package kucoin

import (
	"context"
	"encoding/json"
	"net"
	"sync"
	"time"

	"github.com/c9s/bbgo/pkg/exchange/kucoin/kucoinapi"
	"github.com/c9s/bbgo/pkg/types"
	"github.com/gorilla/websocket"
	"github.com/pkg/errors"
)

const readTimeout = 20 * time.Second

type WebsocketOp struct {
	Op   string      `json:"op"`
	Args interface{} `json:"args"`
}

type WebsocketLogin struct {
	Key        string `json:"apiKey"`
	Passphrase string `json:"passphrase"`
	Timestamp  string `json:"timestamp"`
	Sign       string `json:"sign"`
}

//go:generate callbackgen -type Stream -interface
type Stream struct {
	types.StandardStream

	client     *kucoinapi.RestClient
	conn       *websocket.Conn
	connLock   sync.Mutex
	connCtx    context.Context
	connCancel context.CancelFunc

	bullet     *kucoinapi.Bullet
	publicOnly bool
}

func NewStream(client *kucoinapi.RestClient) *Stream {
	stream := &Stream{
		client: client,
		StandardStream: types.StandardStream{
			ReconnectC: make(chan struct{}, 1),
		},
	}

	stream.OnConnect(stream.handleConnect)
	return stream
}

func (s *Stream) sendSubscriptions() error {
	cmds, err := convertSubscriptions(s.Subscriptions)
	if err != nil {
		return errors.Wrapf(err, "subscription convert error, subscriptions: %+v", s.Subscriptions)
	}

	for _, cmd := range cmds {
		if err := s.conn.WriteJSON(cmd); err != nil {
			return errors.Wrapf(err, "subscribe write error, cmd: %+v", cmd)
		}
	}

	return nil
}

func (s *Stream) handleConnect() {
	if s.publicOnly {
		if err := s.sendSubscriptions(); err != nil {
			log.WithError(err).Errorf("subscription error")
			return
		}
	} else {
		id := time.Now().UnixMilli()
		cmds := []kucoinapi.WebSocketCommand{
			{
				Id:             id,
				Type:           kucoinapi.WebSocketMessageTypeSubscribe,
				Topic:          "/spotMarket/tradeOrders",
				PrivateChannel: true,
				Response:       true,
			},
			{
				Id:             id + 1,
				Type:           kucoinapi.WebSocketMessageTypeSubscribe,
				Topic:          "/account/balance",
				PrivateChannel: true,
				Response:       true,
			},
		}
		for _, cmd := range cmds {
			if err := s.conn.WriteJSON(cmd); err != nil {
				log.WithError(err).Errorf("private subscribe write error, cmd: %+v", cmd)
			}
		}
	}
}

func (s *Stream) SetPublicOnly() {
	s.publicOnly = true
}

func (s *Stream) Close() error {
	return nil
}

func (s *Stream) Connect(ctx context.Context) error {
	err := s.connect(ctx)
	if err != nil {
		return err
	}

	// start one re-connector goroutine with the base context
	go s.Reconnector(ctx)

	s.EmitStart()
	return nil
}

func (s *Stream) Reconnector(ctx context.Context) {
	for {
		select {
		case <-ctx.Done():
			return

		case <-s.ReconnectC:
			log.Warnf("received reconnect signal, reconnecting...")
			time.Sleep(3 * time.Second)

			if err := s.connect(ctx); err != nil {
				log.WithError(err).Errorf("connect error, try to reconnect again...")
				s.Reconnect()
			}
		}
	}
}

// getEndpoint use the publicOnly flag to check whether we should allocate a public bullet or private bullet
func (s *Stream) getEndpoint() (string, error) {
	var bullet *kucoinapi.Bullet
	var err error
	if s.publicOnly {
		bullet, err = s.client.BulletService.NewGetPublicBulletRequest().Do(nil)
	} else {
		bullet, err = s.client.BulletService.NewGetPrivateBulletRequest().Do(nil)
	}

	if err != nil {
		return "", err
	}

	url, err := bullet.URL()
	if err != nil {
		return "", err
	}

	s.bullet = bullet

	return url.String(), nil
}

func (s *Stream) connect(ctx context.Context) error {
	url, err := s.getEndpoint()
	if err != nil {
		return err
	}

	conn, err := s.StandardStream.Dial(url)
	if err != nil {
		return err
	}

	log.Infof("websocket connected: %s", url)

	// should only start one connection one time, so we lock the mutex
	s.connLock.Lock()

	// ensure the previous context is cancelled
	if s.connCancel != nil {
		s.connCancel()
	}

	// create a new context
	s.connCtx, s.connCancel = context.WithCancel(ctx)

	pingTimeout := s.bullet.PingTimeout()
	conn.SetReadDeadline(time.Now().Add(pingTimeout))
	conn.SetPongHandler(func(string) error {
		conn.SetReadDeadline(time.Now().Add(pingTimeout))
		return nil
	})

	s.conn = conn
	s.connLock.Unlock()

	s.EmitConnect()

	go s.read(s.connCtx)
	go ping(s.connCtx, s, s.bullet.PingInterval())
	return nil
}

func (s *Stream) read(ctx context.Context) {
	defer func() {
		if s.connCancel != nil {
			s.connCancel()
		}
		s.EmitDisconnect()
	}()

	for {
		select {

		case <-ctx.Done():
			return

		default:
			conn := s.Conn()

			if err := conn.SetReadDeadline(time.Now().Add(readTimeout)); err != nil {
				log.WithError(err).Errorf("set read deadline error: %s", err.Error())
			}

			mt, message, err := conn.ReadMessage()
			if err != nil {
				// if it's a network timeout error, we should re-connect
				switch err := err.(type) {

				// if it's a websocket related error
				case *websocket.CloseError:
					if err.Code == websocket.CloseNormalClosure {
						return
					}

					// for unexpected close error, we should re-connect
					// emit reconnect to start a new connection
					s.Reconnect()
					return

				case net.Error:
					log.WithError(err).Error("network error")
					s.Reconnect()
					return

				default:
					log.WithError(err).Error("unexpected connection error")
					s.Reconnect()
					return
				}
			}

			// skip non-text messages
			if mt != websocket.TextMessage {
				continue
			}

			// used for debugging
			// fmt.Println(string(message))

			e, err := parseWebsocketPayload(message)
			if err != nil {
				log.WithError(err).Error("message parse error")
				continue
			}

			// remove bytes, so we won't print them
			e.Data = nil
			log.Infof("event: %+v", e)

			if e != nil && e.Object != nil {
				switch et := e.Object.(type) {

				case *kucoinapi.WebSocketTicker:
				case *kucoinapi.WebSocketOrderBookL2:
				case *kucoinapi.WebSocketKLine:
				case *kucoinapi.WebSocketAccountBalance:
				case *kucoinapi.WebSocketPrivateOrder:

				default:
					log.Warnf("unhandled event: %+v", et)

				}
			}
		}
	}
}

func (s *Stream) Conn() *websocket.Conn {
	s.connLock.Lock()
	conn := s.conn
	s.connLock.Unlock()
	return conn
}

type WebSocketConnector interface {
	Conn() *websocket.Conn
	Reconnect()
}

func ping(ctx context.Context, w WebSocketConnector, interval time.Duration) {
	log.Infof("starting ping worker with interval %s", interval)

	pingTicker := time.NewTicker(interval)
	defer pingTicker.Stop()

	for {
		select {

		case <-ctx.Done():
			log.Debug("ping worker stopped")
			return

		case <-pingTicker.C:
			conn := w.Conn()

			if err := conn.WriteJSON(kucoinapi.WebSocketCommand{
				Id:   time.Now().UnixMilli(),
				Type: "ping",
			}); err != nil {
				log.WithError(err).Error("websocket ping error", err)
				w.Reconnect()
			}

			if err := conn.WriteControl(websocket.PingMessage, nil, time.Now().Add(3*time.Second)); err != nil {
				log.WithError(err).Error("ping error", err)
				w.Reconnect()
			}
		}
	}
}

func parseWebsocketPayload(in []byte) (*kucoinapi.WebSocketResponse, error) {
	var resp kucoinapi.WebSocketResponse
	var err = json.Unmarshal(in, &resp)
	if err != nil {
		return nil, err
	}

	switch resp.Type {
	case kucoinapi.WebSocketMessageTypeAck:
		return &resp, nil

	case kucoinapi.WebSocketMessageTypeMessage:
		switch resp.Subject {
		case kucoinapi.WebSocketSubjectOrderChange:
			var o kucoinapi.WebSocketPrivateOrder
			if err := json.Unmarshal(resp.Data, &o); err != nil {
				return &resp, err
			}
			resp.Object = &o

		case kucoinapi.WebSocketSubjectAccountBalance:
			var o kucoinapi.WebSocketAccountBalance
			if err := json.Unmarshal(resp.Data, &o); err != nil {
				return &resp, err
			}
			resp.Object = &o

		case kucoinapi.WebSocketSubjectTradeCandlesUpdate:
			var o kucoinapi.WebSocketKLine
			if err := json.Unmarshal(resp.Data, &o); err != nil {
				return &resp, err
			}
			resp.Object = &o

		case kucoinapi.WebSocketSubjectTradeL2Update:
			var o kucoinapi.WebSocketOrderBookL2
			if err := json.Unmarshal(resp.Data, &o); err != nil {
				return &resp, err
			}
			resp.Object = &o

		case kucoinapi.WebSocketSubjectTradeTicker:
			var o kucoinapi.WebSocketTicker
			if err := json.Unmarshal(resp.Data, &o); err != nil {
				return &resp, err
			}
			resp.Object = &o

		default:
			// return nil, fmt.Errorf("kucoin: unsupported subject: %s", resp.Subject)

		}
	}

	return &resp, nil
}