server, ics, pages: allow to generate ICS from modules

This adds the ability to generate an ICS file from a module ID, and to
filter it based on its groups.

To do this, you can enter a module ID on the frontpage.  Then, µCS will
fetch the timetable, then return a page where one can select the
group(s) they want to filter (this is enabled by the new
Ics.get_all_groups function).  Then, µCS is able to generate a link to
that calendar, not unlike with a single group ID.

Signed-off-by: Alban Gruin <alban at pa1ch dot fr>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/ics.ml b/src/ics.ml
index 888e9e8..d6d165a 100644
--- a/src/ics.ml
+++ b/src/ics.ml
@@ -17,6 +17,8 @@
 
 open CalendarLib
 
+module StringSet = Set.Make (String)
+
 let to_date = Printer.Calendar.sprint "%Y%m%dT%H%M%S"
 let current_date () = to_date @@ Calendar.now ()
 
@@ -61,6 +63,8 @@ module Event = struct
   let has_groups groups event =
     List.fold_left (fun found group ->
         found || List.exists ((=) group) groups) false event.groups
+
+  let get_groups event = event.groups
 end
 
 type t = Event.t list
@@ -80,6 +84,12 @@ let gen_vtimezone tz =
   else
     ""
 
+let get_all_groups events =
+  let add_groups_to_set set event =
+    List.fold_left (fun set elt -> StringSet.add elt set) set @@ Event.get_groups event in
+  List.fold_left add_groups_to_set StringSet.empty events
+  |> StringSet.to_seq
+
 let to_string tz events =
   let date = current_date () in
   let vtimezone = gen_vtimezone tz in