// NewClientHandler generates a muxed http.Handler with the given parameters to serve etcd client requests.
func NewClientHandler(server *etcdserver.EtcdServer, timeout time.Duration) http.Handler {
	go capabilityLoop(server)

	sec := auth.NewStore(server, timeout)

	kh := &keysHandler{
		sec:     sec,
		server:  server,
		cluster: server.Cluster(),
		timer:   server,
		timeout: timeout,
	}

	sh := &statsHandler{
		stats: server,
	}

	mh := &membersHandler{
		sec:     sec,
		server:  server,
		cluster: server.Cluster(),
		timeout: timeout,
		clock:   clockwork.NewRealClock(),
	}

	dmh := &deprecatedMachinesHandler{
		cluster: server.Cluster(),
	}

	sech := &authHandler{
		sec:     sec,
		cluster: server.Cluster(),
	}

	mux := http.NewServeMux()
	mux.HandleFunc("/", http.NotFound)
	mux.Handle(healthPath, healthHandler(server))
	mux.HandleFunc(versionPath, versionHandler(server.Cluster(), serveVersion))
	mux.Handle(keysPrefix, kh)
	mux.Handle(keysPrefix+"/", kh)
	mux.HandleFunc(statsPrefix+"/store", sh.serveStore)
	mux.HandleFunc(statsPrefix+"/self", sh.serveSelf)
	mux.HandleFunc(statsPrefix+"/leader", sh.serveLeader)
	mux.HandleFunc(varsPath, serveVars)
	mux.HandleFunc(configPath+"/local/log", logHandleFunc)
	mux.Handle(metricsPath, prometheus.Handler())
	mux.Handle(membersPrefix, mh)
	mux.Handle(membersPrefix+"/", mh)
	mux.Handle(deprecatedMachinesPrefix, dmh)
	handleAuth(mux, sech)

	return requestLogger(mux)
}

// TODO: change etcdserver to raft interface when we have it.
//       add test for healthHeadler when we have the interface ready.
func healthHandler(server *etcdserver.EtcdServer) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if !allowMethod(w, r.Method, "GET") {
			return
		}

		if uint64(server.Leader()) == raft.None {
			http.Error(w, `{"health": "false"}`, http.StatusServiceUnavailable)
			return
		}

		// wait for raft's progress
		index := server.Index()
		for i := 0; i < 3; i++ {
			time.Sleep(250 * time.Millisecond)
			if server.Index() > index {
				w.WriteHeader(http.StatusOK)
				w.Write([]byte(`{"health": "true"}`))
				return
			}
		}

		http.Error(w, `{"health": "false"}`, http.StatusServiceUnavailable)
		return
	}
}

// capabilityLoop checks the cluster version every 500ms and updates
// the enabledCapability when the cluster version increased.
// capabilityLoop MUST be ran in a goroutine before checking capability
// or using capabilityHandler.
func capabilityLoop(s *etcdserver.EtcdServer) {
	stopped := s.StopNotify()

	var pv *semver.Version
	for {
		if v := s.ClusterVersion(); v != pv {
			if pv == nil {
				pv = v
			} else if v != nil && pv.LessThan(*v) {
				pv = v
			}
			enableMapMu.Lock()
			enabledMap = capabilityMaps[pv.String()]
			enableMapMu.Unlock()
		}

		select {
		case <-stopped:
			return
		case <-time.After(500 * time.Millisecond):
		}
	}
}