review: feedback cycle 2

Add Prometheus configuration discovery to integration activate command.

Also improve logging to make this more clear to users.

Signed-off-by: Daniel Clark <danielclark@google.com>

pkg/integration/prometheus/prometheus.go

@@ -1,7 +1,14 @@
 package prometheus
 
 import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+
+	"github.com/fatih/color"
 	"github.com/k8sgpt-ai/k8sgpt/pkg/common"
+	"github.com/k8sgpt-ai/k8sgpt/pkg/kubernetes"
 	"github.com/spf13/viper"
 )
 
@@ -17,15 +24,52 @@ func NewPrometheus() *Prometheus {
 	return &Prometheus{}
 }
 
-func (p *Prometheus) Deploy(_ string) error {
+func (p *Prometheus) Deploy(namespace string) error {
 	// no-op
+	color.Green("Activating prometheus integration...")
+	// TODO(pintohutch): add timeout or inherit an upstream context
+	// for better signal management.
+	ctx := context.Background()
+	kubecontext := viper.GetString("kubecontext")
+	kubeconfig := viper.GetString("kubeconfig")
+	client, err := kubernetes.NewClient(kubecontext, kubeconfig)
+	if err != nil {
+		color.Red("Error initialising kubernetes client: %v", err)
+		os.Exit(1)
+	}
+
 	// We just care about existing deployments.
+	// Try and find Prometheus configurations in the cluster using the provided namespace.
+	//
+	// Note: We could cache this state and inject it into the various analyzers
+	// to save additional parsing later.
+	// However, the state of the cluster can change from activation to analysis,
+	// so we would want to run this again on each analyze call anyway.
+	//
+	// One consequence of this is one can run `activate` in one namespace
+	// and run `analyze` in another, without issues, as long as Prometheus
+	// is found in both.
+	// We accept this as a trade-off for the time-being to avoid having the tool
+	// manage Prometheus on the behalf of users.
+	podConfigs, err := findPrometheusPodConfigs(ctx, client.GetClient(), namespace)
+	if err != nil {
+		color.Red("Error discovering Prometheus worklads: %v", err)
+		os.Exit(1)
+	}
+	if len(podConfigs) == 0 {
+		color.Yellow(fmt.Sprintf(`Prometheus installation not found in namespace: %s.
+		Please ensure Prometheus is deployed to analyze.`, namespace))
+		return errors.New("no prometheus installation found")
+	}
+	// Prime state of the analyzer so
+	color.Green("Found existing installation")
 	return nil
 }
 
 func (p *Prometheus) UnDeploy(_ string) error {
 	// no-op
 	// We just care about existing deployments.
+	color.Yellow("Integration will leave Prometheus resources deployed. This is an effective no-op in the cluster.")
 	return nil
 }