/*
Copyright 2018 The Jetstack cert-manager contributors.

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 certificates

import (
	"context"
	"fmt"
	"reflect"
	"strings"
	"time"

	api "k8s.io/api/core/v1"
	k8sErrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	utilerrors "k8s.io/apimachinery/pkg/util/errors"
	"k8s.io/apimachinery/pkg/util/runtime"

	"github.com/golang/glog"
	"github.com/jetstack/cert-manager/pkg/apis/certmanager/v1alpha1"
	"github.com/jetstack/cert-manager/pkg/apis/certmanager/validation"
	"github.com/jetstack/cert-manager/pkg/issuer"
	"github.com/jetstack/cert-manager/pkg/util"
	"github.com/jetstack/cert-manager/pkg/util/errors"
	"github.com/jetstack/cert-manager/pkg/util/kube"
	"github.com/jetstack/cert-manager/pkg/util/pki"
)

const (
	errorIssuerNotFound    = "IssuerNotFound"
	errorIssuerNotReady    = "IssuerNotReady"
	errorIssuerInit        = "IssuerInitError"
	errorSavingCertificate = "SaveCertError"
	errorConfig            = "ConfigError"

	reasonIssuingCertificate  = "IssueCert"
	reasonRenewingCertificate = "RenewCert"

	successCertificateIssued  = "CertIssued"
	successCertificateRenewed = "CertRenewed"

	messageErrorSavingCertificate = "Error saving TLS certificate: "

	messageIssuingCertificate  = "Issuing certificate..."
	messageRenewingCertificate = "Renewing certificate..."

	messageCertificateIssued  = "Certificate issued successfully"
	messageCertificateRenewed = "Certificate renewed successfully"
)

func (c *Controller) Sync(ctx context.Context, crt *v1alpha1.Certificate) (err error) {
	crtCopy := crt.DeepCopy()
	defer func() {
		if _, saveErr := c.updateCertificateStatus(crt, crtCopy); saveErr != nil {
			err = utilerrors.NewAggregate([]error{saveErr, err})
		}
	}()

	el := validation.ValidateCertificate(crtCopy)
	if len(el) > 0 {
		msg := fmt.Sprintf("Resource validation failed: %v", el.ToAggregate())
		crtCopy.UpdateStatusCondition(v1alpha1.CertificateConditionReady, v1alpha1.ConditionFalse, errorConfig, msg, false)
		return
	} else {
		for i, c := range crtCopy.Status.Conditions {
			if c.Type == v1alpha1.CertificateConditionReady {
				if c.Reason == errorConfig && c.Status == v1alpha1.ConditionFalse {
					crtCopy.Status.Conditions = append(crtCopy.Status.Conditions[:i], crtCopy.Status.Conditions[i+1:]...)
					break
				}
			}
		}
	}

	// step zero: check if the referenced issuer exists and is ready
	issuerObj, err := c.getGenericIssuer(crtCopy)

	if err != nil {
		s := fmt.Sprintf("Issuer %s does not exist", err.Error())
		glog.Info(s)
		c.Recorder.Event(crtCopy, api.EventTypeWarning, errorIssuerNotFound, s)
		return err
	}

	el = validation.ValidateCertificateForIssuer(crtCopy, issuerObj)
	if len(el) > 0 {
		msg := fmt.Sprintf("Resource validation failed: %v", el.ToAggregate())
		crtCopy.UpdateStatusCondition(v1alpha1.CertificateConditionReady, v1alpha1.ConditionFalse, errorConfig, msg, false)
		return
	} else {
		for i, c := range crtCopy.Status.Conditions {
			if c.Type == v1alpha1.CertificateConditionReady {
				if c.Reason == errorConfig && c.Status == v1alpha1.ConditionFalse {
					crtCopy.Status.Conditions = append(crtCopy.Status.Conditions[:i], crtCopy.Status.Conditions[i+1:]...)
					break
				}
			}
		}
	}

	issuerReady := issuerObj.HasCondition(v1alpha1.IssuerCondition{
		Type:   v1alpha1.IssuerConditionReady,
		Status: v1alpha1.ConditionTrue,
	})
	if !issuerReady {
		s := fmt.Sprintf("Issuer %s not ready", issuerObj.GetObjectMeta().Name)
		glog.Info(s)
		c.Recorder.Event(crtCopy, api.EventTypeWarning, errorIssuerNotReady, s)
		return fmt.Errorf(s)
	}

	i, err := c.IssuerFactory().IssuerFor(issuerObj)
	if err != nil {
		s := "Error initializing issuer: " + err.Error()
		glog.Info(s)
		c.Recorder.Event(crtCopy, api.EventTypeWarning, errorIssuerInit, s)
		return err
	}

	expectedCN := pki.CommonNameForCertificate(crtCopy)
	expectedDNSNames := pki.DNSNamesForCertificate(crtCopy)
	if expectedCN == "" || len(expectedDNSNames) == 0 {
		// TODO: Set certificate invalid condition on certificate resource
		// TODO: remove this check in favour of resource validation
		return fmt.Errorf("certificate must specify at least one of dnsNames or commonName")
	}

	// grab existing certificate and validate private key
	cert, err := kube.SecretTLSCert(c.secretLister, crtCopy.Namespace, crtCopy.Spec.SecretName)
	// if an error is returned, and that error is something other than
	// IsNotFound or invalid data, then we should return the error.
	if err != nil && !k8sErrors.IsNotFound(err) && !errors.IsInvalidData(err) {
		return err
	}

	// as there is an existing certificate, or we may create one below, we will
	// run scheduleRenewal to schedule a renewal if required at the end of
	// execution.
	defer c.scheduleRenewal(crtCopy)

	// if the certificate was not found, or the certificate data is invalid, we
	// should issue a new certificate.
	// if the certificate is valid for a list of domains other than those
	// listed in the certificate spec, we should re-issue the certificate.
	if k8sErrors.IsNotFound(err) || errors.IsInvalidData(err) ||
		expectedCN != cert.Subject.CommonName || !util.EqualUnsorted(cert.DNSNames, expectedDNSNames) {
		return c.issue(ctx, i, crtCopy)
	}

	// if we should being attempting to renew now, then trigger a renewal
	if c.Context.IssuerOptions.CertificateNeedsRenew(cert) {
		return c.renew(ctx, i, crtCopy)
	}

	return nil
}

// TODO: replace with a call to controllerpkg.Helper.GetGenericIssuer
func (c *Controller) getGenericIssuer(crt *v1alpha1.Certificate) (v1alpha1.GenericIssuer, error) {
	switch crt.Spec.IssuerRef.Kind {
	case "", v1alpha1.IssuerKind:
		return c.issuerLister.Issuers(crt.Namespace).Get(crt.Spec.IssuerRef.Name)
	case v1alpha1.ClusterIssuerKind:
		if c.clusterIssuerLister == nil {
			return nil, fmt.Errorf("cannot get ClusterIssuer for %q as cert-manager is scoped to a single namespace", crt.Name)
		}
		return c.clusterIssuerLister.Get(crt.Spec.IssuerRef.Name)
	default:
		return nil, fmt.Errorf(`invalid value %q for certificate issuer kind. Must be empty, %q or %q`, crt.Spec.IssuerRef.Kind, v1alpha1.IssuerKind, v1alpha1.ClusterIssuerKind)
	}
}

func (c *Controller) scheduleRenewal(crt *v1alpha1.Certificate) {
	key, err := keyFunc(crt)

	if err != nil {
		runtime.HandleError(fmt.Errorf("error getting key for certificate resource: %s", err.Error()))
		return
	}

	cert, err := kube.SecretTLSCert(c.secretLister, crt.Namespace, crt.Spec.SecretName)

	if err != nil {
		runtime.HandleError(fmt.Errorf("[%s/%s] Error getting certificate '%s': %s", crt.Namespace, crt.Name, crt.Spec.SecretName, err.Error()))
		return
	}

	durationUntilExpiry := cert.NotAfter.Sub(time.Now())
	renewIn := durationUntilExpiry - c.Context.IssuerOptions.RenewBeforeExpiryDuration

	c.scheduledWorkQueue.Add(key, renewIn)

	glog.Infof("Certificate %s/%s scheduled for renewal in %d hours", crt.Namespace, crt.Name, renewIn/time.Hour)
}

// issuerKind returns the kind of issuer for a certificate
func issuerKind(crt *v1alpha1.Certificate) string {
	if crt.Spec.IssuerRef.Kind == "" {
		return v1alpha1.IssuerKind
	} else {
		return crt.Spec.IssuerRef.Kind
	}
}

func (c *Controller) updateSecret(crt *v1alpha1.Certificate, namespace string, cert, key []byte) (*api.Secret, error) {
	secret, err := c.Client.CoreV1().Secrets(namespace).Get(crt.Spec.SecretName, metav1.GetOptions{})
	if err != nil && !k8sErrors.IsNotFound(err) {
		return nil, err
	}
	if k8sErrors.IsNotFound(err) {
		secret = &api.Secret{
			ObjectMeta: metav1.ObjectMeta{
				Name:      crt.Spec.SecretName,
				Namespace: namespace,
			},
			Type: api.SecretTypeTLS,
			Data: map[string][]byte{},
		}
	}
	secret.Data[api.TLSCertKey] = cert
	secret.Data[api.TLSPrivateKeyKey] = key

	if secret.Annotations == nil {
		secret.Annotations = make(map[string]string)
	}

	// Note: since this sets annotations based on certificate resource, incorrect
	// annotations will be set if resource and actual certificate somehow get out
	// of sync
	dnsNames := pki.DNSNamesForCertificate(crt)
	cn := pki.CommonNameForCertificate(crt)

	secret.Annotations[v1alpha1.AltNamesAnnotationKey] = strings.Join(dnsNames, ",")
	secret.Annotations[v1alpha1.CommonNameAnnotationKey] = cn

	secret.Annotations[v1alpha1.IssuerNameAnnotationKey] = crt.Spec.IssuerRef.Name
	secret.Annotations[v1alpha1.IssuerKindAnnotationKey] = issuerKind(crt)

	if secret.Labels == nil {
		secret.Labels = make(map[string]string)
	}

	secret.Labels[v1alpha1.CertificateNameKey] = crt.Name

	// if it is a new resource
	if secret.SelfLink == "" {
		secret, err = c.Client.CoreV1().Secrets(namespace).Create(secret)
	} else {
		secret, err = c.Client.CoreV1().Secrets(namespace).Update(secret)
	}
	if err != nil {
		return nil, err
	}
	return secret, nil
}

// return an error on failure. If retrieval is succesful, the certificate data
// and private key will be stored in the named secret
func (c *Controller) issue(ctx context.Context, issuer issuer.Interface, crt *v1alpha1.Certificate) error {
	var err error
	glog.Infof("Preparing certificate %s/%s with issuer", crt.Namespace, crt.Name)
	if err = issuer.Prepare(ctx, crt); err != nil {
		glog.Infof("Error preparing issuer for certificate %s/%s: %v", crt.Namespace, crt.Name, err)
		return err
	}

	s := messageIssuingCertificate
	glog.Info(s)
	c.Recorder.Event(crt, api.EventTypeNormal, reasonIssuingCertificate, s)

	var key, cert []byte
	key, cert, err = issuer.Issue(ctx, crt)

	if err != nil {
		glog.Infof("Error issuing certificate for %s/%s: %v", crt.Namespace, crt.Name, err)
		return err
	}

	if _, err := c.updateSecret(crt, crt.Namespace, cert, key); err != nil {
		s := messageErrorSavingCertificate + err.Error()
		glog.Info(s)
		c.Recorder.Event(crt, api.EventTypeWarning, errorSavingCertificate, s)
		return err
	}

	s = messageCertificateIssued
	glog.Info(s)
	c.Recorder.Event(crt, api.EventTypeNormal, successCertificateIssued, s)
	crt.UpdateStatusCondition(v1alpha1.CertificateConditionReady, v1alpha1.ConditionTrue, successCertificateIssued, s, true)

	return nil
}

// renew will attempt to renew a certificate from the specified issuer, or
// return an error on failure. If renewal is succesful, the certificate data
// and private key will be stored in the named secret
func (c *Controller) renew(ctx context.Context, issuer issuer.Interface, crt *v1alpha1.Certificate) error {
	var err error
	glog.Infof("Preparing certificate %s/%s with issuer", crt.Namespace, crt.Name)
	if err = issuer.Prepare(ctx, crt); err != nil {
		glog.Infof("Error preparing issuer for certificate %s/%s: %v", crt.Namespace, crt.Name, err)
		return err
	}

	s := messageRenewingCertificate
	glog.Info(s)
	c.Recorder.Event(crt, api.EventTypeNormal, reasonRenewingCertificate, s)

	var key, cert []byte
	key, cert, err = issuer.Renew(ctx, crt)

	if err != nil {
		return err
	}

	if _, err := c.updateSecret(crt, crt.Namespace, cert, key); err != nil {
		s := messageErrorSavingCertificate + err.Error()
		glog.Info(s)
		c.Recorder.Event(crt, api.EventTypeWarning, errorSavingCertificate, s)
		return err
	}

	s = messageCertificateRenewed
	glog.Info(s)
	c.Recorder.Event(crt, api.EventTypeNormal, successCertificateRenewed, s)
	crt.UpdateStatusCondition(v1alpha1.CertificateConditionReady, v1alpha1.ConditionTrue, successCertificateRenewed, s, true)

	return nil
}

func (c *Controller) updateCertificateStatus(old, new *v1alpha1.Certificate) (*v1alpha1.Certificate, error) {
	if reflect.DeepEqual(old.Status, new.Status) {
		return nil, nil
	}
	// TODO: replace Update call with UpdateStatus. This requires a custom API
	// server with the /status subresource enabled and/or subresource support
	// for CRDs (https://github.com/kubernetes/kubernetes/issues/38113)
	return c.CMClient.CertmanagerV1alpha1().Certificates(new.Namespace).Update(new)
}