Статистика для дашборда, расширенная #7

src/core/core_user.erl

@@ -6,7 +6,7 @@
 -export([generate_id/0]).
 -export([list_users/0]).
 -export([block/1, unblock/1]).
--export([count_users/0]).
+-export([count_users/0, count_users_by_date/2]).
 
 %% Создание пользователя
 create(Email, Password) ->
@@ -126,6 +126,22 @@ unblock(Id) ->
 count_users() ->
   mnesia:table_info(user, size).
 
+count_users_by_date(From, To) ->
+  All = mnesia:dirty_match_object(#user{_ = '_'}),
+  Filtered = lists:filter(fun(U) ->
+    U#user.created_at >= From andalso U#user.created_at =< To
+                          end, All),
+  Counts = lists:foldl(fun(U, Acc) ->
+    Day = date_part(U#user.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}).