// GetRemoteCA returns the remote endpoint's CA certificate
func GetRemoteCA(ctx context.Context, d digest.Digest, r remotes.Remotes) (RootCA, error) {
	// This TLS Config is intentionally using InsecureSkipVerify. We use the
	// digest instead to check the integrity of the CA certificate.
	insecureCreds := credentials.NewTLS(&tls.Config{InsecureSkipVerify: true})
	conn, peer, err := getGRPCConnection(insecureCreds, r)
	if err != nil {
		return RootCA{}, err
	}
	defer conn.Close()

	client := api.NewCAClient(conn)
	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()
	defer func() {
		if err != nil {
			r.Observe(peer, -remotes.DefaultObservationWeight)
			return
		}
		r.Observe(peer, remotes.DefaultObservationWeight)
	}()
	response, err := client.GetRootCACertificate(ctx, &api.GetRootCACertificateRequest{})
	if err != nil {
		return RootCA{}, err
	}

	if d != "" {
		verifier, err := digest.NewDigestVerifier(d)
		if err != nil {
			return RootCA{}, errors.Wrap(err, "unexpected error getting digest verifier")
		}

		io.Copy(verifier, bytes.NewReader(response.Certificate))

		if !verifier.Verified() {
			return RootCA{}, errors.Errorf("remote CA does not match fingerprint. Expected: %s", d.Hex())

		}
	}

	// Check the validity of the remote Cert
	_, err = helpers.ParseCertificatePEM(response.Certificate)
	if err != nil {
		return RootCA{}, err
	}

	// Create a Pool with our RootCACertificate
	pool := x509.NewCertPool()
	if !pool.AppendCertsFromPEM(response.Certificate) {
		return RootCA{}, errors.New("failed to append certificate to cert pool")
	}

	return RootCA{Cert: response.Certificate, Digest: digest.FromBytes(response.Certificate), Pool: pool}, nil
}

func getGRPCConnection(creds credentials.TransportCredentials, r remotes.Remotes) (*grpc.ClientConn, api.Peer, error) {
	peer, err := r.Select()
	if err != nil {
		return nil, api.Peer{}, err
	}

	opts := []grpc.DialOption{
		grpc.WithTransportCredentials(creds),
		grpc.WithTimeout(5 * time.Second),
		grpc.WithBackoffMaxDelay(5 * time.Second),
	}

	conn, err := grpc.Dial(peer.Addr, opts...)
	if err != nil {
		return nil, api.Peer{}, err
	}
	return conn, peer, nil
}

func (rca *RootCA) getKEKUpdate(ctx context.Context, cert *x509.Certificate, keypair tls.Certificate, r remotes.Remotes) (*KEKData, error) {
	var managerRole bool
	for _, ou := range cert.Subject.OrganizationalUnit {
		if ou == ManagerRole {
			managerRole = true
			break
		}
	}

	if managerRole {
		mtlsCreds := credentials.NewTLS(&tls.Config{ServerName: CARole, RootCAs: rca.Pool, Certificates: []tls.Certificate{keypair}})
		conn, peer, err := getGRPCConnection(mtlsCreds, r)
		if err != nil {
			return nil, err
		}
		defer conn.Close()

		client := api.NewCAClient(conn)
		ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
		defer cancel()
		response, err := client.GetUnlockKey(ctx, &api.GetUnlockKeyRequest{})
		if err != nil {
			if grpc.Code(err) == codes.Unimplemented { // if the server does not support keks, return as if no encryption key was specified
				return &KEKData{}, nil
			}

			r.Observe(peer, -remotes.DefaultObservationWeight)
			return nil, err
		}
		r.Observe(peer, remotes.DefaultObservationWeight)
		return &KEKData{KEK: response.UnlockKey, Version: response.Version.Index}, nil
	}

	// If this is a worker, set to never encrypt. We always want to set to the lock key to nil,
	// in case this was a manager that was demoted to a worker.
	return &KEKData{}, nil
}

// GetRemoteSignedCertificate submits a CSR to a remote CA server address,
// and that is part of a CA identified by a specific certificate pool.
func GetRemoteSignedCertificate(ctx context.Context, csr []byte, token string, rootCAPool *x509.CertPool, r remotes.Remotes, creds credentials.TransportCredentials, nodeInfo chan<- api.IssueNodeCertificateResponse) ([]byte, error) {
	if rootCAPool == nil {
		return nil, errors.New("valid root CA pool required")
	}

	if creds == nil {
		// This is our only non-MTLS request, and it happens when we are boostraping our TLS certs
		// We're using CARole as server name, so an external CA doesn't also have to have ManagerRole in the cert SANs
		creds = credentials.NewTLS(&tls.Config{ServerName: CARole, RootCAs: rootCAPool})
	}

	peer, err := r.Select()
	if err != nil {
		return nil, err
	}

	opts := []grpc.DialOption{
		grpc.WithTransportCredentials(creds),
		grpc.WithTimeout(5 * time.Second),
		grpc.WithBackoffMaxDelay(5 * time.Second),
	}

	conn, err := grpc.Dial(peer.Addr, opts...)
	if err != nil {
		return nil, err
	}
	defer conn.Close()

	// Create a CAClient to retrieve a new Certificate
	caClient := api.NewNodeCAClient(conn)

	// Send the Request and retrieve the request token
	issueRequest := &api.IssueNodeCertificateRequest{CSR: csr, Token: token}
	issueResponse, err := caClient.IssueNodeCertificate(ctx, issueRequest)
	if err != nil {
		return nil, err
	}

	// Send back the NodeID on the nodeInfo, so the caller can know what ID was assigned by the CA
	if nodeInfo != nil {
		nodeInfo <- *issueResponse
	}

	statusRequest := &api.NodeCertificateStatusRequest{NodeID: issueResponse.NodeID}
	expBackoff := events.NewExponentialBackoff(events.ExponentialBackoffConfig{
		Base:   time.Second,
		Factor: time.Second,
		Max:    30 * time.Second,
	})

	// Exponential backoff with Max of 30 seconds to wait for a new retry
	for {
		// Send the Request and retrieve the certificate
		ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
		defer cancel()
		statusResponse, err := caClient.NodeCertificateStatus(ctx, statusRequest)
		if err != nil {
			r.Observe(peer, -remotes.DefaultObservationWeight)
			return nil, err
		}

		// If the certificate was issued, return
		if statusResponse.Status.State == api.IssuanceStateIssued {
			if statusResponse.Certificate == nil {
				return nil, errors.New("no certificate in CertificateStatus response")
			}

			// The certificate in the response must match the CSR
			// we submitted. If we are getting a response for a
			// certificate that was previously issued, we need to
			// retry until the certificate gets updated per our
			// current request.
			if bytes.Equal(statusResponse.Certificate.CSR, csr) {
				r.Observe(peer, remotes.DefaultObservationWeight)
				return statusResponse.Certificate.Certificate, nil
			}
		}

		// If we're still pending, the issuance failed, or the state is unknown
		// let's continue trying.
		expBackoff.Failure(nil, nil)
		time.Sleep(expBackoff.Proceed(nil))
	}
}

// GetRemoteCA returns the remote endpoint's CA certificate
func GetRemoteCA(ctx context.Context, d digest.Digest, r remotes.Remotes) (RootCA, error) {
	// This TLS Config is intentionally using InsecureSkipVerify. Either we're
	// doing TOFU, in which case we don't validate the remote CA, or we're using
	// a user supplied hash to check the integrity of the CA certificate.
	insecureCreds := credentials.NewTLS(&tls.Config{InsecureSkipVerify: true})
	opts := []grpc.DialOption{
		grpc.WithTransportCredentials(insecureCreds),
		grpc.WithTimeout(5 * time.Second),
		grpc.WithBackoffMaxDelay(5 * time.Second),
	}

	peer, err := r.Select()
	if err != nil {
		return RootCA{}, err
	}

	conn, err := grpc.Dial(peer.Addr, opts...)
	if err != nil {
		return RootCA{}, err
	}
	defer conn.Close()

	client := api.NewCAClient(conn)
	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()
	defer func() {
		if err != nil {
			r.Observe(peer, -remotes.DefaultObservationWeight)
			return
		}
		r.Observe(peer, remotes.DefaultObservationWeight)
	}()
	response, err := client.GetRootCACertificate(ctx, &api.GetRootCACertificateRequest{})
	if err != nil {
		return RootCA{}, err
	}

	if d != "" {
		verifier, err := digest.NewDigestVerifier(d)
		if err != nil {
			return RootCA{}, errors.Wrap(err, "unexpected error getting digest verifier")
		}

		io.Copy(verifier, bytes.NewReader(response.Certificate))

		if !verifier.Verified() {
			return RootCA{}, errors.Errorf("remote CA does not match fingerprint. Expected: %s", d.Hex())

		}
	}

	// Check the validity of the remote Cert
	_, err = helpers.ParseCertificatePEM(response.Certificate)
	if err != nil {
		return RootCA{}, err
	}

	// Create a Pool with our RootCACertificate
	pool := x509.NewCertPool()
	if !pool.AppendCertsFromPEM(response.Certificate) {
		return RootCA{}, errors.New("failed to append certificate to cert pool")
	}

	return RootCA{Cert: response.Certificate, Digest: digest.FromBytes(response.Certificate), Pool: pool}, nil
}