TimeRange: Parse duration with d/M/y unit (#1212)

* TimeRange: Parse duration with d/M/y unit

* clean up

* fix lint issue

backend/gtime/time_range.go

@@ -163,8 +163,8 @@ func (t parsableTime) parse() (time.Time, error) {
 	}
 
 	// Duration relative to current time.
-	if diff, err := time.ParseDuration("-" + t.time); err == nil {
-		return t.now.Add(diff), nil
+	if diff, err := ParseDuration(t.time); err == nil {
+		return t.now.Add(-diff), nil
 	}
 
 	// Advanced time string, mimics the frontend's datemath library.

backend/gtime/time_range_test.go

@@ -63,6 +63,21 @@ func TestTimeRange(t *testing.T) {
 		})
 	})
 
+	t.Run("Can parse from 7d", func(t *testing.T) {
+		tr := TimeRange{
+			From: "7d",
+			Now:  now,
+		}
+
+		t.Run("7d", func(t *testing.T) {
+			expected := now.Add(-7 * 24 * time.Hour)
+
+			res, err := tr.ParseFrom()
+			require.Nil(t, err)
+			require.Equal(t, expected.Unix(), res.Unix())
+		})
+	})
+
 	now, err := time.Parse(time.RFC3339Nano, "2020-03-26T15:12:56.000Z")
 	require.Nil(t, err)
 	t.Run("Can parse now-1M/M, now-1M/M", func(t *testing.T) {