/*
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"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"strings"
	"time"

	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/types"
	"sigs.k8s.io/controller-runtime/pkg/reconcile"

	"github.com/go-logr/logr"
	gogithub "github.com/google/go-github/v39/github"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/client-go/tools/record"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"

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

const (
	scaleTargetKey = "scaleTarget"

	keyPrefixEnterprise = "enterprises/"
)

// HorizontalRunnerAutoscalerGitHubWebhook autoscales a HorizontalRunnerAutoscaler and the RunnerDeployment on each
// GitHub Webhook received
type HorizontalRunnerAutoscalerGitHubWebhook struct {
	client.Client
	Log      logr.Logger
	Recorder record.EventRecorder
	Scheme   *runtime.Scheme

	// SecretKeyBytes is the byte representation of the Webhook secret token
	// the administrator is generated and specified in GitHub Web UI.
	SecretKeyBytes []byte

	// Namespace is the namespace to watch for HorizontalRunnerAutoscaler's to be
	// scaled on Webhook.
	// Set to empty for letting it watch for all namespaces.
	Namespace string
	Name      string
}

func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) Reconcile(_ context.Context, request reconcile.Request) (reconcile.Result, error) {
	return ctrl.Result{}, nil
}

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

func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) Handle(w http.ResponseWriter, r *http.Request) {
	var (
		ok bool

		err error
	)

	defer func() {
		if !ok {
			w.WriteHeader(http.StatusInternalServerError)

			if err != nil {
				msg := err.Error()
				if written, err := w.Write([]byte(msg)); err != nil {
					autoscaler.Log.Error(err, "failed writing http error response", "msg", msg, "written", written)
				}
			}
		}
	}()

	defer func() {
		if r.Body != nil {
			r.Body.Close()
		}
	}()

	// respond ok to GET / e.g. for health check
	if r.Method == http.MethodGet {
		ok = true
		fmt.Fprintln(w, "webhook server is running")
		return
	}

	var payload []byte

	if len(autoscaler.SecretKeyBytes) > 0 {
		payload, err = gogithub.ValidatePayload(r, autoscaler.SecretKeyBytes)
		if err != nil {
			autoscaler.Log.Error(err, "error validating request body")

			return
		}
	} else {
		payload, err = ioutil.ReadAll(r.Body)
		if err != nil {
			autoscaler.Log.Error(err, "error reading request body")

			return
		}
	}

	webhookType := gogithub.WebHookType(r)
	event, err := gogithub.ParseWebHook(webhookType, payload)
	if err != nil {
		var s string
		if payload != nil {
			s = string(payload)
		}

		autoscaler.Log.Error(err, "could not parse webhook", "webhookType", webhookType, "payload", s)

		return
	}

	var target *ScaleTarget

	log := autoscaler.Log.WithValues(
		"event", webhookType,
		"hookID", r.Header.Get("X-GitHub-Hook-ID"),
		"delivery", r.Header.Get("X-GitHub-Delivery"),
	)

	var enterpriseEvent struct {
		Enterprise struct {
			Slug string `json:"slug,omitempty"`
		} `json:"enterprise,omitempty"`
	}
	if err := json.Unmarshal(payload, &enterpriseEvent); err != nil {
		var s string
		if payload != nil {
			s = string(payload)
		}
		autoscaler.Log.Error(err, "could not parse webhook payload for extracting enterprise slug", "webhookType", webhookType, "payload", s)
	}
	enterpriseSlug := enterpriseEvent.Enterprise.Slug

	switch e := event.(type) {
	case *gogithub.PushEvent:
		target, err = autoscaler.getScaleUpTarget(
			context.TODO(),
			log,
			e.Repo.GetName(),
			e.Repo.Owner.GetLogin(),
			e.Repo.Owner.GetType(),
			// Most go-github Event types don't seem to contain Enteprirse(.Slug) fields
			// we need, so we parse it by ourselves.
			enterpriseSlug,
			autoscaler.MatchPushEvent(e),
		)
	case *gogithub.PullRequestEvent:
		target, err = autoscaler.getScaleUpTarget(
			context.TODO(),
			log,
			e.Repo.GetName(),
			e.Repo.Owner.GetLogin(),
			e.Repo.Owner.GetType(),
			// Most go-github Event types don't seem to contain Enteprirse(.Slug) fields
			// we need, so we parse it by ourselves.
			enterpriseSlug,
			autoscaler.MatchPullRequestEvent(e),
		)

		if pullRequest := e.PullRequest; pullRequest != nil {
			log = log.WithValues(
				"pullRequest.base.ref", e.PullRequest.Base.GetRef(),
				"action", e.GetAction(),
			)
		}
	case *gogithub.CheckRunEvent:
		target, err = autoscaler.getScaleUpTarget(
			context.TODO(),
			log,
			e.Repo.GetName(),
			e.Repo.Owner.GetLogin(),
			e.Repo.Owner.GetType(),
			// Most go-github Event types don't seem to contain Enteprirse(.Slug) fields
			// we need, so we parse it by ourselves.
			enterpriseSlug,
			autoscaler.MatchCheckRunEvent(e),
		)

		if checkRun := e.GetCheckRun(); checkRun != nil {
			log = log.WithValues(
				"checkRun.status", checkRun.GetStatus(),
				"action", e.GetAction(),
			)
		}
	case *gogithub.WorkflowJobEvent:
		if workflowJob := e.GetWorkflowJob(); workflowJob != nil {
			log = log.WithValues(
				"workflowJob.status", workflowJob.GetStatus(),
				"workflowJob.labels", workflowJob.Labels,
				"repository.name", e.Repo.GetName(),
				"repository.owner.login", e.Repo.Owner.GetLogin(),
				"repository.owner.type", e.Repo.Owner.GetType(),
				"enterprise.slug", enterpriseSlug,
				"action", e.GetAction(),
			)
		}

		labels := e.WorkflowJob.Labels

		switch action := e.GetAction(); action {
		case "queued", "completed":
			target, err = autoscaler.getJobScaleUpTargetForRepoOrOrg(
				context.TODO(),
				log,
				e.Repo.GetName(),
				e.Repo.Owner.GetLogin(),
				e.Repo.Owner.GetType(),
				enterpriseSlug,
				labels,
			)

			if target != nil {
				if e.GetAction() == "queued" {
					target.Amount = 1
				} else if e.GetAction() == "completed" {
					// A nagative amount is processed in the tryScale func as a scale-down request,
					// that erasese the oldest CapacityReservation with the same amount.
					// If the first CapacityReservation was with Replicas=1, this negative scale target erases that,
					// so that the resulting desired replicas decreases by 1.
					target.Amount = -1
				}
			}
		default:
			ok = true

			w.WriteHeader(http.StatusOK)

			log.V(2).Info("Received and ignored a workflow_job event as it triggers neither scale-up nor scale-down", "action", action)

			return
		}
	case *gogithub.PingEvent:
		ok = true

		w.WriteHeader(http.StatusOK)

		msg := "pong"

		if written, err := w.Write([]byte(msg)); err != nil {
			log.Error(err, "failed writing http response", "msg", msg, "written", written)
		}

		log.Info("received ping event")

		return
	default:
		log.Info("unknown event type", "eventType", webhookType)

		return
	}

	if err != nil {
		log.Error(err, "handling check_run event")

		return
	}

	if target == nil {
		log.Info(
			"Scale target not found. If this is unexpected, ensure that there is exactly one repository-wide or organizational runner deployment that matches this webhook event",
		)

		msg := "no horizontalrunnerautoscaler to scale for this github event"

		ok = true

		w.WriteHeader(http.StatusOK)

		if written, err := w.Write([]byte(msg)); err != nil {
			log.Error(err, "failed writing http response", "msg", msg, "written", written)
		}

		return
	}

	if err := autoscaler.tryScale(context.TODO(), target); err != nil {
		log.Error(err, "could not scale up")

		return
	}

	ok = true

	w.WriteHeader(http.StatusOK)

	msg := fmt.Sprintf("scaled %s by %d", target.Name, target.Amount)

	autoscaler.Log.Info(msg)

	if written, err := w.Write([]byte(msg)); err != nil {
		log.Error(err, "failed writing http response", "msg", msg, "written", written)
	}
}

func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) findHRAsByKey(ctx context.Context, value string) ([]v1alpha1.HorizontalRunnerAutoscaler, error) {
	ns := autoscaler.Namespace

	var defaultListOpts []client.ListOption

	if ns != "" {
		defaultListOpts = append(defaultListOpts, client.InNamespace(ns))
	}

	var hras []v1alpha1.HorizontalRunnerAutoscaler

	if value != "" {
		opts := append([]client.ListOption{}, defaultListOpts...)
		opts = append(opts, client.MatchingFields{scaleTargetKey: value})

		if autoscaler.Namespace != "" {
			opts = append(opts, client.InNamespace(autoscaler.Namespace))
		}

		var hraList v1alpha1.HorizontalRunnerAutoscalerList

		if err := autoscaler.List(ctx, &hraList, opts...); err != nil {
			return nil, err
		}

		for _, d := range hraList.Items {
			hras = append(hras, d)
		}
	}

	return hras, nil
}

func matchTriggerConditionAgainstEvent(types []string, eventAction *string) bool {
	if len(types) == 0 {
		return true
	}

	if eventAction == nil {
		return false
	}

	for _, tpe := range types {
		if tpe == *eventAction {
			return true
		}
	}

	return false
}

type ScaleTarget struct {
	v1alpha1.HorizontalRunnerAutoscaler
	v1alpha1.ScaleUpTrigger
}

func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) searchScaleTargets(hras []v1alpha1.HorizontalRunnerAutoscaler, f func(v1alpha1.ScaleUpTrigger) bool) []ScaleTarget {
	var matched []ScaleTarget

	for _, hra := range hras {
		if !hra.ObjectMeta.DeletionTimestamp.IsZero() {
			continue
		}

		for _, scaleUpTrigger := range hra.Spec.ScaleUpTriggers {
			if !f(scaleUpTrigger) {
				continue
			}

			matched = append(matched, ScaleTarget{
				HorizontalRunnerAutoscaler: hra,
				ScaleUpTrigger:             scaleUpTrigger,
			})
		}
	}

	return matched
}

func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) getScaleTarget(ctx context.Context, name string, f func(v1alpha1.ScaleUpTrigger) bool) (*ScaleTarget, error) {
	hras, err := autoscaler.findHRAsByKey(ctx, name)
	if err != nil {
		return nil, err
	}

	autoscaler.Log.V(1).Info(fmt.Sprintf("Found %d HRAs by key", len(hras)), "key", name)

	targets := autoscaler.searchScaleTargets(hras, f)

	n := len(targets)

	if n == 0 {
		return nil, nil
	}

	if n > 1 {
		var scaleTargetIDs []string

		for _, t := range targets {
			scaleTargetIDs = append(scaleTargetIDs, t.HorizontalRunnerAutoscaler.Name)
		}

		autoscaler.Log.Info(
			"Found too many scale targets: "+
				"It must be exactly one to avoid ambiguity. "+
				"Either set Namespace for the webhook-based autoscaler to let it only find HRAs in the namespace, "+
				"or update Repository, Organization, or Enterprise fields in your RunnerDeployment resources to fix the ambiguity.",
			"scaleTargets", strings.Join(scaleTargetIDs, ","))

		return nil, nil
	}

	return &targets[0], nil
}

func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) getScaleUpTarget(ctx context.Context, log logr.Logger, repo, owner, ownerType, enterprise string, f func(v1alpha1.ScaleUpTrigger) bool) (*ScaleTarget, error) {
	repositoryRunnerKey := owner + "/" + repo

	if target, err := autoscaler.getScaleTarget(ctx, repositoryRunnerKey, f); err != nil {
		log.Info("finding repository-wide runner", "repository", repositoryRunnerKey)
		return nil, err
	} else if target != nil {
		log.Info("scale up target is repository-wide runners", "repository", repo)
		return target, nil
	}

	if ownerType == "User" {
		log.V(1).Info("no repository runner found", "organization", owner)

		return nil, nil
	}

	if target, err := autoscaler.getScaleTarget(ctx, owner, f); err != nil {
		log.Info("finding organizational runner", "organization", owner)
		return nil, err
	} else if target != nil {
		log.Info("scale up target is organizational runners", "organization", owner)
		return target, nil
	}

	if enterprise == "" {
		log.V(1).Info("no repository runner or organizational runner found",
			"repository", repositoryRunnerKey,
			"organization", owner,
		)

		return nil, nil
	}

	if target, err := autoscaler.getScaleTarget(ctx, enterpriseKey(enterprise), f); err != nil {
		log.Error(err, "finding enterprise runner", "enterprise", enterprise)
		return nil, err
	} else if target != nil {
		log.Info("scale up target is enterprise runners", "enterprise", enterprise)
		return target, nil
	} else {
		log.V(1).Info("no repository/organizational/enterprise runner found",
			"repository", repositoryRunnerKey,
			"organization", owner,
			"enterprises", enterprise,
		)
	}

	return nil, nil
}

func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) getJobScaleUpTargetForRepoOrOrg(
	ctx context.Context, log logr.Logger, repo, owner, ownerType, enterprise string, labels []string,
) (*ScaleTarget, error) {
	repositoryRunnerKey := owner + "/" + repo

	if target, err := autoscaler.getJobScaleTarget(ctx, repositoryRunnerKey, labels); err != nil {
		log.Info("finding repository-wide runner", "repository", repositoryRunnerKey)
		return nil, err
	} else if target != nil {
		log.Info("job scale up target is repository-wide runners", "repository", repo)
		return target, nil
	}

	if ownerType == "User" {
		log.V(1).Info("no repository runner found", "organization", owner)

		return nil, nil
	}

	if target, err := autoscaler.getJobScaleTarget(ctx, owner, labels); err != nil {
		log.Info("finding organizational runner", "organization", owner)
		return nil, err
	} else if target != nil {
		log.Info("job scale up target is organizational runners", "organization", owner)
		return target, nil
	}

	if enterprise == "" {
		log.V(1).Info("no repository runner or organizational runner found",
			"repository", repositoryRunnerKey,
			"organization", owner,
		)
		return nil, nil
	}

	if target, err := autoscaler.getJobScaleTarget(ctx, enterpriseKey(enterprise), labels); err != nil {
		log.Error(err, "finding enterprise runner", "enterprise", enterprise)
		return nil, err
	} else if target != nil {
		log.Info("scale up target is enterprise runners", "enterprise", enterprise)
		return target, nil
	} else {
		log.V(1).Info("no repository/organizational/enterprise runner found",
			"repository", repositoryRunnerKey,
			"organization", owner,
			"enterprises", enterprise,
		)
	}

	return nil, nil
}

func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) getJobScaleTarget(ctx context.Context, name string, labels []string) (*ScaleTarget, error) {
	hras, err := autoscaler.findHRAsByKey(ctx, name)
	if err != nil {
		return nil, err
	}

	autoscaler.Log.V(1).Info(fmt.Sprintf("Found %d HRAs by key", len(hras)), "key", name)

HRA:
	for _, hra := range hras {
		if !hra.ObjectMeta.DeletionTimestamp.IsZero() {
			continue
		}

		if len(hra.Spec.ScaleUpTriggers) > 1 {
			autoscaler.Log.V(1).Info("Skipping this HRA as it has too many ScaleUpTriggers to be used in workflow_job based scaling", "hra", hra.Name)

			continue
		}

		var duration metav1.Duration

		if len(hra.Spec.ScaleUpTriggers) > 0 {
			duration = hra.Spec.ScaleUpTriggers[0].Duration
		}

		if duration.Duration <= 0 {
			// Try to release the reserved capacity after at least 10 minutes by default,
			// we won't end up in the reserved capacity remained forever in case GitHub somehow stopped sending us "completed" workflow_job events.
			// GitHub usually send us those but nothing is 100% guaranteed, e.g. in case of something went wrong on GitHub :)
			// Probably we'd better make this configurable via custom resources in the future?
			duration.Duration = 10 * time.Minute
		}

		switch hra.Spec.ScaleTargetRef.Kind {
		case "RunnerSet":
			var rs v1alpha1.RunnerSet

			if err := autoscaler.Client.Get(context.Background(), types.NamespacedName{Namespace: hra.Namespace, Name: hra.Spec.ScaleTargetRef.Name}, &rs); err != nil {
				return nil, err
			}

			if len(labels) == 1 && labels[0] == "self-hosted" {
				return &ScaleTarget{HorizontalRunnerAutoscaler: hra, ScaleUpTrigger: v1alpha1.ScaleUpTrigger{Duration: duration}}, nil
			}

			// Ensure that the RunnerSet-managed runners have all the labels requested by the workflow_job.
			for _, l := range labels {
				var matched bool
				for _, l2 := range rs.Spec.Labels {
					if l == l2 {
						matched = true
						break
					}
				}

				if !matched {
					continue HRA
				}
			}

			return &ScaleTarget{HorizontalRunnerAutoscaler: hra, ScaleUpTrigger: v1alpha1.ScaleUpTrigger{Duration: duration}}, nil
		case "RunnerDeployment", "":
			var rd v1alpha1.RunnerDeployment

			if err := autoscaler.Client.Get(context.Background(), types.NamespacedName{Namespace: hra.Namespace, Name: hra.Spec.ScaleTargetRef.Name}, &rd); err != nil {
				return nil, err
			}

			if len(labels) == 1 && labels[0] == "self-hosted" {
				return &ScaleTarget{HorizontalRunnerAutoscaler: hra, ScaleUpTrigger: v1alpha1.ScaleUpTrigger{Duration: duration}}, nil
			}

			// Ensure that the RunnerDeployment-managed runners have all the labels requested by the workflow_job.
			for _, l := range labels {
				var matched bool
				for _, l2 := range rd.Spec.Template.Spec.Labels {
					if l == l2 {
						matched = true
						break
					}
				}

				if !matched {
					continue HRA
				}
			}

			return &ScaleTarget{HorizontalRunnerAutoscaler: hra, ScaleUpTrigger: v1alpha1.ScaleUpTrigger{Duration: duration}}, nil
		default:
			return nil, fmt.Errorf("unsupported scaleTargetRef.kind: %v", hra.Spec.ScaleTargetRef.Kind)
		}
	}

	return nil, nil
}

func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) tryScale(ctx context.Context, target *ScaleTarget) error {
	if target == nil {
		return nil
	}

	copy := target.HorizontalRunnerAutoscaler.DeepCopy()

	amount := 1

	if target.ScaleUpTrigger.Amount != 0 {
		amount = target.ScaleUpTrigger.Amount
	}

	capacityReservations := getValidCapacityReservations(copy)

	if amount > 0 {
		copy.Spec.CapacityReservations = append(capacityReservations, v1alpha1.CapacityReservation{
			ExpirationTime: metav1.Time{Time: time.Now().Add(target.ScaleUpTrigger.Duration.Duration)},
			Replicas:       amount,
		})
	} else if amount < 0 {
		var reservations []v1alpha1.CapacityReservation

		var found bool

		for _, r := range capacityReservations {
			if !found && r.Replicas+amount == 0 {
				found = true
			} else {
				reservations = append(reservations, r)
			}
		}

		copy.Spec.CapacityReservations = reservations
	}

	autoscaler.Log.Info(
		"Patching hra for capacityReservations update",
		"before", target.HorizontalRunnerAutoscaler.Spec.CapacityReservations,
		"after", copy.Spec.CapacityReservations,
	)

	if err := autoscaler.Client.Patch(ctx, copy, client.MergeFrom(&target.HorizontalRunnerAutoscaler)); err != nil {
		return fmt.Errorf("patching horizontalrunnerautoscaler to add capacity reservation: %w", err)
	}

	return nil
}

func getValidCapacityReservations(autoscaler *v1alpha1.HorizontalRunnerAutoscaler) []v1alpha1.CapacityReservation {
	var capacityReservations []v1alpha1.CapacityReservation

	now := time.Now()

	for _, reservation := range autoscaler.Spec.CapacityReservations {
		if reservation.ExpirationTime.Time.After(now) {
			capacityReservations = append(capacityReservations, reservation)
		}
	}

	return capacityReservations
}

func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) SetupWithManager(mgr ctrl.Manager) error {
	name := "webhookbasedautoscaler"
	if autoscaler.Name != "" {
		name = autoscaler.Name
	}

	autoscaler.Recorder = mgr.GetEventRecorderFor(name)

	if err := mgr.GetFieldIndexer().IndexField(context.TODO(), &v1alpha1.HorizontalRunnerAutoscaler{}, scaleTargetKey, func(rawObj client.Object) []string {
		hra := rawObj.(*v1alpha1.HorizontalRunnerAutoscaler)

		if hra.Spec.ScaleTargetRef.Name == "" {
			return nil
		}

		switch hra.Spec.ScaleTargetRef.Kind {
		case "", "RunnerDeployment":
			var rd v1alpha1.RunnerDeployment

			if err := autoscaler.Client.Get(context.Background(), types.NamespacedName{Namespace: hra.Namespace, Name: hra.Spec.ScaleTargetRef.Name}, &rd); err != nil {
				return nil
			}

			keys := []string{rd.Spec.Template.Spec.Repository, rd.Spec.Template.Spec.Organization}

			if enterprise := rd.Spec.Template.Spec.Enterprise; enterprise != "" {
				keys = append(keys, enterpriseKey(enterprise))
			}

			return keys
		case "RunnerSet":
			var rs v1alpha1.RunnerSet

			if err := autoscaler.Client.Get(context.Background(), types.NamespacedName{Namespace: hra.Namespace, Name: hra.Spec.ScaleTargetRef.Name}, &rs); err != nil {
				return nil
			}

			keys := []string{rs.Spec.Repository, rs.Spec.Organization}

			if enterprise := rs.Spec.Enterprise; enterprise != "" {
				keys = append(keys, enterpriseKey(enterprise))
			}

			return keys
		}

		return nil
	}); err != nil {
		return err
	}

	return ctrl.NewControllerManagedBy(mgr).
		For(&v1alpha1.HorizontalRunnerAutoscaler{}).
		Named(name).
		Complete(autoscaler)
}

func enterpriseKey(name string) string {
	return keyPrefixEnterprise + name
}