package control

import (
	"bufio"
	"context"
	cryptorand "crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"encoding/base64"
	"encoding/csv"
	"encoding/hex"
	"fmt"
	"html/template"
	"io"
	"io/ioutil"
	"math/rand"
	"net"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/rancher/k3s/pkg/daemons/config"
	"github.com/sirupsen/logrus"
	"k8s.io/apiserver/pkg/authentication/authenticator"
	certutil "k8s.io/client-go/util/cert"
	"k8s.io/kubernetes/cmd/kube-apiserver/app"
	cmapp "k8s.io/kubernetes/cmd/kube-controller-manager/app"
	sapp "k8s.io/kubernetes/cmd/kube-scheduler/app"
	_ "k8s.io/kubernetes/pkg/client/metrics/prometheus" // for client metric registration
	"k8s.io/kubernetes/pkg/kubeapiserver/authorizer/modes"
	"k8s.io/kubernetes/pkg/master"
	"k8s.io/kubernetes/pkg/proxy/util"
	_ "k8s.io/kubernetes/pkg/util/reflector/prometheus" // for reflector metric registration
	_ "k8s.io/kubernetes/pkg/util/workqueue/prometheus" // for workqueue metric registration
	_ "k8s.io/kubernetes/pkg/version/prometheus"        // for version metric registration
)

var (
	localhostIP        = net.ParseIP("127.0.0.1")
	kubeconfigTemplate = template.Must(template.New("kubeconfig").Parse(`apiVersion: v1
clusters:
- cluster:
    server: {{.URL}}
    certificate-authority-data: {{.CACert}}
  name: local
contexts:
- context:
    cluster: local
    namespace: default
    user: user
  name: Default
current-context: Default
kind: Config
preferences: {}
users:
- name: user
  user:
    username: {{.User}}
    password: {{.Password}}
`))
)

func Server(ctx context.Context, cfg *config.Control) error {
	rand.Seed(time.Now().UTC().UnixNano())

	runtime := &config.ControlRuntime{}
	cfg.Runtime = runtime

	if err := prepare(cfg, runtime); err != nil {
		return err
	}

	cfg.Runtime.Tunnel = setupTunnel()
	util.DisableProxyHostnameCheck = true

	auth, handler, err := apiServer(ctx, cfg, runtime)
	if err != nil {
		return err
	}

	runtime.Handler = handler
	runtime.Authenticator = auth

	if !cfg.NoScheduler {
		scheduler(cfg, runtime)
	}

	controllerManager(cfg, runtime)

	return nil
}

func controllerManager(cfg *config.Control, runtime *config.ControlRuntime) {
	args := []string{
		"--kubeconfig", runtime.KubeConfigSystem,
		"--service-account-private-key-file", runtime.ServiceKey,
		"--allocate-node-cidrs",
		"--cluster-cidr", cfg.ClusterIPRange.String(),
		"--root-ca-file", runtime.TokenCA,
		"--port", "0",
		"--secure-port", "0",
	}
	if cfg.NoLeaderElect {
		args = append(args, "--leader-elect=false")
	}
	args = append(args, cfg.ExtraControllerArgs...)
	command := cmapp.NewControllerManagerCommand()
	command.SetArgs(args)

	go func() {
		logrus.Infof("Running kube-controller-manager %s", config.ArgString(args))
		logrus.Fatalf("controller-manager exited: %v", command.Execute())
	}()
}

func scheduler(cfg *config.Control, runtime *config.ControlRuntime) {
	args := []string{
		"--kubeconfig", runtime.KubeConfigSystem,
		"--port", "0",
		"--secure-port", "0",
	}
	if cfg.NoLeaderElect {
		args = append(args, "--leader-elect=false")
	}
	args = append(args, cfg.ExtraSchedulerAPIArgs...)
	command := sapp.NewSchedulerCommand()
	command.SetArgs(args)

	go func() {
		logrus.Infof("Running kube-scheduler %s", config.ArgString(args))
		logrus.Fatalf("scheduler exited: %v", command.Execute())
	}()
}

func apiServer(ctx context.Context, cfg *config.Control, runtime *config.ControlRuntime) (authenticator.Request, http.Handler, error) {
	var args []string

	if len(cfg.ETCDEndpoints) > 0 {
		args = append(args, "--storage-backend", "etcd3")
		args = append(args, "--etcd-servers", strings.Join(cfg.ETCDEndpoints, ","))
		if cfg.ETCDKeyFile != "" {
			args = append(args, "--etcd-keyfile", cfg.ETCDKeyFile)
		}
		if cfg.ETCDCAFile != "" {
			args = append(args, "--etcd-cafile", cfg.ETCDCAFile)
		}
		if cfg.ETCDCertFile != "" {
			args = append(args, "--etcd-certfile", cfg.ETCDCertFile)
		}
	}

	certDir := filepath.Join(cfg.DataDir, "tls/temporary-certs")
	os.MkdirAll(certDir, 0700)

	args = append(args, "--cert-dir", certDir)
	args = append(args, "--allow-privileged=true")
	args = append(args, "--authorization-mode", strings.Join([]string{modes.ModeNode, modes.ModeRBAC}, ","))
	args = append(args, "--service-account-signing-key-file", runtime.ServiceKey)
	args = append(args, "--service-cluster-ip-range", cfg.ServiceIPRange.String())
	args = append(args, "--advertise-port", strconv.Itoa(cfg.AdvertisePort))
	args = append(args, "--advertise-address", localhostIP.String())
	args = append(args, "--insecure-port", "0")
	args = append(args, "--secure-port", strconv.Itoa(cfg.ListenPort))
	args = append(args, "--bind-address", localhostIP.String())
	args = append(args, "--tls-cert-file", runtime.TLSCert)
	args = append(args, "--tls-private-key-file", runtime.TLSKey)
	args = append(args, "--service-account-key-file", runtime.ServiceKey)
	args = append(args, "--service-account-issuer", "k3s")
	args = append(args, "--api-audiences", "unknown")
	args = append(args, "--basic-auth-file", runtime.PasswdFile)
	args = append(args, "--kubelet-client-certificate", runtime.NodeCert)
	args = append(args, "--kubelet-client-key", runtime.NodeKey)

	args = append(args, cfg.ExtraAPIArgs...)
	command := app.NewAPIServerCommand(ctx.Done())
	command.SetArgs(args)

	go func() {
		logrus.Infof("Running kube-apiserver %s", config.ArgString(args))
		logrus.Fatalf("apiserver exited: %v", command.Execute())
	}()

	startupConfig := <-app.StartupConfig

	return startupConfig.Authenticator, startupConfig.Handler, nil
}

func defaults(config *config.Control) {
	if config.ClusterIPRange == nil {
		_, clusterIPNet, _ := net.ParseCIDR("10.42.0.0/16")
		config.ClusterIPRange = clusterIPNet
	}

	if config.ServiceIPRange == nil {
		_, serviceIPNet, _ := net.ParseCIDR("10.43.0.0/16")
		config.ServiceIPRange = serviceIPNet
	}

	if len(config.ClusterDNS) == 0 {
		config.ClusterDNS = net.ParseIP("10.43.0.10")
	}

	if config.AdvertisePort == 0 {
		config.AdvertisePort = 6445
	}

	if config.ListenPort == 0 {
		config.ListenPort = 6444
	}

	if config.DataDir == "" {
		config.DataDir = "./management-state"
	}
}

func prepare(config *config.Control, runtime *config.ControlRuntime) error {
	var err error

	defaults(config)

	if _, err := os.Stat(config.DataDir); os.IsNotExist(err) {
		if err := os.MkdirAll(config.DataDir, 0700); err != nil {
			return err
		}
	} else if err != nil {
		return err
	}

	config.DataDir, err = filepath.Abs(config.DataDir)
	if err != nil {
		return err
	}

	os.MkdirAll(path.Join(config.DataDir, "tls"), 0700)
	os.MkdirAll(path.Join(config.DataDir, "cred"), 0700)

	name := "localhost"
	runtime.TLSCert = path.Join(config.DataDir, "tls", name+".crt")
	runtime.TLSKey = path.Join(config.DataDir, "tls", name+".key")
	runtime.TLSCA = path.Join(config.DataDir, "tls", "ca.crt")
	runtime.TLSCAKey = path.Join(config.DataDir, "tls", "ca.key")
	runtime.TokenCA = path.Join(config.DataDir, "tls", "token-ca.crt")
	runtime.TokenCAKey = path.Join(config.DataDir, "tls", "token-ca.key")
	runtime.ServiceKey = path.Join(config.DataDir, "tls", "service.key")
	runtime.PasswdFile = path.Join(config.DataDir, "cred", "passwd")
	runtime.KubeConfigSystem = path.Join(config.DataDir, "cred", "kubeconfig-system.yaml")
	runtime.NodeKey = path.Join(config.DataDir, "tls", "token-node.key")
	runtime.NodeCert = path.Join(config.DataDir, "tls", "token-node.crt")

	regen := false
	if _, err := os.Stat(runtime.TLSCA); err != nil {
		regen = true
		if err := genCA(runtime); err != nil {
			return err
		}
	}

	if err := genServiceAccount(runtime); err != nil {
		return err
	}

	if err := genTLS(regen, config, runtime); err != nil {
		return err
	}

	if err := genTokenTLS(config, runtime); err != nil {
		return err
	}

	if err := genUsers(config, runtime); err != nil {
		return err
	}

	return readTokens(runtime)
}

func readTokens(runtime *config.ControlRuntime) error {
	f, err := os.Open(runtime.PasswdFile)
	if err != nil {
		return err
	}
	reader := csv.NewReader(f)
	reader.FieldsPerRecord = -1

	for {
		record, err := reader.Read()
		if err == io.EOF {
			break
		}
		if err != nil {
			return err
		}
		if len(record) < 2 {
			continue
		}

		switch record[1] {
		case "node":
			runtime.NodeToken = "node:" + record[0]
		case "admin":
			runtime.ClientToken = "admin:" + record[0]
		}
	}

	return nil
}

func ensureNodeToken(config *config.Control, runtime *config.ControlRuntime) error {
	if config.ClusterSecret == "" {
		return nil
	}

	f, err := os.Open(runtime.PasswdFile)
	if err != nil {
		return err
	}
	defer f.Close()

	buf := &strings.Builder{}
	scan := bufio.NewScanner(f)
	for scan.Scan() {
		line := scan.Text()
		parts := strings.Split(line, ",")
		if len(parts) < 4 {
			continue
		}
		if parts[1] == "node" {
			if parts[0] == config.ClusterSecret {
				return nil
			}
			parts[0] = config.ClusterSecret
			line = strings.Join(parts, ",")
		}
		buf.WriteString(line)
		buf.WriteString("\n")
	}

	if scan.Err() != nil {
		return scan.Err()
	}

	f.Close()
	return ioutil.WriteFile(runtime.PasswdFile, []byte(buf.String()), 0600)
}

func genUsers(config *config.Control, runtime *config.ControlRuntime) error {
	if s, err := os.Stat(runtime.PasswdFile); err == nil && s.Size() > 0 {
		return ensureNodeToken(config, runtime)
	}

	adminToken, err := getToken()
	if err != nil {
		return err
	}
	systemToken, err := getToken()
	if err != nil {
		return err
	}
	nodeToken, err := getToken()
	if err != nil {
		return err
	}

	if config.ClusterSecret != "" {
		nodeToken = config.ClusterSecret
	}

	passwd := fmt.Sprintf(`%s,admin,admin,system:masters
%s,system,system,system:masters
%s,node,node,system:masters
`, adminToken, systemToken, nodeToken)

	caCertBytes, err := ioutil.ReadFile(runtime.TLSCA)
	if err != nil {
		return err
	}

	caCert := base64.StdEncoding.EncodeToString(caCertBytes)

	if err := kubeConfig(runtime.KubeConfigSystem, fmt.Sprintf("https://localhost:%d", config.ListenPort), caCert,
		"system", systemToken); err != nil {
		return err
	}

	return ioutil.WriteFile(runtime.PasswdFile, []byte(passwd), 0600)
}

func getToken() (string, error) {
	token := make([]byte, 16, 16)
	_, err := cryptorand.Read(token)
	if err != nil {
		return "", err
	}
	return hex.EncodeToString(token), err
}

func genTokenTLS(config *config.Control, runtime *config.ControlRuntime) error {
	regen := false
	if _, err := os.Stat(runtime.TokenCA); err != nil {
		regen = true
		if err := genTokenCA(runtime); err != nil {
			return err
		}
	}

	_, apiServerServiceIP, err := master.DefaultServiceIPRange(*config.ServiceIPRange)
	if err != nil {
		return err
	}

	cfg := certutil.Config{
		CommonName: "kubernetes",
		AltNames: certutil.AltNames{
			DNSNames: []string{"kubernetes.default.svc", "kubernetes.default", "kubernetes", "localhost"},
			IPs:      []net.IP{net.ParseIP("127.0.0.1"), apiServerServiceIP},
		},
		Usages: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageClientAuth},
	}

	if _, err := os.Stat(runtime.NodeCert); err == nil && !regen {
		return nil
	}

	caKeyBytes, err := ioutil.ReadFile(runtime.TokenCAKey)
	if err != nil {
		return err
	}

	caBytes, err := ioutil.ReadFile(runtime.TokenCA)
	if err != nil {
		return err
	}

	caKey, err := certutil.ParsePrivateKeyPEM(caKeyBytes)
	if err != nil {
		return err
	}

	caCert, err := certutil.ParseCertsPEM(caBytes)
	if err != nil {
		return err
	}

	key, err := certutil.NewPrivateKey()
	if err != nil {
		return err
	}

	cert, err := certutil.NewSignedCert(cfg, key, caCert[0], caKey.(*rsa.PrivateKey))
	if err != nil {
		return err
	}

	if err := certutil.WriteKey(runtime.NodeKey, certutil.EncodePrivateKeyPEM(key)); err != nil {
		return err
	}

	return certutil.WriteCert(runtime.NodeCert, append(certutil.EncodeCertPEM(cert), certutil.EncodeCertPEM(caCert[0])...))
}

func genTLS(regen bool, config *config.Control, runtime *config.ControlRuntime) error {
	if !regen {
		_, certErr := os.Stat(runtime.TLSCert)
		_, keyErr := os.Stat(runtime.TLSKey)
		if certErr == nil && keyErr == nil {
			return nil
		}
	}

	_, apiServerServiceIP, err := master.DefaultServiceIPRange(*config.ServiceIPRange)
	if err != nil {
		return err
	}

	cfg := certutil.Config{
		CommonName: "localhost",
		AltNames: certutil.AltNames{
			DNSNames: []string{"kubernetes.default.svc", "kubernetes.default", "kubernetes", "localhost"},
			IPs:      []net.IP{apiServerServiceIP, localhostIP},
		},
		Usages: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
	}

	caKeyBytes, err := ioutil.ReadFile(runtime.TLSCAKey)
	if err != nil {
		return err
	}

	caBytes, err := ioutil.ReadFile(runtime.TLSCA)
	if err != nil {
		return err
	}

	caKey, err := certutil.ParsePrivateKeyPEM(caKeyBytes)
	if err != nil {
		return err
	}

	caCert, err := certutil.ParseCertsPEM(caBytes)
	if err != nil {
		return err
	}

	key, err := certutil.NewPrivateKey()
	if err != nil {
		return err
	}

	cert, err := certutil.NewSignedCert(cfg, key, caCert[0], caKey.(*rsa.PrivateKey))
	if err != nil {
		return err
	}

	if err := certutil.WriteKey(runtime.TLSKey, certutil.EncodePrivateKeyPEM(key)); err != nil {
		return err
	}

	return certutil.WriteCert(runtime.TLSCert, append(certutil.EncodeCertPEM(cert), certutil.EncodeCertPEM(caCert[0])...))
}

func genServiceAccount(runtime *config.ControlRuntime) error {
	_, keyErr := os.Stat(runtime.ServiceKey)
	if keyErr == nil {
		return nil
	}

	key, err := certutil.NewPrivateKey()
	if err != nil {
		return err
	}

	return certutil.WriteKey(runtime.ServiceKey, certutil.EncodePrivateKeyPEM(key))
}

func genTokenCA(runtime *config.ControlRuntime) error {
	caKey, err := certutil.NewPrivateKey()
	if err != nil {
		return err
	}

	cfg := certutil.Config{
		CommonName: fmt.Sprintf("%s-ca@%d", "k3s-token", time.Now().Unix()),
	}

	cert, err := certutil.NewSelfSignedCACert(cfg, caKey)
	if err != nil {
		return err
	}

	if err := certutil.WriteKey(runtime.TokenCAKey, certutil.EncodePrivateKeyPEM(caKey)); err != nil {
		return err
	}

	return certutil.WriteCert(runtime.TokenCA, certutil.EncodeCertPEM(cert))
}

func genCA(runtime *config.ControlRuntime) error {
	caKey, err := certutil.NewPrivateKey()
	if err != nil {
		return err
	}

	cfg := certutil.Config{
		CommonName: fmt.Sprintf("%s-ca@%d", "k3s", time.Now().Unix()),
	}

	cert, err := certutil.NewSelfSignedCACert(cfg, caKey)
	if err != nil {
		return err
	}

	if err := certutil.WriteKey(runtime.TLSCAKey, certutil.EncodePrivateKeyPEM(caKey)); err != nil {
		return err
	}

	return certutil.WriteCert(runtime.TLSCA, certutil.EncodeCertPEM(cert))
}

func kubeConfig(dest, url, cert, user, password string) error {
	data := struct {
		URL      string
		CACert   string
		User     string
		Password string
	}{
		URL:      url,
		CACert:   cert,
		User:     user,
		Password: password,
	}

	output, err := os.Create(dest)
	if err != nil {
		return err
	}
	defer output.Close()

	return kubeconfigTemplate.Execute(output, &data)
}