add: (feat) balances query api

- add address utils
- return uint64 for balances instead of float

pkg/address/address.go

@@ -0,0 +1,45 @@
+package address
+
+import (
+	"encoding/hex"
+	"fmt"
+	"strconv"
+	"strings"
+
+	"golang.org/x/crypto/sha3"
+)
+
+func SarafuAddress(address string) (string, error) {
+	l := len(address)
+
+	if l < 40 || l > 42 {
+		return "", fmt.Errorf("%s is not a valid eth address", address)
+	}
+
+	if len(address) == 42 {
+		return strings.ToLower(address)[2:], nil
+	}
+
+	return strings.ToLower(address), nil
+}
+
+func Checksum(address string) string {
+	address = strings.ToLower(address)
+	address = strings.Replace(address, "0x", "", 1)
+
+	sha := sha3.NewLegacyKeccak256()
+	sha.Write([]byte(address))
+	hash := sha.Sum(nil)
+	hashstr := hex.EncodeToString(hash)
+	result := []string{"0x"}
+	for i, v := range address {
+		res, _ := strconv.ParseInt(string(hashstr[i]), 16, 64)
+		if res > 7 {
+			result = append(result, strings.ToUpper(string(v)))
+			continue
+		}
+		result = append(result, string(v))
+	}
+
+	return strings.Join(result, "")
+}