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Added some much-needed documentation

cron
Jef Roosens 2022-04-11 22:30:22 +02:00
parent 135b6c3d7f
commit 0e5f31e649
Signed by untrusted user: Jef Roosens
GPG Key ID: B75D4F293C7052DB
2 changed files with 28 additions and 12 deletions
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2
src/cron/cron.v
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@ -39,7 +39,7 @@ pub fn cron(conf Config) ? {
// }
mut t := time.Time{
year: 2022
month: 2
month: 12
minute: 9
hour: 13
day: 12

38
src/cron/expression.v
View File

@ -12,13 +12,24 @@ struct CronExpression {
months []int
}
// next calculates the earliest time this cron expression is valid.
// next calculates the earliest time this cron expression is valid. It will
// always pick a moment in the future, even if ref matches completely up to the
// minute. This function conciously does not take gap years into account.
pub fn (ce &CronExpression) next(ref time.Time) ?time.Time {
// For all of these values, the rule is the following: if their value is
// the length of their respective array in the CronExpression object, that
// means we've looped back around. This means that the "bigger" value has
// to be incremented by one. For example, if the minutes have looped
// around, that means that the hour has to be incremented as well.
mut minute_index := 0
mut hour_index := 0
mut day_index := 0
mut month_index := 0
// This chain is the same logic multiple times, namely that if a "bigger"
// value loops around, then the smaller value will always reset as well.
// For example, if we're going to a new day, the hour & minute will always
// be their smallest value again.
for month_index < ce.months.len && ref.month > ce.months[month_index] {
month_index++
}
@ -34,7 +45,9 @@ pub fn (ce &CronExpression) next(ref time.Time) ?time.Time {
}
if hour_index < ce.hours.len {
// For each unit, we calculate what the next value is
// Minute is the only value where we explicitely make sure we
// can't match ref's value exactly. This is to ensure we only
// return values in the future.
for minute_index < ce.minutes.len && ref.minute >= ce.minutes[minute_index] {
minute_index++
}
@ -42,8 +55,9 @@ pub fn (ce &CronExpression) next(ref time.Time) ?time.Time {
}
}
// Sometime we have to shift values one more
// Here, we increment the "bigger" values by one if the smaller ones loop
// around. The order is important, as it allows a sort-of waterfall effect
// to occur which updates all values if required.
if minute_index == ce.minutes.len && hour_index < ce.hours.len {
hour_index += 1
}
@ -60,19 +74,20 @@ pub fn (ce &CronExpression) next(ref time.Time) ?time.Time {
mut hour := ce.hours[hour_index % ce.hours.len]
mut day := ce.days[day_index % ce.days.len]
mut reset := false
// If the day can't be planned in the current month, we go to the next one
// and go back to day one
// Sometimes, we end up with a day that does not exist within the selected
// month, e.g. day 30 in February. When this occurs, we reset day back to
// the smallest value & loop over to the next month that does have this
// day.
if day > days_in_month[ce.months[month_index % ce.months.len] - 1] {
month_index += 1
day = ce.days[0]
month_index += 1
// Make sure we only plan in a month that the day occurs in
for day > days_in_month[ce.months[month_index & ce.months.len] - 1] {
month_index += 1
// Prevent scenario where there are no months that can be scheduled.
// If for whatever reason the day value ends up being something
// that can't be scheduled in any month, we have to make sure we
// don't create an infinite loop.
if month_index == 2 * ce.months.len {
return error('No schedulable moment.')
}
@ -83,6 +98,7 @@ pub fn (ce &CronExpression) next(ref time.Time) ?time.Time {
month := ce.months[month_index % ce.months.len]
mut year := ref.year
// If the month loops over, we need to increment the year.
if month_index >= ce.months.len {
year++
}