From 69b69306097b561b9c2c7dfeafd4aaff460b6fda Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20H=C3=B6rnquist?= <hugo@hornquist.se>
Date: Sat, 20 Apr 2019 22:39:44 +0200
Subject: Add timezone handling.

This is a way to large commit. But I see no feasable way to break it
down into multiple smaller commits.

The main "secret" to solving timezones for recurring events was to
remember to recalculate timezones whenever a new instance of the object
was generated.

This current implementation seems really slow (> 1s). Further testing is
needed.
---
 module/vcalendar.scm | 40 ++++++++++++++++++----------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

(limited to 'module/vcalendar.scm')

diff --git a/module/vcalendar.scm b/module/vcalendar.scm
index 2b664b56..a45e54a2 100644
--- a/module/vcalendar.scm
+++ b/module/vcalendar.scm
@@ -6,6 +6,7 @@
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-19)
   #:use-module (srfi srfi-19 util)
+  #:use-module (srfi srfi-19 setters)
   #:use-module (srfi srfi-26)
   #:use-module ((ice-9 optargs) #:select (define*-public))
   #:use-module (util)
@@ -23,28 +24,23 @@
 (define (parse-dates! cal)
   "Parse all start times into scheme date objects."
 
-  (for-each-in (children cal 'VTIMEZONE)
-               (lambda (tz)
-                 (for-each (lambda (p) (mod! (attr p "DTSTART") string->time-utc))
-                           (children tz))
-
-                  ;; TZSET is the generated recurrence set of a timezone
-                  (set! (attr tz 'X-HNH-TZSET)
-                        (make-tz-set tz))))
-
-  (for-each
-   (lambda (ev)
-     (mod! (attr ev "DTSTART") string->time-utc
-           (attr ev "DTEND")   string->time-utc)
-
-     (when (prop (attr* ev 'DTSTART) 'TZID)
-       (let* ((of (get-tz-offset ev)))
-         (set! (prop (attr* ev 'DTSTART) 'TZID) #f)
-         ;; 5545 says that DTEND is local time iff DTSTART is local time.
-         ;; But who says that will be true...
-         (mod! (attr ev 'DTSTART)
-               (cut subtract-duration <> (make-duration of))))))
-   (children cal 'VEVENT))
+  (for tz in (children cal 'VTIMEZONE)
+       (for-each (lambda (p) (mod! (attr p "DTSTART") string->time-utc))
+                 (children tz))
+
+       ;; TZSET is the generated recurrence set of a timezone
+       (set! (attr tz 'X-HNH-TZSET)
+             (make-tz-set tz)))
+
+  (for ev in (children cal 'VEVENT)
+       (define date (parse-datetime (attr ev 'DTSTART)))
+
+       (mod! (attr ev "DTEND")   string->time-utc)
+       (set! (attr ev "DTSTART") (date->time-utc date))
+
+       (when (prop (attr* ev 'DTSTART) 'TZID)
+         (set! (zone-offset date) (get-tz-offset ev)
+               (attr ev 'DTSTART) (date->time-utc date))))
 
   ;; Return
   cal)
-- 
cgit v1.2.3