/*
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 dns

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

	"github.com/golang/glog"
	"github.com/pkg/errors"
	corev1listers "k8s.io/client-go/listers/core/v1"

	"github.com/jetstack/cert-manager/pkg/apis/certmanager/v1alpha1"
	"github.com/jetstack/cert-manager/pkg/controller"
	"github.com/jetstack/cert-manager/pkg/issuer/acme/dns/acmedns"
	"github.com/jetstack/cert-manager/pkg/issuer/acme/dns/akamai"
	"github.com/jetstack/cert-manager/pkg/issuer/acme/dns/azuredns"
	"github.com/jetstack/cert-manager/pkg/issuer/acme/dns/clouddns"
	"github.com/jetstack/cert-manager/pkg/issuer/acme/dns/cloudflare"
	"github.com/jetstack/cert-manager/pkg/issuer/acme/dns/route53"
	"github.com/jetstack/cert-manager/pkg/issuer/acme/dns/util"
)

const (
	cloudDNSServiceAccountKey = "service-account.json"
)

type solver interface {
	Present(domain, token, key string) error
	CleanUp(domain, token, key string) error
	Timeout() (timeout, interval time.Duration)
}

// dnsProviderConstructors defines how each provider may be constructed.
// It is useful for mocking out a given provider since an alternate set of
// constructors may be set.
type dnsProviderConstructors struct {
	cloudDNS   func(project string, serviceAccount []byte, dns01Nameservers []string) (*clouddns.DNSProvider, error)
	cloudFlare func(email, apikey string, dns01Nameservers []string) (*cloudflare.DNSProvider, error)
	route53    func(accessKey, secretKey, hostedZoneID, region string, ambient bool, dns01Nameservers []string) (*route53.DNSProvider, error)
	azureDNS   func(clientID, clientSecret, subscriptionID, tenentID, resourceGroupName, hostedZoneName string, dns01Nameservers []string) (*azuredns.DNSProvider, error)
	acmeDNS    func(host string, accountJson []byte) (*acmedns.DNSProvider, error)
}

// Solver is a solver for the acme dns01 challenge.
// Given a Certificate object, it determines the correct DNS provider based on
// the certificate, and configures it based on the referenced issuer.
type Solver struct {
	*controller.Context
	secretLister            corev1listers.SecretLister
	dnsProviderConstructors dnsProviderConstructors
}

func (s *Solver) Present(ctx context.Context, issuer v1alpha1.GenericIssuer, _ *v1alpha1.Certificate, ch v1alpha1.ACMEOrderChallenge) error {
	if ch.SolverConfig.DNS01 == nil {
		return fmt.Errorf("challenge dns config must be specified")
	}

	providerName := ch.SolverConfig.DNS01.Provider
	if providerName == "" {
		return fmt.Errorf("dns01 challenge provider name must be set")
	}

	slv, err := s.solverForIssuerProvider(issuer, providerName)
	if err != nil {
		return err
	}

	glog.Infof("Presenting DNS01 challenge for domain %q", ch.Domain)
	return slv.Present(ch.Domain, ch.Token, ch.Key)
}

func (s *Solver) Check(ch v1alpha1.ACMEOrderChallenge) (bool, error) {
	fqdn, value, ttl, err := util.DNS01Record(ch.Domain, ch.Key, s.DNS01Nameservers)
	if err != nil {
		return false, err
	}

	glog.Infof("Checking DNS propagation for %q using name servers: %v", ch.Domain, s.DNS01Nameservers)

	ok, err := util.PreCheckDNS(fqdn, value, s.DNS01Nameservers)
	if err != nil {
		return false, err
	}
	if !ok {
		glog.Infof("DNS record for %q not yet propagated", ch.Domain)
		return false, nil
	}

	glog.Infof("Waiting DNS record TTL (%ds) to allow propagation of DNS record for domain %q", ttl, fqdn)
	time.Sleep(time.Second * time.Duration(ttl))
	glog.Infof("ACME DNS01 validation record propagated for %q", fqdn)

	return true, nil
}

func (s *Solver) CleanUp(ctx context.Context, issuer v1alpha1.GenericIssuer, _ *v1alpha1.Certificate, ch v1alpha1.ACMEOrderChallenge) error {
	if ch.SolverConfig.DNS01 == nil {
		return fmt.Errorf("challenge dns config must be specified")
	}

	providerName := ch.SolverConfig.DNS01.Provider
	if providerName == "" {
		return fmt.Errorf("dns01 challenge provider name must be set")
	}

	slv, err := s.solverForIssuerProvider(issuer, providerName)
	if err != nil {
		return err
	}

	return slv.CleanUp(ch.Domain, ch.Token, ch.Key)
}

// solverForIssuerProvider returns a Solver for the given providerName.
// The providerName is the name of an ACME DNS-01 challenge provider as
// specified on the Issuer resource for the Solver.
//
// This method is exported so that only the provider name is required in order
// to obtain an instance of a Solver. This is useful when cleaning up old
// challenges after the ACME challenge configuration on the Certificate has
// been removed by the user.
func (s *Solver) solverForIssuerProvider(issuer v1alpha1.GenericIssuer, providerName string) (solver, error) {
	resourceNamespace := s.ResourceNamespace(issuer)
	providerConfig, err := issuer.GetSpec().ACME.DNS01.Provider(providerName)
	if err != nil {
		return nil, err
	}

	var impl solver
	switch {
	case providerConfig.Akamai != nil:
		clientToken, err := s.loadSecretData(&providerConfig.Akamai.ClientToken, resourceNamespace)
		if err != nil {
			return nil, errors.Wrap(err, "error getting akamai client token")
		}

		clientSecret, err := s.loadSecretData(&providerConfig.Akamai.ClientSecret, resourceNamespace)
		if err != nil {
			return nil, errors.Wrap(err, "error getting akamai client secret")
		}

		accessToken, err := s.loadSecretData(&providerConfig.Akamai.AccessToken, resourceNamespace)
		if err != nil {
			return nil, errors.Wrap(err, "error getting akamai access token")
		}

		impl, err = akamai.NewDNSProvider(
			providerConfig.Akamai.ServiceConsumerDomain,
			string(clientToken),
			string(clientSecret),
			string(accessToken),
			s.DNS01Nameservers)
		if err != nil {
			return nil, errors.Wrap(err, "error instantiating akamai challenge solver")
		}
	case providerConfig.CloudDNS != nil:
		saSecret, err := s.secretLister.Secrets(resourceNamespace).Get(providerConfig.CloudDNS.ServiceAccount.Name)
		if err != nil {
			return nil, fmt.Errorf("error getting clouddns service account: %s", err)
		}

		saKey := providerConfig.CloudDNS.ServiceAccount.Key
		saBytes := saSecret.Data[saKey]

		if len(saBytes) == 0 {
			return nil, fmt.Errorf("specfied key %q not found in secret %s/%s", saKey, saSecret.Namespace, saSecret.Name)
		}

		impl, err = s.dnsProviderConstructors.cloudDNS(providerConfig.CloudDNS.Project, saBytes, s.DNS01Nameservers)
		if err != nil {
			return nil, fmt.Errorf("error instantiating google clouddns challenge solver: %s", err)
		}
	case providerConfig.Cloudflare != nil:
		apiKeySecret, err := s.secretLister.Secrets(resourceNamespace).Get(providerConfig.Cloudflare.APIKey.Name)
		if err != nil {
			return nil, fmt.Errorf("error getting cloudflare service account: %s", err)
		}

		email := providerConfig.Cloudflare.Email
		apiKey := string(apiKeySecret.Data[providerConfig.Cloudflare.APIKey.Key])

		impl, err = s.dnsProviderConstructors.cloudFlare(email, apiKey, s.DNS01Nameservers)
		if err != nil {
			return nil, fmt.Errorf("error instantiating cloudflare challenge solver: %s", err)
		}
	case providerConfig.Route53 != nil:
		secretAccessKey := ""
		if providerConfig.Route53.SecretAccessKey.Name != "" {
			secretAccessKeySecret, err := s.secretLister.Secrets(resourceNamespace).Get(providerConfig.Route53.SecretAccessKey.Name)
			if err != nil {
				return nil, fmt.Errorf("error getting route53 secret access key: %s", err)
			}

			secretAccessKeyBytes, ok := secretAccessKeySecret.Data[providerConfig.Route53.SecretAccessKey.Key]
			if !ok {
				return nil, fmt.Errorf("error getting route53 secret access key: key '%s' not found in secret", providerConfig.Route53.SecretAccessKey.Key)
			}
			secretAccessKey = string(secretAccessKeyBytes)
		}

		impl, err = s.dnsProviderConstructors.route53(
			strings.TrimSpace(providerConfig.Route53.AccessKeyID),
			strings.TrimSpace(secretAccessKey),
			providerConfig.Route53.HostedZoneID,
			providerConfig.Route53.Region,
			s.CanUseAmbientCredentials(issuer),
			s.DNS01Nameservers,
		)
		if err != nil {
			return nil, fmt.Errorf("error instantiating route53 challenge solver: %s", err)
		}
	case providerConfig.AzureDNS != nil:
		clientSecret, err := s.secretLister.Secrets(resourceNamespace).Get(providerConfig.AzureDNS.ClientSecret.Name)
		if err != nil {
			return nil, fmt.Errorf("error getting azuredns client secret: %s", err)
		}

		clientSecretBytes, ok := clientSecret.Data[providerConfig.AzureDNS.ClientSecret.Key]
		if !ok {
			return nil, fmt.Errorf("error getting azure dns client secret: key '%s' not found in secret", providerConfig.AzureDNS.ClientSecret.Key)
		}

		impl, err = s.dnsProviderConstructors.azureDNS(
			providerConfig.AzureDNS.ClientID,
			string(clientSecretBytes),
			providerConfig.AzureDNS.SubscriptionID,
			providerConfig.AzureDNS.TenantID,
			providerConfig.AzureDNS.ResourceGroupName,
			providerConfig.AzureDNS.HostedZoneName,
			s.DNS01Nameservers,
		)
	case providerConfig.AcmeDNS != nil:
		accountsSecret, err := s.secretLister.Secrets(s.resourceNamespace).Get(providerConfig.AcmeDNS.AccountsSecret.Name)
		if err != nil {
			return nil, fmt.Errorf("error getting acmedns accounts secret: %s", err)
		}

		accountsSecretBytes, ok := accountsSecret.Data[providerConfig.AcmeDNS.AccountsSecret.Key]
		if !ok {
			return nil, fmt.Errorf("error getting acmedns accounts secret: key '%s' not found in secret", providerConfig.AcmeDNS.AccountsSecret.Key)
		}

		impl, err = s.dnsProviderConstructors.acmeDNS(providerConfig.AcmeDNS.Host, accountsSecretBytes)
	default:
		return nil, fmt.Errorf("no dns provider config specified for provider %q", providerName)
	}

	return impl, nil
}

func NewSolver(ctx *controller.Context) *Solver {
	return &Solver{
		ctx,
		ctx.KubeSharedInformerFactory.Core().V1().Secrets().Lister(),
		dnsProviderConstructors{
			clouddns.NewDNSProviderServiceAccountBytes,
			cloudflare.NewDNSProviderCredentials,
			route53.NewDNSProvider,
			azuredns.NewDNSProviderCredentials,
			acmedns.NewDNSProviderHostBytes,
		},
	}
}

func (s *Solver) loadSecretData(selector *v1alpha1.SecretKeySelector, ns string) ([]byte, error) {
	secret, err := s.secretLister.Secrets(ns).Get(selector.Name)
	if err != nil {
		return nil, errors.Wrapf(err, "failed to load secret %q", ns+"/"+selector.Name)
	}

	if data, ok := secret.Data[selector.Key]; ok {
		return data, nil
	}

	return nil, errors.Errorf("no key %q in secret %q", selector.Key, ns+"/"+selector.Name)
}