package engine

import (
	"errors"
	"fmt"
	"strings"
	"sync"
	"time"

	exchange "github.com/thrasher-corp/gocryptotrader/exchanges"
	"github.com/thrasher-corp/gocryptotrader/exchanges/binance"
	"github.com/thrasher-corp/gocryptotrader/exchanges/binanceus"
	"github.com/thrasher-corp/gocryptotrader/exchanges/bitfinex"
	"github.com/thrasher-corp/gocryptotrader/exchanges/bitflyer"
	"github.com/thrasher-corp/gocryptotrader/exchanges/bithumb"
	"github.com/thrasher-corp/gocryptotrader/exchanges/bitmex"
	"github.com/thrasher-corp/gocryptotrader/exchanges/bitstamp"
	"github.com/thrasher-corp/gocryptotrader/exchanges/bittrex"
	"github.com/thrasher-corp/gocryptotrader/exchanges/btcmarkets"
	"github.com/thrasher-corp/gocryptotrader/exchanges/btse"
	"github.com/thrasher-corp/gocryptotrader/exchanges/bybit"
	"github.com/thrasher-corp/gocryptotrader/exchanges/coinbasepro"
	"github.com/thrasher-corp/gocryptotrader/exchanges/coinut"
	"github.com/thrasher-corp/gocryptotrader/exchanges/exmo"
	"github.com/thrasher-corp/gocryptotrader/exchanges/gateio"
	"github.com/thrasher-corp/gocryptotrader/exchanges/gemini"
	"github.com/thrasher-corp/gocryptotrader/exchanges/hitbtc"
	"github.com/thrasher-corp/gocryptotrader/exchanges/huobi"
	"github.com/thrasher-corp/gocryptotrader/exchanges/itbit"
	"github.com/thrasher-corp/gocryptotrader/exchanges/kraken"
	"github.com/thrasher-corp/gocryptotrader/exchanges/lbank"
	"github.com/thrasher-corp/gocryptotrader/exchanges/okcoin"
	"github.com/thrasher-corp/gocryptotrader/exchanges/okx"
	"github.com/thrasher-corp/gocryptotrader/exchanges/poloniex"
	"github.com/thrasher-corp/gocryptotrader/exchanges/yobit"
	"github.com/thrasher-corp/gocryptotrader/exchanges/zb"
	"github.com/thrasher-corp/gocryptotrader/log"
)

// vars related to exchange functions
var (
	ErrNoExchangesLoaded     = errors.New("no exchanges have been loaded")
	ErrExchangeNotFound      = errors.New("exchange not found")
	ErrExchangeAlreadyLoaded = errors.New("exchange already loaded")
	ErrExchangeFailedToLoad  = errors.New("exchange failed to load")
	ErrExchangeNameIsEmpty   = errors.New("exchange name is empty")

	errExchangeIsNil         = errors.New("exchange is nil")
	errExchangeAlreadyLoaded = errors.New("exchange already loaded")
)

// CustomExchangeBuilder interface allows external applications to create
// custom/unsupported exchanges that satisfy the IBotExchange interface.
type CustomExchangeBuilder interface {
	NewExchangeByName(name string) (exchange.IBotExchange, error)
}

// ExchangeManager manages what exchanges are loaded
type ExchangeManager struct {
	mtx       sync.Mutex
	exchanges map[string]exchange.IBotExchange
	Builder   CustomExchangeBuilder
}

// NewExchangeManager creates a new exchange manager
func NewExchangeManager() *ExchangeManager {
	return &ExchangeManager{
		exchanges: make(map[string]exchange.IBotExchange),
	}
}

// Add adds an exchange
func (m *ExchangeManager) Add(exch exchange.IBotExchange) error {
	if m == nil {
		return fmt.Errorf("exchange manager: %w", ErrNilSubsystem)
	}
	if exch == nil {
		return fmt.Errorf("exchange manager: %w", errExchangeIsNil)
	}
	m.mtx.Lock()
	defer m.mtx.Unlock()
	_, ok := m.exchanges[strings.ToLower(exch.GetName())]
	if ok {
		return fmt.Errorf("exchange manager: %s %w", exch.GetName(), errExchangeAlreadyLoaded)
	}
	m.exchanges[strings.ToLower(exch.GetName())] = exch
	return nil
}

// GetExchanges returns all stored exchanges
func (m *ExchangeManager) GetExchanges() ([]exchange.IBotExchange, error) {
	if m == nil {
		return nil, fmt.Errorf("exchange manager: %w", ErrNilSubsystem)
	}
	m.mtx.Lock()
	defer m.mtx.Unlock()
	exchs := make([]exchange.IBotExchange, 0, len(m.exchanges))
	for _, exch := range m.exchanges {
		exchs = append(exchs, exch)
	}
	return exchs, nil
}

// RemoveExchange removes an exchange from the manager
func (m *ExchangeManager) RemoveExchange(exchangeName string) error {
	if m == nil {
		return fmt.Errorf("exchange manager: %w", ErrNilSubsystem)
	}

	if exchangeName == "" {
		return fmt.Errorf("exchange manager: %w", ErrExchangeNameIsEmpty)
	}

	m.mtx.Lock()
	defer m.mtx.Unlock()
	exch, ok := m.exchanges[strings.ToLower(exchangeName)]
	if !ok {
		return fmt.Errorf("exchange manager: %s %w", exchangeName, ErrExchangeNotFound)
	}
	err := exch.Shutdown()
	if err != nil {
		return fmt.Errorf("exchange manager: %w", err)
	}
	delete(m.exchanges, strings.ToLower(exchangeName))
	log.Infof(log.ExchangeSys, "%s exchange unloaded successfully.\n", exchangeName)
	return nil
}

// GetExchangeByName returns an exchange by its name if it exists
func (m *ExchangeManager) GetExchangeByName(exchangeName string) (exchange.IBotExchange, error) {
	if m == nil {
		return nil, fmt.Errorf("exchange manager: %w", ErrNilSubsystem)
	}
	if exchangeName == "" {
		return nil, fmt.Errorf("exchange manager: %w", ErrExchangeNameIsEmpty)
	}
	m.mtx.Lock()
	defer m.mtx.Unlock()
	exch, ok := m.exchanges[strings.ToLower(exchangeName)]
	if !ok {
		return nil, fmt.Errorf("exchange manager: %s %w", exchangeName, ErrExchangeNotFound)
	}
	return exch, nil
}

// NewExchangeByName helps create a new exchange to be loaded
func (m *ExchangeManager) NewExchangeByName(name string) (exchange.IBotExchange, error) {
	nameLower := strings.ToLower(name)
	_, err := m.GetExchangeByName(nameLower)
	if err != nil && !errors.Is(err, ErrExchangeNotFound) {
		return nil, fmt.Errorf("exchange manager: %s %w", name, err)
	}
	if err == nil {
		return nil, fmt.Errorf("exchange manager: %s %w", name, ErrExchangeAlreadyLoaded)
	}

	var exch exchange.IBotExchange
	switch nameLower {
	case "binanceus":
		exch = new(binanceus.Binanceus)
	case "binance":
		exch = new(binance.Binance)
	case "bitfinex":
		exch = new(bitfinex.Bitfinex)
	case "bitflyer":
		exch = new(bitflyer.Bitflyer)
	case "bithumb":
		exch = new(bithumb.Bithumb)
	case "bitmex":
		exch = new(bitmex.Bitmex)
	case "bitstamp":
		exch = new(bitstamp.Bitstamp)
	case "bittrex":
		exch = new(bittrex.Bittrex)
	case "btc markets":
		exch = new(btcmarkets.BTCMarkets)
	case "btse":
		exch = new(btse.BTSE)
	case "bybit":
		exch = new(bybit.Bybit)
	case "coinut":
		exch = new(coinut.COINUT)
	case "exmo":
		exch = new(exmo.EXMO)
	case "coinbasepro":
		exch = new(coinbasepro.CoinbasePro)
	case "gateio":
		exch = new(gateio.Gateio)
	case "gemini":
		exch = new(gemini.Gemini)
	case "hitbtc":
		exch = new(hitbtc.HitBTC)
	case "huobi":
		exch = new(huobi.HUOBI)
	case "itbit":
		exch = new(itbit.ItBit)
	case "kraken":
		exch = new(kraken.Kraken)
	case "lbank":
		exch = new(lbank.Lbank)
	case "okcoin":
		exch = new(okcoin.Okcoin)
	case "okx":
		exch = new(okx.Okx)
	case "poloniex":
		exch = new(poloniex.Poloniex)
	case "yobit":
		exch = new(yobit.Yobit)
	case "zb":
		exch = new(zb.ZB)
	default:
		if m.Builder != nil {
			return m.Builder.NewExchangeByName(nameLower)
		}
		return nil, fmt.Errorf("exchange manager: %s, %w", nameLower, ErrExchangeNotFound)
	}
	return exch, nil
}

// Shutdown shuts down all exchanges and unloads them
func (m *ExchangeManager) Shutdown(shutdownTimeout time.Duration) error {
	if m == nil {
		return fmt.Errorf("exchange manager: %w", ErrNilSubsystem)
	}

	if shutdownTimeout < 0 {
		shutdownTimeout = 0
	}

	var lockout sync.Mutex
	timer := time.NewTimer(shutdownTimeout)
	var wg sync.WaitGroup

	m.mtx.Lock()
	defer m.mtx.Unlock()

	lockout.Lock()
	for _, exch := range m.exchanges {
		wg.Add(1)
		go func(wg *sync.WaitGroup, mtx *sync.Mutex, exch exchange.IBotExchange) {
			err := exch.Shutdown()
			if err != nil {
				log.Errorf(log.ExchangeSys, "%s failed to shutdown %v.\n", exch.GetName(), err)
			} else {
				mtx.Lock()
				delete(m.exchanges, strings.ToLower(exch.GetName()))
				mtx.Unlock()
			}
			wg.Done()
		}(&wg, &lockout, exch)
	}
	lockout.Unlock()

	ch := make(chan struct{})
	go func(wg *sync.WaitGroup, finish chan<- struct{}) {
		wg.Wait()
		finish <- struct{}{}
	}(&wg, ch)

	select {
	case <-timer.C:
		// Possible deadlock in a number of operating exchanges.
		lockout.Lock()
		for name := range m.exchanges {
			log.Warnf(log.ExchangeSys, "%s has failed to shutdown within %s, please review.\n", name, shutdownTimeout)
		}
		lockout.Unlock()
	case <-ch:
		// Every exchange has finished their shutdown call.
		lockout.Lock()
		for name := range m.exchanges {
			log.Errorf(log.ExchangeSys, "%s has failed to shutdown due to error, please review.\n", name)
		}
		lockout.Unlock()
	}
	return nil
}