/*
Copyright 2019 The Kubernetes 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 nfdmaster

import (
	"crypto/tls"
	"crypto/x509"
	"fmt"
	"io/ioutil"
	"log"
	"net"
	"os"
	"regexp"
	"sort"
	"strings"
	"time"

	"golang.org/x/net/context"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/peer"
	api "k8s.io/api/core/v1"
	"sigs.k8s.io/node-feature-discovery/pkg/apihelper"
	pb "sigs.k8s.io/node-feature-discovery/pkg/labeler"
	"sigs.k8s.io/node-feature-discovery/pkg/version"
)

const (
	// Namespace for feature labels
	labelNs = "feature.node.kubernetes.io/"

	// Namespace for all NFD-related annotations
	annotationNs = "nfd.node.kubernetes.io/"
)

// package loggers
var (
	stdoutLogger = log.New(os.Stdout, "", log.LstdFlags)
	stderrLogger = log.New(os.Stderr, "", log.LstdFlags)
	nodeName     = os.Getenv("NODE_NAME")
)

// Labels are a Kubernetes representation of discovered features.
type Labels map[string]string

// Annotations are used for NFD-related node metadata
type Annotations map[string]string

// Command line arguments
type Args struct {
	CaFile         string
	CertFile       string
	KeyFile        string
	LabelWhiteList *regexp.Regexp
	NoPublish      bool
	Port           int
	VerifyNodeName bool
}

type NfdMaster interface {
	Run() error
	Stop()
	WaitForReady(time.Duration) bool
}

type nfdMaster struct {
	args   Args
	server *grpc.Server
	ready  chan bool
}

// Create new NfdMaster server instance.
func NewNfdMaster(args Args) (*nfdMaster, error) {
	nfd := &nfdMaster{args: args, ready: make(chan bool, 1)}

	// Check TLS related args
	if args.CertFile != "" || args.KeyFile != "" || args.CaFile != "" {
		if args.CertFile == "" {
			return nfd, fmt.Errorf("--cert-file needs to be specified alongside --key-file and --ca-file")
		}
		if args.KeyFile == "" {
			return nfd, fmt.Errorf("--key-file needs to be specified alongside --cert-file and --ca-file")
		}
		if args.CaFile == "" {
			return nfd, fmt.Errorf("--ca-file needs to be specified alongside --cert-file and --key-file")
		}
	}

	return nfd, nil
}

// Run NfdMaster server. The method returns in case of fatal errors or if Stop()
// is called.
func (m *nfdMaster) Run() error {
	stdoutLogger.Printf("Node Feature Discovery Master %s", version.Get())
	stdoutLogger.Printf("NodeName: '%s'", nodeName)

	// Initialize Kubernetes API helpers
	helper := apihelper.APIHelpers(apihelper.K8sHelpers{})

	if !m.args.NoPublish {
		err := updateMasterNode(helper)
		if err != nil {
			return fmt.Errorf("failed to update master node: %v", err)
		}
	}

	// Create server listening for TCP connections
	lis, err := net.Listen("tcp", fmt.Sprintf(":%d", m.args.Port))
	if err != nil {
		return fmt.Errorf("failed to listen: %v", err)
	}
	// Notify that we're ready to accept connections
	m.ready <- true
	close(m.ready)

	serverOpts := []grpc.ServerOption{}
	// Enable mutual TLS authentication if --cert-file, --key-file or --ca-file
	// is defined
	if m.args.CertFile != "" || m.args.KeyFile != "" || m.args.CaFile != "" {
		// Load cert for authenticating this server
		cert, err := tls.LoadX509KeyPair(m.args.CertFile, m.args.KeyFile)
		if err != nil {
			return fmt.Errorf("failed to load server certificate: %v", err)
		}
		// Load CA cert for client cert verification
		caCert, err := ioutil.ReadFile(m.args.CaFile)
		if err != nil {
			return fmt.Errorf("failed to read root certificate file: %v", err)
		}
		caPool := x509.NewCertPool()
		if ok := caPool.AppendCertsFromPEM(caCert); !ok {
			return fmt.Errorf("failed to add certificate from '%s'", m.args.CaFile)
		}
		// Create TLS config
		tlsConfig := &tls.Config{
			Certificates: []tls.Certificate{cert},
			ClientCAs:    caPool,
			ClientAuth:   tls.RequireAndVerifyClientCert,
		}
		serverOpts = append(serverOpts, grpc.Creds(credentials.NewTLS(tlsConfig)))
	}
	m.server = grpc.NewServer(serverOpts...)
	pb.RegisterLabelerServer(m.server, &labelerServer{args: m.args, apiHelper: helper})
	stdoutLogger.Printf("gRPC server serving on port: %d", m.args.Port)
	return m.server.Serve(lis)
}

// Stop NfdMaster
func (m *nfdMaster) Stop() {
	m.server.Stop()
}

// Wait until NfdMaster is able able to accept connections.
func (m *nfdMaster) WaitForReady(timeout time.Duration) bool {
	select {
	case ready, ok := <-m.ready:
		// Ready if the flag is true or the channel has been closed
		if ready == true || ok == false {
			return true
		}
	case <-time.After(timeout):
		return false
	}
	// We should never end-up here
	return false
}

// Advertise NFD master information
func updateMasterNode(helper apihelper.APIHelpers) error {
	cli, err := helper.GetClient()
	if err != nil {
		return err
	}
	node, err := helper.GetNode(cli, nodeName)
	if err != nil {
		return err
	}

	// Advertise NFD version as an annotation
	addAnnotations(node, Annotations{"master.version": version.Get()})
	err = helper.UpdateNode(cli, node)
	if err != nil {
		stderrLogger.Printf("can't update node: %s", err.Error())
		return err
	}

	return nil
}

// Filter labels if whitelist has been defined
func filterFeatureLabels(labels *Labels, labelWhiteList *regexp.Regexp) {
	for name := range *labels {
		// Skip if label doesn't match labelWhiteList
		if !labelWhiteList.MatchString(name) {
			stderrLogger.Printf("%s does not match the whitelist (%s) and will not be published.", name, labelWhiteList.String())
			delete(*labels, name)
		}
	}
}

// Implement LabelerServer
type labelerServer struct {
	args      Args
	apiHelper apihelper.APIHelpers
}

// Service SetLabels
func (s *labelerServer) SetLabels(c context.Context, r *pb.SetLabelsRequest) (*pb.SetLabelsReply, error) {
	if s.args.VerifyNodeName {
		// Client authorization.
		// Check that the node name matches the CN from the TLS cert
		client, ok := peer.FromContext(c)
		if !ok {
			stderrLogger.Printf("gRPC request error: failed to get peer (client)")
			return &pb.SetLabelsReply{}, fmt.Errorf("failed to get peer (client)")
		}
		tlsAuth, ok := client.AuthInfo.(credentials.TLSInfo)
		if !ok {
			stderrLogger.Printf("gRPC request error: incorrect client credentials from '%v'", client.Addr)
			return &pb.SetLabelsReply{}, fmt.Errorf("incorrect client credentials")
		}
		if len(tlsAuth.State.VerifiedChains) == 0 || len(tlsAuth.State.VerifiedChains[0]) == 0 {
			stderrLogger.Printf("gRPC request error: client certificate verification for '%v' failed", client.Addr)
			return &pb.SetLabelsReply{}, fmt.Errorf("client certificate verification failed")
		}
		cn := tlsAuth.State.VerifiedChains[0][0].Subject.CommonName
		if cn != r.NodeName {
			stderrLogger.Printf("gRPC request error: authorization for %v failed: cert valid for '%s', requested node name '%s'", client.Addr, cn, r.NodeName)
			return &pb.SetLabelsReply{}, fmt.Errorf("request authorization failed: cert valid for '%s', requested node name '%s'", cn, r.NodeName)
		}
	}
	stdoutLogger.Printf("REQUEST Node: %s NFD-version: %s Labels: %s", r.NodeName, r.NfdVersion, r.Labels)

	if !s.args.NoPublish {
		// Advertise NFD worker version and label names as annotations
		keys := make([]string, 0, len(r.Labels))
		for k, _ := range r.Labels {
			keys = append(keys, k)
		}
		sort.Strings(keys)
		annotations := Annotations{"worker.version": r.NfdVersion,
			"feature-labels": strings.Join(keys, ",")}

		err := updateNodeFeatures(s.apiHelper, r.NodeName, r.Labels, annotations)
		if err != nil {
			stderrLogger.Printf("failed to advertise labels: %s", err.Error())
			return &pb.SetLabelsReply{}, err
		}
	}
	return &pb.SetLabelsReply{}, nil
}

// advertiseFeatureLabels advertises the feature labels to a Kubernetes node
// via the API server.
func updateNodeFeatures(helper apihelper.APIHelpers, nodeName string, labels Labels, annotations Annotations) error {
	cli, err := helper.GetClient()
	if err != nil {
		return err
	}

	// Get the worker node object
	node, err := helper.GetNode(cli, nodeName)
	if err != nil {
		return err
	}

	// Remove old labels
	if l, ok := node.Annotations[annotationNs+"feature-labels"]; ok {
		oldLabels := strings.Split(l, ",")
		removeLabels(node, oldLabels)
	}

	// Also, remove all labels with the old prefix, and the old version label
	removeLabelsWithPrefix(node, "node.alpha.kubernetes-incubator.io/nfd")
	removeLabelsWithPrefix(node, "node.alpha.kubernetes-incubator.io/node-feature-discovery")

	// Add labels to the node object.
	addLabels(node, labels)

	// Add annotations
	addAnnotations(node, annotations)

	// Send the updated node to the apiserver.
	err = helper.UpdateNode(cli, node)
	if err != nil {
		stderrLogger.Printf("can't update node: %s", err.Error())
		return err
	}

	return nil
}

// Remove any labels having the given prefix
func removeLabelsWithPrefix(n *api.Node, search string) {
	for k := range n.Labels {
		if strings.HasPrefix(k, search) {
			delete(n.Labels, k)
		}
	}
}

// Removes NFD labels from a Node object
func removeLabels(n *api.Node, labelNames []string) {
	for _, l := range labelNames {
		delete(n.Labels, labelNs+l)
	}
}

// Add NFD labels to a Node object.
func addLabels(n *api.Node, labels map[string]string) {
	for k, v := range labels {
		n.Labels[labelNs+k] = v
	}
}

// Add Annotations to a Node object
func addAnnotations(n *api.Node, annotations map[string]string) {
	for k, v := range annotations {
		n.Annotations[annotationNs+k] = v
	}
}