package destination

import (
	"context"
	"flag"
	"net"
	"os"
	"os/signal"
	"syscall"

	"github.com/linkerd/linkerd2/controller/api/destination"
	"github.com/linkerd/linkerd2/controller/k8s"
	"github.com/linkerd/linkerd2/pkg/admin"
	"github.com/linkerd/linkerd2/pkg/flags"
	pkgK8s "github.com/linkerd/linkerd2/pkg/k8s"
	"github.com/linkerd/linkerd2/pkg/trace"
	"github.com/linkerd/linkerd2/pkg/util"
	log "github.com/sirupsen/logrus"
)

// Main executes the destination subcommand
func Main(args []string) {
	cmd := flag.NewFlagSet("destination", flag.ExitOnError)

	addr := cmd.String("addr", ":8086", "address to serve on")
	metricsAddr := cmd.String("metrics-addr", ":9996", "address to serve scrapable metrics on")
	kubeConfigPath := cmd.String("kubeconfig", "", "path to kube config")
	enableH2Upgrade := cmd.Bool("enable-h2-upgrade", true, "Enable transparently upgraded HTTP2 connections among pods in the service mesh")
	disableIdentity := cmd.Bool("disable-identity", false, "Disable identity configuration")
	controllerNamespace := cmd.String("controller-namespace", "linkerd", "namespace in which Linkerd is installed")
	enableEndpointSlices := cmd.Bool("enable-endpoint-slices", false, "Enable the usage of EndpointSlice informers and resources")
	trustDomain := cmd.String("identity-trust-domain", "", "configures the name suffix used for identities")
	clusterDomain := cmd.String("cluster-domain", "", "kubernetes cluster domain")
	defaultOpaquePorts := cmd.String("default-opaque-ports", "", "configures the default opaque ports")

	traceCollector := flags.AddTraceFlags(cmd)

	flags.ConfigureAndParse(cmd, args)

	stop := make(chan os.Signal, 1)
	signal.Notify(stop, os.Interrupt, syscall.SIGTERM)

	done := make(chan struct{})

	lis, err := net.Listen("tcp", *addr)
	if err != nil {
		log.Fatalf("Failed to listen on %s: %s", *addr, err)
	}

	if *disableIdentity {
		log.Info("Identity is disabled")
	} else {
		if *trustDomain == "" {
			*trustDomain = "cluster.local"
			log.Warnf(" expected trust domain through args (falling back to %s)", *trustDomain)
		}
	}

	if *clusterDomain == "" {
		*clusterDomain = "cluster.local"
		log.Warnf("expected cluster domain through args (falling back to %s)", *clusterDomain)
	}

	opaquePorts, err := util.ParsePorts(*defaultOpaquePorts)
	if err != nil {
		log.Fatalf("Failed to parse opaque Ports %s: %s", *defaultOpaquePorts, err)
	}

	log.Infof("Using default opaque ports: %v", opaquePorts)

	if *traceCollector != "" {
		if err := trace.InitializeTracing("linkerd-destination", *traceCollector); err != nil {
			log.Warnf("failed to initialize tracing: %s", err)
		}
	}

	// we need to create a separate client to check for EndpointSlice access in k8s cluster
	// when slices are enabled and registered, k8sAPI is initialized with 'ES' resource
	k8Client, err := pkgK8s.NewAPI(*kubeConfigPath, "", "", []string{}, 0)
	if err != nil {
		log.Fatalf("Failed to initialize K8s API Client: %s", err)
	}

	ctx := context.Background()

	err = pkgK8s.EndpointSliceAccess(ctx, k8Client)
	if *enableEndpointSlices && err != nil {
		log.Fatalf("Failed to start with EndpointSlices enabled: %s", err)
	}

	var k8sAPI *k8s.API
	if *enableEndpointSlices {
		k8sAPI, err = k8s.InitializeAPI(
			ctx,
			*kubeConfigPath,
			true,
			k8s.Endpoint, k8s.ES, k8s.Pod, k8s.RS, k8s.Svc, k8s.SP, k8s.TS, k8s.Job, k8s.NS, k8s.Node,
		)
	} else {
		k8sAPI, err = k8s.InitializeAPI(
			ctx,
			*kubeConfigPath,
			true,
			k8s.Endpoint, k8s.Pod, k8s.RS, k8s.Svc, k8s.SP, k8s.TS, k8s.Job, k8s.NS, k8s.Node,
		)
	}
	if err != nil {
		log.Fatalf("Failed to initialize K8s API: %s", err)
	}

	server, err := destination.NewServer(
		*addr,
		*controllerNamespace,
		*trustDomain,
		*enableH2Upgrade,
		*enableEndpointSlices,
		k8sAPI,
		*clusterDomain,
		opaquePorts,
		done,
	)

	if err != nil {
		log.Fatalf("Failed to initialize destination server: %s", err)
	}

	k8sAPI.Sync(nil) // blocks until caches are synced

	go func() {
		log.Infof("starting gRPC server on %s", *addr)
		server.Serve(lis)
	}()

	adminServer := admin.NewServer(*metricsAddr)

	go func() {
		log.Infof("starting admin server on %s", *metricsAddr)
		adminServer.ListenAndServe()
	}()

	<-stop

	log.Infof("shutting down gRPC server on %s", *addr)
	close(done)
	server.GracefulStop()
	adminServer.Shutdown(ctx)
}