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|
package chronos
import (
"math"
"time"
)
type TimeUnit int
const (
Minute TimeUnit = iota
Hour
Day
Week
Month
Year
)
var nilTime time.Time
func (tu TimeUnit) String() string {
switch tu {
case Minute:
return "Minute"
case Hour:
return "Hour"
case Day:
return "Day"
case Week:
return "Week"
case Month:
return "Month"
case Year:
return "Year"
default:
return "(Unknown TimeUnit)"
}
}
func (tu TimeUnit) minApprox() time.Duration {
const (
maMinute = time.Minute
maHour = time.Hour
maDay = 24*time.Hour - time.Second
maWeek = 7 * maDay
maMonth = 28 * maDay
maYear = 365 * maDay
)
switch tu {
case Minute:
return maMinute
case Hour:
return maHour
case Day:
return maDay
case Week:
return maWeek
case Month:
return maMonth
case Year:
return maYear
default:
return 0
}
}
func (tu TimeUnit) maxApprox() time.Duration {
const (
maMinute = time.Minute
maHour = time.Hour
maDay = 24*time.Hour + time.Second
maWeek = 7 * maDay
maMonth = 31 * maDay
maYear = 366 * maDay
)
switch tu {
case Minute:
return maMinute
case Hour:
return maHour
case Day:
return maDay
case Week:
return maWeek
case Month:
return maMonth
case Year:
return maYear
default:
return 0
}
}
type Frequency struct {
Unit TimeUnit
Count uint
}
func (f Frequency) addTo(t time.Time, mul uint) time.Time {
sec := t.Second()
min := t.Minute()
hour := t.Hour()
day := t.Day()
month := t.Month()
year := t.Year()
loc := t.Location()
fq := int(f.Count * mul)
switch f.Unit {
case Minute:
return t.Add(time.Minute * time.Duration(fq))
case Hour:
return t.Add(time.Hour * time.Duration(fq))
case Day:
return time.Date(year, month, day+fq, hour, min, sec, 0, loc)
case Week:
return time.Date(year, month, day+fq*7, hour, min, sec, 0, loc)
case Month:
return time.Date(year, month+time.Month(fq), day, hour, min, sec, 0, loc)
case Year:
return time.Date(year+fq, month, day, hour, min, sec, 0, loc)
default:
return nilTime
}
}
func (f Frequency) minApprox() time.Duration { return time.Duration(f.Count) * f.Unit.minApprox() }
func (f Frequency) maxApprox() time.Duration { return time.Duration(f.Count) * f.Unit.maxApprox() }
// Chronos describes a time schedule. It has a start and optional end point and an optional frequency.
type Chronos struct {
Start, End time.Time
Freq Frequency
}
// NextAfter calculates the next time in the schedule after t. If no such time exists, nil is returned (test with Time.IsZero()).
func (c Chronos) NextAfter(t time.Time) time.Time {
if !t.After(c.Start) {
return c.Start
}
if c.Freq.Count == 0 {
return nilTime
}
d := t.Sub(c.Start)
fmin := uint(math.Floor(float64(d) / float64(c.Freq.maxApprox())))
fmax := uint(math.Ceil(float64(d) / float64(c.Freq.minApprox())))
for f := fmin; f <= fmax; f++ {
t2 := c.Freq.addTo(c.Start, f)
if t2.Before(c.Start) || t2.Before(t) {
continue
}
if (!c.End.IsZero()) && t2.After(c.End) {
return nilTime
}
return t2
}
return nilTime // Should actually never happen...
}
|
