package crypto

import (
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/tls"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"math/big"
	"net"
	"os"
	"time"
)

// GenerateSelfSignedCert 生成自签名证书
func GenerateSelfSignedCert(certFile, keyFile string) error {
	priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	if err != nil {
		return err
	}

	serialNumber, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
	if err != nil {
		return err
	}

	template := x509.Certificate{
		SerialNumber: serialNumber,
		Subject: pkix.Name{
			Organization: []string{"GoTunnel"},
			CommonName:   "GoTunnel Server",
		},
		NotBefore:             time.Now(),
		NotAfter:              time.Now().AddDate(10, 0, 0), // 10年有效期
		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
		BasicConstraintsValid: true,
		IPAddresses:           []net.IP{net.ParseIP("127.0.0.1")},
		DNSNames:              []string{"localhost"},
	}

	certDER, err := x509.CreateCertificate(rand.Reader, &template, &template, &priv.PublicKey, priv)
	if err != nil {
		return err
	}

	// 写入证书文件
	certOut, err := os.Create(certFile)
	if err != nil {
		return err
	}
	defer certOut.Close()
	pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: certDER})

	// 写入私钥文件
	keyOut, err := os.Create(keyFile)
	if err != nil {
		return err
	}
	defer keyOut.Close()

	privBytes, err := x509.MarshalECPrivateKey(priv)
	if err != nil {
		return err
	}
	pem.Encode(keyOut, &pem.Block{Type: "EC PRIVATE KEY", Bytes: privBytes})

	return nil
}