/*
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 etcd

import (
	"context"
	"crypto/tls"
	"fmt"
	"net"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/coreos/etcd/clientv3"
	"github.com/coreos/etcd/pkg/transport"
	"github.com/pkg/errors"
	clientset "k8s.io/client-go/kubernetes"
	"k8s.io/klog"
	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
	"k8s.io/kubernetes/cmd/kubeadm/app/util/config"
	"k8s.io/kubernetes/cmd/kubeadm/app/util/staticpod"
)

// ClusterInterrogator is an interface to get etcd cluster related information
type ClusterInterrogator interface {
	ClusterAvailable() (bool, error)
	GetClusterStatus() (map[string]*clientv3.StatusResponse, error)
	GetClusterVersions() (map[string]string, error)
	GetVersion() (string, error)
	HasTLS() bool
	WaitForClusterAvailable(delay time.Duration, retries int, retryInterval time.Duration) (bool, error)
	Sync() error
	AddMember(name string, peerAddrs string) ([]Member, error)
}

// Client provides connection parameters for an etcd cluster
type Client struct {
	Endpoints []string
	TLS       *tls.Config
}

// HasTLS returns true if etcd is configured for TLS
func (c Client) HasTLS() bool {
	return c.TLS != nil
}

// PodManifestsHaveTLS reads the etcd staticpod manifest from disk and returns false if the TLS flags
// are missing from the command list. If all the flags are present it returns true.
func PodManifestsHaveTLS(ManifestDir string) (bool, error) {
	etcdPodPath := constants.GetStaticPodFilepath(constants.Etcd, ManifestDir)
	etcdPod, err := staticpod.ReadStaticPodFromDisk(etcdPodPath)
	if err != nil {
		return false, errors.Wrap(err, "failed to check if etcd pod implements TLS")
	}

	tlsFlags := []string{
		"--cert-file=",
		"--key-file=",
		"--trusted-ca-file=",
		"--client-cert-auth=",
		"--peer-cert-file=",
		"--peer-key-file=",
		"--peer-trusted-ca-file=",
		"--peer-client-cert-auth=",
	}
FlagLoop:
	for _, flag := range tlsFlags {
		for _, container := range etcdPod.Spec.Containers {
			for _, arg := range container.Command {
				if strings.Contains(arg, flag) {
					continue FlagLoop
				}
			}
		}
		// flag not found in any container
		return false, nil
	}
	// all flags were found in container args; pod fully implements TLS
	return true, nil
}

// New creates a new EtcdCluster client
func New(endpoints []string, ca, cert, key string) (*Client, error) {
	client := Client{Endpoints: endpoints}

	if ca != "" || cert != "" || key != "" {
		tlsInfo := transport.TLSInfo{
			CertFile:      cert,
			KeyFile:       key,
			TrustedCAFile: ca,
		}
		tlsConfig, err := tlsInfo.ClientConfig()
		if err != nil {
			return nil, err
		}
		client.TLS = tlsConfig
	}

	return &client, nil
}

// NewFromCluster creates an etcd client for the the etcd endpoints defined in the ClusterStatus value stored in
// the kubeadm-config ConfigMap in kube-system namespace.
// Once created, the client synchronizes client's endpoints with the known endpoints from the etcd membership API (reality check).
func NewFromCluster(client clientset.Interface, certificatesDir string) (*Client, error) {

	// Kubeadm v1.13 should manage v1.12 clusters and v1.13 clusters
	// v1.12 clusters can be have etcd listening on localhost only (if the cluster was created with kubeadm v1.12)
	// or etcd listening on localhost and API server advertise address (if the cluster was created with kubeadm v1.13).
	// The first case should be dropped in v1.14 when support for v1.12 clusters can be removed from the codebase.

	// Detect which type of etcd we are dealing with
	// Please note that this test can be executed only on master nodes during upgrades;
	// For nodes where we are joining a new control plane node instead we should tolerate that the etcd manifest does not
	// exists and try to connect to etcd using API server advertise address; as described above this will lead to a know isse
	// for cluster created with v1.12, but a documented workaround will be provided
	oldManifest := false
	klog.V(1).Infoln("checking etcd manifest")

	etcdManifestFile := constants.GetStaticPodFilepath(constants.Etcd, constants.GetStaticPodDirectory())
	etcdPod, err := staticpod.ReadStaticPodFromDisk(etcdManifestFile)
	if err == nil {
		etcdContainer := etcdPod.Spec.Containers[0]
		for _, arg := range etcdContainer.Command {
			if arg == "--listen-client-urls=https://127.0.0.1:2379" {
				klog.V(1).Infoln("etcd manifest created by kubeadm v1.12")
				oldManifest = true
			}
		}

		// if etcd is listening on localhost only
		if oldManifest == true {
			// etcd cluster has a single member "by design"
			endpoints := []string{fmt.Sprintf("localhost:%d", constants.EtcdListenClientPort)}

			etcdClient, err := New(
				endpoints,
				filepath.Join(certificatesDir, constants.EtcdCACertName),
				filepath.Join(certificatesDir, constants.EtcdHealthcheckClientCertName),
				filepath.Join(certificatesDir, constants.EtcdHealthcheckClientKeyName),
			)
			if err != nil {
				return nil, errors.Wrapf(err, "error creating etcd client for %v endpoint", endpoints)
			}

			return etcdClient, nil
		}
	}

	// etcd is listening on localhost and API server advertise address, and
	// the etcd cluster can have more than one etcd members, so it is necessary to get the
	// list of endpoints from kubeadm cluster status before connecting

	// Gets the cluster status
	clusterStatus, err := config.GetClusterStatus(client)
	if err != nil {
		return nil, err
	}

	// Get the list of etcd endpoints from cluster status
	endpoints := []string{}
	for _, e := range clusterStatus.APIEndpoints {
		endpoints = append(endpoints, GetClientURLByIP(e.AdvertiseAddress))
	}
	klog.V(1).Infof("etcd endpoints read from pods: %s", strings.Join(endpoints, ","))

	// Creates an etcd client
	etcdClient, err := New(
		endpoints,
		filepath.Join(certificatesDir, constants.EtcdCACertName),
		filepath.Join(certificatesDir, constants.EtcdHealthcheckClientCertName),
		filepath.Join(certificatesDir, constants.EtcdHealthcheckClientKeyName),
	)
	if err != nil {
		return nil, errors.Wrapf(err, "error creating etcd client for %v endpoints", endpoints)
	}

	// synchronizes client's endpoints with the known endpoints from the etcd membership.
	err = etcdClient.Sync()
	if err != nil {
		return nil, errors.Wrap(err, "error syncing endpoints with etc")
	}
	klog.V(1).Infof("update etcd endpoints: %s", strings.Join(etcdClient.Endpoints, ","))

	return etcdClient, nil
}

// Sync synchronizes client's endpoints with the known endpoints from the etcd membership.
func (c *Client) Sync() error {
	cli, err := clientv3.New(clientv3.Config{
		Endpoints:   c.Endpoints,
		DialTimeout: 20 * time.Second,
		TLS:         c.TLS,
	})
	if err != nil {
		return err
	}
	defer cli.Close()

	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	err = cli.Sync(ctx)
	cancel()
	if err != nil {
		return err
	}
	klog.V(1).Infof("etcd endpoints read from etcd: %s", strings.Join(cli.Endpoints(), ","))

	c.Endpoints = cli.Endpoints()
	return nil
}

// Member struct defines an etcd member; it is used for avoiding to spread github.com/coreos/etcd dependency
// across kubeadm codebase
type Member struct {
	Name    string
	PeerURL string
}

// AddMember notifies an existing etcd cluster that a new member is joining
func (c Client) AddMember(name string, peerAddrs string) ([]Member, error) {
	cli, err := clientv3.New(clientv3.Config{
		Endpoints:   c.Endpoints,
		DialTimeout: 20 * time.Second,
		TLS:         c.TLS,
	})
	if err != nil {
		return nil, err
	}
	defer cli.Close()

	// Adds a new member to the cluster
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	resp, err := cli.MemberAdd(ctx, []string{peerAddrs})
	cancel()
	if err != nil {
		return nil, err
	}

	// Returns the updated list of etcd members
	ret := []Member{}
	for _, m := range resp.Members {
		// fixes the entry for the joining member (that doesn't have a name set in the initialCluster returned by etcd)
		if m.Name == "" {
			ret = append(ret, Member{Name: name, PeerURL: m.PeerURLs[0]})
		} else {
			ret = append(ret, Member{Name: m.Name, PeerURL: m.PeerURLs[0]})
		}
	}

	return ret, nil
}

// GetVersion returns the etcd version of the cluster.
// An error is returned if the version of all endpoints do not match
func (c Client) GetVersion() (string, error) {
	var clusterVersion string

	versions, err := c.GetClusterVersions()
	if err != nil {
		return "", err
	}
	for _, v := range versions {
		if clusterVersion != "" && clusterVersion != v {
			return "", errors.Errorf("etcd cluster contains endpoints with mismatched versions: %v", versions)
		}
		clusterVersion = v
	}
	if clusterVersion == "" {
		return "", errors.New("could not determine cluster etcd version")
	}
	return clusterVersion, nil
}

// GetClusterVersions returns a map of the endpoints and their associated versions
func (c Client) GetClusterVersions() (map[string]string, error) {
	versions := make(map[string]string)
	statuses, err := c.GetClusterStatus()
	if err != nil {
		return versions, err
	}

	for ep, status := range statuses {
		versions[ep] = status.Version
	}
	return versions, nil
}

// ClusterAvailable returns true if the cluster status indicates the cluster is available.
func (c Client) ClusterAvailable() (bool, error) {
	_, err := c.GetClusterStatus()
	if err != nil {
		return false, err
	}
	return true, nil
}

// GetClusterStatus returns nil for status Up or error for status Down
func (c Client) GetClusterStatus() (map[string]*clientv3.StatusResponse, error) {
	cli, err := clientv3.New(clientv3.Config{
		Endpoints:   c.Endpoints,
		DialTimeout: 5 * time.Second,
		TLS:         c.TLS,
	})
	if err != nil {
		return nil, err
	}
	defer cli.Close()

	clusterStatus := make(map[string]*clientv3.StatusResponse)
	for _, ep := range c.Endpoints {
		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		resp, err := cli.Status(ctx, ep)
		cancel()
		if err != nil {
			return nil, err
		}
		clusterStatus[ep] = resp
	}
	return clusterStatus, nil
}

// WaitForClusterAvailable returns true if all endpoints in the cluster are available after an initial delay and retry attempts, an error is returned otherwise
func (c Client) WaitForClusterAvailable(delay time.Duration, retries int, retryInterval time.Duration) (bool, error) {
	fmt.Printf("[util/etcd] Waiting %v for initial delay\n", delay)
	time.Sleep(delay)
	for i := 0; i < retries; i++ {
		if i > 0 {
			fmt.Printf("[util/etcd] Waiting %v until next retry\n", retryInterval)
			time.Sleep(retryInterval)
		}
		fmt.Printf("[util/etcd] Attempting to see if all cluster endpoints are available %d/%d\n", i+1, retries)
		resp, err := c.ClusterAvailable()
		if err != nil {
			switch err {
			case context.DeadlineExceeded:
				fmt.Println("[util/etcd] Attempt timed out")
			default:
				fmt.Printf("[util/etcd] Attempt failed with error: %v\n", err)
			}
			continue
		}
		return resp, nil
	}
	return false, errors.New("timeout waiting for etcd cluster to be available")
}

// CheckConfigurationIsHA returns true if the given InitConfiguration etcd block appears to be an HA configuration.
func CheckConfigurationIsHA(cfg *kubeadmapi.Etcd) bool {
	return cfg.External != nil && len(cfg.External.Endpoints) > 1
}

// GetClientURL creates an HTTPS URL that uses the configured advertise
// address and client port for the API controller
func GetClientURL(cfg *kubeadmapi.InitConfiguration) string {
	return "https://" + net.JoinHostPort(cfg.LocalAPIEndpoint.AdvertiseAddress, strconv.Itoa(constants.EtcdListenClientPort))
}

// GetPeerURL creates an HTTPS URL that uses the configured advertise
// address and peer port for the API controller
func GetPeerURL(cfg *kubeadmapi.InitConfiguration) string {
	return "https://" + net.JoinHostPort(cfg.LocalAPIEndpoint.AdvertiseAddress, strconv.Itoa(constants.EtcdListenPeerPort))
}

// GetClientURLByIP creates an HTTPS URL based on an IP address
// and the client listening port.
func GetClientURLByIP(ip string) string {
	return "https://" + net.JoinHostPort(ip, strconv.Itoa(constants.EtcdListenClientPort))
}