/*
Copyright 2019 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package cmd

import (
	"fmt"
	"io"
	"os"
	"strings"
	"text/tabwriter"
	"time"

	"github.com/lithammer/dedent"
	"github.com/pkg/errors"
	"github.com/spf13/cobra"
	"k8s.io/klog"

	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/fields"
	"k8s.io/apimachinery/pkg/util/duration"
	clientset "k8s.io/client-go/kubernetes"
	bootstrapapi "k8s.io/cluster-bootstrap/token/api"
	bootstraputil "k8s.io/cluster-bootstrap/token/util"
	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
	kubeadmscheme "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/scheme"
	kubeadmapiv1beta2 "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta2"
	"k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/validation"
	"k8s.io/kubernetes/cmd/kubeadm/app/cmd/options"
	cmdutil "k8s.io/kubernetes/cmd/kubeadm/app/cmd/util"
	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
	tokenphase "k8s.io/kubernetes/cmd/kubeadm/app/phases/bootstraptoken/node"
	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
	"k8s.io/kubernetes/cmd/kubeadm/app/util/apiclient"
	configutil "k8s.io/kubernetes/cmd/kubeadm/app/util/config"
	kubeconfigutil "k8s.io/kubernetes/cmd/kubeadm/app/util/kubeconfig"
)

// NewCmdToken returns cobra.Command for token management
func NewCmdToken(out io.Writer, errW io.Writer) *cobra.Command {
	var kubeConfigFile string
	var dryRun bool
	tokenCmd := &cobra.Command{
		Use:   "token",
		Short: "Manage bootstrap tokens",
		Long: dedent.Dedent(`
			This command manages bootstrap tokens. It is optional and needed only for advanced use cases.

			In short, bootstrap tokens are used for establishing bidirectional trust between a client and a server.
			A bootstrap token can be used when a client (for example a node that is about to join the cluster) needs
			to trust the server it is talking to. Then a bootstrap token with the "signing" usage can be used.
			bootstrap tokens can also function as a way to allow short-lived authentication to the API Server
			(the token serves as a way for the API Server to trust the client), for example for doing the TLS Bootstrap.

			What is a bootstrap token more exactly?
			 - It is a Secret in the kube-system namespace of type "bootstrap.kubernetes.io/token".
			 - A bootstrap token must be of the form "[a-z0-9]{6}.[a-z0-9]{16}". The former part is the public token ID,
			   while the latter is the Token Secret and it must be kept private at all circumstances!
			 - The name of the Secret must be named "bootstrap-token-(token-id)".

			You can read more about bootstrap tokens here:
			  https://kubernetes.io/docs/admin/bootstrap-tokens/
		`),

		// Without this callback, if a user runs just the "token"
		// command without a subcommand, or with an invalid subcommand,
		// cobra will print usage information, but still exit cleanly.
		// We want to return an error code in these cases so that the
		// user knows that their command was invalid.
		RunE: cmdutil.SubCmdRunE("token"),
	}

	options.AddKubeConfigFlag(tokenCmd.PersistentFlags(), &kubeConfigFile)
	tokenCmd.PersistentFlags().BoolVar(&dryRun,
		options.DryRun, dryRun, "Whether to enable dry-run mode or not")

	cfg := &kubeadmapiv1beta2.InitConfiguration{}

	// Default values for the cobra help text
	kubeadmscheme.Scheme.Default(cfg)

	var cfgPath string
	var printJoinCommand bool
	bto := options.NewBootstrapTokenOptions()

	createCmd := &cobra.Command{
		Use:                   "create [token]",
		DisableFlagsInUseLine: true,
		Short:                 "Create bootstrap tokens on the server",
		Long: dedent.Dedent(`
			This command will create a bootstrap token for you.
			You can specify the usages for this token, the "time to live" and an optional human friendly description.

			The [token] is the actual token to write.
			This should be a securely generated random token of the form "[a-z0-9]{6}.[a-z0-9]{16}".
			If no [token] is given, kubeadm will generate a random token instead.
		`),
		Run: func(tokenCmd *cobra.Command, args []string) {
			if len(args) > 0 {
				bto.TokenStr = args[0]
			}
			klog.V(1).Infoln("[token] validating mixed arguments")
			err := validation.ValidateMixedArguments(tokenCmd.Flags())
			kubeadmutil.CheckErr(err)

			err = bto.ApplyTo(cfg)
			kubeadmutil.CheckErr(err)

			klog.V(1).Infoln("[token] getting Clientsets from kubeconfig file")
			kubeConfigFile = cmdutil.GetKubeConfigPath(kubeConfigFile)
			client, err := getClientset(kubeConfigFile, dryRun)
			kubeadmutil.CheckErr(err)

			err = RunCreateToken(out, client, cfgPath, cfg, printJoinCommand, kubeConfigFile)
			kubeadmutil.CheckErr(err)
		},
	}

	options.AddConfigFlag(createCmd.Flags(), &cfgPath)
	createCmd.Flags().BoolVar(&printJoinCommand,
		"print-join-command", false, "Instead of printing only the token, print the full 'kubeadm join' flag needed to join the cluster using the token.")
	bto.AddTTLFlagWithName(createCmd.Flags(), "ttl")
	bto.AddUsagesFlag(createCmd.Flags())
	bto.AddGroupsFlag(createCmd.Flags())
	bto.AddDescriptionFlag(createCmd.Flags())

	tokenCmd.AddCommand(createCmd)
	tokenCmd.AddCommand(NewCmdTokenGenerate(out))

	listCmd := &cobra.Command{
		Use:   "list",
		Short: "List bootstrap tokens on the server",
		Long: dedent.Dedent(`
			This command will list all bootstrap tokens for you.
		`),
		Run: func(tokenCmd *cobra.Command, args []string) {
			kubeConfigFile = cmdutil.GetKubeConfigPath(kubeConfigFile)
			client, err := getClientset(kubeConfigFile, dryRun)
			kubeadmutil.CheckErr(err)

			err = RunListTokens(out, errW, client)
			kubeadmutil.CheckErr(err)
		},
	}
	tokenCmd.AddCommand(listCmd)

	deleteCmd := &cobra.Command{
		Use:                   "delete [token-value] ...",
		DisableFlagsInUseLine: true,
		Short:                 "Delete bootstrap tokens on the server",
		Long: dedent.Dedent(`
			This command will delete a list of bootstrap tokens for you.

			The [token-value] is the full Token of the form "[a-z0-9]{6}.[a-z0-9]{16}" or the
			Token ID of the form "[a-z0-9]{6}" to delete.
		`),
		Run: func(tokenCmd *cobra.Command, args []string) {
			if len(args) < 1 {
				kubeadmutil.CheckErr(errors.Errorf("missing subcommand; 'token delete' is missing token of form %q", bootstrapapi.BootstrapTokenIDPattern))
			}
			kubeConfigFile = cmdutil.GetKubeConfigPath(kubeConfigFile)
			client, err := getClientset(kubeConfigFile, dryRun)
			kubeadmutil.CheckErr(err)

			err = RunDeleteTokens(out, client, args)
			kubeadmutil.CheckErr(err)
		},
	}
	tokenCmd.AddCommand(deleteCmd)

	return tokenCmd
}

// NewCmdTokenGenerate returns cobra.Command to generate new token
func NewCmdTokenGenerate(out io.Writer) *cobra.Command {
	return &cobra.Command{
		Use:   "generate",
		Short: "Generate and print a bootstrap token, but do not create it on the server",
		Long: dedent.Dedent(`
			This command will print out a randomly-generated bootstrap token that can be used with
			the "init" and "join" commands.

			You don't have to use this command in order to generate a token. You can do so
			yourself as long as it is in the format "[a-z0-9]{6}.[a-z0-9]{16}". This
			command is provided for convenience to generate tokens in the given format.

			You can also use "kubeadm init" without specifying a token and it will
			generate and print one for you.
		`),
		Run: func(cmd *cobra.Command, args []string) {
			err := RunGenerateToken(out)
			kubeadmutil.CheckErr(err)
		},
	}
}

// RunCreateToken generates a new bootstrap token and stores it as a secret on the server.
func RunCreateToken(out io.Writer, client clientset.Interface, cfgPath string, initCfg *kubeadmapiv1beta2.InitConfiguration, printJoinCommand bool, kubeConfigFile string) error {
	// ClusterConfiguration is needed just for the call to LoadOrDefaultInitConfiguration
	clusterCfg := &kubeadmapiv1beta2.ClusterConfiguration{
		// KubernetesVersion is not used, but we set this explicitly to avoid
		// the lookup of the version from the internet when executing LoadOrDefaultInitConfiguration
		KubernetesVersion: kubeadmconstants.CurrentKubernetesVersion.String(),
	}
	kubeadmscheme.Scheme.Default(clusterCfg)

	// This call returns the ready-to-use configuration based on the configuration file that might or might not exist and the default cfg populated by flags
	klog.V(1).Infoln("[token] loading configurations")

	// In fact, we don't do any CRI ops at all.
	// This is just to force skipping the CRI detection.
	// Ref: https://github.com/kubernetes/kubeadm/issues/1559
	initCfg.NodeRegistration.CRISocket = kubeadmconstants.DefaultDockerCRISocket

	internalcfg, err := configutil.LoadOrDefaultInitConfiguration(cfgPath, initCfg, clusterCfg)
	if err != nil {
		return err
	}

	klog.V(1).Infoln("[token] creating token")
	if err := tokenphase.CreateNewTokens(client, internalcfg.BootstrapTokens); err != nil {
		return err
	}

	// if --print-join-command was specified, print a machine-readable full `kubeadm join` command
	// otherwise, just print the token
	if printJoinCommand {
		skipTokenPrint := false
		joinCommand, err := cmdutil.GetJoinWorkerCommand(kubeConfigFile, internalcfg.BootstrapTokens[0].Token.String(), skipTokenPrint)
		if err != nil {
			return errors.Wrap(err, "failed to get join command")
		}
		joinCommand = strings.ReplaceAll(joinCommand, "\\\n", "")
		joinCommand = strings.ReplaceAll(joinCommand, "\t", "")
		fmt.Fprintln(out, joinCommand)
	} else {
		fmt.Fprintln(out, internalcfg.BootstrapTokens[0].Token.String())
	}

	return nil
}

// RunGenerateToken just generates a random token for the user
func RunGenerateToken(out io.Writer) error {
	klog.V(1).Infoln("[token] generating random token")
	token, err := bootstraputil.GenerateBootstrapToken()
	if err != nil {
		return err
	}

	fmt.Fprintln(out, token)
	return nil
}

// RunListTokens lists details on all existing bootstrap tokens on the server.
func RunListTokens(out io.Writer, errW io.Writer, client clientset.Interface) error {
	// First, build our selector for bootstrap tokens only
	klog.V(1).Infoln("[token] preparing selector for bootstrap token")
	tokenSelector := fields.SelectorFromSet(
		map[string]string{
			// TODO: We hard-code "type" here until `field_constants.go` that is
			// currently in `pkg/apis/core/` exists in the external API, i.e.
			// k8s.io/api/v1. Should be v1.SecretTypeField
			"type": string(bootstrapapi.SecretTypeBootstrapToken),
		},
	)
	listOptions := metav1.ListOptions{
		FieldSelector: tokenSelector.String(),
	}

	klog.V(1).Infoln("[token] retrieving list of bootstrap tokens")
	secrets, err := client.CoreV1().Secrets(metav1.NamespaceSystem).List(listOptions)
	if err != nil {
		return errors.Wrap(err, "failed to list bootstrap tokens")
	}

	w := tabwriter.NewWriter(out, 10, 4, 3, ' ', 0)
	fmt.Fprintln(w, "TOKEN\tTTL\tEXPIRES\tUSAGES\tDESCRIPTION\tEXTRA GROUPS")
	for _, secret := range secrets.Items {

		// Get the BootstrapToken struct representation from the Secret object
		token, err := kubeadmapi.BootstrapTokenFromSecret(&secret)
		if err != nil {
			fmt.Fprintf(errW, "%v", err)
			continue
		}

		// Get the human-friendly string representation for the token
		humanFriendlyTokenOutput := humanReadableBootstrapToken(token)
		fmt.Fprintln(w, humanFriendlyTokenOutput)
	}
	w.Flush()
	return nil
}

// RunDeleteTokens removes a bootstrap tokens from the server.
func RunDeleteTokens(out io.Writer, client clientset.Interface, tokenIDsOrTokens []string) error {
	for _, tokenIDOrToken := range tokenIDsOrTokens {
		// Assume this is a token id and try to parse it
		tokenID := tokenIDOrToken
		klog.V(1).Infof("[token] parsing token %q", tokenIDOrToken)
		if !bootstraputil.IsValidBootstrapTokenID(tokenIDOrToken) {
			// Okay, the full token with both id and secret was probably passed. Parse it and extract the ID only
			bts, err := kubeadmapiv1beta2.NewBootstrapTokenString(tokenIDOrToken)
			if err != nil {
				return errors.Errorf("given token %q didn't match pattern %q or %q",
					tokenIDOrToken, bootstrapapi.BootstrapTokenIDPattern, bootstrapapi.BootstrapTokenIDPattern)
			}
			tokenID = bts.ID
		}

		tokenSecretName := bootstraputil.BootstrapTokenSecretName(tokenID)
		klog.V(1).Infof("[token] deleting token %q", tokenID)
		if err := client.CoreV1().Secrets(metav1.NamespaceSystem).Delete(tokenSecretName, nil); err != nil {
			return errors.Wrapf(err, "failed to delete bootstrap token %q", tokenID)
		}
		fmt.Fprintf(out, "bootstrap token %q deleted\n", tokenID)
	}
	return nil
}

func humanReadableBootstrapToken(token *kubeadmapi.BootstrapToken) string {
	description := token.Description
	if len(description) == 0 {
		description = "<none>"
	}

	ttl := "<forever>"
	expires := "<never>"
	if token.Expires != nil {
		ttl = duration.ShortHumanDuration(token.Expires.Sub(time.Now()))
		expires = token.Expires.Format(time.RFC3339)
	}

	usagesString := strings.Join(token.Usages, ",")
	if len(usagesString) == 0 {
		usagesString = "<none>"
	}

	groupsString := strings.Join(token.Groups, ",")
	if len(groupsString) == 0 {
		groupsString = "<none>"
	}

	return fmt.Sprintf("%s\t%s\t%s\t%s\t%s\t%s", token.Token.String(), ttl, expires, usagesString, description, groupsString)
}

func getClientset(file string, dryRun bool) (clientset.Interface, error) {
	if dryRun {
		dryRunGetter, err := apiclient.NewClientBackedDryRunGetterFromKubeconfig(file)
		if err != nil {
			return nil, err
		}
		return apiclient.NewDryRunClient(dryRunGetter, os.Stdout), nil
	}
	return kubeconfigutil.ClientSetFromFile(file)
}
