package server

import (
	"context"
	"fmt"
	"io"
	"net"
	"runtime/debug"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/micro/go-micro/broker"
	"github.com/micro/go-micro/codec"
	"github.com/micro/go-micro/metadata"
	"github.com/micro/go-micro/registry"
	"github.com/micro/go-micro/transport"
	"github.com/micro/go-micro/util/addr"
	log "github.com/micro/go-micro/util/log"
	mnet "github.com/micro/go-micro/util/net"
	"github.com/micro/go-micro/util/socket"
)

type rpcServer struct {
	router *router
	exit   chan chan error

	sync.RWMutex
	opts        Options
	handlers    map[string]Handler
	subscribers map[*subscriber][]broker.Subscriber
	// marks the serve as started
	started bool
	// used for first registration
	registered bool
	// graceful exit
	wg *sync.WaitGroup
}

func newRpcServer(opts ...Option) Server {
	options := newOptions(opts...)
	router := newRpcRouter()
	router.hdlrWrappers = options.HdlrWrappers

	return &rpcServer{
		opts:        options,
		router:      router,
		handlers:    make(map[string]Handler),
		subscribers: make(map[*subscriber][]broker.Subscriber),
		exit:        make(chan chan error),
		wg:          wait(options.Context),
	}
}

type rpcRouter struct {
	h func(context.Context, Request, interface{}) error
}

func (r rpcRouter) ServeRequest(ctx context.Context, req Request, rsp Response) error {
	return r.h(ctx, req, rsp)
}

// ServeConn serves a single connection
func (s *rpcServer) ServeConn(sock transport.Socket) {
	var wg sync.WaitGroup
	var mtx sync.RWMutex
	// streams are multiplexed on Micro-Stream or Micro-Id header
	sockets := make(map[string]*socket.Socket)

	defer func() {
		// wait till done
		wg.Wait()

		// close underlying socket
		sock.Close()

		// close the sockets
		mtx.Lock()
		for id, psock := range sockets {
			psock.Close()
			delete(sockets, id)
		}
		mtx.Unlock()

		// recover any panics
		if r := recover(); r != nil {
			log.Log("panic recovered: ", r)
			log.Log(string(debug.Stack()))
		}
	}()

	for {
		var msg transport.Message
		if err := sock.Recv(&msg); err != nil {
			return
		}

		// use Micro-Stream as the stream identifier
		// in the event its blank we'll always process
		// on the same socket
		id := msg.Header["Micro-Stream"]

		// if there's no stream id then its a standard request
		// use the Micro-Id
		if len(id) == 0 {
			id = msg.Header["Micro-Id"]
		}

		// we're starting processing
		wg.Add(1)

		// add to wait group if "wait" is opt-in
		s.Lock()
		swg := s.wg
		s.Unlock()

		if swg != nil {
			swg.Add(1)
		}

		// check we have an existing socket
		mtx.RLock()
		psock, ok := sockets[id]
		mtx.RUnlock()

		// got the socket
		if ok {
			// accept the message
			if err := psock.Accept(&msg); err != nil {
				// delete the socket
				mtx.Lock()
				delete(sockets, id)
				mtx.Unlock()
			}

			// done(1)
			if swg != nil {
				swg.Done()
			}

			wg.Done()

			// continue to the next message
			continue
		}

		// no socket was found
		psock = socket.New()
		psock.SetLocal(sock.Local())
		psock.SetRemote(sock.Remote())

		// load the socket
		psock.Accept(&msg)

		// save a new socket
		mtx.Lock()
		sockets[id] = psock
		mtx.Unlock()

		// now walk the usual path

		// we use this Timeout header to set a server deadline
		to := msg.Header["Timeout"]
		// we use this Content-Type header to identify the codec needed
		ct := msg.Header["Content-Type"]

		// copy the message headers
		hdr := make(map[string]string)
		for k, v := range msg.Header {
			hdr[k] = v
		}

		// set local/remote ips
		hdr["Local"] = sock.Local()
		hdr["Remote"] = sock.Remote()

		// create new context with the metadata
		ctx := metadata.NewContext(context.Background(), hdr)

		// set the timeout from the header if we have it
		if len(to) > 0 {
			if n, err := strconv.ParseUint(to, 10, 64); err == nil {
				ctx, _ = context.WithTimeout(ctx, time.Duration(n))
			}
		}

		// if there's no content type default it
		if len(ct) == 0 {
			msg.Header["Content-Type"] = DefaultContentType
			ct = DefaultContentType
		}

		// setup old protocol
		cf := setupProtocol(&msg)

		// no old codec
		if cf == nil {
			// TODO: needs better error handling
			var err error
			if cf, err = s.newCodec(ct); err != nil {
				sock.Send(&transport.Message{
					Header: map[string]string{
						"Content-Type": "text/plain",
					},
					Body: []byte(err.Error()),
				})

				if swg != nil {
					swg.Done()
				}

				wg.Done()

				return
			}
		}

		rcodec := newRpcCodec(&msg, psock, cf)
		protocol := rcodec.String()

		// check stream id
		var stream bool

		if v := getHeader("Micro-Stream", msg.Header); len(v) > 0 {
			stream = true
		}

		// internal request
		request := &rpcRequest{
			service:     getHeader("Micro-Service", msg.Header),
			method:      getHeader("Micro-Method", msg.Header),
			endpoint:    getHeader("Micro-Endpoint", msg.Header),
			contentType: ct,
			codec:       rcodec,
			header:      msg.Header,
			body:        msg.Body,
			socket:      psock,
			stream:      stream,
		}

		// internal response
		response := &rpcResponse{
			header: make(map[string]string),
			socket: psock,
			codec:  rcodec,
		}

		// set router
		r := Router(s.router)

		// if not nil use the router specified
		if s.opts.Router != nil {
			// create a wrapped function
			handler := func(ctx context.Context, req Request, rsp interface{}) error {
				return s.opts.Router.ServeRequest(ctx, req, rsp.(Response))
			}

			// execute the wrapper for it
			for i := len(s.opts.HdlrWrappers); i > 0; i-- {
				handler = s.opts.HdlrWrappers[i-1](handler)
			}

			// set the router
			r = rpcRouter{handler}
		}

		// wait for processing to exit
		wg.Add(1)

		// process the outbound messages from the socket
		go func(id string, psock *socket.Socket) {
			defer func() {
				// TODO: don't hack this but if its grpc just break out of the stream
				// We do this because the underlying connection is h2 and its a stream
				switch protocol {
				case "grpc":
					sock.Close()
				}

				wg.Done()
			}()

			for {
				// get the message from our internal handler/stream
				m := new(transport.Message)
				if err := psock.Process(m); err != nil {
					// delete the socket
					mtx.Lock()
					delete(sockets, id)
					mtx.Unlock()
					return
				}

				// send the message back over the socket
				if err := sock.Send(m); err != nil {
					return
				}
			}
		}(id, psock)

		// serve the request in a go routine as this may be a stream
		go func(id string, psock *socket.Socket) {
			defer psock.Close()

			// serve the actual request using the request router
			if serveRequestError := r.ServeRequest(ctx, request, response); serveRequestError != nil {
				// write an error response
				writeError := rcodec.Write(&codec.Message{
					Header: msg.Header,
					Error:  serveRequestError.Error(),
					Type:   codec.Error,
				}, nil)

				// if the server request is an EOS error we let the socket know
				// sometimes the socket is already closed on the other side, so we can ignore that error
				alreadyClosed := serveRequestError == lastStreamResponseError && writeError == io.EOF

				// could not write error response
				if writeError != nil && !alreadyClosed {
					log.Logf("rpc: unable to write error response: %v", writeError)
				}
			}

			mtx.Lock()
			delete(sockets, id)
			mtx.Unlock()

			// signal we're done
			if swg != nil {
				swg.Done()
			}

			// done with this socket
			wg.Done()
		}(id, psock)
	}
}

func (s *rpcServer) newCodec(contentType string) (codec.NewCodec, error) {
	if cf, ok := s.opts.Codecs[contentType]; ok {
		return cf, nil
	}
	if cf, ok := DefaultCodecs[contentType]; ok {
		return cf, nil
	}
	return nil, fmt.Errorf("Unsupported Content-Type: %s", contentType)
}

func (s *rpcServer) Options() Options {
	s.RLock()
	opts := s.opts
	s.RUnlock()
	return opts
}

func (s *rpcServer) Init(opts ...Option) error {
	s.Lock()
	for _, opt := range opts {
		opt(&s.opts)
	}

	// update router if its the default
	if s.opts.Router == nil {
		r := newRpcRouter()
		r.hdlrWrappers = s.opts.HdlrWrappers
		r.serviceMap = s.router.serviceMap
		s.router = r
	}

	s.Unlock()
	return nil
}

func (s *rpcServer) NewHandler(h interface{}, opts ...HandlerOption) Handler {
	return s.router.NewHandler(h, opts...)
}

func (s *rpcServer) Handle(h Handler) error {
	s.Lock()
	defer s.Unlock()

	if err := s.router.Handle(h); err != nil {
		return err
	}

	s.handlers[h.Name()] = h

	return nil
}

func (s *rpcServer) NewSubscriber(topic string, sb interface{}, opts ...SubscriberOption) Subscriber {
	return newSubscriber(topic, sb, opts...)
}

func (s *rpcServer) Subscribe(sb Subscriber) error {
	sub, ok := sb.(*subscriber)
	if !ok {
		return fmt.Errorf("invalid subscriber: expected *subscriber")
	}
	if len(sub.handlers) == 0 {
		return fmt.Errorf("invalid subscriber: no handler functions")
	}

	if err := validateSubscriber(sb); err != nil {
		return err
	}

	s.Lock()
	defer s.Unlock()
	_, ok = s.subscribers[sub]
	if ok {
		return fmt.Errorf("subscriber %v already exists", s)
	}
	s.subscribers[sub] = nil
	return nil
}

func (s *rpcServer) Register() error {
	var err error
	var advt, host, port string

	// parse address for host, port
	config := s.Options()

	// check the advertise address first
	// if it exists then use it, otherwise
	// use the address
	if len(config.Advertise) > 0 {
		advt = config.Advertise
	} else {
		advt = config.Address
	}

	if cnt := strings.Count(advt, ":"); cnt >= 1 {
		// ipv6 address in format [host]:port or ipv4 host:port
		host, port, err = net.SplitHostPort(advt)
		if err != nil {
			return err
		}
	} else {
		host = advt
	}

	addr, err := addr.Extract(host)
	if err != nil {
		return err
	}

	// make copy of metadata
	md := make(metadata.Metadata)
	for k, v := range config.Metadata {
		md[k] = v
	}

	// mq-rpc(eg. nats) doesn't need the port. its addr is queue name.
	if port != "" {
		addr = mnet.HostPort(addr, port)
	}

	// register service
	node := &registry.Node{
		Id:       config.Name + "-" + config.Id,
		Address:  addr,
		Metadata: md,
	}

	node.Metadata["transport"] = config.Transport.String()
	node.Metadata["broker"] = config.Broker.String()
	node.Metadata["server"] = s.String()
	node.Metadata["registry"] = config.Registry.String()
	node.Metadata["protocol"] = "mucp"

	s.RLock()
	// Maps are ordered randomly, sort the keys for consistency
	var handlerList []string
	for n, e := range s.handlers {
		// Only advertise non internal handlers
		if !e.Options().Internal {
			handlerList = append(handlerList, n)
		}
	}
	sort.Strings(handlerList)

	var subscriberList []*subscriber
	for e := range s.subscribers {
		// Only advertise non internal subscribers
		if !e.Options().Internal {
			subscriberList = append(subscriberList, e)
		}
	}
	sort.Slice(subscriberList, func(i, j int) bool {
		return subscriberList[i].topic > subscriberList[j].topic
	})

	endpoints := make([]*registry.Endpoint, 0, len(handlerList)+len(subscriberList))
	for _, n := range handlerList {
		endpoints = append(endpoints, s.handlers[n].Endpoints()...)
	}
	for _, e := range subscriberList {
		endpoints = append(endpoints, e.Endpoints()...)
	}
	s.RUnlock()

	service := &registry.Service{
		Name:      config.Name,
		Version:   config.Version,
		Nodes:     []*registry.Node{node},
		Endpoints: endpoints,
	}

	s.Lock()
	registered := s.registered
	s.Unlock()

	if !registered {
		log.Logf("Registry [%s] Registering node: %s", config.Registry.String(), node.Id)
	}

	// create registry options
	rOpts := []registry.RegisterOption{registry.RegisterTTL(config.RegisterTTL)}

	if err := config.Registry.Register(service, rOpts...); err != nil {
		return err
	}

	// already registered? don't need to register subscribers
	if registered {
		return nil
	}

	s.Lock()
	defer s.Unlock()

	s.registered = true

	for sb := range s.subscribers {
		handler := s.createSubHandler(sb, s.opts)
		var opts []broker.SubscribeOption
		if queue := sb.Options().Queue; len(queue) > 0 {
			opts = append(opts, broker.Queue(queue))
		}

		if cx := sb.Options().Context; cx != nil {
			opts = append(opts, broker.SubscribeContext(cx))
		}

		if !sb.Options().AutoAck {
			opts = append(opts, broker.DisableAutoAck())
		}

		sub, err := config.Broker.Subscribe(sb.Topic(), handler, opts...)
		if err != nil {
			return err
		}
		log.Logf("Subscribing %s to topic: %s", node.Id, sub.Topic())
		s.subscribers[sb] = []broker.Subscriber{sub}
	}

	return nil
}

func (s *rpcServer) Deregister() error {
	var err error
	var advt, host, port string

	config := s.Options()

	// check the advertise address first
	// if it exists then use it, otherwise
	// use the address
	if len(config.Advertise) > 0 {
		advt = config.Advertise
	} else {
		advt = config.Address
	}

	if cnt := strings.Count(advt, ":"); cnt >= 1 {
		// ipv6 address in format [host]:port or ipv4 host:port
		host, port, err = net.SplitHostPort(advt)
		if err != nil {
			return err
		}
	} else {
		host = advt
	}

	addr, err := addr.Extract(host)
	if err != nil {
		return err
	}

	// mq-rpc(eg. nats) doesn't need the port. its addr is queue name.
	if port != "" {
		addr = mnet.HostPort(addr, port)
	}

	node := &registry.Node{
		Id:      config.Name + "-" + config.Id,
		Address: addr,
	}

	service := &registry.Service{
		Name:    config.Name,
		Version: config.Version,
		Nodes:   []*registry.Node{node},
	}

	log.Logf("Registry [%s] Deregistering node: %s", config.Registry.String(), node.Id)
	if err := config.Registry.Deregister(service); err != nil {
		return err
	}

	s.Lock()

	if !s.registered {
		s.Unlock()
		return nil
	}

	s.registered = false

	for sb, subs := range s.subscribers {
		for _, sub := range subs {
			log.Logf("Unsubscribing %s from topic: %s", node.Id, sub.Topic())
			sub.Unsubscribe()
		}
		s.subscribers[sb] = nil
	}

	s.Unlock()
	return nil
}

func (s *rpcServer) Start() error {
	s.RLock()
	if s.started {
		s.RUnlock()
		return nil
	}
	s.RUnlock()

	config := s.Options()

	// start listening on the transport
	ts, err := config.Transport.Listen(config.Address)
	if err != nil {
		return err
	}

	log.Logf("Transport [%s] Listening on %s", config.Transport.String(), ts.Addr())

	// swap address
	s.Lock()
	addr := s.opts.Address
	s.opts.Address = ts.Addr()
	s.Unlock()

	// connect to the broker
	if err := config.Broker.Connect(); err != nil {
		return err
	}

	bname := config.Broker.String()

	log.Logf("Broker [%s] Connected to %s", bname, config.Broker.Address())

	// use RegisterCheck func before register
	if err = s.opts.RegisterCheck(s.opts.Context); err != nil {
		log.Logf("Server %s-%s register check error: %s", config.Name, config.Id, err)
	} else {
		// announce self to the world
		if err = s.Register(); err != nil {
			log.Logf("Server %s-%s register error: %s", config.Name, config.Id, err)
		}
	}

	exit := make(chan bool)

	go func() {
		for {
			// listen for connections
			err := ts.Accept(s.ServeConn)

			// TODO: listen for messages
			// msg := broker.Exchange(service).Consume()

			select {
			// check if we're supposed to exit
			case <-exit:
				return
			// check the error and backoff
			default:
				if err != nil {
					log.Logf("Accept error: %v", err)
					time.Sleep(time.Second)
					continue
				}
			}

			// no error just exit
			return
		}
	}()

	go func() {
		t := new(time.Ticker)

		// only process if it exists
		if s.opts.RegisterInterval > time.Duration(0) {
			// new ticker
			t = time.NewTicker(s.opts.RegisterInterval)
		}

		// return error chan
		var ch chan error

	Loop:
		for {
			select {
			// register self on interval
			case <-t.C:
				s.RLock()
				registered := s.registered
				s.RUnlock()
				if err = s.opts.RegisterCheck(s.opts.Context); err != nil && registered {
					log.Logf("Server %s-%s register check error: %s, deregister it", config.Name, config.Id, err)
					// deregister self in case of error
					if err := s.Deregister(); err != nil {
						log.Logf("Server %s-%s deregister error: %s", config.Name, config.Id, err)
					}
				} else {
					if err := s.Register(); err != nil {
						log.Logf("Server %s-%s register error: %s", config.Name, config.Id, err)
					}
				}
			// wait for exit
			case ch = <-s.exit:
				t.Stop()
				close(exit)
				break Loop
			}
		}

		// deregister self
		if err := s.Deregister(); err != nil {
			log.Logf("Server %s-%s deregister error: %s", config.Name, config.Id, err)
		}

		s.Lock()
		swg := s.wg
		s.Unlock()

		// wait for requests to finish
		if swg != nil {
			swg.Wait()
		}

		// close transport listener
		ch <- ts.Close()

		// disconnect the broker
		config.Broker.Disconnect()

		// swap back address
		s.Lock()
		s.opts.Address = addr
		s.Unlock()
	}()

	// mark the server as started
	s.Lock()
	s.started = true
	s.Unlock()

	return nil
}

func (s *rpcServer) Stop() error {
	s.RLock()
	if !s.started {
		s.RUnlock()
		return nil
	}
	s.RUnlock()

	ch := make(chan error)
	s.exit <- ch

	var err error
	select {
	case err = <-ch:
		s.Lock()
		s.started = false
		s.Unlock()
	}

	return err
}

func (s *rpcServer) String() string {
	return "mucp"
}