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(define-module (vcomponent recurrence parse)
#:duplicates (last) ; Replace @var{count}
#:export (parse-recurrence-rule)
#:use-module (srfi srfi-1)
#:use-module (datetime)
#:use-module (srfi srfi-26)
#:use-module (vcomponent recurrence internal)
#:use-module (util)
#:use-module (util exceptions)
#:use-module (ice-9 match))
;; transform into weekday objects from
(define (rfc->datetime-weekday symbol)
(case symbol
[(SU) sun]
[(MO) mon]
[(TU) tue]
[(WE) wed]
[(TH) thu]
[(FR) fri]
[(SA) sat]
[else => (lambda (d) (error "No such day ~a" d))]))
;; @example
;; <weekday> ∈ weekdays
;; <weekdaynum> ::= [[±] <num>] <weekday> ;; +3MO
;; (<weekadynum>, ...)
;; @end example
;;; weekdaynum can contain ±
;;; only used in bywdaylist
;;; only present with by BYDAY
;; Returns a pair, where the @code{car} is the offset
;; and @code{cdr} is the day symbol.
;; The @code{car} may be @code{#f}.
;; str → (<num> . <symb>)
(define (parse-day-spec str)
(let* ((numerical-characters (append '(#\+ #\-) (map integer->char (iota 10 #x30))))
(numbers letters (span (cut memv <> numerical-characters)
(string->list str))))
(cons (string->number (list->string numbers))
(rfc->datetime-weekday (apply symbol letters)))))
(define-macro (quick-case key . cases)
(let ((else-clause (or (assoc-ref cases 'else)
'(error "Guard failed"))))
`(case ,key
,@(map (match-lambda
((key guard '=> body ...)
`((,key) (if (not ,guard)
(begin (warning
"RRULE guard failed for key ~a~% guard: ~a : ~s"
(quote ,key)
(quote ,guard)
(map (lambda (o) (if (procedure? o)
(procedure-name o)
o))
(list ,@guard)))
,@else-clause)
(begin ,@body))))
((key body ...)
`((,key) (begin ,@body)))
(('else body ...)
`(else ,@body)))
cases))))
;; RFC 5545, Section 3.3.10. Recurrence Rule, states that the UNTIL value MUST have
;; the same type as the DTSTART of the event (date or datetime). I have seen events
;; in the wild which didn't follow this. I consider that an user error.
(define* (parse-recurrence-rule str optional: (datetime-parser parse-ics-datetime))
(fold
(lambda (kv o)
(let* (((key val) kv))
(let-lazy
((symb (string->symbol val))
;; NOTE until MUST have the same value type as DTSTART
;; on the object. Idealy we would save that type and
;; check it here. That however is impractical since we
;; might encounter the RRULE field before the DTSTART
;; field.
(date (if (= 8 (string-length val))
(parse-ics-date val)
(parse-ics-datetime val)))
(day (rfc->datetime-weekday (string->symbol val)))
(days (map parse-day-spec (string-split val #\,)))
(num (string->number val))
(nums (map string->number (string-split val #\,))))
;; It's an error to give BYHOUR and smaller for pure dates.
;; 3.3.10. p 41
(quick-case (string->symbol key)
(UNTIL (set (until o) date))
(COUNT (<= 0 num) => (set (count o) num))
(INTERVAL (<= 0 num) => (set (interval o) num))
(FREQ (memv symb intervals) => (set (freq o) symb))
(WKST (memv day weekdays) => (set (wkst o) day))
;; Always positive
(BYSECOND (every (lambda (n) (<= 0 n 60)) nums) => (set (bysecond o) nums))
(BYMINUTE (every (lambda (n) (<= 0 n 59)) nums) => (set (byminute o) nums))
(BYHOUR (every (lambda (n) (<= 0 n 23)) nums) => (set (byhour o) nums))
(BYMONTH (every (lambda (n) (<= 1 n 12)) nums) => (set (bymonth o) nums))
;; May be negative
(BYDAY (every (lambda (p) (memv (cdr p) weekdays)) days) => (set (byday o) days))
(BYMONTHDAY (every (lambda (n) (and (!= n 0) (<= -31 n 31))) nums) => (set (bymonthday o) nums))
(BYYEARDAY (every (lambda (n) (and (!= n 0) (<= -366 n 366))) nums) => (set (byyearday o) nums))
(BYSETPOS (every (lambda (n) (and (!= n 0) (<= -366 n 366))) nums) => (set (bysetpos o) nums))
(BYWEEKNO (every (lambda (n) (and (!= n 0) (<= -53 n 53))) nums) => (set (byweekno o) nums))
(else o)))))
;; obj
(make-recur-rule interval: 1 wkst: mon)
;; ((key val) ...)
(map (cut string-split <> #\=)
(string-split str #\;))))
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