// 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
	}
}

// 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 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.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

}

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

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

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

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

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

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

		rvrsp := &raft.RequestVoteResponse{}
		if _, err = rvrsp.Decode(resp.Body); err != nil && err != io.EOF {
			log.Warn("transporter.vr.decoding.error:", err)
			return nil
		}
		return rvrsp
	}
	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.peerServer.serverStats.SendAppendReq(size)

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

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

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

	if !ok { //this is the first time this follower has been seen
		thisFollowerStats = &raftFollowerStats{}
		thisFollowerStats.Latency.Minimum = 1 << 63
		t.peerServer.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
}

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)
}

// Try all possible ways to find clusters to join
// Include -discovery, -peers and log data in -data-dir
//
// Peer discovery follows this order:
// 1. -discovery
// 2. -peers
// 3. previous peers in -data-dir
func (s *PeerServer) findCluster(discoverURL string, peers []string) {
	// Attempt cluster discovery
	toDiscover := discoverURL != ""
	if toDiscover {
		discoverPeers, discoverErr := s.handleDiscovery(discoverURL)
		// It is registered in discover url
		if discoverErr == nil {
			// start as a leader in a new cluster
			if len(discoverPeers) == 0 {
				log.Debug("This peer is starting a brand new cluster based on discover URL.")
				s.startAsLeader()
			} else {
				s.startAsFollower(discoverPeers)
			}
			return
		}
	}

	hasPeerList := len(peers) > 0
	// if there is log in data dir, append previous peers to peers in config
	// to find cluster
	prevPeers := s.registry.PeerURLs(s.raftServer.Leader(), s.Config.Name)
	for i := 0; i < len(prevPeers); i++ {
		u, err := url.Parse(prevPeers[i])
		if err != nil {
			log.Debug("rejoin cannot parse url: ", err)
		}
		prevPeers[i] = u.Host
	}
	peers = append(peers, prevPeers...)

	// if there is backup peer lists, use it to find cluster
	if len(peers) > 0 {
		ok := s.joinCluster(peers)
		if !ok {
			log.Warn("No living peers are found!")
		} else {
			log.Debugf("%s restart as a follower based on peers[%v]", s.Config.Name)
			return
		}
	}

	if !s.raftServer.IsLogEmpty() {
		log.Debug("Entire cluster is down! %v will restart the cluster.", s.Config.Name)
		return
	}

	if toDiscover {
		log.Fatalf("Discovery failed, no available peers in backup list, and no log data")
	}

	if hasPeerList {
		log.Fatalf("No available peers in backup list, and no log data")
	}

	log.Infof("This peer is starting a brand new cluster now.")
	s.startAsLeader()
}

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

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

	s.raftServer.SetElectionTimeout(s.ElectionTimeout)
	s.raftServer.SetHeartbeatTimeout(s.HeartbeatTimeout)

	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.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.name)
	}

	s.closeChan = make(chan bool)

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

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

	// start to response to raft requests
	return s.startTransport(s.tlsConf.Scheme, s.tlsConf.Server)
}

func GetHandler(w http.ResponseWriter, req *http.Request, s Server) error {
	var err error
	var event *store.Event

	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")
	sorted := (req.FormValue("sorted") == "true")

	if req.FormValue("wait") == "true" { // watch
		// Create a command to watch from a given index (default 0).
		var sinceIndex uint64 = 0

		waitIndex := req.FormValue("waitIndex")
		if waitIndex != "" {
			sinceIndex, err = strconv.ParseUint(string(req.FormValue("waitIndex")), 10, 64)
			if err != nil {
				return etcdErr.NewError(etcdErr.EcodeIndexNaN, "Watch From Index", s.Store().Index())
			}
		}

		// Start the watcher on the store.
		eventChan, err := s.Store().Watch(key, recursive, sinceIndex)
		if err != nil {
			return etcdErr.NewError(500, key, s.Store().Index())
		}

		cn, _ := w.(http.CloseNotifier)
		closeChan := cn.CloseNotify()

		select {
		case <-closeChan:
			return nil
		case event = <-eventChan:
		}

	} else { //get
		// Retrieve the key from the store.
		event, err = s.Store().Get(key, recursive, sorted)
		if err != nil {
			return err
		}
	}

	w.Header().Set("Content-Type", "application/json")
	w.Header().Add("X-Etcd-Index", fmt.Sprint(s.Store().Index()))
	w.Header().Add("X-Raft-Index", fmt.Sprint(s.CommitIndex()))
	w.Header().Add("X-Raft-Term", fmt.Sprint(s.Term()))
	w.WriteHeader(http.StatusOK)
	b, _ := json.Marshal(event)

	w.Write(b)

	return nil
}