package bitstamp

import (
	"encoding/json"
	"errors"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/gorilla/websocket"
	"github.com/thrasher-corp/gocryptotrader/currency"
	"github.com/thrasher-corp/gocryptotrader/exchanges/asset"
	"github.com/thrasher-corp/gocryptotrader/exchanges/orderbook"
	"github.com/thrasher-corp/gocryptotrader/exchanges/websocket/wshandler"
	log "github.com/thrasher-corp/gocryptotrader/logger"
)

const (
	bitstampWSURL = "wss://ws.bitstamp.net"
)

// WsConnect connects to a websocket feed
func (b *Bitstamp) WsConnect() error {
	if !b.Websocket.IsEnabled() || !b.IsEnabled() {
		return errors.New(wshandler.WebsocketNotEnabled)
	}
	var dialer websocket.Dialer
	err := b.WebsocketConn.Dial(&dialer, http.Header{})
	if err != nil {
		return err
	}
	if b.Verbose {
		log.Debugf(log.ExchangeSys, "%s Connected to Websocket.\n", b.Name)
	}

	err = b.seedOrderBook()
	if err != nil {
		b.Websocket.DataHandler <- err
	}

	b.generateDefaultSubscriptions()
	go b.WsHandleData()

	return nil
}

// WsHandleData handles websocket data from WsReadData
func (b *Bitstamp) WsHandleData() {
	b.Websocket.Wg.Add(1)

	defer func() {
		b.Websocket.Wg.Done()
	}()

	for {
		select {
		case <-b.Websocket.ShutdownC:
			return

		default:
			resp, err := b.WebsocketConn.ReadMessage()
			if err != nil {
				b.Websocket.ReadMessageErrors <- err
				return
			}
			b.Websocket.TrafficAlert <- struct{}{}
			wsResponse := websocketResponse{}
			err = json.Unmarshal(resp.Raw, &wsResponse)
			if err != nil {
				b.Websocket.DataHandler <- err
				continue
			}

			switch wsResponse.Event {
			case "bts:request_reconnect":
				if b.Verbose {
					log.Debugf(log.ExchangeSys, "%v - Websocket reconnection request received", b.Name)
				}
				go b.Websocket.Shutdown() // Connection monitor will reconnect

			case "data":
				wsOrderBookTemp := websocketOrderBookResponse{}
				err := json.Unmarshal(resp.Raw, &wsOrderBookTemp)
				if err != nil {
					b.Websocket.DataHandler <- err
					continue
				}

				currencyPair := strings.Split(wsResponse.Channel, "_")
				p := currency.NewPairFromString(strings.ToUpper(currencyPair[2]))

				err = b.wsUpdateOrderbook(wsOrderBookTemp.Data, p, asset.Spot)
				if err != nil {
					b.Websocket.DataHandler <- err
					continue
				}

			case "trade":
				wsTradeTemp := websocketTradeResponse{}

				err := json.Unmarshal(resp.Raw, &wsTradeTemp)
				if err != nil {
					b.Websocket.DataHandler <- err
					continue
				}

				currencyPair := strings.Split(wsResponse.Channel, "_")
				p := currency.NewPairFromString(strings.ToUpper(currencyPair[2]))

				b.Websocket.DataHandler <- wshandler.TradeData{
					Price:        wsTradeTemp.Data.Price,
					Amount:       wsTradeTemp.Data.Amount,
					CurrencyPair: p,
					Exchange:     b.Name,
					AssetType:    asset.Spot,
				}
			}
		}
	}
}

func (b *Bitstamp) generateDefaultSubscriptions() {
	var channels = []string{"live_trades_", "order_book_"}
	enabledCurrencies := b.GetEnabledPairs(asset.Spot)
	var subscriptions []wshandler.WebsocketChannelSubscription
	for i := range channels {
		for j := range enabledCurrencies {
			subscriptions = append(subscriptions, wshandler.WebsocketChannelSubscription{
				Channel: channels[i] + enabledCurrencies[j].Lower().String(),
			})
		}
	}
	b.Websocket.SubscribeToChannels(subscriptions)
}

// Subscribe sends a websocket message to receive data from the channel
func (b *Bitstamp) Subscribe(channelToSubscribe wshandler.WebsocketChannelSubscription) error {
	req := websocketEventRequest{
		Event: "bts:subscribe",
		Data: websocketData{
			Channel: channelToSubscribe.Channel,
		},
	}
	return b.WebsocketConn.SendMessage(req)
}

// Unsubscribe sends a websocket message to stop receiving data from the channel
func (b *Bitstamp) Unsubscribe(channelToSubscribe wshandler.WebsocketChannelSubscription) error {
	req := websocketEventRequest{
		Event: "bts:unsubscribe",
		Data: websocketData{
			Channel: channelToSubscribe.Channel,
		},
	}
	return b.WebsocketConn.SendMessage(req)
}

func (b *Bitstamp) wsUpdateOrderbook(update websocketOrderBook, p currency.Pair, assetType asset.Item) error {
	if len(update.Asks) == 0 && len(update.Bids) == 0 {
		return errors.New("bitstamp_websocket.go error - no orderbook data")
	}

	var asks, bids []orderbook.Item
	for i := range update.Asks {
		target, err := strconv.ParseFloat(update.Asks[i][0], 64)
		if err != nil {
			b.Websocket.DataHandler <- err
			continue
		}

		amount, err := strconv.ParseFloat(update.Asks[i][1], 64)
		if err != nil {
			b.Websocket.DataHandler <- err
			continue
		}

		asks = append(asks, orderbook.Item{Price: target, Amount: amount})
	}

	for i := range update.Bids {
		target, err := strconv.ParseFloat(update.Bids[i][0], 64)
		if err != nil {
			b.Websocket.DataHandler <- err
			continue
		}

		amount, err := strconv.ParseFloat(update.Bids[i][1], 64)
		if err != nil {
			b.Websocket.DataHandler <- err
			continue
		}

		bids = append(bids, orderbook.Item{Price: target, Amount: amount})
	}

	err := b.Websocket.Orderbook.LoadSnapshot(&orderbook.Base{
		Bids:         bids,
		Asks:         asks,
		Pair:         p,
		LastUpdated:  time.Unix(update.Timestamp, 0),
		AssetType:    asset.Spot,
		ExchangeName: b.Name,
	})
	if err != nil {
		return err
	}

	b.Websocket.DataHandler <- wshandler.WebsocketOrderbookUpdate{
		Pair:     p,
		Asset:    assetType,
		Exchange: b.Name,
	}

	return nil
}

func (b *Bitstamp) seedOrderBook() error {
	p := b.GetEnabledPairs(asset.Spot)
	for x := range p {
		orderbookSeed, err := b.GetOrderbook(p[x].String())
		if err != nil {
			return err
		}

		var newOrderBook orderbook.Base
		for i := range orderbookSeed.Asks {
			newOrderBook.Asks = append(newOrderBook.Asks, orderbook.Item{
				Price:  orderbookSeed.Asks[i].Price,
				Amount: orderbookSeed.Asks[i].Amount,
			})
		}
		for i := range orderbookSeed.Bids {
			newOrderBook.Bids = append(newOrderBook.Bids, orderbook.Item{
				Price:  orderbookSeed.Bids[i].Price,
				Amount: orderbookSeed.Bids[i].Amount,
			})
		}
		newOrderBook.Pair = p[x]
		newOrderBook.AssetType = asset.Spot
		newOrderBook.ExchangeName = b.Name

		err = b.Websocket.Orderbook.LoadSnapshot(&newOrderBook)
		if err != nil {
			return err
		}

		b.Websocket.DataHandler <- wshandler.WebsocketOrderbookUpdate{
			Pair:     p[x],
			Asset:    asset.Spot,
			Exchange: b.Name,
		}
	}
	return nil
}