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week.go
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week.go
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package utils
import (
"errors"
"time"
)
type Week struct {
Date time.Time
Year int
WeekNum int
}
type WeekIterator struct {
Start *Week
Current *Week
End *Week
}
// Calculate the actual date which represents the start of the given ISOWeek
func DateFromISOWeek(isoYear int, isoWeek int) (date time.Time) {
// Start at the beginning of the target year, iterate backwards to Monday
date = time.Date(isoYear, 0, 0, 0, 0, 0, 0, time.UTC)
for date.Weekday() != time.Monday {
date = date.AddDate(0, 0, -1)
}
// Iterate forwards to the first week of the target year, this needs to be done
// if the target year doesn't start on a Monday
year, week := date.ISOWeek()
for year < isoYear {
date = date.AddDate(0, 0, 7)
year, week = date.ISOWeek()
}
// Iterate forwards to the correct start week
for week < isoWeek {
date = date.AddDate(0, 0, 7)
_, week = date.ISOWeek()
}
return date
}
// Returns a new Week object given a time.Time
func NewWeek(date time.Time) (week *Week) {
week = &Week{}
// Align to the nearest ISOWeek
week.Year, week.WeekNum = date.ISOWeek()
// Get the start date of the ISOWeek
week.Date = DateFromISOWeek(week.Year, week.WeekNum)
return week
}
// Returns the difference w-u between two Weeks, in terms of number of weeks
func (w *Week) Sub(u *Week) int {
if w.Year >= u.Year {
return ((w.Year - u.Year) * 52) + w.WeekNum - u.WeekNum
} else {
return ((u.Year - w.Year) * -52) - (u.WeekNum - w.WeekNum)
}
}
// Takes in a time range and returns a WeekIterator
func GetWeekIterator(start time.Time, end time.Time) (iter *WeekIterator, err error) {
if start.After(end) {
return nil, errors.New("start time cannot be after end time")
}
return &WeekIterator{Start: NewWeek(start), End: NewWeek(end)}, nil
}
// Returns the next Week from the WeekIterator
func (i *WeekIterator) Next() (week *Week, ok bool) {
if i.Current == nil {
week = i.Start
i.Current = i.Start
return week, true
}
i.Current.Date = i.Current.Date.AddDate(0, 0, 7)
if i.Current.Date.After(i.End.Date) {
return nil, false
}
week = &Week{Date: i.Current.Date}
week.Year, week.WeekNum = week.Date.ISOWeek()
return week, true
}