/*
Copyright 2018 The Kubernetes Authors.

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 config

import (
	"crypto/x509"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"path/filepath"
	"strings"

	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/util/version"
	clientset "k8s.io/client-go/kubernetes"
	"k8s.io/client-go/tools/clientcmd"
	certutil "k8s.io/client-go/util/cert"
	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
	kubeadmscheme "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/scheme"
	"k8s.io/kubernetes/cmd/kubeadm/app/componentconfigs"
	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
)

// FetchConfigFromFileOrCluster fetches configuration required for upgrading your cluster from a file (which has precedence) or a ConfigMap in the cluster
func FetchConfigFromFileOrCluster(client clientset.Interface, w io.Writer, logPrefix, cfgPath string, newControlPlane bool) (*kubeadmapi.InitConfiguration, error) {
	// Load the configuration from a file or the cluster
	initcfg, err := loadConfiguration(client, w, logPrefix, cfgPath, newControlPlane)
	if err != nil {
		return nil, err
	}

	// Apply dynamic defaults
	if err := SetInitDynamicDefaults(initcfg); err != nil {
		return nil, err
	}
	return initcfg, err
}

// loadConfiguration loads the configuration byte slice from either a file or the cluster ConfigMap
func loadConfiguration(client clientset.Interface, w io.Writer, logPrefix, cfgPath string, newControlPlane bool) (*kubeadmapi.InitConfiguration, error) {
	// The config file has the highest priority
	if cfgPath != "" {
		fmt.Fprintf(w, "[%s] Reading configuration options from a file: %s\n", logPrefix, cfgPath)
		return loadInitConfigurationFromFile(cfgPath)
	}

	fmt.Fprintf(w, "[%s] Reading configuration from the cluster...\n", logPrefix)
	fmt.Fprintf(w, "[%s] FYI: You can look at this config file with 'kubectl -n %s get cm %s -oyaml'\n", logPrefix, metav1.NamespaceSystem, constants.InitConfigurationConfigMap)
	return getInitConfigurationFromCluster(constants.KubernetesDir, client, newControlPlane)
}

func loadInitConfigurationFromFile(cfgPath string) (*kubeadmapi.InitConfiguration, error) {
	configBytes, err := ioutil.ReadFile(cfgPath)
	if err != nil {
		return nil, err
	}

	// Unmarshal the versioned configuration populated from the file,
	// convert it to the internal API types, then default and validate
	// NB the file contains multiple YAML, with a combination of
	// 	- a YAML with a InitConfiguration object
	// 	- a YAML with a ClusterConfiguration object (without embedded component configs)
	//	- separated YAML for components configs
	initcfg, err := BytesToInternalConfig(configBytes)
	if err != nil {
		return nil, err
	}

	return initcfg, nil
}

func getInitConfigurationFromCluster(kubeconfigDir string, client clientset.Interface, newControlPlane bool) (*kubeadmapi.InitConfiguration, error) {
	// TODO: This code should support reading the MasterConfiguration key as well for backwards-compat
	// Also, the config map really should be KubeadmConfigConfigMap...
	configMap, err := client.CoreV1().ConfigMaps(metav1.NamespaceSystem).Get(constants.InitConfigurationConfigMap, metav1.GetOptions{})
	if err != nil {
		return nil, err
	}

	// InitConfiguration is composed with data from different places
	initcfg := &kubeadmapi.InitConfiguration{}

	// gets ClusterConfiguration from kubeadm-config
	clusterConfigurationData, ok := configMap.Data[constants.ClusterConfigurationConfigMapKey]
	if !ok {
		return nil, fmt.Errorf("unexpected error when reading kubeadm-config ConfigMap: %s key value pair missing", constants.ClusterConfigurationConfigMapKey)
	}
	if err := runtime.DecodeInto(kubeadmscheme.Codecs.UniversalDecoder(), []byte(clusterConfigurationData), &initcfg.ClusterConfiguration); err != nil {
		return nil, err
	}

	// gets the component configs from the corresponding config maps
	if err := getComponentConfigs(client, &initcfg.ClusterConfiguration); err != nil {
		return nil, err
	}

	// if this isn't a new controlplane instance (e.g. in case of kubeadm upgrades)
	// get nodes specific information as well
	if !newControlPlane {
		// gets the nodeRegistration for the current from the node object
		if err := getNodeRegistration(kubeconfigDir, client, &initcfg.NodeRegistration); err != nil {
			return nil, err
		}
		// gets the APIEndpoint for the current node from then ClusterStatus in the kubeadm-config ConfigMap
		if err := getAPIEndpoint(configMap.Data, initcfg.NodeRegistration.Name, &initcfg.APIEndpoint); err != nil {
			return nil, err
		}
	}

	return initcfg, nil
}

// getNodeRegistration returns the nodeRegistration for the current node
func getNodeRegistration(kubeconfigDir string, client clientset.Interface, nodeRegistration *kubeadmapi.NodeRegistrationOptions) error {
	// gets the name of the current node
	nodeName, err := getNodeNameFromKubeletConfig(kubeconfigDir)
	if err != nil {
		return err
	}

	// gets the corresponding node and retrives attributes stored there.
	node, err := client.CoreV1().Nodes().Get(nodeName, metav1.GetOptions{})
	if err != nil {
		return err
	}

	criSocket, ok := node.ObjectMeta.Annotations[constants.AnnotationKubeadmCRISocket]
	if !ok {
		return fmt.Errorf("Node %s doesn't have %s annotation", nodeName, constants.AnnotationKubeadmCRISocket)
	}

	// returns the nodeRegistration attributes
	nodeRegistration.Name = nodeName
	nodeRegistration.CRISocket = criSocket
	nodeRegistration.Taints = node.Spec.Taints
	// NB. currently nodeRegistration.KubeletExtraArgs isn't stored at node level but only in the kubeadm-flags.env
	//     that isn't modified during upgrades
	//     in future we might reconsider this thus enabling changes to the kubeadm-flags.env during upgrades as well
	return nil
}

// getNodeNameFromConfig gets the node name from a kubelet config file
// TODO: in future we want to switch to a more canonical way for doing this e.g. by having this
//       information in the local kubelet config.yaml
func getNodeNameFromKubeletConfig(kubeconfigDir string) (string, error) {
	// loads the kubelet.conf file
	fileName := filepath.Join(kubeconfigDir, constants.KubeletKubeConfigFileName)
	config, err := clientcmd.LoadFromFile(fileName)
	if err != nil {
		return "", err
	}

	// gets the info about the current user
	authInfo := config.AuthInfos[config.Contexts[config.CurrentContext].AuthInfo]

	// gets the X509 certificate with current user credentials
	var certs []*x509.Certificate
	if len(authInfo.ClientCertificateData) > 0 {
		// if the config file uses an embedded x509 certificate (e.g. kubelet.conf created by kubeadm), parse it
		if certs, err = certutil.ParseCertsPEM(authInfo.ClientCertificateData); err != nil {
			return "", err
		}
	} else if len(authInfo.ClientCertificate) > 0 {
		// if the config file links an external x509 certificate (e.g. kubelet.conf created by TLS bootstrap), load it
		if certs, err = certutil.CertsFromFile(authInfo.ClientCertificate); err != nil {
			return "", err
		}
	} else {
		return "", errors.New("Invalid kubelet.conf. X509 certificate expected")
	}

	// We are only putting one certificate in the certificate pem file, so it's safe to just pick the first one
	// TODO: Support multiple certs here in order to be able to rotate certs
	cert := certs[0]

	// gets the node name from the certificate common name
	return strings.TrimPrefix(cert.Subject.CommonName, constants.NodesUserPrefix), nil
}

// getAPIEndpoint returns the APIEndpoint for the current node
func getAPIEndpoint(data map[string]string, nodeName string, apiEndpoint *kubeadmapi.APIEndpoint) error {
	// gets the ClusterStatus from kubeadm-config
	clusterStatusData, ok := data[constants.ClusterStatusConfigMapKey]
	if !ok {
		return fmt.Errorf("unexpected error when reading kubeadm-config ConfigMap: %s key value pair missing", constants.ClusterStatusConfigMapKey)
	}
	clusterStatus := &kubeadmapi.ClusterStatus{}
	if err := runtime.DecodeInto(kubeadmscheme.Codecs.UniversalDecoder(), []byte(clusterStatusData), clusterStatus); err != nil {
		return err
	}

	// gets the APIEndpoint for the current machine from the ClusterStatus
	e, ok := clusterStatus.APIEndpoints[nodeName]
	if !ok {
		return errors.New("failed to get APIEndpoint information for this node")
	}

	apiEndpoint.AdvertiseAddress = e.AdvertiseAddress
	apiEndpoint.BindPort = e.BindPort
	return nil
}

// getComponentConfigs gets the component configs from the corresponding config maps
func getComponentConfigs(client clientset.Interface, clusterConfiguration *kubeadmapi.ClusterConfiguration) error {
	// some config maps is versioned, so we need the KubernetesVersion for getting the right config map
	k8sVersion := version.MustParseGeneric(clusterConfiguration.KubernetesVersion)
	for kind, registration := range componentconfigs.Known {
		obj, err := registration.GetFromConfigMap(client, k8sVersion)
		if err != nil {
			return err
		}

		if ok := registration.SetToInternalConfig(obj, clusterConfiguration); !ok {
			return fmt.Errorf("couldn't save componentconfig value for kind %q", string(kind))
		}
	}
	return nil
}