package revoking

import (
	"crypto"
	"crypto/rand"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/asn1"
	"fmt"
	"log"
	"math/big"
	"strings"
	"time"
)

var OidCRLReason = asn1.ObjectIdentifier{2, 5, 29, 21}

type CRLReason int

// CRL reason codes as defined in RFC 5280 section 5.3.1
const (
	CRLReasonUnspecified          CRLReason = 0
	CRLReasonKeyCompromise        CRLReason = 1
	CRLReasonCACompromise         CRLReason = 2
	CRLReasonAffiliationChanged   CRLReason = 3
	CRLReasonSuperseded           CRLReason = 4
	CRLReasonCessationOfOperation CRLReason = 5
	CRLReasonCertificateHold      CRLReason = 6
	CRLReasonRemoveFromCRL        CRLReason = 8
	CRLReasonPrivilegeWithdrawn   CRLReason = 9
	CRLReasonAACompromise         CRLReason = 10
)

var crlReasonNames = map[CRLReason]string{
	CRLReasonUnspecified:          "unspecified",
	CRLReasonKeyCompromise:        "keyCompromise",
	CRLReasonCACompromise:         "CACompromise",
	CRLReasonAffiliationChanged:   "affiliationChanged",
	CRLReasonSuperseded:           "superseded",
	CRLReasonCessationOfOperation: "cessationOfOperation",
	CRLReasonCertificateHold:      "certificateHold",
	CRLReasonRemoveFromCRL:        "removeFromCRL",
	CRLReasonPrivilegeWithdrawn:   "privilegeWithdrawn",
	CRLReasonAACompromise:         "AACompromise",
}

func (r CRLReason) String() string {
	if reason, ok := crlReasonNames[r]; ok {
		return reason
	}

	return crlReasonNames[CRLReasonUnspecified]
}

func (r CRLReason) BuildExtension() pkix.Extension {
	extBytes, err := asn1.Marshal(r)
	if err != nil {
		// we can panic here because all values of CRLReason must be ASN.1 marshal-able
		log.Panicf("could not marshal revocation reason: %v", err)
	}

	return pkix.Extension{Id: OidCRLReason, Value: extBytes}
}

// ParseReason takes a reason string and performs a case-insensitive match to a reason code
func ParseReason(rs string) CRLReason {
	for key, name := range crlReasonNames {
		if strings.EqualFold(name, rs) {
			return key
		}
	}

	return CRLReasonUnspecified
}

type X509Revoking struct {
	repository   Repository
	crlAlgorithm x509.SignatureAlgorithm
	crlIssuer    *x509.Certificate
	signer       crypto.Signer
}

type RevokeCertificate struct {
	serialNumber *big.Int
	reason       CRLReason
}

type CertificateRevoked struct {
	serialNumber   *big.Int
	revocationTime time.Time
	reason         string
}

type CRLInformation struct {
	CRL []byte // DER encoded CRL
}

func (r *X509Revoking) Revoke(revokeCertificate *RevokeCertificate) (*pkix.RevokedCertificate, error) {
	revoked := &pkix.RevokedCertificate{
		SerialNumber:   revokeCertificate.serialNumber,
		RevocationTime: time.Now(),
		Extensions:     []pkix.Extension{revokeCertificate.reason.BuildExtension()},
	}

	if err := r.repository.StoreRevocation(revoked); err != nil {
		return nil, err
	}

	return revoked, nil
}

func (r *X509Revoking) CreateCRL() (*CRLInformation, error) {
	revoked, err := r.repository.RevokedCertificates()
	if err != nil {
		return nil, fmt.Errorf("could not get revocation information: %w", err)
	}

	list, err := x509.CreateRevocationList(rand.Reader, &x509.RevocationList{
		SignatureAlgorithm:  r.crlAlgorithm,
		RevokedCertificates: revoked,
	}, r.crlIssuer, r.signer)
	if err != nil {
		return nil, fmt.Errorf("could not sign revocation list: %w", err)
	}

	return &CRLInformation{CRL: list}, nil
}

func NewX509Revoking(
	repo Repository,
	crlAlgorithm x509.SignatureAlgorithm,
	issuer *x509.Certificate,
	signer crypto.Signer,
) *X509Revoking {
	return &X509Revoking{repository: repo, crlAlgorithm: crlAlgorithm, crlIssuer: issuer, signer: signer}
}