Start work on ical output.

1 files changed, 82 insertions, 0 deletions

diff --git a/module/output/ical.scm b/module/output/ical.scm
new file mode 100644
index 00000000..c8d9a11d
--- /dev/null
+++ b/module/output/ical.scm
@@ -0,0 +1,82 @@
+(define-module (output ical)
+  use-module: (ice-9 getopt-long)
+  use-module: (ice-9 format)
+  use-module: (vcomponent)
+  use-module: (srfi srfi-19)
+  use-module: (srfi srfi-19 util)
+  use-module: (srfi srfi-41)
+  use-module: (srfi srfi-41 util)
+  )
+
+(define opt-spec
+  '((from (value #t) (single-char #\f))
+    (to (value #t) (single-char #\t))))
+
+(define (value-format key value)
+  ;; TODO remove once key's are normalized to symbols.
+  (case (string->symbol key)
+    ((DTSTART DTEND)
+     (time->string value "~Y~m~dT~H~M~SZ"))
+    ((DURATION)
+     #; (time->string value "~H~M~S")
+     (let ((s (time-second value)))
+       (format #f "~a~a~a"
+               (floor/ s 3600)
+               (floor/ (modulo s 3600) 60)
+               (modulo s 60))
+       ))
+    (else value)))
+
+(define (escape-chars str)
+  (with-output-to-string
+    (lambda ()
+      (string-for-each (lambda (ch)
+                         (case ch
+                           ((#\, #\\) => (lambda (c) (display "\\") (display c)))
+                           (else (display ch)))
+                         ) str))))
+
+(define (component->ical-string component)
+  (format #t "BEGIN:~a~%" (type component))
+  (for-each (lambda (kv)
+              (let ((key (car kv))
+                    (vline (cdr kv)))
+                ;; key;p1=v;p3=10:value
+                (format #t "~a~:{;~a=~@{~a~^,~}~}:~a~%"
+                        key (properties vline)
+                        (escape-chars (value-format key (value vline)))
+                        )))
+            (attributes component))
+  (for-each component->ical-string (children component))
+  (format #t "END:~a~%" (type component))
+
+  )
+
+(define (print-header)
+  (format #t
+"BEGIN:VCALENDAR
+PRODID:~a
+VERSION:2.0
+CALSCALE:GREGORIAN
+"
+"Hugo"
+))
+
+
+(define (print-footer)
+  (format #t "END:VCALENDAR~%"))
+
+(define-public (ical-main calendars events args)
+  (define opts (getopt-long args opt-spec))
+  (define start (parse-freeform-date (option-ref opts 'from "2019-04-15")))
+  (define end   (parse-freeform-date (option-ref opts 'to   "2019-05-10")))
+
+  (print-header)
+
+  (stream-for-each
+   component->ical-string
+   (filter-sorted-stream (lambda (ev) ((in-date-range? start end)
+                                  (time-utc->date (attr ev 'DTSTART))))
+                         events))
+
+  (print-footer))