Fix reccuring events with exceptions.

An event with an RRULE can have extra VEVENT's which share their UID,
but add a RECCURENCE-ID which contains when the event was supposed to
take place. In place of that time it may supply it's own overriding
time. It may also override other fields.

1 files changed, 15 insertions, 1 deletions

diff --git a/module/vcomponent/recurrence/generate.scm b/module/vcomponent/recurrence/generate.scm
index 84025d2f..0ad30c84 100644
--- a/module/vcomponent/recurrence/generate.scm
+++ b/module/vcomponent/recurrence/generate.scm
@@ -1,4 +1,5 @@
 (define-module (vcomponent recurrence generate)
+  #:use-module ((srfi srfi-1) :select (find))
   #:use-module (srfi srfi-19)           ; Datetime
   #:use-module (srfi srfi-19 util)
   #:use-module (srfi srfi-19 setters)
@@ -85,7 +86,20 @@
   (stream-unfold
 
    ;; Event x Rule → Event
-   car
+   (match-lambda
+     ((e _)
+      (let ((expected-start (attr e 'DTSTART)))
+        ;; If we have alternatives, check them
+        (cond [(attr e 'X-HNH-ALTERNATIVES)
+               (lambda (alternatives)
+                 ;; A recurrence id matching the expected time means that
+                 ;; we have an actuall alternative/exception, use that
+                 ;; instead of the regular event.
+                 (find (lambda (alt) (time=? expected-start (attr alt 'RECURRENCE-ID)))
+                       alternatives))
+               => identity]
+              ;; If we did't have an exception just return the regular event.
+              [else e]))))
 
    ;; Event x Rule → Bool (continue?)
    (match-lambda