From d46183860c1f3f10095e95023adcb79b1896ab0e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20H=C3=B6rnquist?= <hugo@lysator.liu.se>
Date: Fri, 22 Mar 2019 20:11:11 +0100
Subject: Move C and Scheme code into subdirs.

---
 module/vcalendar/recurrence/generate.scm | 126 +++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 module/vcalendar/recurrence/generate.scm

(limited to 'module/vcalendar/recurrence/generate.scm')

diff --git a/module/vcalendar/recurrence/generate.scm b/module/vcalendar/recurrence/generate.scm
new file mode 100644
index 00000000..fae404ec
--- /dev/null
+++ b/module/vcalendar/recurrence/generate.scm
@@ -0,0 +1,126 @@
+(define-module (vcalendar recurrence generate)
+  ;; #:use-module (srfi srfi-1)
+  ;; #: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 control)          ; call-with-escape-continuation
+  #:use-module (ice-9 match)
+  #:use-module (vcalendar)
+  #:use-module (vcalendar datetime)
+  #:use-module (util)
+
+  #:use-module (vcalendar recurrence internal)
+  #:use-module (vcalendar recurrence parse)
+
+  #:export (generate-recurrence-set)
+  )
+
+;;; TODO implement
+;;; EXDATE and RDATE
+
+;;; EXDATE (3.8.5.1)
+;;; comma sepparated list of dates or datetimes.
+;;; Can have TZID parameter
+;;; Specifies list of dates that the event should not happen on, even
+;;; if the RRULE say so.
+;;; Can have VALUE field specifiying "DATE-TIME" or "DATE".
+
+;;; RDATE (3.8.5.2)
+;;; Comma sepparated list of dates the event should happen on.
+;;; Can have TZID parameter.
+;;; Can have VALUE parameter, specyfying "DATE-TIME", "DATE" or "PREIOD".
+;;; PERIOD (see 3.3.9)
+
+(define (seconds-in freq)
+  (case freq
+    ((SECONDLY) 1)
+    ((MINUTELY) 60)
+    ((HOURLY) (* 60 60))
+    ((DAILY) (* 60 60 24))
+    ((WEEKLY) (* 60 60 24 7))))
+
+
+;; BYDAY and the like depend on the freq?
+;; Line 7100
+;; Table @@ 2430
+;; 
+;; Event x Rule → Bool (continue?)
+;; Alternative, monadic solution using <optional>.
+;; @example
+;; (optional->bool
+;;  (do (<$> (cut time<=? (attr last 'DTSTART)) (until r))
+;;      (<$> (negate zero?) (count r))
+;;    (just #t)))
+;; @end example
+(define-stream (recur-event-stream event rule-obj)
+  (stream-unfold
+
+   ;; Event x Rule → Event
+   (match-lambda
+     ((last r)
+      (let ((e (copy-vcomponent last)))   ; new event
+        (cond
+
+         ((memv (freq r) '(SECONDLY MINUTELY HOURLY DAILY WEEKLY))
+          (mod! (attr e 'DTSTART)       ; MUTATE
+                (cut add-duration! <>
+                     (make-duration
+                      (* (interval r)   ; INTERVAL
+                         (seconds-in (freq r)))))))
+
+         ((memv (freq r) '(MONTHLY YEARLY))
+          #f ; Hur fasen beräkrnar man det här!!!!
+          ))
+
+        ;; TODO this is just here for testing
+        (mod! (attr e 'NEW_ATTR) not)   ; MUTATE
+        ;; This segfaults...
+        ;; (set! (attr e 'N) #t)           ; MUTATE
+        ((@ (vcalendar output) print-vcomponent) e)
+        (set! (attr e 'D) #t)
+
+        (set! (attr e 'DTEND)           ; MUTATE
+              (add-duration
+               (attr e 'DTSTART)
+               (attr e 'DURATION)))
+        e)))
+
+   ;; Event x Rule → Bool (continue?)
+   (match-lambda
+     ((e r)
+
+      (or (and (not (until r)) (not (count r)))                   ; Never ending
+          (and=> (count r) (negate zero?))                        ; COUNT
+          (and=> (until r) (cut time<=? (attr e 'DTSTART) <>))))) ; UNTIL
+
+   ;; _ x Rule → (_, (next) Rule)
+   (match-lambda
+     ((e r)
+      (list
+       e (if (count r)
+             ;; Note that this doesn't modify, since r is immutable.
+             (mod! (count r) 1-)
+             r))))
+
+   ;; Seed
+   (list event rule-obj)))
+
+
+(define (generate-recurrence-set event)
+  (unless (attr event "DURATION")
+    (set! (attr event "DURATION")       ; MUTATE
+          (time-difference
+           (attr event "DTEND")
+           (attr event "DTSTART"))))
+  (recur-event-stream event (parse-recurrence-rule (attr event "RRULE"))))
+
+  ;; How doee stream-unfold even work?
+  ;; What element is used as the next seed?
+;;; stream-fold:
+;; (stream-let recur ((base base))
+;;     (if (pred? base)
+;;         (stream-cons (mapper base) (recur (generator base)))
+;;         stream-null))
-- 
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