From d0b955aadd1caaece82f301aafd42868e8908256 Mon Sep 17 00:00:00 2001
From: Pavel Cizinsky <pavel.cizinsky@gmail.com>
Date: Tue, 6 Jan 2026 12:18:00 +0100
Subject: [PATCH] feat(slack): Add environment variable fallback for config

Allow Slack alertmanager to read token, channel, and webhook
from SLACK_TOKEN, SLACK_CHANNEL, and SLACK_WEBHOOK environment
variables when not specified in config. Config values take
precedence over environment variables when both are present.
---
 alertmanager/slack/slack.go      | 12 ++++++
 alertmanager/slack/slack_test.go | 66 ++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)

diff --git a/alertmanager/slack/slack.go b/alertmanager/slack/slack.go
index 3e82508..1f45c94 100644
--- a/alertmanager/slack/slack.go
+++ b/alertmanager/slack/slack.go
@@ -2,6 +2,7 @@ package slack
 
 import (
 	"fmt"
+	"os"
 	"strings"
 
 	"github.com/abahmed/kwatch/config"
@@ -44,6 +45,17 @@ func NewSlack(config map[string]interface{}, appCfg *config.App) *Slack {
 	title, _ := config["title"].(string)
 	text, _ := config["text"].(string)
 
+	// Fall back to environment variables if config values are not set
+	if len(token) == 0 {
+		token = os.Getenv("SLACK_TOKEN")
+	}
+	if len(channel) == 0 {
+		channel = os.Getenv("SLACK_CHANNEL")
+	}
+	if len(webhook) == 0 {
+		webhook = os.Getenv("SLACK_WEBHOOK")
+	}
+
 	// Token takes precedence over webhook
 	if len(token) > 0 {
 		if len(channel) == 0 {
diff --git a/alertmanager/slack/slack_test.go b/alertmanager/slack/slack_test.go
index f03b2c8..baabc60 100644
--- a/alertmanager/slack/slack_test.go
+++ b/alertmanager/slack/slack_test.go
@@ -1,6 +1,7 @@
 package slack
 
 import (
+	"os"
 	"testing"
 
 	"github.com/abahmed/kwatch/config"
@@ -140,3 +141,68 @@ func TestSendEvent(t *testing.T) {
 	}
 	assert.Nil(s.SendEvent(&ev))
 }
+
+func TestSlackEnvVarToken(t *testing.T) {
+	assert := assert.New(t)
+
+	// Set environment variables
+	os.Setenv("SLACK_TOKEN", "xoxb-env-token")
+	os.Setenv("SLACK_CHANNEL", "#env-channel")
+	defer func() {
+		os.Unsetenv("SLACK_TOKEN")
+		os.Unsetenv("SLACK_CHANNEL")
+	}()
+
+	// Empty config should use env vars
+	s := NewSlack(map[string]interface{}{}, &config.App{ClusterName: "dev"})
+	assert.NotNil(s)
+	assert.Equal("xoxb-env-token", s.token)
+	assert.Equal("#env-channel", s.channel)
+	assert.NotNil(s.client)
+}
+
+func TestSlackEnvVarWebhook(t *testing.T) {
+	assert := assert.New(t)
+
+	// Set environment variable
+	os.Setenv("SLACK_WEBHOOK", "https://hooks.slack.com/env-webhook")
+	defer os.Unsetenv("SLACK_WEBHOOK")
+
+	// Empty config should use env var
+	s := NewSlack(map[string]interface{}{}, &config.App{ClusterName: "dev"})
+	assert.NotNil(s)
+	assert.Equal("https://hooks.slack.com/env-webhook", s.webhook)
+}
+
+func TestSlackConfigOverridesEnvVar(t *testing.T) {
+	assert := assert.New(t)
+
+	// Set environment variables
+	os.Setenv("SLACK_TOKEN", "xoxb-env-token")
+	os.Setenv("SLACK_CHANNEL", "#env-channel")
+	defer func() {
+		os.Unsetenv("SLACK_TOKEN")
+		os.Unsetenv("SLACK_CHANNEL")
+	}()
+
+	// Config values should override env vars
+	s := NewSlack(map[string]interface{}{
+		"token":   "xoxb-config-token",
+		"channel": "#config-channel",
+	}, &config.App{ClusterName: "dev"})
+	assert.NotNil(s)
+	assert.Equal("xoxb-config-token", s.token)
+	assert.Equal("#config-channel", s.channel)
+}
+
+func TestSlackEnvVarTokenWithoutChannel(t *testing.T) {
+	assert := assert.New(t)
+
+	// Set only token env var (no channel)
+	os.Setenv("SLACK_TOKEN", "xoxb-env-token")
+	defer os.Unsetenv("SLACK_TOKEN")
+
+	// Should fail because channel is required with token
+	s := NewSlack(map[string]interface{}{}, &config.App{ClusterName: "dev"})
+	assert.Nil(s)
+}