package key

import (
	"crypto/ecdsa"
	"crypto/ed25519"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"errors"
	"fmt"
	"github.com/spf13/cobra"
	"log"
	"math/big"
	"net"
	"os"
	"strings"
	"time"
)

var (
	host       string
	validFrom  string
	validFor   time.Duration
	isCA       bool
	rsaBits    int
	ecdsaCurve string
	ed25519Key bool
	savePath   string
)

func init() {
	KeyCmd.AddCommand(keyGenCmd)
	KeyCmd.PersistentFlags().StringVarP(&host, "host", "", "", "Comma-separated hostnames and IPs to generate a certificate for")
	KeyCmd.PersistentFlags().StringVarP(&validFrom, "start-date", "", "", "Creation date formatted as 2006-01-02")
	KeyCmd.PersistentFlags().DurationVarP(&validFor, "duration", "", 365*24*time.Hour, "Duration that certificate is valid for")
	KeyCmd.PersistentFlags().BoolVarP(&isCA, "ca", "", false, "whether this cert should be its own Certificate Authority")
	KeyCmd.PersistentFlags().IntVarP(&rsaBits, "rsa-bits", "", 2048, "Size of RSA key to generate. Ignored if --ecdsa-curve is set")
	KeyCmd.PersistentFlags().StringVarP(&ecdsaCurve, "ecdsa-curve", "", "", "ECDSA curve to use to generate a key. Valid values are P224, P256 (recommended), P384, P521")
	KeyCmd.PersistentFlags().BoolVarP(&ed25519Key, "ed25519", "", false, "Generate an Ed25519 key")
	KeyCmd.PersistentFlags().StringVarP(&savePath, "save-path", "", "./config/ssl/", "save generate key file path default: ./conf/ssl/")
}

var KeyCmd = &cobra.Command{
	Use:   "key",
	Short: "key generator",
	Long:  "key generator",
}

var keyGenCmd = &cobra.Command{
	Use:              "gen",
	Short:            "key generator",
	Long:             "key generator",
	TraverseChildren: true,
	Run: func(cmd *cobra.Command, args []string) {
		Generate(host, validFrom,
			ValidFor(validFor),
			IsCA(isCA),
			RsaBits(rsaBits),
			EcdsaCurve(ecdsaCurve),
			Ed25519Key(ed25519Key),
			SavePath(savePath),
		)
	},
}

// K host string, validFrom string, ecdsaCurve string, rsaBits int, ed25519Key bool, validFor time.Duration, isCA bool
type K struct {
	hosts      string
	validFrom  string
	ecdsaCurve string
	rsaBits    int
	ed25519Key bool
	validFor   time.Duration
	isCA       bool
	savePath   string
}
type Option func(k *K)

func EcdsaCurve(ecdsaCurve string) Option {
	return func(k *K) {
		k.ecdsaCurve = ecdsaCurve
	}
}

func RsaBits(rsaBits int) Option {
	return func(k *K) {
		k.rsaBits = rsaBits
	}
}

func Ed25519Key(ed25519Key bool) Option {
	return func(k *K) {
		k.ed25519Key = ed25519Key
	}
}

func ValidFor(validFor time.Duration) Option {
	return func(k *K) {
		k.validFor = validFor
	}
}

func IsCA(isCA bool) Option {
	return func(k *K) {
		k.isCA = isCA
	}
}

func SavePath(savePath string) Option {
	return func(k *K) {
		k.savePath = savePath
	}
}

func (k *K) publicKey(priv interface{}) interface{} {
	switch k := priv.(type) {
	case *rsa.PrivateKey:
		return &k.PublicKey
	case *ecdsa.PrivateKey:
		return &k.PublicKey
	case ed25519.PrivateKey:
		return k.Public().(ed25519.PublicKey)
	default:
		return nil
	}
}

func (k *K) saveCertPem(derBytes []byte) {
	certOut, err := os.Create(k.savePath + "cert.pem")
	if err != nil {
		log.Fatalf("Failed to open cert.pem for writing: %v", err)
	}
	if err := pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes}); err != nil {
		log.Fatalf("Failed to write data to cert.pem: %v", err)
	}
	if err := certOut.Close(); err != nil {
		log.Fatalf("Error closing cert.pem: %v", err)
	}

	content := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: derBytes})
	log.Print("\n" + string(content) + "\n")
}

func (k *K) saveKeyPem(priv interface{}) {
	keyOut, err := os.OpenFile(k.savePath+"key.pem", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
	if err != nil {
		log.Fatalf("Failed to open key.pem for writing: %v", err)
		return
	}
	privBytes, err := x509.MarshalPKCS8PrivateKey(priv)
	if err != nil {
		log.Fatalf("Unable to marshal private key: %v", err)
	}
	if err := pem.Encode(keyOut, &pem.Block{Type: "RSA PRIVATE KEY", Bytes: privBytes}); err != nil {
		log.Fatalf("Failed to write data to key.pem: %v", err)
	}
	if err := keyOut.Close(); err != nil {
		log.Fatalf("Error closing key.pem: %v", err)
	}
	content := pem.EncodeToMemory(&pem.Block{Type: "RSA PRIVATE KEY", Bytes: privBytes})
	log.Print("\n" + string(content) + "\n")
}

func (k *K) generatePrivateKey(ecdsaCurve string, rsaBits int, ed25519Key bool) (interface{}, error) {
	var priv interface{}
	var err error
	switch ecdsaCurve {
	case "":
		if ed25519Key {
			_, priv, err = ed25519.GenerateKey(rand.Reader)
		} else {
			priv, err = rsa.GenerateKey(rand.Reader, rsaBits)
		}
	case "P224":
		priv, err = ecdsa.GenerateKey(elliptic.P224(), rand.Reader)
	case "P256":
		priv, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	case "P384":
		priv, err = ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
	case "P521":
		priv, err = ecdsa.GenerateKey(elliptic.P521(), rand.Reader)
	default:
		err = errors.New(fmt.Sprintf("Unrecognized elliptic curve: %q", ecdsaCurve))
	}

	return priv, err
}

func (k *K) notBefore(validFrom string) (time.Time, error) {
	var notBefore time.Time
	var err error
	if len(validFrom) == 0 {
		notBefore = time.Now()
	} else {
		notBefore, err = time.Parse("2006-01-02", validFrom)
	}
	return notBefore, err
}

func parse(hosts string, validFrom string, options ...Option) *K {
	k := &K{
		hosts:     hosts,
		validFrom: validFrom,
	}
	for _, option := range options {
		option(k)
	}
	_ = os.MkdirAll(k.savePath, 0755)
	return k
}

func Generate(host string, validFrom string, option ...Option) {

	k := parse(host, validFrom, option...)

	if len(k.hosts) == 0 {
		log.Fatalf("Missing required --host parameter")
	}

	priv, err := k.generatePrivateKey(k.ecdsaCurve, k.rsaBits, k.ed25519Key)
	if err != nil {
		log.Fatalf("generate key error: %s \n", err.Error())
	}

	// ECDSA, ED25519 and RSA subject keys should have the DigitalSignature
	// KeyUsage bits set in the x509.Certificate template
	keyUsage := x509.KeyUsageDigitalSignature
	// Only RSA subject keys should have the KeyEncipherment KeyUsage bits set. In
	// the context of TLS this KeyUsage is particular to RSA key exchange and
	// authentication.
	if _, isRSA := priv.(*rsa.PrivateKey); isRSA {
		keyUsage |= x509.KeyUsageKeyEncipherment
	}

	notBefore, err := k.notBefore(validFrom)
	if err != nil {
		log.Fatalf("Failed to parse creation date: %v", err)
	}

	notAfter := notBefore.Add(k.validFor)

	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
	if err != nil {
		log.Fatalf("Failed to generate serial number: %v", err)
	}

	template := x509.Certificate{
		SerialNumber: serialNumber,
		Subject: pkix.Name{
			Organization: []string{"Acme Co"},
		},
		NotBefore: notBefore,
		NotAfter:  notAfter,

		KeyUsage:              keyUsage,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
		BasicConstraintsValid: true,
	}

	hosts := strings.Split(k.hosts, ",")
	for _, h := range hosts {
		if ip := net.ParseIP(h); ip != nil {
			template.IPAddresses = append(template.IPAddresses, ip)
		} else {
			template.DNSNames = append(template.DNSNames, h)
		}
	}

	if k.isCA {
		template.IsCA = true
		template.KeyUsage |= x509.KeyUsageCertSign
	}

	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, k.publicKey(priv), priv)
	if err != nil {
		log.Fatalf("Failed to create certificate: %v", err)
	}

	k.saveCertPem(derBytes)
	k.saveKeyPem(priv)
}