/*
Cleans up stale webhookconfigurations created by kyverno that were not cleanedup
*/
package main

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"os"
	"os/signal"
	"sync"
	"syscall"
	"time"

	kyvernov1beta1 "github.com/kyverno/kyverno/api/kyverno/v1beta1"
	kyvernoclient "github.com/kyverno/kyverno/pkg/client/clientset/versioned"
	"github.com/kyverno/kyverno/pkg/clients/dclient"
	"github.com/kyverno/kyverno/pkg/config"
	"github.com/kyverno/kyverno/pkg/leaderelection"
	"github.com/kyverno/kyverno/pkg/logging"
	"github.com/kyverno/kyverno/pkg/tls"
	"github.com/kyverno/kyverno/pkg/utils"
	"go.uber.org/multierr"
	admissionv1 "k8s.io/api/admission/v1"
	coordinationv1 "k8s.io/api/coordination/v1"
	"k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
)

var (
	kubeconfig           string
	setupLog             = logging.WithName("setup")
	clientRateLimitQPS   float64
	clientRateLimitBurst int
	logFormat            string
)

const (
	policyReportKind        string = "PolicyReport"
	clusterPolicyReportKind string = "ClusterPolicyReport"
	convertGenerateRequest  string = "ConvertGenerateRequest"
)

func parseFlags() error {
	logging.Init(nil)
	flag.StringVar(&logFormat, "loggingFormat", logging.TextFormat, "This determines the output format of the logger.")
	flag.StringVar(&kubeconfig, "kubeconfig", "", "Path to a kubeconfig. Only required if out-of-cluster.")
	flag.Float64Var(&clientRateLimitQPS, "clientRateLimitQPS", 0, "Configure the maximum QPS to the Kubernetes API server from Kyverno. Uses the client default if zero.")
	flag.IntVar(&clientRateLimitBurst, "clientRateLimitBurst", 0, "Configure the maximum burst for throttle. Uses the client default if zero.")
	if err := flag.Set("v", "2"); err != nil {
		return err
	}

	flag.Parse()
	return nil
}

func main() {
	// parse flags
	if err := parseFlags(); err != nil {
		fmt.Println("failed to parse flags", err)
		os.Exit(1)
	}
	// setup logger
	if err := logging.Setup(logFormat); err != nil {
		fmt.Println("could not setup logger", err)
		os.Exit(1)
	}
	// os signal handler
	signalCtx, signalCancel := signal.NotifyContext(logging.Background(), os.Interrupt, syscall.SIGTERM)
	defer signalCancel()

	stopCh := signalCtx.Done()

	// create client config
	clientConfig, err := config.CreateClientConfig(kubeconfig, clientRateLimitQPS, clientRateLimitBurst)
	if err != nil {
		setupLog.Error(err, "Failed to build kubeconfig")
		os.Exit(1)
	}

	kubeClient, err := kubernetes.NewForConfig(clientConfig)
	if err != nil {
		setupLog.Error(err, "Failed to create kubernetes client")
		os.Exit(1)
	}

	// DYNAMIC CLIENT
	// - client for all registered resources
	client, err := dclient.NewClient(signalCtx, clientConfig, kubeClient, nil, 15*time.Minute)
	if err != nil {
		setupLog.Error(err, "Failed to create client")
		os.Exit(1)
	}

	pclient, err := kyvernoclient.NewForConfig(clientConfig)
	if err != nil {
		setupLog.Error(err, "Failed to create client")
		os.Exit(1)
	}

	// Exit for unsupported version of kubernetes cluster
	if !utils.HigherThanKubernetesVersion(kubeClient.Discovery(), logging.GlobalLogger(), 1, 16, 0) {
		os.Exit(1)
	}

	requests := []request{
		{policyReportKind},
		{clusterPolicyReportKind},
		{convertGenerateRequest},
	}

	go func() {
		defer signalCancel()
		<-stopCh
	}()

	done := make(chan struct{})
	defer close(done)
	failure := false

	run := func(context.Context) {
		name := tls.GenerateRootCASecretName()
		_, err = kubeClient.CoreV1().Secrets(config.KyvernoNamespace()).Get(context.TODO(), name, metav1.GetOptions{})
		if err != nil {
			logging.V(2).Info("failed to fetch root CA secret", "name", name, "error", err.Error())
			if !errors.IsNotFound(err) {
				os.Exit(1)
			}
		}

		name = tls.GenerateTLSPairSecretName()
		_, err = kubeClient.CoreV1().Secrets(config.KyvernoNamespace()).Get(context.TODO(), name, metav1.GetOptions{})
		if err != nil {
			logging.V(2).Info("failed to fetch TLS Pair secret", "name", name, "error", err.Error())
			if !errors.IsNotFound(err) {
				os.Exit(1)
			}
		}

		if err = acquireLeader(signalCtx, kubeClient); err != nil {
			logging.V(2).Info("Failed to create lease 'kyvernopre-lock'")
			os.Exit(1)
		}

		// use pipeline to pass request to cleanup resources
		in := gen(done, stopCh, requests...)
		// process requests
		// processing routine count : 2
		p1 := process(client, pclient, done, stopCh, in)
		p2 := process(client, pclient, done, stopCh, in)
		// merge results from processing routines
		for err := range merge(done, stopCh, p1, p2) {
			if err != nil {
				failure = true
				logging.Error(err, "failed to cleanup resource")
			}
		}
		// if there is any failure then we fail process
		if failure {
			logging.V(2).Info("failed to cleanup prior configurations")
			os.Exit(1)
		}

		os.Exit(0)
	}

	le, err := leaderelection.New(
		logging.WithName("kyvernopre/LeaderElection"),
		"kyvernopre",
		config.KyvernoNamespace(),
		kubeClient,
		config.KyvernoPodName(),
		run,
		nil,
	)
	if err != nil {
		setupLog.Error(err, "failed to elect a leader")
		os.Exit(1)
	}

	le.Run(signalCtx)
}

func acquireLeader(ctx context.Context, kubeClient kubernetes.Interface) error {
	_, err := kubeClient.CoordinationV1().Leases(config.KyvernoNamespace()).Get(ctx, "kyvernopre-lock", metav1.GetOptions{})
	if err != nil {
		logging.V(2).Info("Lease 'kyvernopre-lock' not found. Starting clean-up...")
	} else {
		logging.V(2).Info("Leader was elected, quitting")
		os.Exit(0)
	}

	lease := coordinationv1.Lease{
		ObjectMeta: metav1.ObjectMeta{
			Name: "kyvernopre-lock",
		},
	}
	_, err = kubeClient.CoordinationV1().Leases(config.KyvernoNamespace()).Create(ctx, &lease, metav1.CreateOptions{})

	return err
}

func executeRequest(client dclient.Interface, kyvernoclient kyvernoclient.Interface, req request) error {
	switch req.kind {
	case convertGenerateRequest:
		return convertGR(kyvernoclient)
	}

	return nil
}

type request struct {
	kind string
}

/* Processing Pipeline
  					-> Process Requests
Generate Requests	-> Process Requests		-> Merge Results
					-> Process Requests
- number of processes can be controlled
- stop processing on SIGTERM OR SIGNKILL signal
- stop processing if any process fails(supported)
*/
// Generates requests to be processed
func gen(done <-chan struct{}, stopCh <-chan struct{}, requests ...request) <-chan request {
	out := make(chan request)
	go func() {
		defer close(out)
		for _, req := range requests {
			select {
			case out <- req:
			case <-done:
				println("done generate")
				return
			case <-stopCh:
				println("shutting down generate")
				return
			}
		}
	}()
	return out
}

// processes the requests
func process(client dclient.Interface, kyvernoclient kyvernoclient.Interface, done <-chan struct{}, stopCh <-chan struct{}, requests <-chan request) <-chan error {
	logger := logging.WithName("process")
	out := make(chan error)
	go func() {
		defer close(out)
		for req := range requests {
			select {
			case out <- executeRequest(client, kyvernoclient, req):
			case <-done:
				logger.Info("done")
				return
			case <-stopCh:
				logger.Info("shutting down")
				return
			}
		}
	}()
	return out
}

// waits for all processes to be complete and merges result
func merge(done <-chan struct{}, stopCh <-chan struct{}, processes ...<-chan error) <-chan error {
	logger := logging.WithName("merge")
	var wg sync.WaitGroup
	out := make(chan error)
	// gets the output from each process
	output := func(ch <-chan error) {
		defer wg.Done()
		for err := range ch {
			select {
			case out <- err:
			case <-done:
				logger.Info("done")
				return
			case <-stopCh:
				logger.Info("shutting down")
				return
			}
		}
	}

	wg.Add(len(processes))
	for _, process := range processes {
		go output(process)
	}

	// close when all the process goroutines are done
	go func() {
		wg.Wait()
		close(out)
	}()
	return out
}

func convertGR(pclient kyvernoclient.Interface) error {
	logger := logging.WithName("convertGenerateRequest")

	var errors []error
	grs, err := pclient.KyvernoV1().GenerateRequests(config.KyvernoNamespace()).List(context.TODO(), metav1.ListOptions{})
	if err != nil {
		logger.Error(err, "failed to list update requests")
		return err
	}
	for _, gr := range grs.Items {
		cp := gr.DeepCopy()
		var request *admissionv1.AdmissionRequest
		if cp.Spec.Context.AdmissionRequestInfo.AdmissionRequest != "" {
			var r admissionv1.AdmissionRequest
			err := json.Unmarshal([]byte(cp.Spec.Context.AdmissionRequestInfo.AdmissionRequest), &r)
			if err != nil {
				logger.Error(err, "failed to unmarshal admission request")
				errors = append(errors, err)
				continue
			}
		}
		ur := &kyvernov1beta1.UpdateRequest{
			ObjectMeta: metav1.ObjectMeta{
				GenerateName: "ur-",
				Namespace:    config.KyvernoNamespace(),
				Labels:       cp.GetLabels(),
			},
			Spec: kyvernov1beta1.UpdateRequestSpec{
				Type:     kyvernov1beta1.Generate,
				Policy:   cp.Spec.Policy,
				Resource: cp.Spec.Resource,
				Context: kyvernov1beta1.UpdateRequestSpecContext{
					UserRequestInfo: kyvernov1beta1.RequestInfo{
						Roles:             cp.Spec.Context.UserRequestInfo.Roles,
						ClusterRoles:      cp.Spec.Context.UserRequestInfo.ClusterRoles,
						AdmissionUserInfo: cp.Spec.Context.UserRequestInfo.AdmissionUserInfo,
					},
					AdmissionRequestInfo: kyvernov1beta1.AdmissionRequestInfoObject{
						AdmissionRequest: request,
						Operation:        cp.Spec.Context.AdmissionRequestInfo.Operation,
					},
				},
			},
		}

		_, err := pclient.KyvernoV1beta1().UpdateRequests(config.KyvernoNamespace()).Create(context.TODO(), ur, metav1.CreateOptions{})
		if err != nil {
			logger.Info("failed to create UpdateRequest", "GR namespace", gr.GetNamespace(), "GR name", gr.GetName(), "err", err.Error())
			errors = append(errors, err)
			continue
		} else {
			logger.Info("successfully created UpdateRequest", "GR namespace", gr.GetNamespace(), "GR name", gr.GetName())
		}

		if err := pclient.KyvernoV1().GenerateRequests(config.KyvernoNamespace()).Delete(context.TODO(), gr.GetName(), metav1.DeleteOptions{}); err != nil {
			errors = append(errors, err)
			logger.Error(err, "failed to delete GR")
		}
	}

	err = multierr.Combine(errors...)
	return err
}