refactor: reduce code duplication in exchange clients

client/base.go

@@ -0,0 +1,20 @@
+package client
+
+import (
+	"fmt"
+	"time"
+)
+
+type BaseClient struct {
+	AccessKey string
+	ApiSecret string
+	nonce     int64
+}
+
+func (c *BaseClient) GetNonce() string {
+	if c.nonce == 0 {
+		c.nonce = time.Now().Unix()
+	}
+	c.nonce++
+	return fmt.Sprintf("%d", c.nonce)
+}

client/bitbank/bitbank.go

@@ -7,38 +7,26 @@ import (
 	"log"
 	"net/http"
 	"strconv"
-	"time"
 
+	"github.com/pomadev/dollar-cost-averaging-bot/client"
 	"github.com/pomadev/dollar-cost-averaging-bot/client/common"
 )
 
 const (
 	PUBLIC_API_URL  = "https://public.bitbank.cc"
 	PRIVATE_API_URL = "https://api.bitbank.cc/v1"
-	BTC_JPY         = "btc_jpy"
-	ETH_JPY         = "eth_jpy"
 )
 
 type BitbankClient struct {
-	AccessKey string
-	ApiSecret string
-	nonce     int64
-}
-
-func (c *BitbankClient) getNonce() string {
-	if c.nonce == 0 {
-		c.nonce = time.Now().Unix()
-	}
-	c.nonce++
-	return fmt.Sprintf("%d", c.nonce)
+	client.BaseClient
 }
 
 func (c *BitbankClient) OrderBTC(yen int64) (string, string, error) {
-	return c.order(BTC_JPY, yen)
+	return c.order(string(client.BTCJPY), yen)
 }
 
 func (c *BitbankClient) OrderETH(yen int64) (string, string, error) {
-	return c.order(ETH_JPY, yen)
+	return c.order(string(client.ETHJPY), yen)
 }
 
 type orderRequest struct {
@@ -79,7 +67,7 @@ func (c *BitbankClient) order(pair string, yen int64) (string, string, error) {
 	if err != nil {
 		return "", "", fmt.Errorf("Failed to create request: %s", err)
 	}
-	nonce := c.getNonce()
+	nonce := c.GetNonce()
 	req.Header.Set("ACCESS-KEY", c.AccessKey)
 	req.Header.Set("ACCESS-NONCE", nonce)
 	req.Header.Set("ACCESS-SIGNATURE", common.MakeSign(nonce+string(requestBodyJson), c.ApiSecret))

client/bitflyer/bitflyer.go

@@ -6,37 +6,25 @@ import (
 	"fmt"
 	"log"
 	"net/http"
-	"time"
 
+	"github.com/pomadev/dollar-cost-averaging-bot/client"
 	"github.com/pomadev/dollar-cost-averaging-bot/client/common"
 )
 
 const (
 	API_URL = "https://api.bitflyer.com/v1/"
-	BTC_JPY = "BTC_JPY"
-	ETH_JPY = "ETH_JPY"
 )
 
 type BitflyerClient struct {
-	AccessKey string
-	ApiSecret string
-	nonce     int64
-}
-
-func (c *BitflyerClient) getNonce() string {
-	if c.nonce == 0 {
-		c.nonce = time.Now().Unix()
-	}
-	c.nonce++
-	return fmt.Sprintf("%d", c.nonce)
+	client.BaseClient
 }
 
 func (c *BitflyerClient) OrderBTC(yen int64) (string, string, error) {
-	return c.order(BTC_JPY, yen)
+	return c.order("BTC_JPY", yen)
 }
 
 func (c *BitflyerClient) OrderETH(yen int64) (string, string, error) {
-	return c.order(ETH_JPY, yen)
+	return c.order("ETH_JPY", yen)
 }
 
 type orderRequest struct {
@@ -56,9 +44,9 @@ func (c *BitflyerClient) order(pair string, yen int64) (string, string, error) {
 		return "", "", fmt.Errorf("Failed to get price: %s", err)
 	}
 	var amount float64
-	if pair == BTC_JPY {
+	if pair == "BTC_JPY" {
 		amount = common.CalcAmount(price, yen, 1000)
-	} else if pair == ETH_JPY {
+	} else if pair == "ETH_JPY" {
 		amount = common.CalcAmount(price, yen, 100)
 	} else {
 		amount = 0
@@ -81,7 +69,7 @@ func (c *BitflyerClient) order(pair string, yen int64) (string, string, error) {
 	if err != nil {
 		return "", "", fmt.Errorf("Failed to create request: %s", err)
 	}
-	nonce := c.getNonce()
+	nonce := c.GetNonce()
 	req.Header.Set("ACCESS-KEY", c.AccessKey)
 	req.Header.Set("ACCESS-TIMESTAMP", nonce)
 	req.Header.Set("ACCESS-SIGN", common.MakeSign(nonce+"POST"+"/v1/me/sendchildorder"+string(requestBodyJson), c.ApiSecret))

client/client.go

@@ -8,12 +8,19 @@ import (
 	"github.com/pomadev/dollar-cost-averaging-bot/client/bitflyer"
 )
 
-type client interface {
+type Client interface {
 	OrderBTC(int64) (string, string, error)
 	OrderETH(int64) (string, string, error)
 }
 
-func CreateClient(exchange string) (client, error) {
+type Pair string
+
+const (
+	BTCJPY Pair = "btc_jpy"
+	ETHJPY Pair = "eth_jpy"
+)
+
+func CreateClient(exchange string) (Client, error) {
 	accessKey := os.Getenv("ACCESS_KEY")
 	apiSecret := os.Getenv("API_SECRET")
 	if accessKey == "" || apiSecret == "" {
@@ -22,9 +29,9 @@ func CreateClient(exchange string) (client, error) {
 
 	switch exchange {
 	case "bitbank":
-		return &bitbank.BitbankClient{AccessKey: accessKey, ApiSecret: apiSecret}, nil
+		return &bitbank.BitbankClient{BaseClient: BaseClient{AccessKey: accessKey, ApiSecret: apiSecret}}, nil
 	case "bitflyer":
-		return &bitflyer.BitflyerClient{AccessKey: accessKey, ApiSecret: apiSecret}, nil
+		return &bitflyer.BitflyerClient{BaseClient: BaseClient{AccessKey: accessKey, ApiSecret: apiSecret}}, nil
 	default:
 		return nil, fmt.Errorf("Unknown exchange: %s", exchange)
 	}

client/common/http.go

@@ -0,0 +1,40 @@
+package common
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"net/http"
+)
+
+func DoJSONRequest(method, url string, headers map[string]string, body interface{}) (*http.Response, error) {
+	var requestBody []byte
+	var err error
+	if body != nil {
+		requestBody, err = json.Marshal(body)
+		if err != nil {
+			return nil, fmt.Errorf("failed to marshal request body: %w", err)
+		}
+	}
+
+	req, err := http.NewRequest(method, url, bytes.NewReader(requestBody))
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+
+	for key, value := range headers {
+		req.Header.Set(key, value)
+	}
+
+	if body != nil && req.Header.Get("Content-Type") == "" {
+		req.Header.Set("Content-Type", "application/json")
+	}
+
+	client := &http.Client{}
+	return client.Do(req)
+}
+
+func DecodeJSONResponse(resp *http.Response, target interface{}) error {
+	defer resp.Body.Close()
+	return json.NewDecoder(resp.Body).Decode(target)
+}