add Strftime method and Strptime function

README.md

@@ -91,6 +91,8 @@ If you have a feature request, please open an issue. It would be great if you co
 - [Advance](https://pkg.go.dev/github.com/Code-Hex/synchro#Time.Advance)
   - `Advance` allows you to specify the date and time components you want to increment and make modifications.
 - [Period](https://pkg.go.dev/github.com/Code-Hex/synchro#Period)
+- [Strptime](https://pkg.go.dev/github.com/Code-Hex/synchro#Strptime)
+- [Strftime](https://pkg.go.dev/github.com/Code-Hex/synchro#Time.Strftime)
 
 
 ## TODO

go.mod

@@ -3,3 +3,5 @@ module github.com/Code-Hex/synchro
 go 1.20.0
 
 require github.com/google/go-cmp v0.5.9
+
+require github.com/itchyny/timefmt-go v0.1.5

go.sum

@@ -1,2 +1,4 @@
 github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
 github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/itchyny/timefmt-go v0.1.5 h1:G0INE2la8S6ru/ZI5JecgyzbbJNs5lG1RcBqa7Jm6GE=
+github.com/itchyny/timefmt-go v0.1.5/go.mod h1:nEP7L+2YmAbT2kZ2HfSs1d8Xtw9LY8D2stDBckWakZ8=

time.go

@@ -3,6 +3,8 @@ package synchro
 import (
 	"math"
 	"time"
+
+	"github.com/itchyny/timefmt-go"
 )
 
 type empty[T TimeZone] struct{}
@@ -108,3 +110,115 @@ func (t Time[T]) DiffInCalendarDays(u Time[T]) int {
 	u1 := u.Truncate(day)
 	return int(math.Ceil(float64(t1.Sub(u1)) / float64(day)))
 }
+
+// Strftime formats the time according to the given format string.
+//
+// This method is a wrapper for the [github.com/itchyny/timefmt-go] library.
+//
+// Example:
+//   - %Y-%m-%d %H:%M:%S => 2023-09-02 14:09:56
+//   - %a, %d %b %Y %T %z => Sat, 02 Sep 2023 14:09:56 +0900
+//
+// The format string should follow the format of [strftime(3)] in man pages.
+// The following list shows the supported format specifiers:
+//   - %a: Abbreviated weekday name (Sun)
+//   - %A: Full weekday name (Sunday)
+//   - %b: Abbreviated month name (Jan)
+//   - %B: Full month name (January)
+//   - %c: Date and time representation
+//   - %C: Year divided by 100 (00-99)
+//   - %d: Day of the month (01-31)
+//   - %D: Short MM/DD/YY date, equivalent to %m/%d/%y
+//   - %e: Day of the month, with a space preceding single digits ( 1-31)
+//   - %F: Equivalent to %Y-%m-%d (the ISO 8601 date format)
+//   - %g: Week-based year, last two digits (00-99)
+//   - %G: Week-based year
+//   - %h: Abbreviated month name (Jan)
+//   - %H: Hour in 24h format (00-23)
+//   - %I: Hour in 12h format (01-12)
+//   - %j: Day of the year (001-366)
+//   - %m: Month as a decimal number (01-12)
+//   - %M: Minute (00-59)
+//   - %n: New-line character
+//   - %p: AM or PM designation
+//   - %P: am or pm designation
+//   - %r: 12-hour clock time
+//   - %R: 24-hour HH:MM time, equivalent to %H:%M
+//   - %S: Second (00-59)
+//   - %t: Horizontal-tab character
+//   - %T: 24-hour clock time, equivalent to %H:%M:%S
+//   - %u: ISO 8601 weekday as number with Monday as 1 (1-7)
+//   - %U: Week number with the first Sunday as the first day of week (00-53)
+//   - %V: ISO 8601 week number (01-53)
+//   - %w: Weekday as a decimal number with Sunday as 0 (0-6)
+//   - %W: Week number with the first Monday as the first day of week (00-53)
+//   - %x: Date representation
+//   - %X: Time representation
+//   - %y: Year, last two digits (00-99)
+//   - %Y: Year
+//   - %z: ISO 8601 offset from UTC in timezone (+HHMM)
+//   - %Z: Timezone name or abbreviation
+//   - %+: Extended date and time representation
+//   - %::z: Colon-separated offset from UTC in timezone (e.g. +05:00)
+//   - %:::z: Like %::z, but with optional seconds
+//
+// [strftime(3)]: https://linux.die.net/man/3/strftime
+// [github.com/itchyny/timefmt-go]: https://github.com/itchyny/timefmt-go
+func (t Time[T]) Strftime(format string) string {
+	return timefmt.Format(t.StdTime(), format)
+}
+
+// Strptime parses time string with the default location.
+// The location is also used to parse the time zone name (%Z).
+//
+// The format string should follow the format of [strptime(3)] in man pages.
+// The following list shows the supported format specifiers:
+//   - %a: abbreviated weekday name
+//   - %A: full weekday name
+//   - %b: abbreviated month name
+//   - %B: full month name
+//   - %c: preferred date and time representation
+//   - %C: century number (00-99)
+//   - %d: day of the month (01-31)
+//   - %D: same as %m/%d/%y
+//   - %e: day of the month (1-31)
+//   - %F: same as %Y-%m-%d
+//   - %g: last two digits of the year (00-99)
+//   - %G: year as a 4-digit number
+//   - %h: same as %b
+//   - %H: hour (00-23)
+//   - %I: hour (01-12)
+//   - %j: day of the year (001-366)
+//   - %m: month (01-12)
+//   - %M: minute (00-59)
+//   - %n: newline character
+//   - %p: either "am" or "pm" according to the given time value
+//   - %r: time in a.m. and p.m. notation
+//   - %R: time in 24 hour notation
+//   - %S: second (00-60)
+//   - %t: tab character
+//   - %T: current time, equal to %H:%M:%S
+//   - %u: weekday as a number (1-7)
+//   - %U: week number of the current year, starting with the first Sunday as the first day of the first week
+//   - %V: week number of the current year, starting with the first week that has at least 4 days in the new year
+//   - %w: day of the week as a decimal, Sunday being 0
+//   - %W: week number of the current year, starting with the first Monday as the first day of the first week
+//   - %x: preferred date representation without the time
+//   - %X: preferred time representation without the date
+//   - %y: year without a century (00-99)
+//   - %Y: year with century
+//   - %z: time zone offset, such as "-0700"
+//   - %Z: time zone name, such as "UTC" or "GMT"
+//
+// This is a wrapper for the [github.com/itchyny/timefmt-go] library.
+//
+// [strptime(3)]: https://linux.die.net/man/3/strptime
+// [github.com/itchyny/timefmt-go]: https://github.com/itchyny/timefmt-go
+func Strptime[T TimeZone](source string, format string) (Time[T], error) {
+	var tz T
+	tm, err := timefmt.ParseInLocation(source, format, tz.Location())
+	if err != nil {
+		return Time[T]{}, err
+	}
+	return In[T](tm), nil
+}

time_test.go

@@ -614,3 +614,23 @@ func TestDiffInCalendarDays(t *testing.T) {
 		})
 	}
 }
+
+func ExampleTime_Strftime() {
+	t := synchro.New[tz.AsiaTokyo](2023, 9, 2, 14, 9, 56, 0)
+	fmt.Println(t.Strftime("%Y-%m-%d %H:%M:%S"))
+	fmt.Println(t.Strftime("%a, %d %b %Y %T %z"))
+	// Output:
+	// 2023-09-02 14:09:56
+	// Sat, 02 Sep 2023 14:09:56 +0900
+}
+
+func ExampleStrptime() {
+	t, _ := synchro.Strptime[tz.AsiaTokyo]("2023-09-02 14:09:56", "%Y-%m-%d %H:%M:%S")
+	fmt.Println(t)
+
+	_, err := synchro.Strptime[tz.UTC]("invalid", "%Y")
+	fmt.Println("error", err) // Returns an error as the layout is not a valid time value
+	// Output:
+	// 2023-09-02 14:09:56 +0900 JST
+	// error failed to parse "invalid" with "%Y": cannot parse %Y
+}