Add check command

cmd/tk/check.go

+package main
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+
+	"github.com/spf13/cobra"
+	"k8s.io/client-go/kubernetes"
+	_ "k8s.io/client-go/plugin/pkg/client/auth"
+	"k8s.io/client-go/tools/clientcmd"
+)
+
+var checkCmd = &cobra.Command{
+	Use:   "check --pre",
+	Short: "Check for potential problems",
+	Long: `
+The check command will perform a series of checks to validate that
+the local environment and Kubernetes cluster are configured correctly.`,
+	Example: `  check --pre`,
+	RunE:    runCheckCmd,
+}
+
+var (
+	kubeconfig string
+	checkPre   bool
+)
+
+func init() {
+	if home := homeDir(); home != "" {
+		checkCmd.Flags().StringVarP(&kubeconfig, "kubeconfig", "", filepath.Join(home, ".kube", "config"),
+			"path to the kubeconfig file")
+	} else {
+		checkCmd.Flags().StringVarP(&kubeconfig, "kubeconfig", "", "",
+			"absolute path to the kubeconfig file")
+	}
+	checkCmd.Flags().BoolVarP(&checkPre, "pre", "", false,
+		"only run pre-installation checks")
+
+	rootCmd.AddCommand(checkCmd)
+}
+
+func runCheckCmd(cmd *cobra.Command, args []string) error {
+	if !checkLocal() {
+		os.Exit(1)
+	}
+	if checkPre {
+		fmt.Println(`✔`, "all prerequisites checks passed")
+		return nil
+	}
+
+	if !checkRemote() {
+		os.Exit(1)
+	} else {
+		fmt.Println(`✔`, "all checks passed")
+	}
+	return nil
+}
+
+func homeDir() string {
+	if h := os.Getenv("HOME"); h != "" {
+		return h
+	}
+	return os.Getenv("USERPROFILE") // windows
+}
+
+func checkLocal() bool {
+	ok := true
+	for _, cmd := range []string{"kubectl", "kustomize"} {
+		_, err := exec.LookPath(cmd)
+		if err != nil {
+			fmt.Println(`✗`, cmd, "not found")
+			ok = false
+		} else {
+			fmt.Println(`✔`, cmd, "found")
+		}
+	}
+	return ok
+}
+
+func checkRemote() bool {
+	config, err := clientcmd.BuildConfigFromFlags("", kubeconfig)
+	if err != nil {
+		fmt.Println(`✗`, "kubernetes client initialization failed", err.Error())
+		return false
+	}
+
+	client, err := kubernetes.NewForConfig(config)
+	if err != nil {
+		fmt.Println(`✗`, "kubernetes client initialization failed", err.Error())
+		return false
+	}
+
+	ver, err := client.Discovery().ServerVersion()
+	if err != nil {
+		fmt.Println(`✗`, "kubernetes API call failed", err.Error())
+		return false
+	}
+
+	fmt.Println(`✔`, "kubernetes version", ver.String())
+	return true
+}