Add JSON unmarshallers for numeric types from util (#83)

Uint160, Uint256, Fixed8 now have UnmarshalJSON method.

pkg/util/fixed8_test.go

@@ -1,6 +1,7 @@
 package util
 
 import (
+	"encoding/json"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -18,7 +19,7 @@ func TestNewFixed8(t *testing.T) {
 func TestFixed8DecodeString(t *testing.T) {
 	// Fixed8DecodeString works correctly with integers
 	ivalues := []string{"9000", "100000000", "5", "10945"}
-	for _, val:= range ivalues {
+	for _, val := range ivalues {
 		n, err := Fixed8DecodeString(val)
 		assert.Nil(t, err)
 		assert.Equal(t, val, n.String())
@@ -36,3 +37,21 @@ func TestFixed8DecodeString(t *testing.T) {
 	assert.Nil(t, err)
 	assert.Equal(t, Fixed8(90123410000), n)
 }
+
+func TestFixed8UnmarshalJSON(t *testing.T) {
+	fl := float64(123.45)
+	str := "123.45"
+	expected, _ := Fixed8DecodeString(str)
+
+	// UnmarshalJSON should decode floats
+	var u1 Fixed8
+	s, _ := json.Marshal(fl)
+	assert.Nil(t, json.Unmarshal(s, &u1))
+	assert.Equal(t, expected, u1)
+
+	// UnmarshalJSON should decode strings
+	var u2 Fixed8
+	s, _ = json.Marshal(str)
+	assert.Nil(t, json.Unmarshal(s, &u2))
+	assert.Equal(t, expected, u2)
+}