// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

package kubernetes

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"strings"
	"text/tabwriter"
	"time"

	"github.com/cosi-project/runtime/pkg/resource"
	"github.com/cosi-project/runtime/pkg/state"
	"github.com/talos-systems/go-retry/retry"
	v1 "k8s.io/api/core/v1"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/client-go/discovery"
	"k8s.io/client-go/dynamic"
	"k8s.io/client-go/rest"

	"github.com/talos-systems/talos/pkg/cluster"
	"github.com/talos-systems/talos/pkg/kubernetes"
	"github.com/talos-systems/talos/pkg/machinery/client"
	v1alpha1config "github.com/talos-systems/talos/pkg/machinery/config/types/v1alpha1"
	machinetype "github.com/talos-systems/talos/pkg/machinery/config/types/v1alpha1/machine"
	"github.com/talos-systems/talos/pkg/machinery/constants"
	"github.com/talos-systems/talos/pkg/resources/config"
)

// UpgradeProvider are the cluster interfaces required by upgrade process.
type UpgradeProvider interface {
	cluster.ClientProvider
	cluster.K8sProvider
}

var deprecations = map[string][]string{
	// https://kubernetes.io/blog/2021/07/14/upcoming-changes-in-kubernetes-1-22/#api-changes
	"1.21->1.22": {
		"validatingwebhookconfigurations.v1beta1.admissionregistration.k8s.io",
		"mutatingwebhookconfigurations.v1beta1.admissionregistration.k8s.io",
		"customresourcedefinitions.v1beta1.apiextensions.k8s.io",
		"apiservices.v1beta1.apiregistration.k8s.io",
		"leases.v1beta1.coordination.k8s.io",
		"ingresses.v1beta1.extensions",
		"ingresses.v1beta1.networking.k8s.io",
	},
}

// UpgradeTalosManaged the Kubernetes control plane.
//
//nolint:gocyclo
func UpgradeTalosManaged(ctx context.Context, cluster UpgradeProvider, options UpgradeOptions) error {
	switch path := options.Path(); path {
	// nothing for all those
	case "1.19->1.19":
	case "1.19->1.20":
	case "1.20->1.20":
	case "1.20->1.21":
	case "1.21->1.21":
	case "1.21->1.22":
	case "1.22->1.22":

	default:
		return fmt.Errorf("unsupported upgrade path %q (from %q to %q)", path, options.FromVersion, options.ToVersion)
	}

	if err := checkDeprecated(ctx, cluster, options); err != nil {
		return err
	}

	k8sClient, err := cluster.K8sHelper(ctx)
	if err != nil {
		return fmt.Errorf("error building kubernetes client: %w", err)
	}

	options.masterNodes, err = k8sClient.NodeIPs(ctx, machinetype.TypeControlPlane)
	if err != nil {
		return fmt.Errorf("error fetching master nodes: %w", err)
	}

	if len(options.masterNodes) == 0 {
		return fmt.Errorf("no master nodes discovered")
	}

	options.Log("discovered master nodes %q", options.masterNodes)

	for _, service := range []string{kubeAPIServer, kubeControllerManager, kubeScheduler} {
		if err = upgradeConfigPatch(ctx, cluster, options, service); err != nil {
			return fmt.Errorf("failed updating service %q: %w", service, err)
		}
	}

	if err = upgradeDaemonset(ctx, k8sClient.Clientset, kubeProxy, options); err != nil {
		if apierrors.IsNotFound(err) {
			options.Log("kube-proxy skipped as DaemonSet was not found")
		} else {
			return fmt.Errorf("error updating kube-proxy: %w", err)
		}
	}

	return nil
}

func upgradeConfigPatch(ctx context.Context, cluster UpgradeProvider, options UpgradeOptions, service string) error {
	options.Log("updating %q to version %q", service, options.ToVersion)

	for _, node := range options.masterNodes {
		if err := upgradeNodeConfigPatch(ctx, cluster, options, service, node); err != nil {
			return fmt.Errorf("error updating node %q: %w", node, err)
		}
	}

	return nil
}

//nolint:gocyclo
func upgradeNodeConfigPatch(ctx context.Context, cluster UpgradeProvider, options UpgradeOptions, service, node string) error {
	ctx, cancel := context.WithCancel(ctx)
	defer cancel()

	c, err := cluster.Client()
	if err != nil {
		return fmt.Errorf("error building Talos API client: %w", err)
	}

	ctx = client.WithNodes(ctx, node)

	options.Log(" > %q: starting update", node)

	watchClient, err := c.Resources.Watch(ctx, config.NamespaceName, config.K8sControlPlaneType, service)
	if err != nil {
		return fmt.Errorf("error watching service configuration: %w", err)
	}

	// first response is resource definition
	_, err = watchClient.Recv()
	if err != nil {
		return fmt.Errorf("error watching config: %w", err)
	}

	// second is the initial state
	watchInitial, err := watchClient.Recv()
	if err != nil {
		return fmt.Errorf("error watching config: %w", err)
	}

	if watchInitial.EventType != state.Created {
		return fmt.Errorf("unexpected event type: %d", watchInitial.EventType)
	}

	skipConfigWait := false

	err = patchNodeConfig(ctx, cluster, node, upgradeConfigPatcher(options, service, watchInitial.Resource))
	if err != nil {
		if errors.Is(err, errUpdateSkipped) {
			skipConfigWait = true
		} else {
			return fmt.Errorf("error patching node config: %w", err)
		}
	}

	if options.DryRun {
		return nil
	}

	options.Log(" > %q: machine configuration patched", node)
	options.Log(" > %q: waiting for API server state pod update", node)

	var expectedConfigVersion string

	if !skipConfigWait {
		var watchUpdated client.WatchResponse

		watchUpdated, err = watchClient.Recv()
		if err != nil {
			return fmt.Errorf("error watching config: %w", err)
		}

		if watchUpdated.EventType != state.Updated {
			return fmt.Errorf("unexpected event type: %d", watchInitial.EventType)
		}

		expectedConfigVersion = watchUpdated.Resource.Metadata().Version().String()
	} else {
		expectedConfigVersion = watchInitial.Resource.Metadata().Version().String()
	}

	if err = retry.Constant(3*time.Minute, retry.WithUnits(10*time.Second)).Retry(func() error {
		return checkPodStatus(ctx, cluster, service, node, expectedConfigVersion)
	}); err != nil {
		return err
	}

	options.Log(" < %q: successfully updated", node)

	return nil
}

var errUpdateSkipped = fmt.Errorf("update skipped")

//nolint:gocyclo,cyclop
func upgradeConfigPatcher(options UpgradeOptions, service string, configResource resource.Resource) func(config *v1alpha1config.Config) error {
	return func(config *v1alpha1config.Config) error {
		if config.ClusterConfig == nil {
			config.ClusterConfig = &v1alpha1config.ClusterConfig{}
		}

		configData := configResource.(*resource.Any).Value().(map[string]interface{}) //nolint:errcheck,forcetypeassert
		configImage := configData["image"].(string)                                   //nolint:errcheck,forcetypeassert

		logUpdate := func(oldImage string) {
			parts := strings.Split(oldImage, ":")
			version := options.FromVersion

			if oldImage == "" {
				version = options.FromVersion
			}

			if len(parts) > 1 {
				version = parts[1]
			}

			options.Log(" > update %s: %s -> %s", service, version, options.ToVersion)

			if options.DryRun {
				options.Log(" > skipped in dry-run")
			}
		}

		switch service {
		case kubeAPIServer:
			if config.ClusterConfig.APIServerConfig == nil {
				config.ClusterConfig.APIServerConfig = &v1alpha1config.APIServerConfig{}
			}

			image := fmt.Sprintf("%s:v%s", constants.KubernetesAPIServerImage, options.ToVersion)

			if config.ClusterConfig.APIServerConfig.ContainerImage == image || configImage == image {
				return errUpdateSkipped
			}

			logUpdate(config.ClusterConfig.APIServerConfig.ContainerImage)

			if options.DryRun {
				return errUpdateSkipped
			}

			config.ClusterConfig.APIServerConfig.ContainerImage = image
		case kubeControllerManager:
			if config.ClusterConfig.ControllerManagerConfig == nil {
				config.ClusterConfig.ControllerManagerConfig = &v1alpha1config.ControllerManagerConfig{}
			}

			image := fmt.Sprintf("%s:v%s", constants.KubernetesControllerManagerImage, options.ToVersion)

			if config.ClusterConfig.ControllerManagerConfig.ContainerImage == image || configImage == image {
				return errUpdateSkipped
			}

			logUpdate(config.ClusterConfig.ControllerManagerConfig.ContainerImage)

			if options.DryRun {
				return errUpdateSkipped
			}

			config.ClusterConfig.ControllerManagerConfig.ContainerImage = image
		case kubeScheduler:
			if config.ClusterConfig.SchedulerConfig == nil {
				config.ClusterConfig.SchedulerConfig = &v1alpha1config.SchedulerConfig{}
			}

			image := fmt.Sprintf("%s:v%s", constants.KubernetesSchedulerImage, options.ToVersion)

			if config.ClusterConfig.SchedulerConfig.ContainerImage == image || configImage == image {
				return errUpdateSkipped
			}

			logUpdate(config.ClusterConfig.SchedulerConfig.ContainerImage)

			if options.DryRun {
				return errUpdateSkipped
			}

			config.ClusterConfig.SchedulerConfig.ContainerImage = image
		default:
			return fmt.Errorf("unsupported service %q", service)
		}

		return nil
	}
}

//nolint:gocyclo
func checkPodStatus(ctx context.Context, cluster UpgradeProvider, service, node, configVersion string) error {
	k8sClient, err := cluster.K8sHelper(ctx)
	if err != nil {
		return fmt.Errorf("error building kubernetes client: %w", err)
	}

	pods, err := k8sClient.CoreV1().Pods(namespace).List(ctx, metav1.ListOptions{
		LabelSelector: fmt.Sprintf("k8s-app = %s", service),
	})
	if err != nil {
		if kubernetes.IsRetryableError(err) {
			return retry.ExpectedError(err)
		}

		return err
	}

	podFound := false

	for _, pod := range pods.Items {
		if pod.Status.HostIP != node {
			continue
		}

		podFound = true

		if pod.Annotations[constants.AnnotationStaticPodConfigVersion] != configVersion {
			return retry.ExpectedError(fmt.Errorf("config version mismatch: got %q, expected %q", pod.Annotations[constants.AnnotationStaticPodConfigVersion], configVersion))
		}

		ready := false

		for _, condition := range pod.Status.Conditions {
			if condition.Type != "Ready" {
				continue
			}

			if condition.Status == "True" {
				ready = true

				break
			}
		}

		if !ready {
			return retry.ExpectedError(fmt.Errorf("pod is not ready"))
		}

		break
	}

	if !podFound {
		return retry.ExpectedError(fmt.Errorf("pod not found in the API server state"))
	}

	return nil
}

//nolint:gocyclo,cyclop
func checkDeprecated(ctx context.Context, cluster UpgradeProvider, options UpgradeOptions) error {
	options.Log("checking for resource APIs to be deprecated in version %s", options.ToVersion)

	config, err := cluster.K8sRestConfig(ctx)
	if err != nil {
		return err
	}

	config.WarningHandler = rest.NewWarningWriter(io.Discard, rest.WarningWriterOptions{})

	k8sClient, err := dynamic.NewForConfig(config)
	if err != nil {
		return fmt.Errorf("error building kubernetes client: %w", err)
	}

	staticClient, err := cluster.K8sHelper(ctx)
	if err != nil {
		return fmt.Errorf("error building kubernetes client: %s", err)
	}

	hasDeprecated := false

	warnings := bytes.NewBuffer([]byte{})

	w := tabwriter.NewWriter(warnings, 0, 0, 3, ' ', 0)

	resources, ok := deprecations[options.Path()]
	if !ok {
		return nil
	}

	var namespaces *v1.NamespaceList

	namespaces, err = staticClient.CoreV1().Namespaces().List(ctx, metav1.ListOptions{})
	if err != nil {
		return err
	}

	dc, err := discovery.NewDiscoveryClientForConfig(config)
	if err != nil {
		return err
	}

	serverResources, err := dc.ServerPreferredNamespacedResources()
	if err != nil {
		return err
	}

	namespacedResources := map[string]struct{}{}

	for _, list := range serverResources {
		for _, resource := range list.APIResources {
			namespacedResources[resource.Name] = struct{}{}
		}
	}

	for _, resource := range resources {
		gvr, _ := schema.ParseResourceArg(resource)

		if gvr == nil {
			return fmt.Errorf("failed to parse group version resource %s", resource)
		}

		var res *unstructured.UnstructuredList

		count := 0

		probeResources := func(namespaces ...v1.Namespace) error {
			r := k8sClient.Resource(*gvr)

			namespaceNames := make([]string, 0, len(namespaces))

			for _, ns := range namespaces {
				namespaceNames = append(namespaceNames, ns.Name)
			}

			if len(namespaceNames) == 0 {
				namespaceNames = append(namespaceNames, "default")
			}

			for _, ns := range namespaceNames {
				if ns != "default" {
					r.Namespace(ns)
				}

				res, err = r.List(ctx, metav1.ListOptions{})
				if err != nil {
					if apierrors.IsNotFound(err) {
						return nil
					}

					return err
				}

				count += len(res.Items)
			}

			return nil
		}

		checkNamespaces := []v1.Namespace{}

		if _, ok := namespacedResources[gvr.Resource]; ok {
			checkNamespaces = namespaces.Items
		}

		if err = probeResources(checkNamespaces...); err != nil {
			return err
		}

		if count > 0 {
			if !hasDeprecated {
				fmt.Fprintf(w, "RESOURCE\tCOUNT\n")
			}

			hasDeprecated = true

			fmt.Fprintf(w, "%s\t%d\n", resource, len(res.Items))
		}
	}

	if hasDeprecated {
		if err = w.Flush(); err != nil {
			return err
		}

		options.Log("WARNING: found resources which are going to be deprecated/migrated in the version %s", options.ToVersion)
		options.Log(warnings.String())
	}

	return nil
}