utils: BigInt implements UnmarshalJSON and MarshalJSON. Unittests inc…

…luded for peace of mind, although code does not actually do much.

utils/utils.go

@@ -2,6 +2,7 @@ package utils
 
 import (
 	"bufio"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"math/big"
@@ -157,3 +158,21 @@ func (b *BigInt) validate() error {
 	}
 	return nil
 }
+
+// UnmarshalJSON implements encoding/json/RawMessage.UnmarshalJSON
+func (b *BigInt) UnmarshalJSON(data []byte) error {
+	err := json.Unmarshal(data, &b.Int)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// MarshalJSON calls json.Marshal() on the BigInt.Int field.
+func (b *BigInt) MarshalJSON() ([]byte, error) {
+	if b == nil {
+		return []byte("null"), nil
+	}
+	return json.Marshal(b.Int)
+}

utils/utils_test.go

@@ -2,12 +2,29 @@ package utils
 
 import (
 	"errors"
+	"fmt"
 	"math"
 	"math/big"
 	"reflect"
 	"testing"
 )
 
+func TestBigInt(t *testing.T) {
+	realBig := big.Int{}
+	realBig.SetUint64(math.MaxUint64)
+	result := big.Int{}
+	fmt.Println(realBig, result)
+	fmt.Println(result.Add(&realBig, big.NewInt(10)))
+
+	var customBig = BigInt{&big.Int{}}
+	customBig.SetUint64(math.MaxUint64)
+	fmt.Println(customBig)
+
+	var resultBig = BigInt{&big.Int{}}
+	resultBig.Add(customBig.Int, big.NewInt(1000))
+	fmt.Println(resultBig)
+}
+
 func TestValidate(t *testing.T) {
 	var amount = BigInt{&big.Int{}}
 	var tests = []struct {
@@ -29,3 +46,35 @@ func TestValidate(t *testing.T) {
 		}
 	}
 }
+
+func TestUnmarshalJSON(t *testing.T) {
+	maxuint64AsString := []byte("18446744073709551615")
+	maxuint64AsBigInt := BigInt{&big.Int{}}
+	maxuint64AsBigInt.SetString("18446744073709551615", 10)
+
+	overuint64AsString := []byte("28446744073709551615")
+	overuint64AsBigInt := BigInt{&big.Int{}}
+	overuint64AsBigInt.SetString("28446744073709551615", 10)
+
+	negBigIntAsString := []byte("-1")
+	negBigIntAsBigInt := BigInt{&big.Int{}}
+	negBigIntAsBigInt.SetString("-1", 10)
+
+	var amount = BigInt{&big.Int{}}
+	var tests = []struct {
+		input    []byte
+		expected BigInt
+	}{
+		{[]byte("0"), BigInt{&big.Int{}}},
+		{maxuint64AsString, maxuint64AsBigInt},
+		{overuint64AsString, overuint64AsBigInt},
+		{negBigIntAsString, negBigIntAsBigInt},
+	}
+
+	for _, test := range tests {
+		amount.UnmarshalJSON(test.input)
+		if amount.Cmp(test.expected.Int) != 0 {
+			t.Errorf("Test Failed: %v inputted, %v expected, %#v received", test.input, test.expected, amount)
+		}
+	}
+}