private/currency: add strictcsv support to microunit

Change-Id: Iad2f6a07f189f2faa1d13bdb82dfa320921f6938

private/currency/microunit.go

@@ -5,6 +5,7 @@ package currency
 
 import (
 	"math"
+	"strconv"
 
 	"github.com/shopspring/decimal"
 	"github.com/zeebo/errs"
@@ -59,3 +60,16 @@ func MicroUnitFromDecimal(d decimal.Decimal) (MicroUnit, error) {
 	}
 	return MicroUnit{v: m.IntPart()}, nil
 }
+
+// MarshalCSV does the custom marshaling of MicroUnits.
+func (m MicroUnit) MarshalCSV() (string, error) { return strconv.FormatInt(m.v, 10), nil }
+
+// UnmarshalCSV reads the MicroUnit in CSV form.
+func (m *MicroUnit) UnmarshalCSV(s string) (err error) {
+	v, err := strconv.ParseInt(s, 10, 64)
+	if err != nil {
+		return err
+	}
+	m.v = v
+	return nil
+}

private/currency/microunit_test.go

@@ -7,6 +7,8 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/require"
+
+	"storj.io/common/strictcsv"
 )
 
 func TestMicroUnitToFloatString(t *testing.T) {
@@ -18,3 +20,21 @@ func TestMicroUnitFromFloatString(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, NewMicroUnit(12340), m)
 }
+
+func TestMicroUnitCSV(t *testing.T) {
+	type row struct {
+		Foo MicroUnit `csv:"foo"`
+		Bar MicroUnit `csv:"bar"`
+	}
+	exp := row{
+		Foo: NewMicroUnit(1),
+		Bar: NewMicroUnit(2),
+	}
+
+	csv, err := strictcsv.MarshalString(exp)
+	require.NoError(t, err)
+
+	var got row
+	require.NoError(t, strictcsv.UnmarshalString(csv, &got))
+	require.Equal(t, exp, got)
+}