rrule

type Frequency int

type InvalidBehavior int

type Iterator interface {
	// Peek returns the next time without advancing the iterator, or nil if
	// the iterator has ended.
	Peek() *time.Time

	// Next returns the next time and advances the iterator. Nil is
	// returned if the iterator has ended.
	Next() *time.Time
}

type QualifiedWeekday struct {
	// N, when non-zero, says which instance of the weekday relative to
	// some greater duration. -3 would be "third from the last".
	N  int
	WD time.Weekday
}

type RRule struct {
	Frequency Frequency

	// Either Until or Count may be set, but not both
	Until         time.Time
	UntilFloating bool // If true, the RRule will encode using local time (no offset).

	Count uint64

	// Dtstart is not actually part of the RRule when
	// encoded, but it's included here as a field because
	// it's required when expading the pattern.
	//
	// If zero, time.Now is used when an iterator is generated.
	Dtstart time.Time

	// 0 means the default value, which is 1.
	Interval int

	BySeconds     []int // 0 to 59
	ByMinutes     []int // 0 to 59
	ByHours       []int // 0 to 23
	ByWeekdays    []QualifiedWeekday
	ByMonthDays   []int // 1 to 31
	ByWeekNumbers []int // 1 to 53
	ByMonths      []time.Month
	ByYearDays    []int // 1 to 366
	BySetPos      []int // -366 to 366

	// InvalidBehavior defines how to behave when a generated date wouldn't
	// exist, like February 31st.
	InvalidBehavior InvalidBehavior

	WeekStart *time.Weekday // if nil, Monday
}

type RScale int

type Recurrence struct {
	// Dtstart specifies the time to begin recurrence. If zero, time.Now is
	// used when an iterator is generated.  The location of Dtstart is the
	// location that will be used to process the recurrence, which is
	// particularly relevant for calculations affected by Daylight Savings.
	Dtstart time.Time

	// FloatingLocation determines how the Recurrence is encoded to string.
	// If true, Dtstart, RDates, and ExDates will be written in local time,
	// excluding the offset or timezone indicator, to represent a local time
	// independent of timezone. See ParseRecurrence or RFC 5545 for more
	// detail.
	FloatingLocation bool

	// Patterns and instances to include. Repeated instances are included only
	// once, even if defined by multiple patterns.
	//
	// The Dtstart property of RRule and ExRule patterns are
	// ignored, including when the above Dtstart property is zero.
	RRules []RRule
	RDates []time.Time

	// Patterns and instances to exclude. These take precedence over the
	// inclusions. Note: this feature was deprecated in RFC5545, noting its
	// limited (and buggy) adoption and real-world use case. It is
	// implemented here, nonetheless, for maximum flexibility and
	// compatibility.
	ExRules []RRule
	ExDates []time.Time
}