Add currency translation mapping

For example BTC is also XBT

currency/translation/translation.go

@@ -0,0 +1,32 @@
+package translation
+
+import (
+	"errors"
+
+	"github.com/thrasher-/gocryptotrader/currency/pair"
+)
+
+var translations = map[pair.CurrencyItem]pair.CurrencyItem{
+	"BTC":  "XBT",
+	"DOGE": "XDG",
+	"USD":  "USDT",
+}
+
+// GetTranslation returns similar strings for a particular currency
+func GetTranslation(currency pair.CurrencyItem) (pair.CurrencyItem, error) {
+	result, ok := translations[currency]
+	if !ok {
+		return "", errors.New("no translation found for specified currency")
+	}
+
+	return result, nil
+}
+
+// HasTranslation returns whether or not a particular currency has a translation
+func HasTranslation(currency pair.CurrencyItem) bool {
+	_, ok := translations[currency]
+	if !ok {
+		return false
+	}
+	return true
+}

currency/translation/translation_test.go

@@ -0,0 +1,42 @@
+package translation
+
+import (
+	"testing"
+
+	"github.com/thrasher-/gocryptotrader/currency/pair"
+)
+
+func TestGetTranslation(t *testing.T) {
+	currencyPair := pair.NewCurrencyPair("BTC", "USD")
+	expected := pair.CurrencyItem("XBT")
+	actual, err := GetTranslation(currencyPair.FirstCurrency)
+	if err != nil {
+		t.Error("GetTranslation: failed to retrieve translation for BTC")
+	}
+
+	if expected != actual {
+		t.Error("GetTranslation: translation result was different to expected result")
+	}
+
+	currencyPair.FirstCurrency = "ETH"
+	_, err = GetTranslation(currencyPair.FirstCurrency)
+	if err == nil {
+		t.Error("GetTranslation: no error on non translatable currency")
+	}
+}
+
+func TestHasTranslation(t *testing.T) {
+	currencyPair := pair.NewCurrencyPair("BTC", "USD")
+	expected := true
+	actual := HasTranslation(currencyPair.FirstCurrency)
+	if expected != actual {
+		t.Error("HasTranslation: translation result was different to expected result")
+	}
+
+	currencyPair.FirstCurrency = "ETH"
+	expected = false
+	actual = HasTranslation(currencyPair.FirstCurrency)
+	if expected != actual {
+		t.Error("HasTranslation: translation result was different to expected result")
+	}
+}