From eacbef8d861fba48d8d893a02a3491a4915f65a1 Mon Sep 17 00:00:00 2001
From: Yi <felixfang71@gmail.com>
Date: Mon, 19 Aug 2019 04:25:39 +0100
Subject: [PATCH] Fix the issue that alarm info part shows undefined when alarm
 is based on expression

---
 index.js     | 11 ++++++++---
 package.json |  2 +-
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/index.js b/index.js
index c61ab4e..b9efda2 100644
--- a/index.js
+++ b/index.js
@@ -233,13 +233,13 @@ var handleCloudWatch = function(event, context) {
   var region = event.Records[0].EventSubscriptionArn.split(":")[3];
   var subject = "AWS CloudWatch Notification";
   var alarmName = message.AlarmName;
-  var metricName = message.Trigger.MetricName;
   var oldState = message.OldStateValue;
   var newState = message.NewStateValue;
   var alarmDescription = message.AlarmDescription;
   var alarmReason = message.NewStateReason;
   var trigger = message.Trigger;
   var color = "warning";
+  var alarmConfigInfo;
 
   if (message.NewStateValue === "ALARM") {
       color = "danger";
@@ -247,6 +247,12 @@ var handleCloudWatch = function(event, context) {
       color = "good";
   }
 
+  if (Array.isArray(trigger.Metrics) && trigger.Metrics.length > 0) {
+    alarmConfigInfo = "Expression based alarm";
+  } else {
+    alarmConfigInfo = trigger.Statistic + " " + trigger.MetricName;
+  }
+
   var slackMessage = {
     text: "*" + subject + "*",
     attachments: [
@@ -257,8 +263,7 @@ var handleCloudWatch = function(event, context) {
           { "title": "Alarm Description", "value": alarmDescription, "short": false},
           {
             "title": "Trigger",
-            "value": trigger.Statistic + " "
-              + metricName + " "
+            "value": alarmConfigInfo + " "
               + trigger.ComparisonOperator + " "
               + trigger.Threshold + " for "
               + trigger.EvaluationPeriods + " period(s) of "
diff --git a/package.json b/package.json
index 6e1e021..15d9e24 100644
--- a/package.json
+++ b/package.json
@@ -2,7 +2,7 @@
   "name": "lambda-cloudwatch-slack",
   "version": "0.3.0",
   "description": "Better Slack notifications for AWS CloudWatch",
-  "authors": [    
+  "authors": [
     "Christopher Reichert <creichert07@gmail.com>",
     "Cody Reichert <codyreichert@gmail.com>",
     "Alexandr Promakh <s-promakh@ya.ru>"