From 0bfdb8ce894453b1022e9a37662cf13d8289025d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20H=C3=B6rnquist?= <hugo@hornquist.se>
Date: Mon, 11 Mar 2019 00:07:35 +0100
Subject: Work on RRULE's.

---
 srfi/srfi-19/util.scm | 19 +++++--------
 vcalendar/recur.scm   | 75 +++++++++++++++++++++++++++++++++++++++++----------
 2 files changed, 68 insertions(+), 26 deletions(-)

diff --git a/srfi/srfi-19/util.scm b/srfi/srfi-19/util.scm
index 81dd7ec5..c0a7fd5e 100644
--- a/srfi/srfi-19/util.scm
+++ b/srfi/srfi-19/util.scm
@@ -5,8 +5,9 @@
   #:export (copy-date
             drop-time! drop-time
             today?
-            seconds minutes hours days weeks 
-            time-add
+            ;; seconds minutes hours days weeks
+            ;; time-add
+            make-duration
             time->string))
 
 #;
@@ -33,21 +34,15 @@ attribute set to 0. Can also be seen as \"Start of day\""
               ((date-second) 0)
               ((date-nanosecond) 0)))
 
-
-(define seconds  1)
-(define minutes 60)
-(define hours   (* 60 minutes))
-(define days    (* 24 hours))
-(define weeks   (* 7 days))
-
-(define (time-add time amount unit)
-  (add-duration time (make-time time-duration 0 (* amount unit))))
+(define (make-duration s)
+  (make-time time-duration 0 s))
 
 (define (today? time)
   (let* ((now (date->time-utc (drop-time (current-date))))
-         (then (time-add now 1 days)))
+         (then (add-duration now (make-duration (* 60 60 24)))))
     (and (time<=? now time)
          (time<=? time then))))
 
 (define* (time->string time #:optional (format "~c"))
   (date->string (time-utc->date time) format))
+
diff --git a/vcalendar/recur.scm b/vcalendar/recur.scm
index db3adc2f..ccdb3aa7 100644
--- a/vcalendar/recur.scm
+++ b/vcalendar/recur.scm
@@ -134,26 +134,57 @@
    (map (cut string-split <> #\=)
         (string-split str #\;))))
 
+(define (seconds-in interval)
+  (case interval
+    ((SECONDLY) 1)
+    ((MINUTELY) 60 )
+    ((HOURLY) (* 60 60))
+    ((DAILY) (* 60 60 24))
+    ((WEEKLY) (* 60 60 24 7))))
+
 (define (generate-next event rule)
+
+  (when (count rule)
+    (set! (count rule)
+          (1- (count rule)))
+
+    (when (zero? (count rule))
+      ;; TODO early return
+      (values '() '())))
+
+
   (let ((ne (copy-vcomponent event)))   ; new event
-    (case (freq rule)
-      ((WEEKLY)
-       (mod! (attr ne "DTSTART") (cut time-add <> 1 weeks))
+    (cond
 
-       (set! (attr ne "DTEND")
-             (add-duration (attr ne "DTSTART")
-                           (attr ne "DURATION")))
-       (values ne rule))
+     ;; BYDAY and the like depend on the freq?
+     ;; Line 7100
+     ;; Table @ 2430
 
-      ((DAILY)
-       (mod! (attr ne "DTSTART") (cut time-add <> 1 days))
+     ((memv (freq rule) '(SECONDLY MINUTELY HOURLY DAILY WEEKLY))
+      (mod! (attr ne "DTSTART")
+            (cut add-duration! <>
+                 (make-duration (* (interval rule)
+                                   (seconds-in (freq rule)))))))
+     ((memv (freq rule) '(MONTHLY YEARLY))
+      ;; Hur fasen beräkrnar man det här!!!!
+      )
+     (else #f))
 
-       (set! (attr ne "DTEND")
-             (add-duration  (attr ne "DTSTART")
-                            (attr ne "DURATION")))
-       (values ne rule))
 
-      (else (values '() rule)))))
+    ;; Make sure DTSTART is updated before this point
+
+    (and=> (until rule)
+        (lambda (u)
+          (when (time<? u (attr ne "DTSTART"))
+            ;; TODO early return
+            (values '() '()))))
+
+
+    (set! (attr ne "DTEND")
+          (add-duration (attr ne "DTSTART")
+                        (attr ne "DURATION")))
+
+    (values ne rule)))
 
 (define-stream (recur-event-stream event rule-obj)
   (stream-cons event
@@ -162,6 +193,22 @@
                      stream-null
                      (recur-event-stream next-event next-rule)))))
 
+;;; 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 (recur-event event)
   (unless (attr event "DURATION")
     (set! (attr event "DURATION")
-- 
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