/*
Copyright 2021 The Karmada 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 cordon

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"

	"github.com/spf13/cobra"
	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/strategicpatch"
	"k8s.io/kubectl/pkg/util/templates"

	clusterv1alpha1 "github.com/karmada-io/karmada/pkg/apis/cluster/v1alpha1"
	karmadaclientset "github.com/karmada-io/karmada/pkg/generated/clientset/versioned"
	"github.com/karmada-io/karmada/pkg/karmadactl/options"
	"github.com/karmada-io/karmada/pkg/karmadactl/util"
	utilcomp "github.com/karmada-io/karmada/pkg/karmadactl/util/completion"
)

var (
	cordonLong = templates.LongDesc(`
		Mark cluster as unschedulable.`)

	uncordonLong = templates.LongDesc(`
		Mark cluster as schedulable.`)

	cordonExample = templates.Examples(`
		# Mark cluster "foo" as unschedulable.
		%[1]s cordon foo`)
	uncordonExample = templates.Examples(`
		# Mark cluster "foo" as schedulable.
		%[1]s uncordon foo`)
)

const (
	// DesiredCordon a flag indicate karmadactl.RunCordonOrUncordon cordon a cluster,
	// cordon prevent new resource scheduler to cordoned cluster.
	DesiredCordon = iota
	// DesiredUnCordon a flag indicate karmadactl.RunCordonOrUncordon uncordon a cluster.
	DesiredUnCordon
)

// NewCmdCordon defines the `cordon` command that mark cluster as unschedulable.
func NewCmdCordon(f util.Factory, parentCommand string) *cobra.Command {
	opts := CommandCordonOption{}

	cmd := &cobra.Command{
		Use:                   "cordon CLUSTER",
		Short:                 "Mark cluster as unschedulable",
		Long:                  cordonLong,
		Example:               fmt.Sprintf(cordonExample, parentCommand),
		SilenceUsage:          true,
		DisableFlagsInUseLine: true,
		ValidArgsFunction:     utilcomp.SpecifiedResourceTypeAndNameCompletionFunc(f, []string{"cluster"}),
		RunE: func(_ *cobra.Command, args []string) error {
			if err := opts.Complete(args); err != nil {
				return err
			}
			if err := RunCordonOrUncordon(DesiredCordon, f, opts); err != nil {
				return err
			}
			return nil
		},
		Annotations: map[string]string{
			util.TagCommandGroup: util.GroupClusterManagement,
		},
	}

	flags := cmd.Flags()
	options.AddKubeConfigFlags(flags)
	flags.BoolVar(&opts.DryRun, "dry-run", false, "Run the command in dry-run mode, without making any server requests.")

	utilcomp.RegisterCompletionFuncForKarmadaContextFlag(cmd)
	return cmd
}

// NewCmdUncordon defines the `uncordon` command that mark cluster as schedulable.
func NewCmdUncordon(f util.Factory, parentCommand string) *cobra.Command {
	opts := CommandCordonOption{}

	cmd := &cobra.Command{
		Use:                   "uncordon CLUSTER",
		Short:                 "Mark cluster as schedulable",
		Long:                  uncordonLong,
		Example:               fmt.Sprintf(uncordonExample, parentCommand),
		SilenceUsage:          true,
		DisableFlagsInUseLine: true,
		ValidArgsFunction:     utilcomp.SpecifiedResourceTypeAndNameCompletionFunc(f, []string{"cluster"}),
		RunE: func(_ *cobra.Command, args []string) error {
			if err := opts.Complete(args); err != nil {
				return err
			}
			if err := RunCordonOrUncordon(DesiredUnCordon, f, opts); err != nil {
				return err
			}
			return nil
		},
		Annotations: map[string]string{
			util.TagCommandGroup: util.GroupClusterManagement,
		},
	}

	flags := cmd.Flags()
	options.AddKubeConfigFlags(flags)
	flags.BoolVar(&opts.DryRun, "dry-run", false, "Run the command in dry-run mode, without making any server requests.")

	utilcomp.RegisterCompletionFuncForKarmadaContextFlag(cmd)
	return cmd
}

// CommandCordonOption holds all command options for cordon and uncordon
type CommandCordonOption struct {
	// ClusterName is the cluster's name that we are going to join with.
	ClusterName string

	// DryRun tells if run the command in dry-run mode, without making any server requests.
	DryRun bool
}

// Complete ensures that options are valid and marshals them if necessary.
func (o *CommandCordonOption) Complete(args []string) error {
	// Get cluster name from the command args.
	if len(args) == 0 {
		return errors.New("cluster name is required")
	}
	if len(args) > 1 {
		return errors.New("more than one cluster name is not supported")
	}
	o.ClusterName = args[0]
	return nil
}

// RunCordonOrUncordon exec marks the cluster unschedulable or schedulable according to desired.
// if true cordon cluster otherwise uncordon cluster.
func RunCordonOrUncordon(desired int, f util.Factory, opts CommandCordonOption) error {
	cordonOrUncordon := "cordon"
	if desired == DesiredUnCordon {
		cordonOrUncordon = "un" + cordonOrUncordon
	}

	karmadaClient, err := f.KarmadaClientSet()
	if err != nil {
		return err
	}

	cluster, err := karmadaClient.ClusterV1alpha1().Clusters().Get(context.TODO(), opts.ClusterName, metav1.GetOptions{})
	if err != nil {
		return err
	}

	cordonHelper := newCordonHelper(cluster)
	if !cordonHelper.updateIfRequired(desired) {
		fmt.Printf("%s cluster %s\n", cluster.Name, alreadyStr(desired))
		return nil
	}

	if !opts.DryRun {
		err := cordonHelper.patchOrReplace(karmadaClient)
		if err != nil {
			return err
		}
	}

	fmt.Printf("%s cluster %sed\n", cluster.Name, cordonOrUncordon)
	return nil
}

// cordonHelper wraps functionality to cordon/uncordon cluster
type cordonHelper struct {
	cluster *clusterv1alpha1.Cluster
	desired int
}

// newCordonHelper returns a new CordonHelper that help execute
// the cordon and uncordon commands
func newCordonHelper(cluster *clusterv1alpha1.Cluster) *cordonHelper {
	return &cordonHelper{
		cluster: cluster,
	}
}

// updateIfRequired returns true if unscheduler taint isn't already set,
// or false when no change is needed
func (c *cordonHelper) updateIfRequired(desired int) bool {
	c.desired = desired

	if desired == DesiredCordon && !c.hasUnschedulerTaint() {
		return true
	}

	if desired == DesiredUnCordon && c.hasUnschedulerTaint() {
		return true
	}

	return false
}

func (c *cordonHelper) hasUnschedulerTaint() bool {
	unschedulerTaint := corev1.Taint{
		Key:    clusterv1alpha1.TaintClusterUnscheduler,
		Effect: corev1.TaintEffectNoSchedule,
	}

	for _, taint := range c.cluster.Spec.Taints {
		if taint.MatchTaint(&unschedulerTaint) {
			return true
		}
	}

	return false
}

// patchOrReplace uses given karmada clientset to update the cluster unschedulable scheduler, either by patching or
// updating the given cluster object; it may return error if the object cannot be encoded as
// JSON, or if either patch or update calls fail; it will also return error whenever creating a patch has failed
func (c *cordonHelper) patchOrReplace(karmadaClient karmadaclientset.Interface) error {
	client := karmadaClient.ClusterV1alpha1().Clusters()
	oldData, err := json.Marshal(c.cluster)
	if err != nil {
		return err
	}

	unschedulerTaint := corev1.Taint{
		Key:    clusterv1alpha1.TaintClusterUnscheduler,
		Effect: corev1.TaintEffectNoSchedule,
	}

	if c.desired == DesiredCordon {
		c.cluster.Spec.Taints = append(c.cluster.Spec.Taints, unschedulerTaint)
	}

	if c.desired == DesiredUnCordon {
		for i, n := 0, len(c.cluster.Spec.Taints); i < n; i++ {
			if c.cluster.Spec.Taints[i].MatchTaint(&unschedulerTaint) {
				c.cluster.Spec.Taints[i] = c.cluster.Spec.Taints[n-1]
				c.cluster.Spec.Taints = c.cluster.Spec.Taints[:n-1]
				break
			}
		}
	}

	newData, err := json.Marshal(c.cluster)
	if err != nil {
		return err
	}

	patchBytes, err := strategicpatch.CreateTwoWayMergePatch(oldData, newData, c.cluster)
	if err == nil {
		_, err = client.Patch(context.TODO(), c.cluster.Name, types.MergePatchType, patchBytes, metav1.PatchOptions{})
	} else {
		_, err = client.Update(context.TODO(), c.cluster, metav1.UpdateOptions{})
	}
	return err
}

func alreadyStr(desired int) string {
	if desired == DesiredCordon {
		return "already cordoned"
	}
	return "already uncordoned"
}