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(define-module (vcalendar recur)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-8) ; Recieve
#:use-module (srfi srfi-9 gnu) ; Records
#:use-module (srfi srfi-19) ; Datetime
#:use-module (srfi srfi-19 util)
#:use-module (srfi srfi-26) ; Cut
#:use-module (srfi srfi-41) ; Streams
#:use-module (ice-9 curried-definitions)
;; #:use-module (ice-9 match)
#:use-module (vcalendar)
#:use-module (vcalendar datetime)
#:use-module (util)
#:export (recur-event))
;; (build-recur-rules "FREQ=HOURLY")
;; ;; => #<<recur-rule> freq: HOURLY until: #f count: #f interval: #f>
;; (build-recur-rules "FREQ=HOURLY;COUNT=3")
;; ;; => #<<recur-rule> freq: HOURLY until: #f count: 3 interval: #f>
;; (build-recur-rules "FREQ=ERR;COUNT=3")
;; ;; => #<<recur-rule> freq: #f until: #f count: 3 interval: #f>
;; (build-recur-rules "FREQ=HOURLY;COUNT=err")
;; ;; => #<<recur-rule> freq: HOURLY until: #f count: #f interval: #f>
;; (build-recur-rules "FREQ=HOURLY;COUNT=-1")
;; ;; => #<<recur-rule> freq: HOURLY until: #f count: #f interval: #f>
(define-quick-record recur-rule
freq until count interval bysecond byminute byhour wkst)
(define (build-recur-rules str)
"Takes a RECUR value (string), and returuns a <recur-rule> object"
(catch #t
(lambda () (%build-recur-rules str))
(lambda (err cont obj key val . rest)
(let ((fmt (case err
((unfulfilled-constraint)
"ERR ~a [~a] doesn't fulfill constraint of type [~a], ignoring~%")
((invalid-value)
"ERR ~a [~a] for key [~a], ignoring.~%")
(else "~a ~a ~a"))))
(format #t fmt err val key))
(cont obj))))
;;; A special form of case only useful in build-recur-rules above.
;;; Each case is on the form (KEY val check-proc) where:
;;; `key` is what should be matched against, and what is used for the setter
;;; `val` is the value to bind to the loop object and
;;; `check` is something the object must conform to
(define-syntax-rule (throw-returnable symb args ...)
(call/cc (lambda (cont) (throw symb cont args ...))))
;;; TODO
;;; something with this will only properly compiled if run interactively.
;;; But once compiled from the repl it stays compiled from script
;;; And script can run it, it just complains and keeps recompiling.
(define ((handle-case stx obj) key val proc)
(with-syntax ((skey (datum->syntax
stx (symbol-downcase (syntax->datum key)))))
#`((#,key)
(let ((v #,val))
(cond ((not v) (throw-returnable 'invalid-value #,obj (quote #,key) v))
((#,proc #,val) (set! (skey #,obj) v))
(else (set! (skey #,obj)
(throw-returnable 'unfulfilled-constraint
#,obj (quote #,key) v))))))))
(define-syntax quick-case
(lambda (stx)
(syntax-case stx ()
((_ var-key obj (key val proc) ...)
#`(case var-key
#,@(map (handle-case stx #'obj)
#'(key ...)
#'(val ...)
#'(proc ...))
(else obj))))))
(define weekdays
'(SU MO TU WE TH FR SA))
(define intervals
'(SECONDLY MINUTELY HOURLY DAILY WEEKLY MONTHLY YEARLY))
(define (string->number-list val delim)
(map string->number (string-split val delim)))
(define (string->symbols val delim)
(map string->symbol (string-split val delim)))
(define (%build-recur-rules str)
(fold
(lambda (lst obj)
(let* (((key val) lst))
(quick-case (string->symbol key) obj
(FREQ (string->symbol val) (cut memv <> intervals))
(UNTIL (parse-datetime val) identity)
(COUNT (string->number val) (cut <= 0 <>))
(INTERVAL (string->number val) (cut <= 0 <>))
(BYSECOND (string->number-list val #\,) (cut every (cut <= 0 <> 60) <>))
(BYMINUTE (string->number-list val #\,) (cut every (cut <= 0 <> 59) <>))
(BYHOUR (string->number-list val #\,) (cut every (cut <= 0 <> 23) <>))
;; TODO implement these
;; (BYDAY)
;; (BYMONTHDAY)
;; (BYYEARDAY)
;; (BYWEEKNO)
;; (BYMONTH)
;; (BYSETPOS)
(WKST (string->symbol val) (cut memv <> weekdays))
)))
;; obj
((record-constructor <recur-rule> '(interval wkst)) 1 'MO)
;; ((key val) ...)
(map (cut string-split <> #\=)
(string-split str #\;))))
(define (generate-next event rule)
(let ((new-event (copy-vcomponent event)))
(case (freq rule)
((WEEKLY)
(transform-attr! new-event "DTSTART" (cut time-add <> 1 weeks))
(set! (attr new-event "DTEND")
(add-duration (attr new-event "DTSTART")
(attr new-event "DURATION")))
(values new-event rule))
((DAILY)
(transform-attr! new-event "DTSTART" (cut time-add <> 1 days))
(set! (attr new-event "DTEND")
(add-duration (attr new-event "DTSTART")
(attr new-event "DURATION")))
(values new-event rule))
(else (values '() rule)))))
(define-stream (recur-event-stream event rule-obj)
(stream-cons event
(receive (next-event next-rule)
(generate-next event rule-obj)
(if (null? next-event)
stream-null
(recur-event-stream next-event next-rule)))))
(define (recur-event event)
(unless (attr event "DURATION")
(set! (attr event "DURATION")
(time-difference
(attr event "DTEND")
(attr event "DTSTART"))))
(recur-event-stream event (build-recur-rules (attr event "RRULE"))))
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