// Copyright 2020 The Monogon Project Authors.
//
// SPDX-License-Identifier: Apache-2.0
//
// 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 kubernetes

import (
	"context"
	"fmt"
	"net"
	"os"
	"time"

	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
	"k8s.io/client-go/informers"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/tools/clientcmd"

	"source.monogon.dev/metropolis/node/core/localstorage"
	"source.monogon.dev/metropolis/node/core/network/dns"
	"source.monogon.dev/metropolis/node/kubernetes/clusternet"
	"source.monogon.dev/metropolis/node/kubernetes/nfproxy"
	"source.monogon.dev/metropolis/node/kubernetes/pki"
	"source.monogon.dev/metropolis/node/kubernetes/reconciler"
	"source.monogon.dev/metropolis/pkg/supervisor"
	apb "source.monogon.dev/metropolis/proto/api"
)

type Config struct {
	AdvertiseAddress net.IP
	ServiceIPRange   net.IPNet
	ClusterNet       net.IPNet

	KPKI                    *pki.PKI
	Root                    *localstorage.Root
	CorednsRegistrationChan chan *dns.ExtraDirective
}

type Service struct {
	c Config
}

func New(c Config) *Service {
	s := &Service{
		c: c,
	}
	return s
}

func (s *Service) Run(ctx context.Context) error {
	controllerManagerConfig, err := getPKIControllerManagerConfig(ctx, s.c.KPKI)
	if err != nil {
		return fmt.Errorf("could not generate controller manager pki config: %w", err)
	}
	controllerManagerConfig.clusterNet = s.c.ClusterNet
	schedulerConfig, err := getPKISchedulerConfig(ctx, s.c.KPKI)
	if err != nil {
		return fmt.Errorf("could not generate scheduler pki config: %w", err)
	}

	masterKubeconfig, err := s.c.KPKI.Kubeconfig(ctx, pki.Master)
	if err != nil {
		return fmt.Errorf("could not generate master kubeconfig: %w", err)
	}

	rawClientConfig, err := clientcmd.NewClientConfigFromBytes(masterKubeconfig)
	if err != nil {
		return fmt.Errorf("could not generate kubernetes client config: %w", err)
	}

	clientConfig, err := rawClientConfig.ClientConfig()
	clientSet, err := kubernetes.NewForConfig(clientConfig)
	if err != nil {
		return fmt.Errorf("could not generate kubernetes client: %w", err)
	}

	informerFactory := informers.NewSharedInformerFactory(clientSet, 5*time.Minute)

	hostname, err := os.Hostname()
	if err != nil {
		return fmt.Errorf("failed to get hostname: %w", err)
	}

	dnsHostIP := s.c.AdvertiseAddress // TODO: Which IP to use

	apiserver := &apiserverService{
		KPKI:                        s.c.KPKI,
		AdvertiseAddress:            s.c.AdvertiseAddress,
		ServiceIPRange:              s.c.ServiceIPRange,
		EphemeralConsensusDirectory: &s.c.Root.Ephemeral.Consensus,
	}

	kubelet := kubeletService{
		NodeName:           hostname,
		ClusterDNS:         []net.IP{dnsHostIP},
		KubeletDirectory:   &s.c.Root.Data.Kubernetes.Kubelet,
		EphemeralDirectory: &s.c.Root.Ephemeral,
		KPKI:               s.c.KPKI,
	}

	csiPlugin := csiPluginServer{
		KubeletDirectory: &s.c.Root.Data.Kubernetes.Kubelet,
		VolumesDirectory: &s.c.Root.Data.Volumes,
	}

	csiProvisioner := csiProvisionerServer{
		NodeName:         hostname,
		Kubernetes:       clientSet,
		InformerFactory:  informerFactory,
		VolumesDirectory: &s.c.Root.Data.Volumes,
	}

	clusternet := clusternet.Service{
		NodeName:        hostname,
		Kubernetes:      clientSet,
		ClusterNet:      s.c.ClusterNet,
		InformerFactory: informerFactory,
		DataDirectory:   &s.c.Root.Data.Kubernetes.ClusterNetworking,
	}

	nfproxy := nfproxy.Service{
		ClusterCIDR: s.c.ClusterNet,
		ClientSet:   clientSet,
	}

	for _, sub := range []struct {
		name     string
		runnable supervisor.Runnable
	}{
		{"apiserver", apiserver.Run},
		{"controller-manager", runControllerManager(*controllerManagerConfig)},
		{"scheduler", runScheduler(*schedulerConfig)},
		{"kubelet", kubelet.Run},
		{"reconciler", reconciler.Run(clientSet)},
		{"csi-plugin", csiPlugin.Run},
		{"csi-provisioner", csiProvisioner.Run},
		{"clusternet", clusternet.Run},
		{"nfproxy", nfproxy.Run},
	} {
		err := supervisor.Run(ctx, sub.name, sub.runnable)
		if err != nil {
			return fmt.Errorf("could not run sub-service %q: %w", sub.name, err)
		}
	}

	supervisor.Logger(ctx).Info("Registering K8s CoreDNS")
	clusterDNSDirective := dns.NewKubernetesDirective("cluster.local", masterKubeconfig)
	s.c.CorednsRegistrationChan <- clusterDNSDirective

	supervisor.Signal(ctx, supervisor.SignalHealthy)
	<-ctx.Done()
	s.c.CorednsRegistrationChan <- dns.CancelDirective(clusterDNSDirective)
	return nil
}

// GetDebugKubeconfig issues a kubeconfig for an arbitrary given identity. Useful for debugging and testing.
func (s *Service) GetDebugKubeconfig(ctx context.Context, request *apb.GetDebugKubeconfigRequest) (*apb.GetDebugKubeconfigResponse, error) {
	client, err := s.c.KPKI.VolatileClient(ctx, request.Id, request.Groups)
	if err != nil {
		return nil, status.Errorf(codes.Unavailable, "Failed to get volatile client certificate: %v", err)
	}
	kubeconfig, err := pki.Kubeconfig(ctx, s.c.KPKI.KV, client)
	if err != nil {
		return nil, status.Errorf(codes.Unavailable, "Failed to generate kubeconfig: %v", err)
	}
	return &apb.GetDebugKubeconfigResponse{DebugKubeconfig: string(kubeconfig)}, nil
}