// Response to append entries request
func (ps *PeerServer) AppendEntriesHttpHandler(w http.ResponseWriter, req *http.Request) {
	start := time.Now()
	aereq := &raft.AppendEntriesRequest{}

	if _, err := aereq.Decode(req.Body); err != nil {
		http.Error(w, "", http.StatusBadRequest)
		log.Warnf("[recv] BADREQUEST %s/log/append [%v]", ps.Config.URL, err)
		return
	}

	log.Debugf("[recv] POST %s/log/append [%d]", ps.Config.URL, len(aereq.Entries))

	ps.serverStats.RecvAppendReq(aereq.LeaderName, int(req.ContentLength))

	resp := ps.raftServer.AppendEntries(aereq)

	if resp == nil {
		log.Warn("[ae] Error: nil response")
		http.Error(w, "", http.StatusInternalServerError)
		return
	}

	if !resp.Success() {
		log.Debugf("[Append Entry] Step back")
	}

	if _, err := resp.Encode(w); err != nil {
		log.Warn("[ae] Error: %v", err)
		http.Error(w, "", http.StatusInternalServerError)
		return
	}

	(*ps.metrics).Timer("timer.appendentries.handle").UpdateSince(start)
}

// 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.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

}

// Sends AppendEntries RPCs to a peer when the server is the leader.
func (t *transporter) SendAppendEntriesRequest(server raft.Server, peer *raft.Peer, req *raft.AppendEntriesRequest) *raft.AppendEntriesResponse {
	var b bytes.Buffer

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

	size := b.Len()

	t.serverStats.SendAppendReq(size)

	u, _ := t.registry.PeerURL(peer.Name)

	log.Debugf("Send LogEntries to %s ", u)

	thisFollowerStats, ok := t.followersStats.Followers[peer.Name]

	if !ok { //this is the first time this follower has been seen
		thisFollowerStats = &raftFollowerStats{}
		thisFollowerStats.Latency.Minimum = 1 << 63
		t.followersStats.Followers[peer.Name] = thisFollowerStats
	}

	start := time.Now()

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

	end := time.Now()

	if err != nil {
		log.Debugf("Cannot send AppendEntriesRequest to %s: %s", u, err)
		if ok {
			thisFollowerStats.Fail()
		}
		return nil
	} else {
		if ok {
			thisFollowerStats.Succ(end.Sub(start))
		}
	}

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

		t.CancelWhenTimeout(httpRequest)

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

	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.Config.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.Config.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")
			}
		}

	}
}

// Start the raft server
func (s *PeerServer) Start(snapshot bool, cluster []string) error {
	// LoadSnapshot
	if snapshot {
		err := s.raftServer.LoadSnapshot()

		if err == nil {
			log.Debugf("%s finished load snapshot", s.Config.Name)
		} else {
			log.Debug(err)
		}
	}

	s.raftServer.Start()

	if s.raftServer.IsLogEmpty() {
		// start as a leader in a new cluster
		if len(cluster) == 0 {
			s.startAsLeader()
		} else {
			s.startAsFollower(cluster)
		}

	} else {
		// Rejoin the previous cluster
		cluster = s.registry.PeerURLs(s.raftServer.Leader(), s.Config.Name)
		for i := 0; i < len(cluster); i++ {
			u, err := url.Parse(cluster[i])
			if err != nil {
				log.Debug("rejoin cannot parse url: ", err)
			}
			cluster[i] = u.Host
		}
		ok := s.joinCluster(cluster)
		if !ok {
			log.Warn("the entire cluster is down! this peer will restart the cluster.")
		}

		log.Debugf("%s restart as a follower", s.Config.Name)
	}

	s.closeChan = make(chan bool)

	go s.monitorSync()
	go s.monitorTimeoutThreshold(s.closeChan)

	// open the snapshot
	if snapshot {
		go s.monitorSnapshot()
	}

	return nil
}

// Response to vote request
func (ps *PeerServer) VoteHttpHandler(w http.ResponseWriter, req *http.Request) {
	rvreq := &raft.RequestVoteRequest{}

	if _, err := rvreq.Decode(req.Body); err != nil {
		http.Error(w, "", http.StatusBadRequest)
		log.Warnf("[recv] BADREQUEST %s/vote [%v]", ps.Config.URL, err)
		return
	}

	log.Debugf("[recv] POST %s/vote [%s]", ps.Config.URL, rvreq.CandidateName)

	resp := ps.raftServer.RequestVote(rvreq)

	if resp == nil {
		log.Warn("[vote] Error: nil response")
		http.Error(w, "", http.StatusInternalServerError)
		return
	}

	if _, err := resp.Encode(w); err != nil {
		log.Warn("[vote] Error: %v", err)
		http.Error(w, "", http.StatusInternalServerError)
		return
	}
}

// Response to recover from snapshot request
func (ps *PeerServer) SnapshotHttpHandler(w http.ResponseWriter, req *http.Request) {
	ssreq := &raft.SnapshotRequest{}

	if _, err := ssreq.Decode(req.Body); err != nil {
		http.Error(w, "", http.StatusBadRequest)
		log.Warnf("[recv] BADREQUEST %s/snapshot [%v]", ps.Config.URL, err)
		return
	}

	log.Debugf("[recv] POST %s/snapshot", ps.Config.URL)

	resp := ps.raftServer.RequestSnapshot(ssreq)

	if resp == nil {
		log.Warn("[ss] Error: nil response")
		http.Error(w, "", http.StatusInternalServerError)
		return
	}

	if _, err := resp.Encode(w); err != nil {
		log.Warn("[ss] Error: %v", err)
		http.Error(w, "", http.StatusInternalServerError)
		return
	}
}

func GetHandler(w http.ResponseWriter, req *http.Request, s Server) error {
	vars := mux.Vars(req)
	key := "/" + vars["key"]

	// Help client to redirect the request to the current leader
	if req.FormValue("consistent") == "true" && s.State() != raft.Leader {
		leader := s.Leader()
		hostname, _ := s.ClientURL(leader)

		url, err := url.Parse(hostname)
		if err != nil {
			log.Warn("Redirect cannot parse hostName ", hostname)
			return err
		}
		url.RawQuery = req.URL.RawQuery
		url.Path = req.URL.Path

		log.Debugf("Redirect consistent get to %s", url.String())
		http.Redirect(w, req, url.String(), http.StatusTemporaryRedirect)
		return nil
	}

	recursive := (req.FormValue("recursive") == "true")
	sort := (req.FormValue("sorted") == "true")
	waitIndex := req.FormValue("waitIndex")
	stream := (req.FormValue("stream") == "true")

	if req.FormValue("wait") == "true" {
		return handleWatch(key, recursive, stream, waitIndex, w, s)
	}

	return handleGet(key, recursive, sort, w, s)
}

// Checks whether a given version is supported.
func (ps *PeerServer) VersionCheckHttpHandler(w http.ResponseWriter, req *http.Request) {
	log.Debugf("[recv] Get %s%s ", ps.Config.URL, req.URL.Path)
	vars := mux.Vars(req)
	version, _ := strconv.Atoi(vars["version"])
	if version >= store.MinVersion() && version <= store.MaxVersion() {
		w.WriteHeader(http.StatusOK)
	} else {
		w.WriteHeader(http.StatusForbidden)
	}
}

func (s *PeerServer) startAsLeader() {
	// leader need to join self as a peer
	for {
		_, err := s.raftServer.Do(NewJoinCommand(store.MinVersion(), store.MaxVersion(), s.raftServer.Name(), s.Config.URL, s.server.URL()))
		if err == nil {
			break
		}
	}
	log.Debugf("%s start as a leader", s.Config.Name)
}

// Remove a server from the cluster
func (c *RemoveCommand) Apply(context raft.Context) (interface{}, error) {
	ps, _ := context.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 = context.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 == context.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 context.CommitIndex() > ps.joinIndex && ps.joinIndex != 0 {
			log.Debugf("server [%s] is removed", context.Server().Name())
			os.Exit(0)
		} else {
			// else ignore remove
			log.Debugf("ignore previous remove command.")
		}
	}

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

	return b, err
}

// DashboardHttpHandler either uses the compiled in virtual filesystem for the
// dashboard assets or if ETCD_DASHBOARD_DIR is set uses that as the source of
// assets.
func HttpHandler() (handler http.Handler) {
	handler = http.HandlerFunc(memoryFileServer)

	// Serve the dashboard from a filesystem if the magic env variable is enabled
	dashDir := os.Getenv("ETCD_DASHBOARD_DIR")
	if len(dashDir) != 0 {
		log.Debugf("Using dashboard directory %s", dashDir)
		handler = http.FileServer(http.Dir(dashDir))
	}

	return handler
}

// Removes a node from the registry.
func (r *Registry) Unregister(name string) error {
	r.Lock()
	defer r.Unlock()

	// Remove from cache.
	// delete(r.nodes, name)

	// Remove the key from the store.
	_, err := r.store.Delete(path.Join(RegistryKey, name), false, false)
	log.Debugf("Unregister: %s", name)
	return err
}

// Adds a node to the registry.
func (r *Registry) Register(name string, peerURL string, machURL string) error {
	r.Lock()
	defer r.Unlock()

	// Write data to store.
	key := path.Join(RegistryKey, name)
	v := url.Values{}
	v.Set("raft", peerURL)
	v.Set("etcd", machURL)
	_, err := r.store.Create(key, false, v.Encode(), false, store.Permanent)
	log.Debugf("Register: %s", name)
	return err
}

// Response to remove request
func (ps *PeerServer) RemoveHttpHandler(w http.ResponseWriter, req *http.Request) {
	if req.Method != "DELETE" {
		w.WriteHeader(http.StatusMethodNotAllowed)
		return
	}

	vars := mux.Vars(req)
	command := &RemoveCommand{
		Name: vars["name"],
	}

	log.Debugf("[recv] Remove Request [%s]", command.Name)

	ps.server.Dispatch(command, w, req)
}

// Upgrades the current store version to the next version.
func (ps *PeerServer) UpgradeHttpHandler(w http.ResponseWriter, req *http.Request) {
	log.Debugf("[recv] Get %s/version", ps.Config.URL)

	// Check if upgrade is possible for all nodes.
	if err := ps.Upgradable(); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	// Create an upgrade command from the current version.
	c := ps.store.CommandFactory().CreateUpgradeCommand()
	if err := ps.server.Dispatch(c, w, req); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	w.WriteHeader(http.StatusOK)
}

// Adds a server handler to the router.
func (s *Server) handleFunc(r *mux.Router, path string, f func(http.ResponseWriter, *http.Request) error) *mux.Route {

	// Wrap the standard HandleFunc interface to pass in the server reference.
	return r.HandleFunc(path, func(w http.ResponseWriter, req *http.Request) {
		// Log request.
		log.Debugf("[recv] %s %s %s [%s]", req.Method, s.URL(), req.URL.Path, req.RemoteAddr)

		// Execute handler function and return error if necessary.
		if err := f(w, req); err != nil {
			if etcdErr, ok := err.(*etcdErr.Error); ok {
				log.Debug("Return error: ", (*etcdErr).Error())
				w.Header().Set("Content-Type", "application/json")
				etcdErr.Write(w)
			} else {
				http.Error(w, err.Error(), http.StatusInternalServerError)
			}
		}
	})
}

func (s *PeerServer) joinCluster(cluster []string) bool {
	for _, peer := range cluster {
		if len(peer) == 0 {
			continue
		}

		err := s.joinByPeer(s.raftServer, peer, s.Config.Scheme)
		if err == nil {
			log.Debugf("%s joined the cluster via peer %s", s.Config.Name, peer)
			return true

		}

		if _, ok := err.(etcdErr.Error); ok {
			log.Fatal(err)
		}

		log.Warnf("Attempt to join via %s failed: %s", peer, err)
	}

	return false
}

// Response to the join request
func (ps *PeerServer) JoinHttpHandler(w http.ResponseWriter, req *http.Request) {
	command := &JoinCommand{}

	err := uhttp.DecodeJsonRequest(req, command)
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		return
	}

	log.Debugf("Receive Join Request from %s", command.Name)
	err = ps.server.Dispatch(command, w, req)

	// Return status.
	if err != nil {
		if etcdErr, ok := err.(*etcdErr.Error); ok {
			log.Debug("Return error: ", (*etcdErr).Error())
			etcdErr.Write(w)
		} else {
			http.Error(w, err.Error(), http.StatusInternalServerError)
		}
	}
}

func memoryFileServer(w http.ResponseWriter, req *http.Request) {
	log.Debugf("[recv] %s %s [%s]", req.Method, req.URL.Path, req.RemoteAddr)
	upath := req.URL.Path
	if len(upath) == 0 {
		upath = "index.html"
	}

	// TODO: use the new mux to do this work
	dir, file := path.Split(upath)
	if file == "browser" || file == "stats" {
		file = file + ".html"
	}
	upath = path.Join(dir, file)
	b, err := resources.Asset(upath)

	if err != nil {
		http.Error(w, upath+": File not found", http.StatusNotFound)
		return
	}

	http.ServeContent(w, req, upath, time.Time{}, bytes.NewReader(b))
	return
}