/*
Copyright 2021-2022 CAcert Inc.
SPDX-License-Identifier: Apache-2.0

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 revoking_test

import (
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/asn1"
	"errors"
	"fmt"
	"math/big"
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"

	"git.cacert.org/cacert-gosigner/pkg/x509/revoking"
)

type testRepo struct {
	crlNumber *big.Int
	revoked   []pkix.RevokedCertificate
}

func (t *testRepo) NextCRLNumber() (*big.Int, error) {
	newNumber := new(big.Int).Add(t.crlNumber, big.NewInt(1))

	t.crlNumber = newNumber

	return t.crlNumber, nil
}

func (t *testRepo) RevokedCertificates() ([]pkix.RevokedCertificate, error) {
	result := make([]pkix.RevokedCertificate, len(t.revoked))

	copy(result, t.revoked)

	return result, nil
}

func (t *testRepo) StoreRevocation(revoked *pkix.RevokedCertificate) error {
	t.revoked = append(t.revoked, *revoked)

	return nil
}

type brokenRepo struct{}

func (r *brokenRepo) NextCRLNumber() (*big.Int, error) {
	return nil, errors.New("don't know")
}

func (r *brokenRepo) RevokedCertificates() ([]pkix.RevokedCertificate, error) {
	return nil, errors.New("no revocations for you")
}

func (*brokenRepo) StoreRevocation(_ *pkix.RevokedCertificate) error {
	return errors.New("cannot store")
}

type brokenRepoNoCrlNumber struct {
}

func (b brokenRepoNoCrlNumber) StoreRevocation(_ *pkix.RevokedCertificate) error {
	// do nothing
	return nil
}

func (b brokenRepoNoCrlNumber) RevokedCertificates() ([]pkix.RevokedCertificate, error) {
	return make([]pkix.RevokedCertificate, 0), nil
}

func (b brokenRepoNoCrlNumber) NextCRLNumber() (*big.Int, error) {
	return nil, errors.New("don't know")
}

type brokenRepoNoRevocations struct {
}

func (b brokenRepoNoRevocations) StoreRevocation(_ *pkix.RevokedCertificate) error {
	// do nothing
	return nil
}

func (b brokenRepoNoRevocations) RevokedCertificates() ([]pkix.RevokedCertificate, error) {
	return nil, errors.New("no revocations known")
}

func (b brokenRepoNoRevocations) NextCRLNumber() (*big.Int, error) {
	return nil, nil
}

func randomSerial(t *testing.T) *big.Int {
	t.Helper()

	serial, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
	if err != nil {
		t.Fatalf("could not generate random serial number: %v", err)
	}

	return serial
}

func TestX509Revoking_Revoke(t *testing.T) {
	testRepository := testRepo{revoked: make([]pkix.RevokedCertificate, 0), crlNumber: big.NewInt(0)}

	caKey, caCertificate := prepareTestCA(t)

	r := revoking.NewX509Revoking(&testRepository, x509.ECDSAWithSHA256, caCertificate, caKey)

	serial, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
	if err != nil {
		t.Errorf("could not create random serial: %v", err)
	}

	revoke, err := r.Revoke(revoking.NewRevokeCertificate(serial, revoking.CRLReasonKeyCompromise))
	assert.NoError(t, err)

	assert.Equal(t, revoking.CRLReasonKeyCompromise.BuildExtension(), revoke.Extensions[0])
	assert.Equal(t, serial, revoke.SerialNumber)

	var found bool

	for _, r := range testRepository.revoked {
		if r.SerialNumber.Cmp(serial) == 0 {
			found = true
		}
	}

	assert.True(t, found)
}

func TestX509Revoking_Revoke_BrokenRepo(t *testing.T) {
	caKey, caCertificate := prepareTestCA(t)

	r := revoking.NewX509Revoking(&brokenRepo{}, x509.SHA256WithRSA, caCertificate, caKey)

	serial, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
	if err != nil {
		t.Errorf("could not create random serial: %v", err)
	}

	revoke, err := r.Revoke(revoking.NewRevokeCertificate(serial, revoking.CRLReasonKeyCompromise))

	assert.Error(t, err)
	assert.ErrorContains(t, err, "could not store revocation")
	assert.Nil(t, revoke)
}

func TestX509Revoking_CreateCRL(t *testing.T) {
	key, certificate := prepareTestCA(t)

	r := revoking.NewX509Revoking(
		&testRepo{revoked: make([]pkix.RevokedCertificate, 0), crlNumber: big.NewInt(0)},
		x509.SHA256WithRSA,
		certificate,
		key,
	)

	serial, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
	if err != nil {
		t.Errorf("could not create random serial: %v", err)
	}

	_, err = r.Revoke(revoking.NewRevokeCertificate(serial, revoking.CRLReasonKeyCompromise))
	require.NoError(t, err)

	crl, err := r.CreateCRL()

	assert.NoError(t, err)
	assert.NotNil(t, crl)
	assert.NotEmpty(t, crl.CRL)

	parsedCRL, err := x509.ParseCRL(crl.CRL)

	assert.NoError(t, err)

	assert.ElementsMatch(t, certificate.Subject.ToRDNSequence(), parsedCRL.TBSCertList.Issuer)

	var found bool

	for _, item := range parsedCRL.TBSCertList.RevokedCertificates {
		if item.SerialNumber.Cmp(serial) == 0 {
			found = true

			assert.Contains(t, item.Extensions, revoking.CRLReasonKeyCompromise.BuildExtension())
		}
	}

	assert.True(t, found)
}

func TestX509Revoking_CreateCRL_BrokenRepoNoRevocations(t *testing.T) {
	caKey, caCertificate := prepareTestCA(t)

	r := revoking.NewX509Revoking(&brokenRepoNoRevocations{}, x509.SHA256WithRSA, caCertificate, caKey)

	serial, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
	if err != nil {
		t.Errorf("could not create random serial: %v", err)
	}

	_, err = r.Revoke(revoking.NewRevokeCertificate(serial, revoking.CRLReasonKeyCompromise))
	require.NoError(t, err)

	crl, err := r.CreateCRL()

	assert.Error(t, err)
	assert.ErrorContains(t, err, "could not get revocation information")
	assert.Nil(t, crl)
}

func TestX509Revoking_CreateCRL_BrokenRepoNoCRLNumber(t *testing.T) {
	caKey, caCertificate := prepareTestCA(t)

	r := revoking.NewX509Revoking(&brokenRepoNoCrlNumber{}, x509.SHA256WithRSA, caCertificate, caKey)

	serial, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
	if err != nil {
		t.Errorf("could not create random serial: %v", err)
	}

	_, err = r.Revoke(revoking.NewRevokeCertificate(serial, revoking.CRLReasonKeyCompromise))
	require.NoError(t, err)

	crl, err := r.CreateCRL()

	assert.Error(t, err)
	assert.ErrorContains(t, err, "could not get next CRL number")
	assert.Nil(t, crl)
}

func TestX509Revoking_CreateCRL_WrongAlgorithm(t *testing.T) {
	key, certificate := prepareTestCA(t)

	r := revoking.NewX509Revoking(
		&testRepo{revoked: make([]pkix.RevokedCertificate, 0), crlNumber: big.NewInt(0)},
		x509.ECDSAWithSHA256,
		certificate,
		key,
	)

	serial, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
	if err != nil {
		t.Errorf("could not create random serial: %v", err)
	}

	_, err = r.Revoke(revoking.NewRevokeCertificate(serial, revoking.CRLReasonKeyCompromise))
	require.NoError(t, err)

	crl, err := r.CreateCRL()

	assert.Error(t, err)
	assert.ErrorContains(t, err, "could not sign revocation list")
	assert.Nil(t, crl)
}

func prepareTestCA(t *testing.T) (*rsa.PrivateKey, *x509.Certificate) {
	t.Helper()

	caKey, err := rsa.GenerateKey(rand.Reader, 3072)
	if err != nil {
		t.Fatalf("could not generate key pair: %v", err)
	}

	caTemplate := &x509.Certificate{
		Subject:               pkix.Name{CommonName: "Test CA"},
		SerialNumber:          randomSerial(t),
		IsCA:                  true,
		MaxPathLenZero:        true,
		BasicConstraintsValid: true,
		KeyUsage:              x509.KeyUsageCertSign | x509.KeyUsageCRLSign,
	}

	certificateBytes, err := x509.CreateCertificate(rand.Reader, caTemplate, caTemplate, caKey.Public(), caKey)
	if err != nil {
		t.Fatalf("could not self-sign CA certificate: %v", err)
	}

	caCertificate, err := x509.ParseCertificate(certificateBytes)
	if err != nil {
		t.Fatalf("could not create test CA certificate: %v", err)
	}

	return caKey, caCertificate
}

func TestCRLReason_BuildExtension(t *testing.T) {
	reasons := []revoking.CRLReason{
		revoking.CRLReasonUnspecified,
		revoking.CRLReasonKeyCompromise,
		revoking.CRLReasonCACompromise,
		revoking.CRLReasonAffiliationChanged,
		revoking.CRLReasonSuperseded,
		revoking.CRLReasonCessationOfOperation,
		revoking.CRLReasonCertificateHold,
		revoking.CRLReasonRemoveFromCRL,
		revoking.CRLReasonPrivilegeWithdrawn,
		revoking.CRLReasonAACompromise,
	}

	for _, reason := range reasons {
		t.Run(fmt.Sprintf("reason %d", int(reason)), func(t *testing.T) {
			ext := reason.BuildExtension()

			assert.Equal(t, revoking.OidCRLReason, ext.Id)

			var value int

			rest, err := asn1.Unmarshal(ext.Value, &value)
			assert.NoError(t, err)
			assert.Len(t, rest, 0)
			assert.Equal(t, value, int(reason))
		})
	}
}

func TestCRLReason_String(t *testing.T) {
	reasons := []revoking.CRLReason{
		revoking.CRLReasonUnspecified,
		revoking.CRLReasonKeyCompromise,
		revoking.CRLReasonCACompromise,
		revoking.CRLReasonAffiliationChanged,
		revoking.CRLReasonSuperseded,
		revoking.CRLReasonCessationOfOperation,
		revoking.CRLReasonCertificateHold,
		revoking.CRLReasonRemoveFromCRL,
		revoking.CRLReasonPrivilegeWithdrawn,
		revoking.CRLReasonAACompromise,
	}

	for _, reason := range reasons {
		t.Run(fmt.Sprintf("reason %d", int(reason)), func(t *testing.T) {
			assert.NotEmpty(t, reason.String())
		})
	}

	var customReason revoking.CRLReason = 40

	assert.Equal(t, customReason.String(), revoking.CRLReasonUnspecified.String())
}

func TestParseReason(t *testing.T) {
	expected := map[string]revoking.CRLReason{
		"keyCompromise": revoking.CRLReasonKeyCompromise,
		"kEyCoMpRoMiSe": revoking.CRLReasonKeyCompromise,
		"unknown":       revoking.CRLReasonUnspecified,
		"":              revoking.CRLReasonUnspecified,
	}

	for key, reason := range expected {
		t.Run(fmt.Sprintf("parse '%s'", key), func(t *testing.T) {
			assert.Equal(t, revoking.ParseReason(key), reason)
		})
	}
}