/*
Copyright 2020 The actions-runner-controller 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 controllers

import (
	"context"
	"errors"
	"fmt"
	gogithub "github.com/google/go-github/v33/github"
	"github.com/summerwind/actions-runner-controller/hash"
	"strings"
	"time"

	"github.com/go-logr/logr"
	kerrors "k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/client-go/tools/record"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"

	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"

	"github.com/summerwind/actions-runner-controller/api/v1alpha1"
	"github.com/summerwind/actions-runner-controller/github"
)

const (
	containerName = "runner"
	finalizerName = "runner.actions.summerwind.dev"

	LabelKeyPodTemplateHash = "pod-template-hash"

	retryDelayOnGitHubAPIRateLimitError = 30 * time.Second
)

// RunnerReconciler reconciles a Runner object
type RunnerReconciler struct {
	client.Client
	Log          logr.Logger
	Recorder     record.EventRecorder
	Scheme       *runtime.Scheme
	GitHubClient *github.Client
	RunnerImage  string
	DockerImage  string
}

// +kubebuilder:rbac:groups=actions.summerwind.dev,resources=runners,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups=actions.summerwind.dev,resources=runners/finalizers,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups=actions.summerwind.dev,resources=runners/status,verbs=get;update;patch
// +kubebuilder:rbac:groups=core,resources=pods,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups=core,resources=pods/finalizers,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups=core,resources=events,verbs=create;patch

func (r *RunnerReconciler) Reconcile(req ctrl.Request) (ctrl.Result, error) {
	ctx := context.Background()
	log := r.Log.WithValues("runner", req.NamespacedName)

	var runner v1alpha1.Runner
	if err := r.Get(ctx, req.NamespacedName, &runner); err != nil {
		return ctrl.Result{}, client.IgnoreNotFound(err)
	}

	err := runner.Validate()
	if err != nil {
		log.Info("Failed to validate runner spec", "error", err.Error())
		return ctrl.Result{}, nil
	}

	if runner.ObjectMeta.DeletionTimestamp.IsZero() {
		finalizers, added := addFinalizer(runner.ObjectMeta.Finalizers)

		if added {
			newRunner := runner.DeepCopy()
			newRunner.ObjectMeta.Finalizers = finalizers

			if err := r.Update(ctx, newRunner); err != nil {
				log.Error(err, "Failed to update runner")
				return ctrl.Result{}, err
			}

			return ctrl.Result{}, nil
		}
	} else {
		finalizers, removed := removeFinalizer(runner.ObjectMeta.Finalizers)

		if removed {
			if len(runner.Status.Registration.Token) > 0 {
				ok, err := r.unregisterRunner(ctx, runner.Spec.Enterprise, runner.Spec.Organization, runner.Spec.Repository, runner.Name)
				if err != nil {
					if errors.Is(err, &gogithub.RateLimitError{}) {
						// We log the underlying error when we failed calling GitHub API to list or unregisters,
						// or the runner is still busy.
						log.Error(
							err,
							fmt.Sprintf(
								"Failed to unregister runner due to GitHub API rate limits. Delaying retry for %s to avoid excessive GitHub API calls",
								retryDelayOnGitHubAPIRateLimitError,
							),
						)

						return ctrl.Result{RequeueAfter: retryDelayOnGitHubAPIRateLimitError}, err
					}

					return ctrl.Result{}, err
				}

				if !ok {
					log.V(1).Info("Runner no longer exists on GitHub")
				}
			} else {
				log.V(1).Info("Runner was never registered on GitHub")
			}

			newRunner := runner.DeepCopy()
			newRunner.ObjectMeta.Finalizers = finalizers

			if err := r.Update(ctx, newRunner); err != nil {
				log.Error(err, "Failed to update runner")
				return ctrl.Result{}, err
			}

			log.Info("Removed runner from GitHub", "repository", runner.Spec.Repository, "organization", runner.Spec.Organization)
		}

		return ctrl.Result{}, nil
	}

	var pod corev1.Pod
	if err := r.Get(ctx, req.NamespacedName, &pod); err != nil {
		if !kerrors.IsNotFound(err) {
			return ctrl.Result{}, err
		}

		if updated, err := r.updateRegistrationToken(ctx, runner); err != nil {
			return ctrl.Result{}, err
		} else if updated {
			return ctrl.Result{Requeue: true}, nil
		}

		newPod, err := r.newPod(runner)
		if err != nil {
			log.Error(err, "Could not create pod")
			return ctrl.Result{}, err
		}

		if err := r.Create(ctx, &newPod); err != nil {
			log.Error(err, "Failed to create pod resource")
			return ctrl.Result{}, err
		}

		r.Recorder.Event(&runner, corev1.EventTypeNormal, "PodCreated", fmt.Sprintf("Created pod '%s'", newPod.Name))
		log.Info("Created runner pod", "repository", runner.Spec.Repository)
	} else {
		// If pod has ended up succeeded we need to restart it
		// Happens e.g. when dind is in runner and run completes
		restart := pod.Status.Phase == corev1.PodSucceeded

		if !restart && runner.Status.Phase != string(pod.Status.Phase) {
			updated := runner.DeepCopy()
			updated.Status.Phase = string(pod.Status.Phase)
			updated.Status.Reason = pod.Status.Reason
			updated.Status.Message = pod.Status.Message

			if err := r.Status().Update(ctx, updated); err != nil {
				log.Error(err, "Failed to update runner status")
				return ctrl.Result{}, err
			}

			return ctrl.Result{}, nil
		}

		if !pod.ObjectMeta.DeletionTimestamp.IsZero() {
			deletionTimeout := 1 * time.Minute
			currentTime := time.Now()
			deletionDidTimeout := currentTime.Sub(pod.DeletionTimestamp.Add(deletionTimeout)) > 0

			if deletionDidTimeout {
				log.Info(
					"Pod failed to delete itself in a timely manner. "+
						"This is typically the case when a Kubernetes node became unreachable "+
						"and the kube controller started evicting nodes. Forcefully deleting the pod to not get stuck.",
					"podDeletionTimestamp", pod.DeletionTimestamp,
					"currentTime", currentTime,
					"configuredDeletionTimeout", deletionTimeout,
				)

				var force int64 = 0
				// forcefully delete runner as we would otherwise get stuck if the node stays unreachable
				if err := r.Delete(ctx, &pod, &client.DeleteOptions{GracePeriodSeconds: &force}); err != nil {
					// probably
					if !kerrors.IsNotFound(err) {
						log.Error(err, "Failed to forcefully delete pod resource ...")
						return ctrl.Result{}, err
					}
					// forceful deletion finally succeeded
					return ctrl.Result{Requeue: true}, nil
				}

				r.Recorder.Event(&runner, corev1.EventTypeNormal, "PodDeleted", fmt.Sprintf("Forcefully deleted pod '%s'", pod.Name))
				log.Info("Forcefully deleted runner pod", "repository", runner.Spec.Repository)
				// give kube manager a little time to forcefully delete the stuck pod
				return ctrl.Result{RequeueAfter: 3 * time.Second}, err
			} else {
				return ctrl.Result{}, err
			}
		}

		if pod.Status.Phase == corev1.PodRunning {
			for _, status := range pod.Status.ContainerStatuses {
				if status.Name != containerName {
					continue
				}

				if status.State.Terminated != nil && status.State.Terminated.ExitCode == 0 {
					restart = true
				}
			}
		}

		if updated, err := r.updateRegistrationToken(ctx, runner); err != nil {
			return ctrl.Result{}, err
		} else if updated {
			return ctrl.Result{Requeue: true}, nil
		}

		newPod, err := r.newPod(runner)
		if err != nil {
			log.Error(err, "Could not create pod")
			return ctrl.Result{}, err
		}

		notRegistered := false

		runnerBusy, err := r.GitHubClient.IsRunnerBusy(ctx, runner.Spec.Enterprise, runner.Spec.Organization, runner.Spec.Repository, runner.Name)
		if err != nil {
			var e *github.RunnerNotFound
			if errors.As(err, &e) {
				log.V(1).Info("Failed to check if runner is busy. Either this runner has never been successfully registered to GitHub or it still needs more time.", "runnerName", runner.Name)

				notRegistered = true
			} else {
				var e *gogithub.RateLimitError
				if errors.As(err, &e) {
					// We log the underlying error when we failed calling GitHub API to list or unregisters,
					// or the runner is still busy.
					log.Error(
						err,
						fmt.Sprintf(
							"Failed to check if runner is busy due to Github API rate limit. Retrying in %s to avoid excessive GitHub API calls",
							retryDelayOnGitHubAPIRateLimitError,
						),
					)

					return ctrl.Result{RequeueAfter: retryDelayOnGitHubAPIRateLimitError}, err
				}

				return ctrl.Result{}, err
			}
		}

		// See the `newPod` function called above for more information
		// about when this hash changes.
		curHash := pod.Labels[LabelKeyPodTemplateHash]
		newHash := newPod.Labels[LabelKeyPodTemplateHash]

		if !runnerBusy && curHash != newHash {
			restart = true
		}

		registrationTimeout := 10 * time.Minute
		currentTime := time.Now()
		registrationDidTimeout := currentTime.Sub(pod.CreationTimestamp.Add(registrationTimeout)) > 0

		if notRegistered && registrationDidTimeout {
			log.Info(
				"Runner failed to register itself to GitHub in timely manner. "+
					"Recreating the pod to see if it resolves the issue. "+
					"CAUTION: If you see this a lot, you should investigate the root cause. "+
					"See https://github.com/summerwind/actions-runner-controller/issues/288",
				"podCreationTimestamp", pod.CreationTimestamp,
				"currentTime", currentTime,
				"configuredRegistrationTimeout", registrationTimeout,
			)

			restart = true
		}

		// Don't do anything if there's no need to restart the runner
		if !restart {
			return ctrl.Result{}, nil
		}

		// Delete current pod if recreation is needed
		if err := r.Delete(ctx, &pod); err != nil {
			log.Error(err, "Failed to delete pod resource")
			return ctrl.Result{}, err
		}

		r.Recorder.Event(&runner, corev1.EventTypeNormal, "PodDeleted", fmt.Sprintf("Deleted pod '%s'", newPod.Name))
		log.Info("Deleted runner pod", "repository", runner.Spec.Repository)
	}

	return ctrl.Result{}, nil
}

func (r *RunnerReconciler) unregisterRunner(ctx context.Context, enterprise, org, repo, name string) (bool, error) {
	runners, err := r.GitHubClient.ListRunners(ctx, enterprise, org, repo)
	if err != nil {
		return false, err
	}

	id := int64(0)
	for _, runner := range runners {
		if runner.GetName() == name {
			if runner.GetBusy() {
				return false, fmt.Errorf("runner is busy")
			}
			id = runner.GetID()
			break
		}
	}

	if id == int64(0) {
		return false, nil
	}

	if err := r.GitHubClient.RemoveRunner(ctx, enterprise, org, repo, id); err != nil {
		return false, err
	}

	return true, nil
}

func (r *RunnerReconciler) updateRegistrationToken(ctx context.Context, runner v1alpha1.Runner) (bool, error) {
	if runner.IsRegisterable() {
		return false, nil
	}

	log := r.Log.WithValues("runner", runner.Name)

	rt, err := r.GitHubClient.GetRegistrationToken(ctx, runner.Spec.Enterprise, runner.Spec.Organization, runner.Spec.Repository, runner.Name)
	if err != nil {
		r.Recorder.Event(&runner, corev1.EventTypeWarning, "FailedUpdateRegistrationToken", "Updating registration token failed")
		log.Error(err, "Failed to get new registration token")
		return false, err
	}

	updated := runner.DeepCopy()
	updated.Status.Registration = v1alpha1.RunnerStatusRegistration{
		Organization: runner.Spec.Organization,
		Repository:   runner.Spec.Repository,
		Labels:       runner.Spec.Labels,
		Token:        rt.GetToken(),
		ExpiresAt:    metav1.NewTime(rt.GetExpiresAt().Time),
	}

	if err := r.Status().Update(ctx, updated); err != nil {
		log.Error(err, "Failed to update runner status")
		return false, err
	}

	r.Recorder.Event(&runner, corev1.EventTypeNormal, "RegistrationTokenUpdated", "Successfully update registration token")
	log.Info("Updated registration token", "repository", runner.Spec.Repository)

	return true, nil
}

func (r *RunnerReconciler) newPod(runner v1alpha1.Runner) (corev1.Pod, error) {
	var (
		privileged      bool = true
		dockerdInRunner bool = runner.Spec.DockerdWithinRunnerContainer != nil && *runner.Spec.DockerdWithinRunnerContainer
		dockerEnabled   bool = runner.Spec.DockerEnabled == nil || *runner.Spec.DockerEnabled
	)

	runnerImage := runner.Spec.Image
	if runnerImage == "" {
		runnerImage = r.RunnerImage
	}

	workDir := runner.Spec.WorkDir
	if workDir == "" {
		workDir = "/runner/_work"
	}

	runnerImagePullPolicy := runner.Spec.ImagePullPolicy
	if runnerImagePullPolicy == "" {
		runnerImagePullPolicy = corev1.PullAlways
	}

	env := []corev1.EnvVar{
		{
			Name:  "RUNNER_NAME",
			Value: runner.Name,
		},
		{
			Name:  "RUNNER_ORG",
			Value: runner.Spec.Organization,
		},
		{
			Name:  "RUNNER_REPO",
			Value: runner.Spec.Repository,
		},
		{
			Name:  "RUNNER_ENTERPRISE",
			Value: runner.Spec.Enterprise,
		},
		{
			Name:  "RUNNER_LABELS",
			Value: strings.Join(runner.Spec.Labels, ","),
		},
		{
			Name:  "RUNNER_GROUP",
			Value: runner.Spec.Group,
		},
		{
			Name:  "RUNNER_TOKEN",
			Value: runner.Status.Registration.Token,
		},
		{
			Name:  "DOCKERD_IN_RUNNER",
			Value: fmt.Sprintf("%v", dockerdInRunner),
		},
		{
			Name:  "GITHUB_URL",
			Value: r.GitHubClient.GithubBaseURL,
		},
		{
			Name:  "RUNNER_WORKDIR",
			Value: workDir,
		},
	}

	env = append(env, runner.Spec.Env...)

	labels := map[string]string{}

	for k, v := range runner.Labels {
		labels[k] = v
	}

	// This implies that...
	//
	// (1) We recreate the runner pod whenever the runner has changes in:
	// - metadata.labels (excluding "runner-template-hash" added by the parent RunnerReplicaSet
	// - metadata.annotations
	// - metadata.spec (including image, env, organization, repository, group, and so on)
	// - GithubBaseURL setting of the controller (can be configured via GITHUB_ENTERPRISE_URL)
	//
	// (2) We don't recreate the runner pod when there are changes in:
	// - runner.status.registration.token
	//   - This token expires and changes hourly, but you don't need to recreate the pod due to that.
	//     It's the opposite.
	//     An unexpired token is required only when the runner agent is registering itself on launch.
	//
	//     In other words, the registered runner doesn't get invalidated on registration token expiration.
	//     A registered runner's session and the a registration token seem to have two different and independent
	//     lifecycles.
	//
	//     See https://github.com/summerwind/actions-runner-controller/issues/143 for more context.
	labels[LabelKeyPodTemplateHash] = hash.FNVHashStringObjects(
		filterLabels(runner.Labels, LabelKeyRunnerTemplateHash),
		runner.Annotations,
		runner.Spec,
		r.GitHubClient.GithubBaseURL,
	)

	pod := corev1.Pod{
		ObjectMeta: metav1.ObjectMeta{
			Name:        runner.Name,
			Namespace:   runner.Namespace,
			Labels:      labels,
			Annotations: runner.Annotations,
		},
		Spec: corev1.PodSpec{
			RestartPolicy: "OnFailure",
			Containers: []corev1.Container{
				{
					Name:            containerName,
					Image:           runnerImage,
					ImagePullPolicy: runnerImagePullPolicy,
					Env:             env,
					EnvFrom:         runner.Spec.EnvFrom,
					SecurityContext: &corev1.SecurityContext{
						// Runner need to run privileged if it contains DinD
						Privileged: runner.Spec.DockerdWithinRunnerContainer,
					},
					Resources: runner.Spec.Resources,
				},
			},
		},
	}

	if !dockerdInRunner && dockerEnabled {
		runnerVolumeName := "runner"
		runnerVolumeMountPath := "/runner"

		pod.Spec.Volumes = []corev1.Volume{
			{
				Name: "work",
				VolumeSource: corev1.VolumeSource{
					EmptyDir: &corev1.EmptyDirVolumeSource{},
				},
			},
			{
				Name: runnerVolumeName,
				VolumeSource: corev1.VolumeSource{
					EmptyDir: &corev1.EmptyDirVolumeSource{},
				},
			},
			{
				Name: "certs-client",
				VolumeSource: corev1.VolumeSource{
					EmptyDir: &corev1.EmptyDirVolumeSource{},
				},
			},
		}
		pod.Spec.Containers[0].VolumeMounts = []corev1.VolumeMount{
			{
				Name:      "work",
				MountPath: workDir,
			},
			{
				Name:      runnerVolumeName,
				MountPath: runnerVolumeMountPath,
			},
			{
				Name:      "certs-client",
				MountPath: "/certs/client",
				ReadOnly:  true,
			},
		}
		pod.Spec.Containers[0].Env = append(pod.Spec.Containers[0].Env, []corev1.EnvVar{
			{
				Name:  "DOCKER_HOST",
				Value: "tcp://localhost:2376",
			},
			{
				Name:  "DOCKER_TLS_VERIFY",
				Value: "1",
			},
			{
				Name:  "DOCKER_CERT_PATH",
				Value: "/certs/client",
			},
		}...)
		pod.Spec.Containers = append(pod.Spec.Containers, corev1.Container{
			Name:  "docker",
			Image: r.DockerImage,
			VolumeMounts: []corev1.VolumeMount{
				{
					Name:      "work",
					MountPath: workDir,
				},
				{
					Name:      runnerVolumeName,
					MountPath: runnerVolumeMountPath,
				},
				{
					Name:      "certs-client",
					MountPath: "/certs/client",
				},
			},
			Env: []corev1.EnvVar{
				{
					Name:  "DOCKER_TLS_CERTDIR",
					Value: "/certs",
				},
			},
			SecurityContext: &corev1.SecurityContext{
				Privileged: &privileged,
			},
			Resources: runner.Spec.DockerdContainerResources,
		})

	}

	if len(runner.Spec.Containers) != 0 {
		pod.Spec.Containers = runner.Spec.Containers
		for i := 0; i < len(pod.Spec.Containers); i++ {
			if pod.Spec.Containers[i].Name == containerName {
				pod.Spec.Containers[i].Env = append(pod.Spec.Containers[i].Env, env...)
			}
		}
	}

	if len(runner.Spec.VolumeMounts) != 0 {
		pod.Spec.Containers[0].VolumeMounts = append(pod.Spec.Containers[0].VolumeMounts, runner.Spec.VolumeMounts...)
	}

	if len(runner.Spec.Volumes) != 0 {
		pod.Spec.Volumes = append(pod.Spec.Volumes, runner.Spec.Volumes...)
	}
	if len(runner.Spec.InitContainers) != 0 {
		pod.Spec.InitContainers = append(pod.Spec.InitContainers, runner.Spec.InitContainers...)
	}

	if runner.Spec.NodeSelector != nil {
		pod.Spec.NodeSelector = runner.Spec.NodeSelector
	}
	if runner.Spec.ServiceAccountName != "" {
		pod.Spec.ServiceAccountName = runner.Spec.ServiceAccountName
	}
	if runner.Spec.AutomountServiceAccountToken != nil {
		pod.Spec.AutomountServiceAccountToken = runner.Spec.AutomountServiceAccountToken
	}

	if len(runner.Spec.SidecarContainers) != 0 {
		pod.Spec.Containers = append(pod.Spec.Containers, runner.Spec.SidecarContainers...)
	}

	if runner.Spec.SecurityContext != nil {
		pod.Spec.SecurityContext = runner.Spec.SecurityContext
	}

	if len(runner.Spec.ImagePullSecrets) != 0 {
		pod.Spec.ImagePullSecrets = runner.Spec.ImagePullSecrets
	}

	if runner.Spec.Affinity != nil {
		pod.Spec.Affinity = runner.Spec.Affinity
	}

	if len(runner.Spec.Tolerations) != 0 {
		pod.Spec.Tolerations = runner.Spec.Tolerations
	}

	if len(runner.Spec.EphemeralContainers) != 0 {
		pod.Spec.EphemeralContainers = runner.Spec.EphemeralContainers
	}

	if runner.Spec.TerminationGracePeriodSeconds != nil {
		pod.Spec.TerminationGracePeriodSeconds = runner.Spec.TerminationGracePeriodSeconds
	}

	if err := ctrl.SetControllerReference(&runner, &pod, r.Scheme); err != nil {
		return pod, err
	}

	return pod, nil
}

func (r *RunnerReconciler) SetupWithManager(mgr ctrl.Manager) error {
	r.Recorder = mgr.GetEventRecorderFor("runner-controller")

	return ctrl.NewControllerManagedBy(mgr).
		For(&v1alpha1.Runner{}).
		Owns(&corev1.Pod{}).
		Complete(r)
}

func addFinalizer(finalizers []string) ([]string, bool) {
	exists := false
	for _, name := range finalizers {
		if name == finalizerName {
			exists = true
		}
	}

	if exists {
		return finalizers, false
	}

	return append(finalizers, finalizerName), true
}

func removeFinalizer(finalizers []string) ([]string, bool) {
	removed := false
	result := []string{}

	for _, name := range finalizers {
		if name == finalizerName {
			removed = true
			continue
		}
		result = append(result, name)
	}

	return result, removed
}