AB#2639 Add functions to fetch k8s and helm version of Constellation (#637)

Signed-off-by: Daniel Weiße <dw@edgeless.systems>

cli/internal/helm/client.go

@@ -0,0 +1,55 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+package helm
+
+import (
+	"fmt"
+
+	"helm.sh/helm/v3/pkg/action"
+	"helm.sh/helm/v3/pkg/cli"
+)
+
+// Client handles interaction with helm.
+type Client struct {
+	config *action.Configuration
+}
+
+// NewClient returns a new initializes client for the namespace Client.
+func NewClient(kubeConfigPath, helmNamespace string) (*Client, error) {
+	settings := cli.New()
+	settings.KubeConfig = kubeConfigPath // constants.AdminConfFilename
+
+	actionConfig := &action.Configuration{}
+	if err := actionConfig.Init(settings.RESTClientGetter(), helmNamespace, "secret", nil); err != nil {
+		return nil, fmt.Errorf("initializing config: %w", err)
+	}
+
+	return &Client{config: actionConfig}, nil
+}
+
+// CurrentVersion returns the version of the currently installed helm release.
+func (c *Client) CurrentVersion(release string) (string, error) {
+	client := action.NewList(c.config)
+	client.Filter = release
+	rel, err := client.Run()
+	if err != nil {
+		return "", err
+	}
+
+	if len(rel) == 0 {
+		return "", fmt.Errorf("release %s not found", release)
+	}
+	if len(rel) > 1 {
+		return "", fmt.Errorf("multiple releases found for %s", release)
+	}
+
+	if rel[0] == nil || rel[0].Chart == nil || rel[0].Chart.Metadata == nil {
+		return "", fmt.Errorf("received invalid release %s", release)
+	}
+
+	return rel[0].Chart.Metadata.Version, nil
+}