forked from vieter-v/vieter
158 lines
3.3 KiB
V
158 lines
3.3 KiB
V
module cron
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import math
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import time
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const days_in_month = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
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struct CronExpression {
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minutes []int
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hours []int
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days []int
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months []int
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}
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// next calculates the earliest time this cron expression is valid.
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pub fn (ce &CronExpression) next(ref time.Time) ?time.Time {
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mut minute_index := 0
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mut hour_index := 0
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mut day_index := 0
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mut month_index := 0
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for month_index < ce.months.len && ref.month > ce.months[month_index] {
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month_index++
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}
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if month_index < ce.months.len {
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for day_index < ce.days.len && ref.day > ce.days[day_index] {
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day_index++
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}
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if day_index < ce.days.len {
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for hour_index < ce.hours.len && ref.hour > ce.hours[hour_index] {
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hour_index++
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}
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if hour_index < ce.hours.len {
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// For each unit, we calculate what the next value is
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for minute_index < ce.minutes.len && ref.minute >= ce.minutes[minute_index] {
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minute_index++
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}
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}
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}
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}
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// Sometime we have to shift values one more
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if minute_index == ce.minutes.len && hour_index < ce.hours.len {
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hour_index += 1
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}
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if hour_index == ce.hours.len && day_index < ce.days.len {
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day_index += 1
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}
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if day_index == ce.days.len && month_index < ce.months.len {
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month_index += 1
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}
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mut minute := ce.minutes[minute_index % ce.minutes.len]
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mut hour := ce.hours[hour_index % ce.hours.len]
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mut day := ce.days[day_index % ce.days.len]
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mut reset := false
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// If the day can't be planned in the current month, we go to the next one
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// and go back to day one
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if day > days_in_month[ce.months[month_index % ce.months.len] - 1] {
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month_index += 1
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day = ce.days[0]
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// Make sure we only plan in a month that the day occurs in
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for day > days_in_month[ce.months[month_index & ce.months.len] - 1] {
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month_index += 1
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// Prevent scenario where there are no months that can be scheduled.
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if month_index == 2 * ce.months.len {
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return error('No schedulable moment.')
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}
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}
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}
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month := ce.months[month_index % ce.months.len]
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mut year := ref.year
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if month_index >= ce.months.len {
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year++
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}
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return time.Time{
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year: year
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month: month
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day: day
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minute: minute
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hour: hour
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}
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}
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fn (ce &CronExpression) next_from_now() ?time.Time {
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return ce.next(time.now())
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}
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// parse_range parses a given string into a range of sorted integers, if
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// possible.
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fn parse_range(s string, min int, max int) ?[]int {
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mut out := []int{}
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mut start := min
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mut interval := 1
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if s != '*' {
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exps := s.split('/')
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start = math.min(max, math.max(exps[0].int(), min))
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if exps.len > 1 {
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interval = exps[1].int()
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}
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// Here, s solely consists of a number, so that's the only value we
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// should return.
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else {
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return [start]
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}
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}
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if interval == 0 {
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return []
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}
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for start <= max {
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out << start
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start += interval
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}
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return out
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}
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// min hour day month day-of-week
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fn parse_expression(exp string) ?CronExpression {
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mut parts := exp.split(' ')
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if parts.len < 2 || parts.len > 4 {
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return error('Expression must contain between 2 and 4 space-separated parts.')
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}
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// For ease of use, we allow the user to only specify as many parts as they
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// need.
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for parts.len < 4 {
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parts << '*'
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}
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return CronExpression{
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minutes: parse_range(parts[0], 0, 59) ?
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hours: parse_range(parts[1], 0, 23) ?
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days: parse_range(parts[2], 1, 31) ?
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months: parse_range(parts[3], 1, 12) ?
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}
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}
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