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ferret/pkg/stdlib/datetime/unit.go
2020-02-01 23:44:31 -05:00

114 lines
2.2 KiB
Go

package datetime
import (
"strings"
"time"
"github.com/pkg/errors"
)
// Unit specifies an unit of time (Millisecond, Second...).
type Unit int
const (
Millisecond Unit = iota
Second
Minute
Hour
Day
Week
Month
Year
)
var nanoseconds = []float64{
1e6,
1e9,
6e10,
36e11,
864e11,
6048e11,
26784e11,
31536e12,
}
// Nanosecond returns representation of an Unit
// in nanosconds
func (u Unit) Nanosecond() float64 {
return nanoseconds[u]
}
// IsDatesEqual check if two partial dates match.
// This case the day means not the amount of days in Time,
// but the day of the month.
// The same rules applied to each unit.
func IsDatesEqual(tm1, tm2 time.Time, u Unit) bool {
switch u {
case Millisecond:
tm1Msec := tm1.Nanosecond() / 1e6
tm2Msec := tm2.Nanosecond() / 1e6
return tm1Msec == tm2Msec
case Second:
return tm1.Second() == tm2.Second()
case Minute:
return tm1.Minute() == tm2.Minute()
case Hour:
return tm1.Hour() == tm2.Hour()
case Day:
return tm1.Day() == tm2.Day()
case Week:
tm1Wk := tm1.Day() / 7
tm2Wk := tm2.Day() / 7
return tm1Wk == tm2Wk
case Month:
return tm1.Month() == tm2.Month()
case Year:
return tm1.Year() == tm2.Year()
}
return false
}
// AddUnit add amount given in u to tm
func AddUnit(tm time.Time, amount int, u Unit) (res time.Time) {
if u < Day {
return tm.Add(time.Duration(amount) * time.Duration(int64(u.Nanosecond())))
}
switch u {
case Day:
res = tm.AddDate(0, 0, amount*1)
case Week:
res = tm.AddDate(0, 0, amount*7)
case Month:
res = tm.AddDate(0, amount*1, 0)
case Year:
res = tm.AddDate(amount*1, 0, 0)
}
return
}
// UnitFromString returns true and an Unit object if
// Unit with that name exists. Returns false, otherwise.
func UnitFromString(s string) (Unit, error) {
switch strings.ToLower(s) {
case "y", "year", "years":
return Year, nil
case "m", "month", "months":
return Month, nil
case "w", "week", "weeks":
return Week, nil
case "d", "day", "days":
return Day, nil
case "h", "hour", "hours":
return Hour, nil
case "i", "minute", "minutes":
return Minute, nil
case "s", "second", "seconds":
return Second, nil
case "f", "millisecond", "milliseconds":
return Millisecond, nil
}
return -1, errors.Errorf("no such unit '%s'", s)
}