fix json marshal/unmarshal (#143)

common/public_key.go

@@ -4,6 +4,7 @@ import (
 	"crypto/sha256"
 	"encoding/json"
 	"errors"
+	"fmt"
 
 	"filippo.io/edwards25519"
 	"github.com/mr-tron/base58"
@@ -66,10 +67,30 @@ func (p PublicKey) Bytes() []byte {
 	return p[:]
 }
 
-func (p *PublicKey) MarshalJSON() ([]byte, error) {
+func (p PublicKey) MarshalJSON() ([]byte, error) {
 	return json.Marshal(p.ToBase58())
 }
 
+func (p *PublicKey) UnmarshalJSON(data []byte) error {
+	var s string
+	err := json.Unmarshal(data, &s)
+	if err != nil {
+		return err
+	}
+
+	b, err := base58.Decode(s)
+	if err != nil {
+		return err
+	}
+	if len(b) != 32 {
+		return fmt.Errorf("a valid pubkey should be a 32-byte array. got: %v", len(b))
+	}
+
+	*p = PublicKeyFromString(s)
+
+	return nil
+}
+
 func IsOnCurve(p PublicKey) bool {
 	_, err := new(edwards25519.Point).SetBytes(p.Bytes())
 	return err == nil

common/public_key_test.go

@@ -1,9 +1,12 @@
 package common
 
 import (
+	"encoding/json"
 	"errors"
 	"reflect"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestPublicKeyFromBytes(t *testing.T) {
@@ -238,3 +241,30 @@ func TestIsOnCurve(t *testing.T) {
 		})
 	}
 }
+
+func TestPublicKey_JSON(t *testing.T) {
+	type A struct {
+		P PublicKey `json:"pubkey"`
+	}
+
+	a1 := A{
+		P: PublicKeyFromString("EvN4kgKmCmYzdbd5kL8Q8YgkUW5RoqMTpBczrfLExtx7"),
+	}
+	b, err := json.Marshal(a1)
+	assert.Nil(t, err)
+	assert.Equal(t, `{"pubkey":"EvN4kgKmCmYzdbd5kL8Q8YgkUW5RoqMTpBczrfLExtx7"}`, string(b))
+
+	var a2 A
+	err = json.Unmarshal(b, &a2)
+	assert.Nil(t, err)
+
+	assert.Equal(t, a1, a2)
+
+	var a3 A
+	err = json.Unmarshal([]byte(`{"pubkey":"0"}`), &a3)
+	assert.Equal(t, err, errors.New("invalid base58 digit ('0')"))
+
+	var a4 A
+	err = json.Unmarshal([]byte(`{"pubkey":"EvN4kgKmCmYzdbd5kL8Q8YgkUW5RoqMTpBczrfLExtx123"}`), &a4)
+	assert.Equal(t, err, errors.New("a valid pubkey should be a 32-byte array. got: 34"))
+}