/*
Copyright 2017 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 upgrade

import (
	"context"
	"fmt"
	"os"
	"time"

	"github.com/pkg/errors"

	batchv1 "k8s.io/api/batch/v1"
	v1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/apimachinery/pkg/util/wait"
	clientset "k8s.io/client-go/kubernetes"
	"k8s.io/klog/v2"
	"k8s.io/utils/ptr"

	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
	"k8s.io/kubernetes/cmd/kubeadm/app/images"
	"k8s.io/kubernetes/cmd/kubeadm/app/preflight"
	"k8s.io/kubernetes/cmd/kubeadm/app/util/output"
)

// healthCheck is a helper struct for easily performing healthchecks against the cluster and printing the output
type healthCheck struct {
	name   string
	client clientset.Interface
	cfg    *kubeadmapi.ClusterConfiguration
	// f is invoked with a k8s client and a kubeadm ClusterConfiguration passed to it. Should return an optional error
	f func(clientset.Interface, *kubeadmapi.ClusterConfiguration) error
}

// Check is part of the preflight.Checker interface
func (c *healthCheck) Check() (warnings, errors []error) {
	if err := c.f(c.client, c.cfg); err != nil {
		return nil, []error{err}
	}
	return nil, nil
}

// Name is part of the preflight.Checker interface
func (c *healthCheck) Name() string {
	return c.name
}

// CheckClusterHealth makes sure:
// - the cluster can accept a workload
// - all control-plane Nodes are Ready
// - (if static pod-hosted) that all required Static Pod manifests exist on disk
func CheckClusterHealth(client clientset.Interface, cfg *kubeadmapi.ClusterConfiguration, ignoreChecksErrors sets.Set[string], printer output.Printer) error {
	_, _ = printer.Println("[upgrade] Running cluster health checks")

	healthChecks := []preflight.Checker{
		&healthCheck{
			name:   "CreateJob",
			client: client,
			cfg:    cfg,
			f:      createJob,
		},
		&healthCheck{
			name:   "ControlPlaneNodesReady",
			client: client,
			f:      controlPlaneNodesReady,
		},
		&healthCheck{
			name: "StaticPodManifest",
			f:    staticPodManifestHealth,
		},
	}

	return preflight.RunChecks(healthChecks, os.Stderr, ignoreChecksErrors)
}

// createJob is a check that verifies that a Job can be created in the cluster
func createJob(client clientset.Interface, cfg *kubeadmapi.ClusterConfiguration) error {
	const (
		prefix        = "upgrade-health-check"
		fieldSelector = "spec.unschedulable=false"
		ns            = metav1.NamespaceSystem
		timeout       = 15 * time.Second
	)
	var (
		err, lastError error
		ctx            = context.Background()
		nodes          *v1.NodeList
		listOptions    = metav1.ListOptions{Limit: 1, FieldSelector: fieldSelector}
	)

	// If client.Discovery().RESTClient() is nil, the fake client is used.
	// Return early because the kubeadm dryrun dynamic client only handles the core/v1 GroupVersion.
	if client.Discovery().RESTClient() == nil {
		fmt.Printf("[upgrade/health] Would create the Job with the prefix %q in namespace %q and wait until it completes\n", prefix, ns)
		return nil
	}

	// Check if there is at least one Node where a Job's Pod can schedule. If not, skip this preflight check.
	err = wait.PollUntilContextTimeout(ctx, time.Second*1, timeout, true, func(_ context.Context) (bool, error) {
		nodes, err = client.CoreV1().Nodes().List(context.Background(), listOptions)
		if err != nil {
			klog.V(2).Infof("Could not list Nodes with field selector %q: %v", fieldSelector, err)
			lastError = err
			return false, nil
		}
		return true, nil
	})
	if err != nil {
		return errors.Wrap(lastError, "could not check if there is at least one Node that can schedule a test Pod")
	}

	if len(nodes.Items) == 0 {
		klog.Warning("The preflight check \"CreateJob\" was skipped because there are no schedulable Nodes in the cluster.")
		return nil
	}

	// Prepare Job
	job := &batchv1.Job{
		ObjectMeta: metav1.ObjectMeta{
			GenerateName: prefix + "-",
			Namespace:    ns,
		},
		Spec: batchv1.JobSpec{
			BackoffLimit:            ptr.To[int32](0),
			TTLSecondsAfterFinished: ptr.To[int32](int32(timeout.Seconds()) + 5), // Make sure it's more than 'timeout'.
			Template: v1.PodTemplateSpec{
				Spec: v1.PodSpec{
					RestartPolicy: v1.RestartPolicyNever,
					SecurityContext: &v1.PodSecurityContext{
						RunAsUser:    ptr.To[int64](999),
						RunAsGroup:   ptr.To[int64](999),
						RunAsNonRoot: ptr.To(true),
					},
					Tolerations: []v1.Toleration{
						{
							Key:    constants.LabelNodeRoleControlPlane,
							Effect: v1.TaintEffectNoSchedule,
						},
					},
					Containers: []v1.Container{
						{
							Name:  prefix,
							Image: images.GetPauseImage(cfg),
							Args:  []string{"-v"},
						},
					},
				},
			},
		},
	}

	// Create the Job, but retry if it fails
	klog.V(2).Infof("Creating a Job with the prefix %q in the namespace %q", prefix, ns)
	var jobName string
	err = wait.PollUntilContextTimeout(ctx, time.Second*1, timeout, true, func(_ context.Context) (bool, error) {
		createdJob, err := client.BatchV1().Jobs(ns).Create(context.Background(), job, metav1.CreateOptions{})
		if err != nil {
			klog.V(2).Infof("Could not create a Job with the prefix %q in the namespace %q, retrying: %v", prefix, ns, err)
			lastError = err
			return false, nil
		}

		jobName = createdJob.Name
		return true, nil
	})
	if err != nil {
		return errors.Wrapf(lastError, "could not create a Job with the prefix %q in the namespace %q", prefix, ns)
	}

	// Wait for the Job to complete
	err = wait.PollUntilContextTimeout(ctx, time.Second*1, timeout, true, func(_ context.Context) (bool, error) {
		job, err := client.BatchV1().Jobs(ns).Get(context.Background(), jobName, metav1.GetOptions{})
		if err != nil {
			lastError = err
			klog.V(2).Infof("could not get Job %q in the namespace %q, retrying: %v", jobName, ns, err)
			return false, nil
		}
		for _, cond := range job.Status.Conditions {
			if cond.Type == batchv1.JobComplete {
				return true, nil
			}
		}
		lastError = errors.Errorf("no condition of type %v", batchv1.JobComplete)
		klog.V(2).Infof("Job %q in the namespace %q is not yet complete, retrying", jobName, ns)
		return false, nil
	})
	if err != nil {
		return errors.Wrapf(lastError, "Job %q in the namespace %q did not complete in %v", jobName, ns, timeout)
	}

	klog.V(2).Infof("Job %q in the namespace %q completed", jobName, ns)

	return nil
}

// controlPlaneNodesReady checks whether all control-plane Nodes in the cluster are in the Running state
func controlPlaneNodesReady(client clientset.Interface, _ *kubeadmapi.ClusterConfiguration) error {
	selectorControlPlane := labels.SelectorFromSet(map[string]string{
		constants.LabelNodeRoleControlPlane: "",
	})
	nodes, err := client.CoreV1().Nodes().List(context.Background(), metav1.ListOptions{
		LabelSelector: selectorControlPlane.String(),
	})
	if err != nil {
		return errors.Wrapf(err, "could not list nodes labeled with %q", constants.LabelNodeRoleControlPlane)
	}

	notReadyControlPlanes := getNotReadyNodes(nodes.Items)
	if len(notReadyControlPlanes) != 0 {
		return errors.Errorf("there are NotReady control-planes in the cluster: %v", notReadyControlPlanes)
	}
	return nil
}

// staticPodManifestHealth makes sure the required static pods are presents
func staticPodManifestHealth(_ clientset.Interface, _ *kubeadmapi.ClusterConfiguration) error {
	var nonExistentManifests []string
	for _, component := range constants.ControlPlaneComponents {
		manifestFile := constants.GetStaticPodFilepath(component, constants.GetStaticPodDirectory())
		if _, err := os.Stat(manifestFile); os.IsNotExist(err) {
			nonExistentManifests = append(nonExistentManifests, manifestFile)
		}
	}
	if len(nonExistentManifests) == 0 {
		return nil
	}
	return errors.Errorf("The control plane seems to be Static Pod-hosted, but some of the manifests don't seem to exist on disk. This probably means you're running 'kubeadm upgrade' on a remote machine, which is not supported for a Static Pod-hosted cluster. Manifest files not found: %v", nonExistentManifests)
}

// getNotReadyNodes returns a string slice of nodes in the cluster that are NotReady
func getNotReadyNodes(nodes []v1.Node) []string {
	var notReadyNodes []string
	for _, node := range nodes {
		for _, condition := range node.Status.Conditions {
			if condition.Type == v1.NodeReady && condition.Status != v1.ConditionTrue {
				notReadyNodes = append(notReadyNodes, node.ObjectMeta.Name)
			}
		}
	}
	return notReadyNodes
}