    .pipe(createLogFormatter(argv))
+    .pipe(process.stdout);
+};