package bbgo

import (
	"bytes"
	"context"
	"fmt"
	"image/png"
	"io/ioutil"
	stdlog "log"
	"math/rand"
	"os"
	"strings"
	"sync"
	"time"

	"github.com/pkg/errors"
	"github.com/pquerna/otp"
	log "github.com/sirupsen/logrus"
	"github.com/slack-go/slack"
	"github.com/spf13/viper"
	"gopkg.in/tucnak/telebot.v2"

	"github.com/c9s/bbgo/pkg/exchange"
	"github.com/c9s/bbgo/pkg/fixedpoint"
	"github.com/c9s/bbgo/pkg/interact"
	"github.com/c9s/bbgo/pkg/notifier/slacknotifier"
	"github.com/c9s/bbgo/pkg/notifier/telegramnotifier"
	"github.com/c9s/bbgo/pkg/service"
	googleservice "github.com/c9s/bbgo/pkg/service/google"
	"github.com/c9s/bbgo/pkg/slack/slacklog"
	"github.com/c9s/bbgo/pkg/types"
	"github.com/c9s/bbgo/pkg/util"
)

func init() {
	// randomize pulling
	rand.Seed(time.Now().UnixNano())
}

var defaultSyncBufferPeriod = 30 * time.Minute

// IsBackTesting is a global variable that indicates the current environment is back-test or not.
var IsBackTesting = false

var BackTestService *service.BacktestService

func SetBackTesting(s *service.BacktestService) {
	BackTestService = s
	IsBackTesting = s != nil
}

var LoadedExchangeStrategies = make(map[string]SingleExchangeStrategy)
var LoadedCrossExchangeStrategies = make(map[string]CrossExchangeStrategy)

func RegisterStrategy(key string, s interface{}) {
	loaded := 0
	if d, ok := s.(SingleExchangeStrategy); ok {
		LoadedExchangeStrategies[key] = d
		loaded++
	}

	if d, ok := s.(CrossExchangeStrategy); ok {
		LoadedCrossExchangeStrategies[key] = d
		loaded++
	}

	if loaded == 0 {
		panic(fmt.Errorf("%T does not implement SingleExchangeStrategy or CrossExchangeStrategy", s))
	}
}

var emptyTime time.Time

type SyncStatus int

const (
	SyncNotStarted SyncStatus = iota
	Syncing
	SyncDone
)

// Environment presents the real exchange data layer
type Environment struct {
	// built-in service
	DatabaseService   *service.DatabaseService
	OrderService      *service.OrderService
	TradeService      *service.TradeService
	ProfitService     *service.ProfitService
	PositionService   *service.PositionService
	BacktestService   *service.BacktestService
	RewardService     *service.RewardService
	MarginService     *service.MarginService
	SyncService       *service.SyncService
	AccountService    *service.AccountService
	WithdrawService   *service.WithdrawService
	DepositService    *service.DepositService
	PersistentService *service.PersistenceServiceFacade

	// external services
	GoogleSpreadSheetService *googleservice.SpreadSheetService

	// startTime is the time of start point (which is used in the backtest)
	startTime time.Time

	// syncStartTime is the time point we want to start the sync (for trades and orders)
	syncStartTime time.Time
	syncMutex     sync.Mutex

	syncStatusMutex sync.Mutex
	syncStatus      SyncStatus
	syncConfig      *SyncConfig

	loggingConfig     *LoggingConfig
	environmentConfig *EnvironmentConfig

	sessions map[string]*ExchangeSession
}

func NewEnvironment() *Environment {
	now := time.Now()
	return &Environment{
		// default trade scan time
		syncStartTime: now.AddDate(-1, 0, 0), // defaults to sync from 1 year ago
		sessions:      make(map[string]*ExchangeSession),
		startTime:     now,

		syncStatus: SyncNotStarted,
	}
}

func (environ *Environment) Logger() log.FieldLogger {
	if environ.loggingConfig != nil && len(environ.loggingConfig.Fields) > 0 {
		return log.WithFields(environ.loggingConfig.Fields)
	}

	return log.StandardLogger()
}

func (environ *Environment) Session(name string) (*ExchangeSession, bool) {
	s, ok := environ.sessions[name]
	return s, ok
}

func (environ *Environment) Sessions() map[string]*ExchangeSession {
	return environ.sessions
}

func (environ *Environment) SetLogging(config *LoggingConfig) {
	environ.loggingConfig = config
}

func (environ *Environment) SelectSessions(names ...string) map[string]*ExchangeSession {
	if len(names) == 0 {
		return environ.sessions
	}

	sessions := make(map[string]*ExchangeSession)
	for _, name := range names {
		if s, ok := environ.Session(name); ok {
			sessions[name] = s
		}
	}

	return sessions
}

func (environ *Environment) ConfigureDatabase(ctx context.Context, config *Config) error {
	// configureDB configures the database service based on the environment variable
	var dbDriver string
	var dbDSN string
	var extraPkgNames []string

	if config != nil && config.DatabaseConfig != nil {
		dbDriver = config.DatabaseConfig.Driver
		dbDSN = config.DatabaseConfig.DSN
		extraPkgNames = config.DatabaseConfig.ExtraMigrationPackages
	}

	if val, ok := os.LookupEnv("DB_DRIVER"); ok {
		dbDriver = val
	}

	if val, ok := os.LookupEnv("DB_DSN"); ok {
		dbDSN = val
	} else if val, ok := os.LookupEnv("SQLITE3_DSN"); ok && (dbDriver == "" || dbDriver == "sqlite3") {
		dbDSN = val
		dbDriver = "sqlite3"
	} else if val, ok := os.LookupEnv("MYSQL_URL"); ok && (dbDriver == "" || dbDriver == "mysql") {
		dbDSN = val
		dbDriver = "mysql"
	}

	// database is optional
	if dbDriver == "" || dbDSN == "" {
		return nil
	}

	return environ.ConfigureDatabaseDriver(ctx, dbDriver, dbDSN, extraPkgNames...)
}

func (environ *Environment) ConfigureDatabaseDriver(ctx context.Context, driver string, dsn string, extraPkgNames ...string) error {
	environ.DatabaseService = service.NewDatabaseService(driver, dsn)
	environ.DatabaseService.AddMigrationPackages(extraPkgNames...)

	err := environ.DatabaseService.Connect()
	if err != nil {
		return err
	}

	if err := environ.DatabaseService.Upgrade(ctx); err != nil {
		return err
	}

	// get the db connection pool object to create other services
	db := environ.DatabaseService.DB
	environ.OrderService = &service.OrderService{DB: db}
	environ.TradeService = &service.TradeService{DB: db}
	environ.RewardService = &service.RewardService{DB: db}
	environ.AccountService = &service.AccountService{DB: db}
	environ.ProfitService = &service.ProfitService{DB: db}
	environ.PositionService = &service.PositionService{DB: db}
	environ.MarginService = &service.MarginService{DB: db}
	environ.WithdrawService = &service.WithdrawService{DB: db}
	environ.DepositService = &service.DepositService{DB: db}
	environ.SyncService = &service.SyncService{
		TradeService:    environ.TradeService,
		OrderService:    environ.OrderService,
		RewardService:   environ.RewardService,
		MarginService:   environ.MarginService,
		WithdrawService: &service.WithdrawService{DB: db},
		DepositService:  &service.DepositService{DB: db},
	}

	return nil
}

// AddExchangeSession adds the existing exchange session or pre-created exchange session
func (environ *Environment) AddExchangeSession(name string, session *ExchangeSession) *ExchangeSession {
	environ.sessions[name] = session
	return session
}

// AddExchange adds the given exchange with the session name, this is the default
func (environ *Environment) AddExchange(name string, exchange types.Exchange) (session *ExchangeSession) {
	session = NewExchangeSession(name, exchange)
	return environ.AddExchangeSession(name, session)
}

func (environ *Environment) ConfigureService(ctx context.Context, srvConfig *ServiceConfig) error {
	if srvConfig.GoogleSpreadSheetService != nil {
		environ.GoogleSpreadSheetService = googleservice.NewSpreadSheetService(ctx, srvConfig.GoogleSpreadSheetService.JsonTokenFile, srvConfig.GoogleSpreadSheetService.SpreadSheetID)
	}

	return nil
}

func (environ *Environment) ConfigureExchangeSessions(userConfig *Config) error {
	// if sessions are not defined, we detect the sessions automatically
	if len(userConfig.Sessions) == 0 {
		return environ.AddExchangesByViperKeys()
	}

	return environ.AddExchangesFromSessionConfig(userConfig.Sessions)
}

func (environ *Environment) AddExchangesByViperKeys() error {
	for _, n := range types.SupportedExchanges {
		if viper.IsSet(string(n) + "-api-key") {
			exMinimal, err := exchange.NewWithEnvVarPrefix(n, "")
			if err != nil {
				return err
			}

			if ex, ok := exMinimal.(types.Exchange); ok {
				environ.AddExchange(n.String(), ex)
			} else {
				log.Errorf("exchange %T does not implement types.Exchange", exMinimal)
			}
		}
	}

	return nil
}

func (environ *Environment) AddExchangesFromSessionConfig(sessions map[string]*ExchangeSession) error {
	for sessionName, session := range sessions {
		if err := session.InitExchange(sessionName, nil); err != nil {
			return err
		}

		environ.AddExchangeSession(sessionName, session)
	}

	return nil
}

func (environ *Environment) IsBackTesting() bool {
	return environ.BacktestService != nil
}

// Init prepares the data that will be used by the strategies
func (environ *Environment) Init(ctx context.Context) (err error) {
	for n := range environ.sessions {
		var session = environ.sessions[n]
		if err = session.Init(ctx, environ); err != nil {
			// we can skip initialized sessions
			if err != ErrSessionAlreadyInitialized {
				return err
			}
		}
	}

	return
}

// Start initializes the symbols data streams
func (environ *Environment) Start(ctx context.Context) (err error) {
	for n := range environ.sessions {
		var session = environ.sessions[n]
		if err = session.InitSymbols(ctx, environ); err != nil {
			return err
		}
	}
	return
}

func (environ *Environment) SetStartTime(t time.Time) *Environment {
	environ.startTime = t
	return environ
}

func (environ *Environment) StartTime() time.Time {
	return environ.startTime
}

// SetSyncStartTime overrides the default trade scan time (-7 days)
func (environ *Environment) SetSyncStartTime(t time.Time) *Environment {
	environ.syncStartTime = t
	return environ
}

func (environ *Environment) BindSync(config *SyncConfig) {
	// skip this if we are running back-test
	if environ.BacktestService != nil {
		return
	}

	// If trade service is configured, we have the db configured
	if environ.TradeService == nil {
		return
	}

	if config == nil || config.UserDataStream == nil {
		return
	}

	environ.syncConfig = config

	tradeWriterCreator := func(session *ExchangeSession) func(trade types.Trade) {
		return func(trade types.Trade) {
			trade.IsMargin = session.Margin
			trade.IsFutures = session.Futures
			if session.Margin {
				trade.IsIsolated = session.IsolatedMargin
			} else if session.Futures {
				trade.IsIsolated = session.IsolatedFutures
			}

			// The StrategyID field and the PnL field needs to be updated by the strategy.
			// trade.StrategyID, trade.PnL
			if err := environ.TradeService.Insert(trade); err != nil {
				log.WithError(err).Errorf("trade insert error: %+v", trade)
			}
		}
	}

	orderWriterCreator := func(session *ExchangeSession) func(order types.Order) {
		return func(order types.Order) {
			order.IsMargin = session.Margin
			order.IsFutures = session.Futures
			if session.Margin {
				order.IsIsolated = session.IsolatedMargin
			} else if session.Futures {
				order.IsIsolated = session.IsolatedFutures
			}

			switch order.Status {
			case types.OrderStatusFilled, types.OrderStatusCanceled:
				if order.ExecutedQuantity.Sign() > 0 {
					if err := environ.OrderService.Insert(order); err != nil {
						log.WithError(err).Errorf("order insert error: %+v", order)
					}
				}
			}
		}
	}

	for _, session := range environ.sessions {
		// avoid using the iterator variable.
		s2 := session
		// if trade sync is on, we will write all received trades
		if config.UserDataStream.Trades {
			tradeWriter := tradeWriterCreator(s2)
			session.UserDataStream.OnTradeUpdate(tradeWriter)
		}

		if config.UserDataStream.FilledOrders {
			orderWriter := orderWriterCreator(s2)
			session.UserDataStream.OnOrderUpdate(orderWriter)
		}
	}
}

func (environ *Environment) Connect(ctx context.Context) error {
	log.Debugf("starting interaction...")
	if err := interact.Start(ctx); err != nil {
		return err
	}

	for n := range environ.sessions {
		// avoid using the placeholder variable for the session because we use that in the callbacks
		var session = environ.sessions[n]
		var logger = log.WithField("session", n)

		if len(session.Subscriptions) == 0 {
			logger.Warnf("exchange session %s has no subscriptions", session.Name)
		} else {
			// add the subscribe requests to the stream
			for _, s := range session.Subscriptions {
				logger.Infof("subscribing %s %s %v", s.Symbol, s.Channel, s.Options)
				session.MarketDataStream.Subscribe(s.Channel, s.Symbol, s.Options)
			}
		}

		logger.Infof("connecting %s market data stream...", session.Name)
		if err := session.MarketDataStream.Connect(ctx); err != nil {
			return err
		}

		if !session.PublicOnly {
			logger.Infof("connecting %s user data stream...", session.Name)
			if err := session.UserDataStream.Connect(ctx); err != nil {
				return err
			}
		}
	}

	return nil
}

func (environ *Environment) IsSyncing() (status SyncStatus) {
	environ.syncStatusMutex.Lock()
	status = environ.syncStatus
	environ.syncStatusMutex.Unlock()
	return status
}

func (environ *Environment) setSyncing(status SyncStatus) {
	environ.syncStatusMutex.Lock()
	environ.syncStatus = status
	environ.syncStatusMutex.Unlock()
}

func (environ *Environment) syncWithUserConfig(ctx context.Context, userConfig *Config) error {
	sessions := environ.sessions
	selectedSessions := userConfig.Sync.Sessions
	if len(selectedSessions) > 0 {
		sessions = environ.SelectSessions(selectedSessions...)
	}

	since := defaultSyncSinceTime()
	if userConfig.Sync.Since != nil {
		since = userConfig.Sync.Since.Time()
	}

	environ.SetSyncStartTime(since)

	syncSymbolMap, restSymbols := categorizeSyncSymbol(userConfig.Sync.Symbols)
	for _, session := range sessions {
		syncSymbols := restSymbols
		if ss, ok := syncSymbolMap[session.Name]; ok {
			syncSymbols = append(syncSymbols, ss...)
		}

		if err := environ.syncSession(ctx, session, since, syncSymbols...); err != nil {
			return err
		}

		if userConfig.Sync.DepositHistory {
			if err := environ.SyncService.SyncDepositHistory(ctx, session.Exchange, since); err != nil {
				return err
			}
		}

		if userConfig.Sync.WithdrawHistory {
			if err := environ.SyncService.SyncWithdrawHistory(ctx, session.Exchange, since); err != nil {
				return err
			}
		}

		if userConfig.Sync.RewardHistory {
			if err := environ.SyncService.SyncRewardHistory(ctx, session.Exchange, since); err != nil {
				return err
			}
		}

		if userConfig.Sync.MarginHistory {
			if err := environ.SyncService.SyncMarginHistory(ctx, session.Exchange,
				since,
				userConfig.Sync.MarginAssets...); err != nil {
				return err
			}
		}
	}

	return nil
}

// Sync syncs all registered exchange sessions
func (environ *Environment) Sync(ctx context.Context, userConfig ...*Config) error {
	if environ.SyncService == nil {
		return nil
	}

	environ.syncMutex.Lock()
	defer environ.syncMutex.Unlock()

	environ.setSyncing(Syncing)
	defer environ.setSyncing(SyncDone)

	// sync by the defined user config
	if len(userConfig) > 0 && userConfig[0] != nil && userConfig[0].Sync != nil {
		return environ.syncWithUserConfig(ctx, userConfig[0])
	}

	// the default sync logics
	since := defaultSyncSinceTime()
	for _, session := range environ.sessions {
		if err := environ.syncSession(ctx, session, since); err != nil {
			return err
		}
	}

	return nil
}

func (environ *Environment) RecordAsset(t time.Time, session *ExchangeSession, assets types.AssetMap) {
	// skip for back-test
	if environ.BacktestService != nil {
		return
	}

	if environ.DatabaseService == nil || environ.AccountService == nil {
		return
	}

	if err := environ.AccountService.InsertAsset(
		t,
		session.Name,
		session.ExchangeName,
		session.SubAccount,
		session.Margin,
		session.IsolatedMargin,
		session.IsolatedMarginSymbol,
		assets); err != nil {
		log.WithError(err).Errorf("can not insert asset record")
	}
}

func (environ *Environment) RecordPosition(position *types.Position, trade types.Trade, profit *types.Profit) {
	// skip for back-test
	if environ.BacktestService != nil {
		return
	}

	if environ.DatabaseService == nil || environ.ProfitService == nil || environ.PositionService == nil {
		return
	}

	// guard: set profit info to position if the strategy info is empty
	if profit != nil {
		if position.Strategy == "" && profit.Strategy != "" {
			position.Strategy = profit.Strategy
		}

		if position.StrategyInstanceID == "" && profit.StrategyInstanceID != "" {
			position.StrategyInstanceID = profit.StrategyInstanceID
		}
	}

	log.Infof("recordPosition: position = %s, trade = %+v, profit = %+v", position.Base.String(), trade, profit)
	if profit != nil {
		if err := environ.PositionService.Insert(position, trade, profit.Profit); err != nil {
			log.WithError(err).Errorf("can not insert position record")
		}

		if err := environ.ProfitService.Insert(*profit); err != nil {
			log.WithError(err).Errorf("can not insert profit record: %+v", profit)
		}
	} else {
		if err := environ.PositionService.Insert(position, trade, fixedpoint.Zero); err != nil {
			log.WithError(err).Errorf("can not insert position record")
		}
	}
}

func (environ *Environment) RecordProfit(profit types.Profit) {
	// skip for back-test
	if environ.BacktestService != nil {
		return
	}

	if environ.DatabaseService == nil {
		return
	}
	if environ.ProfitService == nil {
		return
	}

	if err := environ.ProfitService.Insert(profit); err != nil {
		log.WithError(err).Errorf("can not insert profit record: %+v", profit)
	}
}

func (environ *Environment) SyncSession(ctx context.Context, session *ExchangeSession, defaultSymbols ...string) error {
	if environ.SyncService == nil {
		return nil
	}

	environ.syncMutex.Lock()
	defer environ.syncMutex.Unlock()

	environ.setSyncing(Syncing)
	defer environ.setSyncing(SyncDone)

	since := defaultSyncSinceTime()
	return environ.syncSession(ctx, session, since, defaultSymbols...)
}

func (environ *Environment) syncSession(
	ctx context.Context, session *ExchangeSession, syncStartTime time.Time, defaultSymbols ...string,
) error {
	symbols, err := session.getSessionSymbols(defaultSymbols...)
	if err != nil {
		return err
	}

	log.Infof("syncing symbols %v from session %s", symbols, session.Name)

	syncBufferPeriod := -defaultSyncBufferPeriod
	if environ.environmentConfig != nil && environ.environmentConfig.SyncBufferPeriod != nil {
		syncBufferPeriod = -environ.environmentConfig.SyncBufferPeriod.Duration()
	}

	if syncBufferPeriod > 0 {
		log.Warnf("syncBufferPeriod should be a negative number, given: %d", syncBufferPeriod)
	}

	syncEndTime := time.Now().Add(syncBufferPeriod)
	return environ.SyncService.SyncSessionSymbols(ctx, session.Exchange, syncStartTime, syncEndTime, symbols...)
}

func (environ *Environment) ConfigureNotificationSystem(ctx context.Context, userConfig *Config) error {
	// setup default notification config
	if userConfig.Notifications == nil {
		userConfig.Notifications = &NotificationConfig{}
	}

	var isolation = GetIsolationFromContext(ctx)
	var persistence = isolation.persistenceServiceFacade.Get()

	err := environ.setupInteraction(persistence)
	if err != nil {
		return err
	}

	// setup slack
	slackToken := viper.GetString("slack-token")
	if len(slackToken) > 0 && userConfig.Notifications != nil {
		environ.setupSlack(userConfig, slackToken, persistence)
	}

	// check if telegram bot token is defined
	telegramBotToken := viper.GetString("telegram-bot-token")
	if len(telegramBotToken) > 0 {
		if err := environ.setupTelegram(userConfig, telegramBotToken, persistence); err != nil {
			return err
		}
	}

	if userConfig.Notifications != nil {
		if err := environ.ConfigureNotification(userConfig.Notifications); err != nil {
			return err
		}
	}

	return nil
}

func (environ *Environment) ConfigureNotification(config *NotificationConfig) error {
	if config.Switches != nil {
		if config.Switches.Trade {
			tradeHandler := func(trade types.Trade) {
				Notify(trade)
			}

			for _, session := range environ.sessions {
				session.UserDataStream.OnTradeUpdate(tradeHandler)
			}
		}

		if config.Switches.OrderUpdate {
			orderUpdateHandler := func(order types.Order) {
				Notify(order)
			}

			for _, session := range environ.sessions {
				session.UserDataStream.OnOrderUpdate(orderUpdateHandler)
			}
		}
	}

	return nil
}

// getAuthStoreID returns the authentication store id
// if telegram bot token is defined, the bot id will be used.
// if not, env var $USER will be used.
// if both are not defined, a default "default" will be used.
func getAuthStoreID() string {
	telegramBotToken := viper.GetString("telegram-bot-token")
	if len(telegramBotToken) > 0 {
		tt := strings.Split(telegramBotToken, ":")
		return tt[0]
	}

	userEnv := os.Getenv("USER")
	if userEnv != "" {
		return userEnv
	}

	return "default"
}

func (environ *Environment) setupInteraction(persistence service.PersistenceService) error {
	var otpQRCodeImagePath = "otp.png"
	var key *otp.Key
	var keyURL string
	var authStore = environ.getAuthStore(persistence)

	if v, ok := util.GetEnvVarBool("FLUSH_OTP_KEY"); v && ok {
		log.Warnf("flushing otp key...")
		if err := authStore.Reset(); err != nil {
			return err
		}
	}

	if err := authStore.Load(&keyURL); err != nil {
		log.Warnf("telegram session not found, generating new one-time password key for new telegram session...")

		newKey, err := setupNewOTPKey(otpQRCodeImagePath)
		if err != nil {
			return errors.Wrapf(err, "failed to setup totp (time-based one time password) key")
		}

		key = newKey
		keyURL = key.URL()
		if err := authStore.Save(keyURL); err != nil {
			return err
		}

		printOtpAuthGuide(otpQRCodeImagePath)

	} else if keyURL != "" {
		key, err = otp.NewKeyFromURL(keyURL)
		if err != nil {
			log.WithError(err).Errorf("can not load otp key from url: %s, generating new otp key", keyURL)

			newKey, err := setupNewOTPKey(otpQRCodeImagePath)
			if err != nil {
				return errors.Wrapf(err, "failed to setup totp (time-based one time password) key")
			}

			key = newKey
			keyURL = key.URL()
			if err := authStore.Save(keyURL); err != nil {
				return err
			}

			printOtpAuthGuide(otpQRCodeImagePath)
		} else {
			log.Infof("otp key loaded: %s", util.MaskKey(key.Secret()))
			printOtpAuthGuide(otpQRCodeImagePath)
		}
	}

	authStrict := false
	authMode := interact.AuthModeToken
	authToken := viper.GetString("telegram-bot-auth-token")

	if authToken != "" && key != nil {
		authStrict = true
	} else if authToken != "" {
		authMode = interact.AuthModeToken
	} else if key != nil {
		authMode = interact.AuthModeOTP
	}

	if authMode == interact.AuthModeToken {
		log.Debugf("found interaction auth token, using token mode for authorization...")
		printAuthTokenGuide(authToken)
	}

	interact.AddCustomInteraction(&interact.AuthInteract{
		Strict: authStrict,
		Mode:   authMode,
		Token:  authToken, // can be empty string here
		// pragma: allowlist nextline secret
		OneTimePasswordKey: key, // can be nil here
	})
	return nil
}

func (environ *Environment) getAuthStore(persistence service.PersistenceService) service.Store {
	id := getAuthStoreID()
	return persistence.NewStore("bbgo", "auth", id)
}

func (environ *Environment) setupSlack(userConfig *Config, slackToken string, persistence service.PersistenceService) {
	conf := userConfig.Notifications.Slack
	if conf == nil {
		return
	}

	if !strings.HasPrefix(slackToken, "xoxb-") {
		log.Error("SLACK_BOT_TOKEN must have the prefix \"xoxb-\".")
		return
	}

	// app-level token (for specific api)
	slackAppToken := viper.GetString("slack-app-token")
	if len(slackAppToken) > 0 && !strings.HasPrefix(slackAppToken, "xapp-") {
		log.Errorf("SLACK_APP_TOKEN must have the prefix \"xapp-\".")
		return
	}

	if conf.ErrorChannel != "" {
		log.Debugf("found slack configured, setting up log hook...")
		log.AddHook(slacklog.NewLogHook(slackToken, conf.ErrorChannel))
	}

	log.Debugf("adding slack notifier with default channel: %s", conf.DefaultChannel)

	var slackOpts = []slack.Option{
		slack.OptionLog(stdlog.New(os.Stdout, "api: ", stdlog.Lshortfile|stdlog.LstdFlags)),
	}

	if len(slackAppToken) > 0 {
		slackOpts = append(slackOpts, slack.OptionAppLevelToken(slackAppToken))
	}

	if b, ok := util.GetEnvVarBool("DEBUG_SLACK"); ok {
		slackOpts = append(slackOpts, slack.OptionDebug(b))
	}

	var client = slack.New(slackToken, slackOpts...)

	var notifier = slacknotifier.New(client, conf.DefaultChannel)
	Notification.AddNotifier(notifier)

	// allocate a store, so that we can save the chatID for the owner
	var messenger = interact.NewSlack(client)

	var sessions = interact.SlackSessionMap{}
	var sessionStore = persistence.NewStore("bbgo", "slack")
	if err := sessionStore.Load(&sessions); err != nil {

	} else {
		// TODO: this is not necessary for slack, but we should find a way to restore the sessions
		/*
			for _, session := range sessions {
				if session.IsAuthorized() {
					// notifier.AddChat(session.Chat)
				}
			}
			messenger.RestoreSessions(sessions)
			messenger.OnAuthorized(func(userSession *interact.SlackSession) {
				if userSession.IsAuthorized() {
					// notifier.AddChat(userSession.Chat)
				}
			})
		*/
	}

	interact.AddMessenger(messenger)
}

func (environ *Environment) setupTelegram(
	userConfig *Config, telegramBotToken string, persistence service.PersistenceService,
) error {
	tt := strings.Split(telegramBotToken, ":")
	telegramID := tt[0]

	bot, err := telebot.NewBot(telebot.Settings{
		// You can also set custom API URL.
		// If field is empty it equals to "https://api.telegram.org".
		// URL: "http://195.129.111.17:8012",
		Token:  telegramBotToken,
		Poller: &telebot.LongPoller{Timeout: 10 * time.Second},
	})

	if err != nil {
		return err
	}

	var opts []telegramnotifier.Option
	if userConfig.Notifications != nil && userConfig.Notifications.Telegram != nil {
		log.Infof("telegram broadcast is enabled")
		opts = append(opts, telegramnotifier.UseBroadcast())
	}

	var notifier = telegramnotifier.New(bot, opts...)
	Notification.AddNotifier(notifier)

	log.AddHook(telegramnotifier.NewLogHook(notifier))

	// allocate a store, so that we can save the chatID for the owner
	var messenger = interact.NewTelegram(bot)

	var sessions = interact.TelegramSessionMap{}
	var sessionStore = persistence.NewStore("bbgo", "telegram", telegramID)
	if err := sessionStore.Load(&sessions); err != nil {
		if err != service.ErrPersistenceNotExists {
			log.WithError(err).Errorf("unexpected persistence error")
		}
	} else {
		for _, session := range sessions {
			if session.IsAuthorized() {
				notifier.AddChat(session.Chat)
			}
		}

		// you must restore the session after the notifier updates
		messenger.RestoreSessions(sessions)
	}

	messenger.OnAuthorized(func(userSession *interact.TelegramSession) {
		if userSession.IsAuthorized() {
			notifier.AddChat(userSession.Chat)
		}

		log.Infof("user session %d got authorized, saving telegram sessions...", userSession.User.ID)
		if err := sessionStore.Save(messenger.Sessions()); err != nil {
			log.WithError(err).Errorf("telegram session save error")
		}
	})

	interact.AddMessenger(messenger)
	return nil
}

func writeOTPKeyAsQRCodePNG(key *otp.Key, imagePath string) error {
	// Convert TOTP key into a PNG
	var buf bytes.Buffer
	img, err := key.Image(512, 512)
	if err != nil {
		return err
	}

	if err := png.Encode(&buf, img); err != nil {
		return err
	}

	if err := ioutil.WriteFile(imagePath, buf.Bytes(), 0644); err != nil {
		return err
	}

	return nil
}

// setupNewOTPKey generates a new otp key and save the secret as a qrcode image
func setupNewOTPKey(qrcodeImagePath string) (*otp.Key, error) {
	key, err := service.NewDefaultTotpKey()
	if err != nil {
		return nil, errors.Wrapf(err, "failed to setup totp (time-based one time password) key")
	}

	printOtpKey(key)

	if err := writeOTPKeyAsQRCodePNG(key, qrcodeImagePath); err != nil {
		return nil, err
	}

	return key, nil
}

func printOtpKey(key *otp.Key) {
	fmt.Println("")
	fmt.Println("====================================================================")
	fmt.Println("               PLEASE STORE YOUR OTP KEY SAFELY                     ")
	fmt.Println("====================================================================")
	fmt.Printf("  Issuer:       %s\n", key.Issuer())
	fmt.Printf("  AccountName:  %s\n", key.AccountName())
	fmt.Printf("  Secret:       %s\n", key.Secret())
	fmt.Printf("  Key URL:      %s\n", key.URL())
	fmt.Println("====================================================================")
	fmt.Println("")
}

func printOtpAuthGuide(qrcodeImagePath string) {
	fmt.Printf(`
To scan your OTP QR code, please run the following command:
	
	open %s

For telegram, send the auth command with the generated one-time password to the bbgo bot you created to enable the notification:

	/auth

`, qrcodeImagePath)
}

func printAuthTokenGuide(token string) {
	fmt.Printf(`
For telegram, send the following command to the bbgo bot you created to enable the notification:

	/auth

And then enter your token

	%s

`, token)
}

func (session *ExchangeSession) getSessionSymbols(defaultSymbols ...string) ([]string, error) {
	if session.IsolatedMargin {
		return []string{session.IsolatedMarginSymbol}, nil
	}

	if len(defaultSymbols) > 0 {
		return defaultSymbols, nil
	}

	return session.FindPossibleAssetSymbols()
}

func defaultSyncSinceTime() time.Time {
	return time.Now().AddDate(0, -6, 0)
}