// Package server package server provides service interfaces and libraries.
// including:
// tcp/http server library.
// rpc service library with addon functionality.
// service discory and registration Logic.
// statistic lib.
package server

import (
	"context"
	"flag"
	"github.com/opentracing/opentracing-go"
	"net/http"
	"net/rpc"
	"sparrow/pkg/tracing"
	"time"
)

// server is a singleton
var serverInstance *Server = nil

// Server server
type Server struct {
	// required
	name string
	// optional
	rpcServer  *RPCServer  // RPC server
	tcpServer  *TCPServer  // TCP server
	httpServer *HTTPServer // HTTP server
	timerTask  TimerTask   // timer task
	udpServer  *UDPServer
	// functions
	serverManager *ServerManager // service registration&discovery manager
	rpcClient     *RPCClient     // rpc client
	prome         *Prometheus
}

// Init init the server with specific name.
func Init(name string) error {
	if serverInstance == nil {
		// read config
		flag.Parse()
		// read network info
		readNetInterfaces()
		// log
		err := InitLog(name, *confLogLevel)
		if err != nil {
			return err
		}

		// server instance
		serverInstance = &Server{
			name: name,
		}
		// init service manager
		serverInstance.serverManager, err = NewServerManager(name, *confEtcd)
		if err != nil {
			return err
		}

		// create RPC client
		serverInstance.rpcClient, err = NewRPCClient()
		if err != nil {
			return err
		}
		if *confProme != "" {
			p := NewPrometheus(name)
			serverInstance.prome = p
			go func() {
				if err = p.Start(*confProme); err != nil {
					Log.Errorf("prometheus start error:%s", err.Error())
				}
			}()
		}
		Log.Infof("server %s init success.", name)

	}
	return nil
}

// RegisterTCPHandler register TCP handler class
func RegisterTCPHandler(handler TCPHandler) error {
	if serverInstance == nil {
		return errorf(errServerNotInit)
	}
	if serverInstance.tcpServer == nil {
		if *confTCPHost == "" {
			return errorf(errMissingFlag, FlagTCPHost)
		}

		addr, err := fixHostIp(*confTCPHost)
		if err != nil {
			return errorf(errWrongHostAddr, *confTCPHost)
		}

		serverInstance.tcpServer = &TCPServer{
			addr:    addr,
			handler: handler,
			useTls:  *confUseTls,
		}
	}
	return nil
}

// RegisterUDPHandler register UDP handler class
func RegisterUDPHandler(handler UDPHandler) error {
	if serverInstance == nil {
		return errorf(errServerNotInit)
	}
	if serverInstance.udpServer == nil {
		if *confUDPHost == "" {
			return errorf(errMissingFlag, FlagUDPHost)
		}
		addr, err := fixHostIp(*confUDPHost)
		if err != nil {
			return errorf(errWrongHostAddr, *confUDPHost)
		}
		serverInstance.udpServer = &UDPServer{
			addr:    addr,
			handler: handler,
		}
	}
	return nil
}

// RegisterHTTPHandler register HTTP handler class
func RegisterHTTPHandler(handler http.Handler) error {
	if serverInstance == nil {
		return errorf(errServerNotInit)
	}
	if serverInstance.httpServer == nil {
		if *confHTTPHost == "" {
			return errorf(errMissingFlag, FlagHTTPHost)
		}

		addr, err := fixHostIp(*confHTTPHost)
		if err != nil {
			return errorf(errWrongHostAddr, FlagHTTPHost)
		}

		serverInstance.httpServer = &HTTPServer{
			addr:     addr,
			handler:  handler,
			useHttps: *confUseHttps,
		}
	}
	return nil
}

// RegisterRPCHandler register RPC handler class
func RegisterRPCHandler(rcvr interface{}) error {
	if serverInstance == nil {
		return errorf(errServerNotInit)
	}
	if serverInstance.rpcServer == nil {
		if *confRPCHost == "" {
			return errorf(errMissingFlag, FlagRPCHost)
		}

		addr, err := fixHostIp(*confRPCHost)
		if err != nil {
			return errorf(errWrongHostAddr, *confRPCHost)
		}

		err = rpc.Register(rcvr)
		if err != nil {
			return errorf("Cannot Resgister RPC service: %s", err)
		}

		handler := rpcHandler{}

		serverInstance.rpcServer = &RPCServer{
			TCPServer{
				addr:    addr,
				handler: &handler,
				useTls:  false, // rpc service do not use tls because it's in internal network
			},
		}
	}
	return nil
}

// RegisterTimerTask register timer task
func RegisterTimerTask(task TimerTask) error {
	if serverInstance == nil {
		return errorf(errServerNotInit)
	}
	if serverInstance.timerTask == nil {
		serverInstance.timerTask = task
	}
	return nil
}

// RPCCallByName rpc call by name
func RPCCallByName(ctx context.Context, serverName string, serverMethod string, args interface{}, reply interface{}) error {
	if serverInstance == nil {
		return errorf(errServerNotInit)
	}
	return serverInstance.rpcClient.Call(serverName, serverMethod, args, reply)
}

// RPCCallByHost rpc call by host
func RPCCallByHost(host string, serverMethod string, args interface{}, reply interface{}) error {
	if serverInstance == nil {
		return errorf(errServerNotInit)
	}

	return serverInstance.rpcClient.CallHost(host, serverMethod, args, reply)
}

// GetServerHosts get server's hosts by server name and service type
func GetServerHosts(serverName string, hostType string) ([]string, error) {
	if serverInstance == nil {
		return nil, errorf(errServerNotInit)
	}

	return serverInstance.serverManager.GetServerHosts(serverName, hostType)
}

// GetRPCHost get this server's rpc host
func GetRPCHost() string {
	if serverInstance == nil || serverInstance.rpcServer == nil {
		return ""
	}

	return serverInstance.rpcServer.addr.externalIp
}

// GetHTTPHost get this server's http host addr
func GetHTTPHost() string {
	if serverInstance == nil || serverInstance.httpServer == nil {
		return ""
	}
	return serverInstance.httpServer.addr.externalIp
}

// Run start service
func Run() error {
	if serverInstance == nil {
		return errorf(errServerNotInit)
	}

	if serverInstance.tcpServer != nil {
		err := serverInstance.tcpServer.Start()
		if err != nil {
			return err
		}
		Log.Info("starting tcp server ... OK")
	}

	if serverInstance.httpServer != nil {
		err := serverInstance.httpServer.Start()
		if err != nil {
			return err
		}
		Log.Info("starting http server ... OK")
	}

	if serverInstance.udpServer != nil {
		err := serverInstance.udpServer.Start()
		if err != nil {
			return err
		}
		Log.Infof("starting udp server ... OK")
	}

	if serverInstance.rpcServer != nil {
		err := serverInstance.rpcServer.Start()
		if err != nil {
			return err
		}
		Log.Info("starting rpc server ... OK")
	}
	// server manager update
	err := serverInstance.serverManager.RegisterServer()
	if err != nil {
		Log.Warnf("RegisterServer error: %s", err)
	} else {
		Log.Info("RegisterServer Success")
	}
	tracer, closer := tracing.Init(serverInstance.name)
	// opentracing
	defer closer.Close()
	opentracing.InitGlobalTracer(tracer)
	Log.Info("sever launch successfully!")

	// loop to do something
	for {
		err := serverInstance.serverManager.UpdateServerHosts()
		if err != nil {
			Log.Errorf("UpdateServerHosts error: %s", err)
		} else {
			Log.Info("UpdateServerHosts Success")
		}

		//timer task
		if serverInstance.timerTask != nil {
			serverInstance.timerTask.DoTask()
		}

		time.Sleep(60 * time.Second)
	}
}

func addCallCount() {
	if serverInstance.prome != nil {
		serverInstance.prome.CallCnt.WithLabelValues(serverInstance.name).Inc()
	}
}

func RegisterMetric(metrics ...*Metric) {
	serverInstance.prome.RegisterMetrics("", metrics...)
}