/*
Copyright IBM Corp. 2016 All Rights Reserved.

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 comm

import (
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/tls"
	"crypto/x509"
	"encoding/pem"
	"errors"
	"fmt"
	"math/big"
	"os"

	"github.com/hyperledger/fabric/common/util"
	gutil "github.com/hyperledger/fabric/gossip/util"
	"golang.org/x/net/context"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/peer"
)

func writeFile(filename string, keyType string, data []byte) error {
	f, err := os.Create(filename)
	if err != nil {
		return err
	}
	defer f.Close()
	return pem.Encode(f, &pem.Block{Type: keyType, Bytes: data})
}

func GenerateCertificatesOrPanic() tls.Certificate {
	privKeyFile := fmt.Sprintf("key.%d.priv", gutil.RandomUInt64())
	certKeyFile := fmt.Sprintf("cert.%d.pub", gutil.RandomUInt64())

	defer os.Remove(privKeyFile)
	defer os.Remove(certKeyFile)
	privateKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	if err != nil {
		panic(err)
	}

	sn, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
	if err != nil {
		panic(err)
	}
	template := x509.Certificate{
		KeyUsage:     x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
		SerialNumber: sn,
		ExtKeyUsage:  []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
	}
	rawBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &privateKey.PublicKey, privateKey)
	if err != nil {
		panic(err)
	}
	err = writeFile(certKeyFile, "CERTIFICATE", rawBytes)
	if err != nil {
		panic(err)
	}
	privBytes, err := x509.MarshalECPrivateKey(privateKey)
	if err != nil {
		panic(err)
	}
	err = writeFile(privKeyFile, "EC PRIVATE KEY", privBytes)
	if err != nil {
		panic(err)
	}
	cert, err := tls.LoadX509KeyPair(certKeyFile, privKeyFile)
	if err != nil {
		panic(err)
	}
	if len(cert.Certificate) == 0 {
		panic(errors.New("Certificate chain is empty"))
	}
	return cert
}

func certHashFromRawCert(rawCert []byte) []byte {
	if len(rawCert) == 0 {
		return nil
	}
	return util.ComputeSHA256(rawCert)
}

// ExtractCertificateHash extracts the hash of the certificate from the stream
func extractCertificateHashFromContext(ctx context.Context) []byte {
	pr, extracted := peer.FromContext(ctx)
	if !extracted {
		return nil
	}

	authInfo := pr.AuthInfo
	if authInfo == nil {
		return nil
	}

	tlsInfo, isTLSConn := authInfo.(credentials.TLSInfo)
	if !isTLSConn {
		return nil
	}
	certs := tlsInfo.State.PeerCertificates
	if len(certs) == 0 {
		return nil
	}
	raw := certs[0].Raw
	return certHashFromRawCert(raw)
}