// Sends SnapshotRecoveryRequest RPCs to a peer when the server is the candidate.
func (t *transporter) SendSnapshotRecoveryRequest(server raft.Server, peer *raft.Peer, req *raft.SnapshotRecoveryRequest) *raft.SnapshotRecoveryResponse {
	var b bytes.Buffer

	if _, err := req.Encode(&b); err != nil {
		log.Warn("transporter.ss.encoding.error:", err)
		return nil
	}

	u, _ := t.peerServer.registry.PeerURL(peer.Name)
	log.Debugf("Send Snapshot Recovery from %s to %s", server.Name(), u)

	resp, httpRequest, err := t.Post(fmt.Sprintf("%s/snapshotRecovery", u), &b)

	if err != nil {
		log.Debugf("Cannot send Snapshot Recovery to %s : %s", u, err)
	}

	if resp != nil {
		defer resp.Body.Close()

		t.CancelWhenTimeout(httpRequest)

		ssrrsp := &raft.SnapshotRecoveryResponse{}
		if _, err = ssrrsp.Decode(resp.Body); err != nil && err != io.EOF {
			log.Warn("transporter.ssr.decoding.error:", err)
			return nil
		}
		return ssrrsp
	}
	return nil

}

// Send join requests to peer.
func (s *PeerServer) joinByPeer(server raft.Server, peer string, scheme string) error {
	var b bytes.Buffer

	// t must be ok
	t, _ := server.Transporter().(*transporter)

	// Our version must match the leaders version
	versionURL := url.URL{Host: peer, Scheme: scheme, Path: "/version"}
	version, err := getVersion(t, versionURL)
	if err != nil {
		return fmt.Errorf("Error during join version check: %v", err)
	}
	if version < store.MinVersion() || version > store.MaxVersion() {
		return fmt.Errorf("Unable to join: cluster version is %d; version compatibility is %d - %d", version, store.MinVersion(), store.MaxVersion())
	}

	json.NewEncoder(&b).Encode(NewJoinCommand(store.MinVersion(), store.MaxVersion(), server.Name(), s.url, s.server.URL()))

	joinURL := url.URL{Host: peer, Scheme: scheme, Path: "/join"}

	log.Debugf("Send Join Request to %s", joinURL.String())

	resp, req, err := t.Post(joinURL.String(), &b)

	for {
		if err != nil {
			return fmt.Errorf("Unable to join: %v", err)
		}
		if resp != nil {
			defer resp.Body.Close()

			t.CancelWhenTimeout(req)

			if resp.StatusCode == http.StatusOK {
				b, _ := ioutil.ReadAll(resp.Body)
				s.joinIndex, _ = binary.Uvarint(b)
				return nil
			}
			if resp.StatusCode == http.StatusTemporaryRedirect {
				address := resp.Header.Get("Location")
				log.Debugf("Send Join Request to %s", address)
				json.NewEncoder(&b).Encode(NewJoinCommand(store.MinVersion(), store.MaxVersion(), server.Name(), s.url, s.server.URL()))
				resp, req, err = t.Post(address, &b)

			} else if resp.StatusCode == http.StatusBadRequest {
				log.Debug("Reach max number peers in the cluster")
				decoder := json.NewDecoder(resp.Body)
				err := &etcdErr.Error{}
				decoder.Decode(err)
				return *err
			} else {
				return fmt.Errorf("Unable to join")
			}
		}

	}
}

// Delete the key
func (c *DeleteCommand) Apply(server raft.Server) (interface{}, error) {
	s, _ := server.StateMachine().(store.Store)

	e, err := s.Delete(c.Key, c.Recursive)

	if err != nil {
		log.Debug(err)
		return nil, err
	}

	return e, nil
}

// Set the key-value pair if the current value of the key equals to the given prevValue
func (c *CompareAndDeleteCommand) Apply(server raft.Server) (interface{}, error) {
	s, _ := server.StateMachine().(store.Store)

	e, err := s.CompareAndDelete(c.Key, c.PrevValue, c.PrevIndex)

	if err != nil {
		log.Debug(err)
		return nil, err
	}

	return e, nil
}

// Create node
func (c *CreateCommand) Apply(server raft.Server) (interface{}, error) {
	s, _ := server.StateMachine().(store.Store)

	e, err := s.Create(c.Key, c.Dir, c.Value, c.Unique, c.ExpireTime)

	if err != nil {
		log.Debug(err)
		return nil, err
	}

	return e, nil
}

// Create node
func (c *SetCommand) Apply(server raft.Server) (interface{}, error) {
	s, _ := server.StateMachine().(store.Store)

	// create a new node or replace the old node.
	e, err := s.Set(c.Key, c.Value, c.ExpireTime)

	if err != nil {
		log.Debug(err)
		return nil, err
	}

	return e, nil
}

// Join a server to the cluster
func (c *JoinCommand) Apply(server raft.Server) (interface{}, error) {
	ps, _ := server.Context().(*PeerServer)

	b := make([]byte, 8)
	binary.PutUvarint(b, server.CommitIndex())

	// Make sure we're not getting a cached value from the registry.
	ps.registry.Invalidate(c.Name)

	// Check if the join command is from a previous peer, who lost all its previous log.
	if _, ok := ps.registry.ClientURL(c.Name); ok {
		return b, nil
	}

	// Check peer number in the cluster
	if ps.registry.Count() == ps.MaxClusterSize {
		log.Debug("Reject join request from ", c.Name)
		return []byte{0}, etcdErr.NewError(etcdErr.EcodeNoMorePeer, "", server.CommitIndex())
	}

	// Add to shared peer registry.
	ps.registry.Register(c.Name, c.RaftURL, c.EtcdURL)

	// Add peer in raft
	err := server.AddPeer(c.Name, "")

	// Add peer stats
	if c.Name != ps.RaftServer().Name() {
		ps.followersStats.Followers[c.Name] = &raftFollowerStats{}
		ps.followersStats.Followers[c.Name].Latency.Minimum = 1 << 63
	}

	return b, err
}

func (c SyncCommand) Apply(server raft.Server) (interface{}, error) {
	s, _ := server.StateMachine().(store.Store)
	s.DeleteExpiredKeys(c.Time)

	return nil, nil
}

// Remove a server from the cluster
func (c *RemoveCommand) Apply(server raft.Server) (interface{}, error) {
	ps, _ := server.Context().(*PeerServer)

	// Remove node from the shared registry.
	err := ps.registry.Unregister(c.Name)

	// Delete from stats
	delete(ps.followersStats.Followers, c.Name)

	if err != nil {
		log.Debugf("Error while unregistering: %s (%v)", c.Name, err)
		return []byte{0}, err
	}

	// Remove peer in raft
	err = server.RemovePeer(c.Name)
	if err != nil {
		log.Debugf("Unable to remove peer: %s (%v)", c.Name, err)
		return []byte{0}, err
	}

	if c.Name == server.Name() {
		// the removed node is this node

		// if the node is not replaying the previous logs
		// and the node has sent out a join request in this
		// start. It is sure that this node received a new remove
		// command and need to be removed
		if server.CommitIndex() > ps.joinIndex && ps.joinIndex != 0 {
			log.Debugf("server [%s] is removed", server.Name())
			os.Exit(0)
		} else {
			// else ignore remove
			log.Debugf("ignore previous remove command.")
		}
	}

	b := make([]byte, 8)
	binary.PutUvarint(b, server.CommitIndex())

	return b, err
}

func (s *PeerServer) SetRaftServer(raftServer raft.Server) {
	s.snapConf = &snapshotConf{
		checkingInterval: time.Second * 3,
		// this is not accurate, we will update raft to provide an api
		lastIndex:   raftServer.CommitIndex(),
		snapshotThr: uint64(s.Config.SnapshotCount),
	}

	raftServer.AddEventListener(raft.StateChangeEventType, s.raftEventLogger)
	raftServer.AddEventListener(raft.LeaderChangeEventType, s.raftEventLogger)
	raftServer.AddEventListener(raft.TermChangeEventType, s.raftEventLogger)
	raftServer.AddEventListener(raft.AddPeerEventType, s.raftEventLogger)
	raftServer.AddEventListener(raft.RemovePeerEventType, s.raftEventLogger)
	raftServer.AddEventListener(raft.HeartbeatTimeoutEventType, s.raftEventLogger)
	raftServer.AddEventListener(raft.ElectionTimeoutThresholdEventType, s.raftEventLogger)

	raftServer.AddEventListener(raft.HeartbeatEventType, s.recordMetricEvent)

	s.raftServer = raftServer
}