support --period

cmd/cli/flag.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"strings"
+	"time"
 )
 
 type FlagStringArray []string
@@ -33,3 +34,35 @@ func (fileList *FileList) Set(s string) error {
 	}
 	return (*FlagStringArray)(fileList).Set(s)
 }
+
+type Period struct {
+	Start time.Time
+	Stop  time.Time
+}
+
+func (period Period) Empty() bool {
+	return period.Stop.Sub(period.Start) == 0
+}
+
+func (period *Period) String() string {
+	return fmt.Sprintf("%s..%s", period.Start, period.Stop)
+}
+
+func (period *Period) Set(s string) error {
+	if result, err := time.Parse("2006", s); err == nil {
+		period.Start = result
+		period.Stop = result.AddDate(1, 0, 0).Add(-1 * time.Minute)
+		return nil
+	}
+	if result, err := time.Parse("2006-01", s); err == nil {
+		period.Start = result
+		period.Stop = result.AddDate(0, 1, 0).Add(-1 * time.Minute)
+		return nil
+	}
+	if result, err := time.Parse("2006-01-02", s); err == nil {
+		period.Start = result
+		period.Stop = result.AddDate(0, 0, 1).Add(-1 * time.Minute)
+		return nil
+	}
+	return fmt.Errorf("unimplemented format: %s", s)
+}