Inject a noop slack client in case no slack token is set (#13)

Fixes #12

pkg/handlers/launch.go

@@ -150,6 +150,10 @@ type launchHandler struct {
 
 // NewLaunchHandler returns an handler that launches a k6 load test.
 func NewLaunchHandler(client k6.Client, kubeClient kubernetes.Interface, slackClient slack.Client) (http.Handler, error) {
+	if slackClient == nil {
+		return nil, errors.New("unexpected state. Slack client is nil")
+	}
+
 	return &launchHandler{
 		client:          client,
 		kubeClient:      kubeClient,

pkg/slack/client.go

@@ -12,8 +12,9 @@ type slackClientWrapper struct {
 
 func NewClient(token string) Client {
 	if token == "" {
-		return nil
+		return &noopClient{}
 	}
+
 	return &slackClientWrapper{
 		client: slack.New(token),
 	}

pkg/slack/noop.go

@@ -0,0 +1,28 @@
+package slack
+
+import (
+	log "github.com/sirupsen/logrus"
+)
+
+type noopClient struct{}
+
+func (c *noopClient) SendMessages(channels []string, text, context string) (map[string]string, error) {
+	if len(channels) > 0 {
+		log.Debugf("Slack disabled. Would've sent the following message: %s", text)
+	}
+	return nil, nil
+}
+
+func (c *noopClient) UpdateMessages(slackMessages map[string]string, text, context string) error {
+	if len(slackMessages) > 0 {
+		log.Debugf("Slack disabled. Would've updated messages to: %s", text)
+	}
+	return nil
+}
+
+func (c *noopClient) AddFileToThreads(slackMessages map[string]string, fileName, content string) error {
+	if len(slackMessages) > 0 {
+		log.Debugf("Slack disabled. Would've uploaded file named: %s", fileName)
+	}
+	return nil
+}