xdr: Add a custom marshaller for claim predicate timestamp

xdr/json.go

@@ -3,15 +3,62 @@ package xdr
 import (
 	"encoding/json"
 	"fmt"
+	"regexp"
+	"strconv"
 	"time"
+
+	"github.com/stellar/go/support/errors"
 )
 
+// ISO8601Time is a timestamp which supports parsing dates which have a year outside the 0000..9999 range
+type ISO8601Time struct {
+	time.Time
+}
+
+// reISO8601 is the regular expression used to parse date strings in the
+// ISO 8601 extended format, with or without an expanded year representation.
+var reISO8601 = regexp.MustCompile(`^([-+]?\d{4,})-(\d{2})-(\d{2})`)
+
+// MarshalJSON serializes the timestamp to a string
+func (t ISO8601Time) MarshalJSON() ([]byte, error) {
+	return []byte(fmt.Sprintf(`"%s"`, t.Format(time.RFC3339))), nil
+}
+
+// UnmarshalJSON parses a JSON string into a ISO8601Time instance.
+func (t *ISO8601Time) UnmarshalJSON(b []byte) error {
+	if string(b) == "null" {
+		return nil
+	}
+	if b[0] != '"' || b[len(b)-1] != '"' {
+		return fmt.Errorf("%s does not begin and end with double quotes", b)
+	}
+	trimmed := string(b[1 : len(b)-1])
+	m := reISO8601.FindStringSubmatch(trimmed)
+
+	if len(m) != 4 {
+		return fmt.Errorf("UnmarshalJSON: cannot parse %s", trimmed)
+	}
+	// No need to check for errors since the regexp guarantees the matches
+	// are valid integers
+	year, _ := strconv.Atoi(m[1])
+	month, _ := strconv.Atoi(m[2])
+	day, _ := strconv.Atoi(m[3])
+
+	ts, err := time.Parse(time.RFC3339, "2006-01-02"+trimmed[len(m[0]):])
+	if err != nil {
+		return errors.Wrap(err, "Could not extract time")
+	}
+
+	t.Time = time.Date(year, time.Month(month), day, ts.Hour(), ts.Minute(), ts.Second(), ts.Nanosecond(), ts.Location())
+	return nil
+}
+
 type claimPredicateJSON struct {
 	And           *[]claimPredicateJSON `json:"and,omitempty"`
 	Or            *[]claimPredicateJSON `json:"or,omitempty"`
 	Not           *claimPredicateJSON   `json:"not,omitempty"`
 	Unconditional bool                  `json:"unconditional,omitempty"`
-	AbsBefore     *time.Time            `json:"abs_before,omitempty"`
+	AbsBefore     *ISO8601Time          `json:"abs_before,omitempty"`
 	RelBefore     *int64                `json:"rel_before,string,omitempty"`
 }
 
@@ -98,8 +145,8 @@ func (c ClaimPredicate) toJSON() (claimPredicateJSON, error) {
 		payload.Not = new(claimPredicateJSON)
 		*payload.Not, err = c.MustNotPredicate().toJSON()
 	case ClaimPredicateTypeClaimPredicateBeforeAbsoluteTime:
-		payload.AbsBefore = new(time.Time)
-		*payload.AbsBefore = time.Unix(int64(c.MustAbsBefore()), 0).UTC()
+		payload.AbsBefore = new(ISO8601Time)
+		*payload.AbsBefore = ISO8601Time{time.Unix(int64(c.MustAbsBefore()), 0).UTC()}
 	case ClaimPredicateTypeClaimPredicateBeforeRelativeTime:
 		payload.RelBefore = new(int64)
 		*payload.RelBefore = int64(c.MustRelBefore())

xdr/json_test.go

@@ -2,6 +2,7 @@ package xdr
 
 import (
 	"encoding/json"
+	"math"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -57,3 +58,47 @@ func TestClaimPredicateJSON(t *testing.T) {
 
 	assert.Equal(t, serializedBase64, parsedBase64)
 }
+
+func TestAbsBeforeTimestamps(t *testing.T) {
+	const year = 365 * 24 * 60 * 60
+	for _, testCase := range []struct {
+		unix     int64
+		expected string
+	}{
+		{
+			0,
+			`{"abs_before":"1970-01-01T00:00:00Z"}`,
+		},
+		{
+			900 * year,
+			`{"abs_before":"2869-05-27T00:00:00Z"}`,
+		},
+		{
+			math.MaxInt64,
+			`{"abs_before":"292277026596-12-04T15:30:07Z"}`,
+		},
+		{
+			-10,
+			`{"abs_before":"1969-12-31T23:59:50Z"}`,
+		},
+		{
+			math.MinInt64,
+			// this serialization doesn't make sense but at least it doesn't crash the marshaller
+			`{"abs_before":"292277026596-12-04T15:30:08Z"}`,
+		},
+	} {
+		xdrSec := Int64(testCase.unix)
+		source := ClaimPredicate{
+			Type:      ClaimPredicateTypeClaimPredicateBeforeAbsoluteTime,
+			AbsBefore: &xdrSec,
+		}
+
+		serialized, err := json.Marshal(source)
+		assert.NoError(t, err)
+		assert.JSONEq(t, testCase.expected, string(serialized))
+
+		var parsed ClaimPredicate
+		assert.NoError(t, json.Unmarshal(serialized, &parsed))
+		assert.Equal(t, *parsed.AbsBefore, *source.AbsBefore)
+	}
+}