all: refactor exchange factory to return the minimal implementation

pkg/bbgo/environment.go

@@ -228,12 +228,16 @@ func (environ *Environment) ConfigureExchangeSessions(userConfig *Config) error
 func (environ *Environment) AddExchangesByViperKeys() error {
 	for _, n := range types.SupportedExchanges {
 		if viper.IsSet(string(n) + "-api-key") {
-			ex, err := exchange.NewWithEnvVarPrefix(n, "")
+			exMinimal, err := exchange.NewWithEnvVarPrefix(n, "")
 			if err != nil {
 				return err
 			}
 
-			environ.AddExchange(n.String(), ex)
+			if ex, ok := exMinimal.(types.Exchange); ok {
+				environ.AddExchange(n.String(), ex)
+			} else {
+				log.Errorf("exchange %T does not implement types.Exchange", exMinimal)
+			}
 		}
 	}
 

pkg/bbgo/session.go

@@ -703,21 +703,39 @@ func (session *ExchangeSession) FindPossibleSymbols() (symbols []string, err err
 	return symbols, nil
 }
 
+// newBasicPrivateExchange allocates a basic exchange instance with the user private credentials
+func (session *ExchangeSession) newBasicPrivateExchange(exchangeName types.ExchangeName) (types.Exchange, error) {
+	var err error
+	var exMinimal types.ExchangeMinimal
+	if session.Key != "" && session.Secret != "" {
+		exMinimal, err = exchange2.New(exchangeName, session.Key, session.Secret, session.Passphrase)
+	} else {
+		exMinimal, err = exchange2.NewWithEnvVarPrefix(exchangeName, session.EnvVarPrefix)
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	if ex, ok := exMinimal.(types.Exchange); ok {
+		return ex, nil
+	}
+
+	return nil, fmt.Errorf("exchange %T does not implement types.Exchange", exMinimal)
+}
+
 // InitExchange initialize the exchange instance and allocate memory for fields
 // In this stage, the session var could be loaded from the JSON config, so the pointer fields are still nil
 // The Init method will be called after this stage, environment.Init will call the session.Init method later.
 func (session *ExchangeSession) InitExchange(name string, ex types.Exchange) error {
 	var err error
 	var exchangeName = session.ExchangeName
+
 	if ex == nil {
 		if session.PublicOnly {
 			ex, err = exchange2.NewPublic(exchangeName)
 		} else {
-			if session.Key != "" && session.Secret != "" {
-				ex, err = exchange2.New(exchangeName, session.Key, session.Secret, session.Passphrase)
-			} else {
-				ex, err = exchange2.NewWithEnvVarPrefix(exchangeName, session.EnvVarPrefix)
-			}
+			ex, err = session.newBasicPrivateExchange(exchangeName)
 		}
 	}
 

pkg/exchange/factory.go

@@ -6,6 +6,7 @@ import (
 	"strings"
 
 	"github.com/c9s/bbgo/pkg/exchange/binance"
+	"github.com/c9s/bbgo/pkg/exchange/bitget"
 	"github.com/c9s/bbgo/pkg/exchange/kucoin"
 	"github.com/c9s/bbgo/pkg/exchange/max"
 	"github.com/c9s/bbgo/pkg/exchange/okex"
@@ -13,10 +14,19 @@ import (
 )
 
 func NewPublic(exchangeName types.ExchangeName) (types.Exchange, error) {
-	return New(exchangeName, "", "", "")
+	exMinimal, err := New(exchangeName, "", "", "")
+	if err != nil {
+		return nil, err
+	}
+
+	if ex, ok := exMinimal.(types.Exchange); ok {
+		return ex, nil
+	}
+
+	return nil, fmt.Errorf("exchange %T does not implement types.Exchange", exMinimal)
 }
 
-func New(n types.ExchangeName, key, secret, passphrase string) (types.Exchange, error) {
+func New(n types.ExchangeName, key, secret, passphrase string) (types.ExchangeMinimal, error) {
 	switch n {
 
 	case types.ExchangeBinance:
@@ -31,8 +41,8 @@ func New(n types.ExchangeName, key, secret, passphrase string) (types.Exchange,
 	case types.ExchangeKucoin:
 		return kucoin.New(key, secret, passphrase), nil
 
-	// case types.ExchangeBitget:
-	// 	return bitget.New(key, secret, passphrase), nil
+	case types.ExchangeBitget:
+		return bitget.New(key, secret, passphrase), nil
 
 	default:
 		return nil, fmt.Errorf("unsupported exchange: %v", n)
@@ -42,7 +52,7 @@ func New(n types.ExchangeName, key, secret, passphrase string) (types.Exchange,
 
 // NewWithEnvVarPrefix allocate and initialize the exchange instance with the given environment variable prefix
 // When the varPrefix is a empty string, the default exchange name will be used as the prefix
-func NewWithEnvVarPrefix(n types.ExchangeName, varPrefix string) (types.Exchange, error) {
+func NewWithEnvVarPrefix(n types.ExchangeName, varPrefix string) (types.ExchangeMinimal, error) {
 	if len(varPrefix) == 0 {
 		varPrefix = n.String()
 	}

pkg/types/exchange.go

@@ -81,6 +81,9 @@ type Exchange interface {
 	ExchangeTradeService
 }
 
+// ExchangeBasic is the new type for replacing the original Exchange interface
+type ExchangeBasic = Exchange
+
 // ExchangeOrderQueryService provides an interface for querying the order status via order ID or client order ID
 //
 //go:generate mockgen -destination=mocks/mock_exchange_order_query.go -package=mocks . ExchangeOrderQueryService