Support Kraken and use "github.com/buger/jsonparser" to save my life

README.md

@@ -16,7 +16,7 @@ Token-ticker (or `tt` for short) is a CLI tool for those who are both **Crypto i
 
  * Auto refresh on a specified interval, watch prices in live update mode
  * Proxy aware HTTP request, for easy access to blocked exchanges
- * Real-time prices from 11+ exchanges
+ * Real-time prices from 12+ exchanges
 
 ### Supported Exchanges
 
@@ -31,6 +31,7 @@ Token-ticker (or `tt` for short) is a CLI tool for those who are both **Crypto i
  * [HitBTC](https://hitbtc.com/)
  * [BigONE](https://big.one/)
  * [Poloniex](https://poloniex.com/)
+ * [Kraken](https://www.kraken.com/)
  * _still adding..._
 
 ### Installation

exchange/kraken.go

@@ -0,0 +1,150 @@
+package exchange
+
+import (
+	"errors"
+	"fmt"
+	"github.com/buger/jsonparser"
+	"github.com/sirupsen/logrus"
+	"io/ioutil"
+	"math"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// https://www.kraken.com/help/api
+const krakenBaseApi = "https://api.kraken.com/0/public/"
+
+type krakenClient struct {
+	exchangeBaseClient
+	AccessKey string
+	SecretKey string
+}
+
+func NewkrakenClient(httpClient *http.Client) *krakenClient {
+	return &krakenClient{exchangeBaseClient: *newExchangeBase(krakenBaseApi, httpClient)}
+}
+
+func (client *krakenClient) GetName() string {
+	return "Kraken"
+}
+
+/**
+Read response and check any potential errors
+*/
+func (client *krakenClient) readResponse(resp *http.Response) ([]byte, error) {
+	defer resp.Body.Close()
+	content, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	var errorMsg []string
+	jsonparser.ArrayEach(content, func(value []byte, dataType jsonparser.ValueType, offset int, err error) {
+		if dataType == jsonparser.String {
+			errorMsg = append(errorMsg, string(value))
+		}
+	}, "error")
+	if len(errorMsg) != 0 {
+		return nil, errors.New(strings.Join(errorMsg, ", "))
+	}
+
+	if resp.StatusCode != 200 {
+		return nil, errors.New(resp.Status)
+	}
+	return content, nil
+}
+
+func (client *krakenClient) GetKlinePrice(symbol string, since time.Time, interval int) (float64, error) {
+	symbolUpperCase := strings.ToUpper(symbol)
+	resp, err := client.httpGet("OHLC", map[string]string{
+		"pair":     symbolUpperCase,
+		"since":    strconv.FormatInt(since.Unix(), 10),
+		"interval": strconv.Itoa(interval),
+	})
+	if err != nil {
+		return 0, err
+	}
+
+	content, err := client.readResponse(resp)
+	if err != nil {
+		return 0, err
+	}
+	// jsonparser saved my life, no need to struggle with different/weird response types
+	klineBytes, dataType, _, err := jsonparser.Get(content, "result", symbolUpperCase, "[0]")
+	if err != nil {
+		return 0, err
+	}
+	if dataType != jsonparser.Array {
+		return 0, fmt.Errorf("kline should be an array, getting %s", dataType)
+	}
+
+	timestamp, err := jsonparser.GetInt(klineBytes, "[0]")
+	if err != nil {
+		return 0, err
+	}
+	openPrice, err := jsonparser.GetString(klineBytes, "[1]")
+	if err != nil {
+		return 0, err
+	}
+	logrus.Debugf("%s - Kline for %s uses open price at %s", client.GetName(), since.Local(),
+		time.Unix(timestamp, 0).Local())
+	return strconv.ParseFloat(openPrice, 64)
+}
+
+func (client *krakenClient) GetSymbolPrice(symbol string) (*SymbolPrice, error) {
+	resp, err := client.httpGet("Ticker", map[string]string{"pair": strings.ToUpper(symbol)})
+	if err != nil {
+		return nil, err
+	}
+
+	content, err := client.readResponse(resp)
+	if err != nil {
+		return nil, err
+	}
+
+	lastPriceString, err := jsonparser.GetString(content, "result", strings.ToUpper(symbol), "c", "[0]")
+	if err != nil {
+		return nil, err
+	}
+	lastPrice, err := strconv.ParseFloat(lastPriceString, 64)
+	if err != nil {
+		return nil, err
+	}
+
+	time.Sleep(time.Second) // API call rate limit
+	var (
+		now              = time.Now()
+		percentChange1h  = math.MaxFloat64
+		percentChange24h = math.MaxFloat64
+	)
+	price1hAgo, err := client.GetKlinePrice(symbol, now.Add(-61*time.Minute), 1)
+	if err != nil {
+		logrus.Warnf("%s - Failed to get price 1 hour ago, error: %v\n", client.GetName(), err)
+	} else if price1hAgo != 0 {
+		percentChange1h = (lastPrice - price1hAgo) / price1hAgo * 100
+	}
+	price24hAgo, err := client.GetKlinePrice(symbol, now.Add(-24*time.Hour), 5)
+	if err != nil {
+		logrus.Warnf("%s - Failed to get price 24 hours ago, error: %v\n", client.GetName(), err)
+	} else if price24hAgo != 0 {
+		percentChange24h = (lastPrice - price24hAgo) / price24hAgo * 100
+	}
+
+	return &SymbolPrice{
+		Symbol:           symbol,
+		Price:            lastPriceString,
+		UpdateAt:         time.Now(),
+		Source:           client.GetName(),
+		PercentChange1h:  percentChange1h,
+		PercentChange24h: percentChange24h,
+	}, nil
+}
+
+func init() {
+	register((&krakenClient{}).GetName(), func(client *http.Client) ExchangeClient {
+		// Limited by type system in Go, I hate wrapper/adapter
+		return NewkrakenClient(client)
+	})
+}

exchange/kraken_test.go

@@ -0,0 +1,48 @@
+package exchange
+
+import (
+	"net/http"
+	"testing"
+	"time"
+)
+
+func TestKrakenClient(t *testing.T) {
+
+	var client = NewkrakenClient(http.DefaultClient)
+
+	t.Run("GetKlinePrice", func(t *testing.T) {
+		_, err := client.GetKlinePrice("EOSETh", time.Now().Add(-61*time.Minute), 1)
+
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+	})
+
+	t.Run("GetKlinePrice of unknown symbol", func(t *testing.T) {
+		_, err := client.GetKlinePrice("fasfas", time.Now().Add(-61*time.Minute), 1)
+
+		if err == nil {
+			t.Fatalf("Expecting error when fetching unknown price, but get nil")
+		}
+		t.Logf("Returned error is `%v`, expected?", err)
+	})
+
+	t.Run("GetSymbolPrice", func(t *testing.T) {
+		sp, err := client.GetSymbolPrice("EOSETh")
+
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+		if sp.Price == "" {
+			t.Fatalf("Get an empty price?")
+		}
+	})
+
+	t.Run("GetUnexistSymbolPrice", func(t *testing.T) {
+		_, err := client.GetSymbolPrice("ABC123")
+
+		if err == nil {
+			t.Fatalf("Should throws on invalid symbol")
+		}
+	})
+}

glide.yaml

@@ -7,3 +7,4 @@ import:
 - package: github.com/spf13/pflag
 - package: github.com/fatih/color
   version: ~1.6.0
+- package: github.com/buger/jsonparser

token_ticker.example.yaml

@@ -65,4 +65,8 @@ exchanges:
 
 - name: Poloniex
   tokens:
-  - BTC_ETH
+  - BTC_ETH
+
+- name: Kraken
+  tokens:
+  - EOSETH