/*
Copyright IBM Corp. All Rights Reserved.

SPDX-License-Identifier: Apache-2.0
*/
package ca

import (
	"crypto"
	"crypto/ecdsa"
	"crypto/rand"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"io/ioutil"
	"math/big"
	"net"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/hyperledger/fabric/bccsp/utils"
	"github.com/hyperledger/fabric/common/tools/cryptogen/csp"
)

type CA struct {
	Name               string
	Country            string
	Province           string
	Locality           string
	OrganizationalUnit string
	StreetAddress      string
	PostalCode         string
	//SignKey  *ecdsa.PrivateKey
	Signer   crypto.Signer
	SignCert *x509.Certificate
}

// NewCA creates an instance of CA and saves the signing key pair in
// baseDir/name
func NewCA(baseDir, org, name, country, province, locality, orgUnit, streetAddress, postalCode string) (*CA, error) {

	var response error
	var ca *CA

	err := os.MkdirAll(baseDir, 0755)
	if err == nil {
		priv, signer, err := csp.GeneratePrivateKey(baseDir)
		response = err
		if err == nil {
			// get public signing certificate
			ecPubKey, err := csp.GetECPublicKey(priv)
			response = err
			if err == nil {
				template := x509Template()
				//this is a CA
				template.IsCA = true
				template.KeyUsage |= x509.KeyUsageDigitalSignature |
					x509.KeyUsageKeyEncipherment | x509.KeyUsageCertSign |
					x509.KeyUsageCRLSign
				template.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageAny}

				//set the organization for the subject
				subject := subjectTemplateAdditional(country, province, locality, orgUnit, streetAddress, postalCode)
				subject.Organization = []string{org}
				subject.CommonName = name

				template.Subject = subject
				template.SubjectKeyId = priv.SKI()

				x509Cert, err := genCertificateECDSA(baseDir, name, &template, &template,
					ecPubKey, signer)
				response = err
				if err == nil {
					ca = &CA{
						Name:               name,
						Signer:             signer,
						SignCert:           x509Cert,
						Country:            country,
						Province:           province,
						Locality:           locality,
						OrganizationalUnit: orgUnit,
						StreetAddress:      streetAddress,
						PostalCode:         postalCode,
					}
				}
			}
		}
	}
	return ca, response
}

// SignCertificate creates a signed certificate based on a built-in template
// and saves it in baseDir/name
func (ca *CA) SignCertificate(baseDir, name string, ous, sans []string, pub *ecdsa.PublicKey,
	ku x509.KeyUsage, eku []x509.ExtKeyUsage) (*x509.Certificate, error) {

	template := x509Template()
	template.KeyUsage = ku
	template.ExtKeyUsage = eku

	//set the organization for the subject
	subject := subjectTemplateAdditional(ca.Country, ca.Province, ca.Locality, ca.OrganizationalUnit, ca.StreetAddress, ca.PostalCode)
	subject.CommonName = name

	subject.OrganizationalUnit = append(subject.OrganizationalUnit, ous...)

	template.Subject = subject
	for _, san := range sans {
		// try to parse as an IP address first
		ip := net.ParseIP(san)
		if ip != nil {
			template.IPAddresses = append(template.IPAddresses, ip)
		} else {
			template.DNSNames = append(template.DNSNames, san)
		}
	}

	cert, err := genCertificateECDSA(baseDir, name, &template, ca.SignCert,
		pub, ca.Signer)

	if err != nil {
		return nil, err
	}

	return cert, nil
}

// default template for X509 subject
func subjectTemplate() pkix.Name {
	return pkix.Name{
		Country:  []string{"US"},
		Locality: []string{"San Francisco"},
		Province: []string{"California"},
	}
}

// Additional for X509 subject
func subjectTemplateAdditional(country, province, locality, orgUnit, streetAddress, postalCode string) pkix.Name {
	name := subjectTemplate()
	if len(country) >= 1 {
		name.Country = []string{country}
	}
	if len(province) >= 1 {
		name.Province = []string{province}
	}

	if len(locality) >= 1 {
		name.Locality = []string{locality}
	}
	if len(orgUnit) >= 1 {
		name.OrganizationalUnit = []string{orgUnit}
	}
	if len(streetAddress) >= 1 {
		name.StreetAddress = []string{streetAddress}
	}
	if len(postalCode) >= 1 {
		name.PostalCode = []string{postalCode}
	}
	return name
}

// default template for X509 certificates
func x509Template() x509.Certificate {

	// generate a serial number
	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
	serialNumber, _ := rand.Int(rand.Reader, serialNumberLimit)

	// set expiry to around 10 years
	expiry := 3650 * 24 * time.Hour
	// backdate 5 min
	notBefore := time.Now().Add(-5 * time.Minute).UTC()

	//basic template to use
	x509 := x509.Certificate{
		SerialNumber:          serialNumber,
		NotBefore:             notBefore,
		NotAfter:              notBefore.Add(expiry).UTC(),
		BasicConstraintsValid: true,
	}
	return x509

}

// generate a signed X509 certificate using ECDSA
func genCertificateECDSA(baseDir, name string, template, parent *x509.Certificate, pub *ecdsa.PublicKey,
	priv interface{}) (*x509.Certificate, error) {

	//create the x509 public cert
	certBytes, err := x509.CreateCertificate(rand.Reader, template, parent, pub, priv)
	if err != nil {
		return nil, err
	}

	//write cert out to file
	fileName := filepath.Join(baseDir, name+"-cert.pem")
	certFile, err := os.Create(fileName)
	if err != nil {
		return nil, err
	}
	//pem encode the cert
	err = pem.Encode(certFile, &pem.Block{Type: "CERTIFICATE", Bytes: certBytes})
	certFile.Close()
	if err != nil {
		return nil, err
	}

	x509Cert, err := x509.ParseCertificate(certBytes)
	if err != nil {
		return nil, err
	}
	return x509Cert, nil
}

// LoadCertificateECDSA load a ecdsa cert from a file in cert path
func LoadCertificateECDSA(certPath string) (*x509.Certificate, error) {
	var cert *x509.Certificate
	var err error

	walkFunc := func(path string, info os.FileInfo, err error) error {
		if strings.HasSuffix(path, ".pem") {
			rawCert, err := ioutil.ReadFile(path)
			if err != nil {
				return err
			}
			block, _ := pem.Decode(rawCert)
			cert, err = utils.DERToX509Certificate(block.Bytes)
		}
		return nil
	}

	err = filepath.Walk(certPath, walkFunc)
	if err != nil {
		return nil, err
	}

	return cert, err
}