/*
Copyright 2021 Alibaba Group Holding Limited.

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 ssl

import (
	"bytes"
	"crypto/ecdsa"
	"crypto/ed25519"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"math/big"
	"time"
)

// https://go.dev/src/crypto/tls/generate_cert.go

func 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 MarshalCert(cert []byte) ([]byte, error) {
	buf := &bytes.Buffer{}
	err := pem.Encode(buf, &pem.Block{
		Type:  "CERTIFICATE",
		Bytes: cert,
	})
	if err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}

func MarshalKey(priv interface{}) ([]byte, error) {
	keyBytes, err := x509.MarshalPKCS8PrivateKey(priv)
	if err != nil {
		return nil, err
	}
	buf := &bytes.Buffer{}
	err = pem.Encode(buf, &pem.Block{
		Type:  "RSA PRIVATE KEY",
		Bytes: keyBytes,
	})
	if err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}

func GenerateCA(rsaBits int, domain string) (*x509.Certificate, *rsa.PrivateKey, []byte, error) {
	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
	if err != nil {
		return nil, nil, nil, err
	}

	cert := &x509.Certificate{
		SerialNumber: serialNumber,
		Subject: pkix.Name{
			Organization: []string{"PolarDB-X"},
			CommonName:   domain,
		},
		NotBefore: time.Now(),
		NotAfter:  time.Now().AddDate(10, 0, 0),
		IsCA:      true,
		ExtKeyUsage: []x509.ExtKeyUsage{
			x509.ExtKeyUsageClientAuth,
			x509.ExtKeyUsageServerAuth,
		},
		KeyUsage:              x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
		BasicConstraintsValid: true,
	}

	priv, err := rsa.GenerateKey(rand.Reader, rsaBits)
	if err != nil {
		return nil, nil, nil, err
	}

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

	return cert, priv, certBytes, nil
}

func GenerateSelfSignedCert(caCert *x509.Certificate, caPriv interface{}, rsaBits int, domain string) (*x509.Certificate, *rsa.PrivateKey, []byte, error) {
	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
	if err != nil {
		return nil, nil, nil, err
	}

	cert := &x509.Certificate{
		SerialNumber: serialNumber,
		Subject: pkix.Name{
			Organization: []string{"PolarDB-X"},
			CommonName:   domain,
		},
		NotBefore: time.Now(),
		NotAfter:  time.Now().AddDate(10, 0, 0),
		ExtKeyUsage: []x509.ExtKeyUsage{
			x509.ExtKeyUsageClientAuth,
			x509.ExtKeyUsageServerAuth,
		},
		KeyUsage: x509.KeyUsageDigitalSignature,
	}

	priv, err := rsa.GenerateKey(rand.Reader, rsaBits)
	if err != nil {
		return nil, nil, nil, err
	}

	certBytes, err := x509.CreateCertificate(rand.Reader, cert, caCert, &priv.PublicKey, caPriv)
	if err != nil {
		return nil, nil, nil, err
	}

	return cert, priv, certBytes, nil
}