// Copyright (c) 2019 SAP SE or an SAP affiliate company. All rights reserved. This file is licensed under the Apache Software License, v. 2 except as noted otherwise in the LICENSE file
//
// 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 etcdencryption

import (
	"encoding/base64"
	"fmt"
	"io"
	"time"

	"github.com/gardener/gardener/pkg/operation/common"

	corev1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/runtime/serializer/json"
	"k8s.io/apimachinery/pkg/runtime/serializer/versioning"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	apiserverconfigv1 "k8s.io/apiserver/pkg/apis/config/v1"
)

var (
	codec runtime.Codec
)

func init() {
	scheme := runtime.NewScheme()
	utilruntime.Must(apiserverconfigv1.AddToScheme(scheme))
	serializer := json.NewYAMLSerializer(json.DefaultMetaFactory, scheme, scheme)
	codec = versioning.NewDefaultingCodecForScheme(
		scheme,
		serializer,
		serializer,
		apiserverconfigv1.SchemeGroupVersion,
		apiserverconfigv1.SchemeGroupVersion)
}

// NewEncryptionConfiguration creates an EncryptionConfiguration from the key and state
func NewEncryptionConfiguration(encryptionConfig *EncryptionConfig) *apiserverconfigv1.EncryptionConfiguration {
	encryptionKeys := make([]apiserverconfigv1.Key, len(encryptionConfig.EncryptionKeys))
	for i, keyData := range encryptionConfig.EncryptionKeys {
		encryptionKeys[i].Name = keyData.Name
		encryptionKeys[i].Secret = keyData.Key
	}
	aesConfiguration := &apiserverconfigv1.AESConfiguration{Keys: encryptionKeys}

	aescbcProviderConfiguration := apiserverconfigv1.ProviderConfiguration{AESCBC: aesConfiguration}
	identityProviderConfiguration := apiserverconfigv1.ProviderConfiguration{Identity: &apiserverconfigv1.IdentityConfiguration{}}

	providerConfigs := []apiserverconfigv1.ProviderConfiguration{}
	if !encryptionConfig.ForcePlainTextResources {
		providerConfigs = append(providerConfigs, aescbcProviderConfiguration, identityProviderConfiguration)
	} else {
		providerConfigs = append(providerConfigs, identityProviderConfiguration, aescbcProviderConfiguration)
	}

	resourceConfig := apiserverconfigv1.ResourceConfiguration{
		Resources: []string{common.EtcdEncryptionEncryptedResourceSecrets},
		Providers: providerConfigs,
	}

	return &apiserverconfigv1.EncryptionConfiguration{
		Resources: []apiserverconfigv1.ResourceConfiguration{resourceConfig},
	}
}

// NewEncryptionKey creates a new random encryption key with a name containing the timestamp.
// The reader should return random data suitable for cryptographic use, otherwise the security
// of encryption might be compromised.
func NewEncryptionKey(t time.Time, r io.Reader) (*apiserverconfigv1.Key, error) {
	keyName := NewEncryptionKeyName(t)
	keySecret, err := NewEncryptionKeySecret(r)
	if err != nil {
		return nil, err
	}

	return &apiserverconfigv1.Key{
		Name:   keyName,
		Secret: keySecret,
	}, nil
}

// NewEncryptionKeyName creates a new key with the given timestamp.
func NewEncryptionKeyName(t time.Time) string {
	return fmt.Sprintf("%s%d", common.EtcdEncryptionKeyPrefix, t.Unix())
}

// NewEncryptionKeySecret reads common.EtcdEncryptionSecretLen bytes from the given reader
// and base-64 encodes the data.
// The reader should return random data suitable for cryptographic use, otherwise the security
// of encryption might be compromised.
func NewEncryptionKeySecret(r io.Reader) (string, error) {
	buf := make([]byte, common.EtcdEncryptionKeySecretLen)
	if _, err := io.ReadFull(r, buf); err != nil {
		return "", fmt.Errorf("could not read enough data: %v", err)
	}

	sEnc := base64.StdEncoding.EncodeToString(buf)
	return sEnc, nil
}

// Load decodes an EncryptionConfiguration from the given data.
func Load(data []byte) (*apiserverconfigv1.EncryptionConfiguration, error) {
	ec := &apiserverconfigv1.EncryptionConfiguration{}
	if _, _, err := codec.Decode(data, nil, ec); err != nil {
		return nil, err
	}

	return ec, nil
}

// Write encodes an EncryptionConfiguration.
func Write(ec *apiserverconfigv1.EncryptionConfiguration) ([]byte, error) {
	return runtime.Encode(codec, ec)
}

func findResourceConfigurationForResource(configs []apiserverconfigv1.ResourceConfiguration, resource string) (*apiserverconfigv1.ResourceConfiguration, error) {
	for _, config := range configs {
		for _, r := range config.Resources {
			if r == resource {
				return &config, nil
			}
		}
	}
	return nil, fmt.Errorf("no resource configuration found for resource %q", resource)
}

var errConfigurationNotFound = fmt.Errorf("no encryption configuration at %s", common.EtcdEncryptionSecretFileName)

// IsConfigurationNotFoundError checks if the given error is an error when the encryption
// configuration is not found at the common.EtcdEncryptionSecretFileName key of the data section
// of a secret.
func IsConfigurationNotFoundError(err error) bool {
	return err == errConfigurationNotFound
}

// ReadSecret reads and validates the EncryptionConfiguration of the given secret.
func ReadSecret(secret *corev1.Secret) (*apiserverconfigv1.EncryptionConfiguration, error) {
	confData, ok := secret.Data[common.EtcdEncryptionSecretFileName]
	if !ok {
		return nil, errConfigurationNotFound
	}

	conf, err := Load(confData)
	if err != nil {
		return nil, err
	}

	return conf, nil
}

// UpdateSecret writes the EncryptionConfiguration to the common.EtcdEncryptionSecretFileName key
// in the data section of the given secret.
func UpdateSecret(secret *corev1.Secret, conf *apiserverconfigv1.EncryptionConfiguration) error {
	if secret.Data == nil {
		secret.Data = make(map[string][]byte)
	}

	confData, err := Write(conf)
	if err != nil {
		return err
	}

	secret.Data[common.EtcdEncryptionSecretFileName] = confData
	return nil
}

// GetSecretKeyForResources returns the AESCBC key name and AESCBC key secret which is used to encrypt the resource.
// If the AESCBC is not found then it returns empty strings.
func GetSecretKeyForResources(config *apiserverconfigv1.EncryptionConfiguration, resources string) (string, string, error) {
	conf, err := findResourceConfigurationForResource(config.Resources, resources)
	if err != nil {
		return "", "", err
	}

	for _, providerConfig := range conf.Providers {
		if providerConfig.AESCBC != nil {
			return providerConfig.AESCBC.Keys[0].Name, providerConfig.AESCBC.Keys[0].Secret, nil
		}
	}
	return "", "", nil
}