can pass duration to period

cmd/cli/flag.go

@@ -3,6 +3,8 @@ package cli
 import (
 	"fmt"
 	"os"
+	"regexp"
+	"strconv"
 	"strings"
 	"time"
 )
@@ -63,21 +65,71 @@ func (period *Period) Set(s string) error {
 }
 
 func (period *Period) setStartStop(s string) error {
-	stop, err := period.setT(s, &period.Start)
+	stop, err := period.setT(time.Now(), s, &period.Start)
 	period.Stop = stop
 	return err
 }
 
 func (period *Period) setStop(s string) error {
-	_, err := period.setT(s, &period.Stop)
+	_, err := period.setT(time.Now(), s, &period.Stop)
 	return err
 }
 
-func (*Period) setT(s string, t *time.Time) (time.Time, error) {
+func (*Period) setT(now time.Time, s string, t *time.Time) (time.Time, error) {
 	if s == "" {
 		*t = time.Unix(0, 0)
 		return time.Now().AddDate(100, 0, 0), nil
 	}
+	if submatches := regexp.MustCompile(`[+-]?(?P<years>[0-9]+y)?(?P<months>[0-9]+mo)?(?P<weeks>[0-9]+w)?(?P<days>[0-9]+d)?([0-9]+[a-z])?`).FindStringSubmatch(s); len(submatches) > 0 {
+		s2 := s
+		result := now
+		scalar := time.Duration(1)
+		if strings.HasPrefix(s2, "-") {
+			scalar = -1
+		}
+
+		for i, submatch := range submatches[1 : len(submatches)-1] {
+			if len(submatch) == 0 {
+				continue
+			}
+
+			unit := submatch[len(submatch)-1]
+			if submatch[len(submatch)-1] == 'o' { // mo
+				submatch = submatch[:len(submatch)-1]
+			}
+
+			n, err := strconv.Atoi(submatch[:len(submatch)-1])
+			if err != nil {
+				return time.Time{}, err
+			}
+
+			for i := 0; i < n; i++ {
+				switch unit {
+				case 'y':
+					result = result.AddDate(int(scalar*1), 0, 0)
+				case 'o':
+					result = result.AddDate(0, int(scalar*1), 0)
+				case 'w':
+					result = result.AddDate(0, 0, int(scalar*7))
+				case 'd':
+					result = result.AddDate(0, 0, int(scalar*1))
+				}
+			}
+
+			s2 = strings.ReplaceAll(s2, submatches[i+1], "")
+		}
+
+		if stdDuration := strings.TrimLeft(s2, "+-"); stdDuration != "" {
+			if d, err := time.ParseDuration(stdDuration); err == nil {
+				result = result.Add(scalar * d)
+			}
+		}
+
+		if result != now {
+			*t = result
+			return result.AddDate(100, 0, 0), nil
+		}
+	}
 	if result, err := time.Parse("2006", s); err == nil {
 		*t = result
 		return result.AddDate(1, 0, 0).Add(-1 * time.Minute), nil