Статистика для дашборда, расширенная #7

src/core/core_event.erl

@@ -4,7 +4,7 @@
 -export([create/4, create_recurring/5, get_by_id/1, list_by_calendar/1,
   update/2, delete/1, materialize_occurrence/3]).
 -export([generate_id/0]).
--export([count_events/0]).
+-export([count_events/0, count_events_by_date/2]).
 
 %% Создание одиночного события
 create(CalendarId, Title, StartTime, Duration) ->
@@ -171,6 +171,22 @@ delete(Id) ->
 count_events() ->
   mnesia:table_info(event, size).
 
+count_events_by_date(From, To) ->
+  All = mnesia:dirty_match_object(#event{_ = '_'}),
+  Filtered = lists:filter(fun(E) ->
+    E#event.created_at >= From andalso E#event.created_at =< To
+                          end, All),
+  Counts = lists:foldl(fun(E, Acc) ->
+    Day = date_part(E#event.created_at),
+    case lists:keyfind(Day, 1, Acc) of
+      false -> [{Day, 1} | Acc];
+      {Day, C} -> lists:keyreplace(Day, 1, Acc, {Day, C+1})
+    end
+                       end, [], Filtered),
+  lists:sort(Counts).
+
+date_part({{Y,M,D}, _}) -> {Y,M,D}.
+
 %% Внутренние функции
 generate_id() ->
   base64:encode(crypto:strong_rand_bytes(16), #{mode => urlsafe, padding => false}).