allow check if archive is empty for or user or room

src/mod_mam.erl

@@ -40,7 +40,8 @@
 	 muc_process_iq/2, muc_filter_message/3, message_is_archived/3,
 	 delete_old_messages/2, get_commands_spec/0, msg_to_el/4,
 	 get_room_config/4, set_room_option/3, offline_message/1, export/1,
-	 mod_options/1, remove_mam_for_user_with_peer/3, remove_mam_for_user/2]).
+	 mod_options/1, remove_mam_for_user_with_peer/3, remove_mam_for_user/2,
+	 is_empty_for_user/2, is_empty_for_room/3]).
 
 -include("xmpp.hrl").
 -include("logger.hrl").
@@ -72,6 +73,8 @@
 -callback use_cache(binary()) -> boolean().
 -callback cache_nodes(binary()) -> [node()].
 -callback remove_from_archive(binary(), binary(), jid() | none) -> ok | {error, any()}.
+-callback is_empty_for_user(binary(), binary()) -> boolean().
+-callback is_empty_for_room(binary(), binary(), binary()) -> boolean().
 
 -optional_callbacks([use_cache/1, cache_nodes/1]).
 
@@ -572,6 +575,20 @@ export(LServer) ->
     Mod = gen_mod:db_mod(LServer, ?MODULE),
     Mod:export(LServer).
 
+-spec is_empty_for_user(binary(), binary()) -> boolean().
+is_empty_for_user(User, Server) ->
+    LUser = jid:nodeprep(User),
+    LServer = jid:nameprep(Server),
+    Mod = gen_mod:db_mod(LServer, ?MODULE),
+    Mod:is_empty_for_user(LUser, LServer).
+
+-spec is_empty_for_room(binary(), binary(), binary()) -> boolean().
+is_empty_for_room(LServer, Name, Host) ->
+    LName = jid:nodeprep(Name),
+    LHost = jid:nameprep(Host),
+    Mod = gen_mod:db_mod(LServer, ?MODULE),
+    Mod:is_empty_for_room(LServer, LName, LHost).
+
 %%%===================================================================
 %%% Internal functions
 %%%===================================================================

src/mod_mam_mnesia.erl

@@ -28,7 +28,8 @@
 
 %% API
 -export([init/2, remove_user/2, remove_room/3, delete_old_messages/3,
-	 extended_fields/0, store/8, write_prefs/4, get_prefs/2, select/6, remove_from_archive/3]).
+	 extended_fields/0, store/8, write_prefs/4, get_prefs/2, select/6, remove_from_archive/3,
+	 is_empty_for_user/2, is_empty_for_room/3]).
 
 -include_lib("stdlib/include/ms_transform.hrl").
 -include("xmpp.hrl").
@@ -198,6 +199,13 @@ select(_LServer, JidRequestor,
     erlang:garbage_collect(),
     Result.
 
+is_empty_for_user(LUser, LServer) ->
+	not lists:member({LUser, LServer},
+		mnesia:dirty_all_keys(archive_msg)).
+
+is_empty_for_room(_LServer, LName, LHost) ->
+    is_empty_for_user(LName, LHost).
+
 %%%===================================================================
 %%% Internal functions
 %%%===================================================================

src/mod_mam_sql.erl

@@ -30,7 +30,8 @@
 
 %% API
 -export([init/2, remove_user/2, remove_room/3, delete_old_messages/3,
-	 extended_fields/0, store/8, write_prefs/4, get_prefs/2, select/6, export/1, remove_from_archive/3]).
+	 extended_fields/0, store/8, write_prefs/4, get_prefs/2, select/6, export/1, remove_from_archive/3,
+	 is_empty_for_user/2, is_empty_for_room/3]).
 
 -include_lib("stdlib/include/ms_transform.hrl").
 -include("xmpp.hrl").
@@ -264,6 +265,23 @@ export(_Server) ->
               []
       end}].
 
+is_empty_for_user(LUser, LServer) ->
+    case ejabberd_sql:sql_query(
+	   LServer,
+	   ?SQL("select @(count(*))d from archive"
+                " where username=%(LUser)s and %(LServer)H")) of
+		{selected, [{Res}]} ->
+			case Res of
+				0 -> true;
+				_ -> false
+			end;
+		_ -> false
+	end.
+
+is_empty_for_room(LServer, LName, LHost) ->
+    LUser = jid:encode({LName, LHost, <<>>}),
+    is_empty_for_user(LUser, LServer).
+
 %%%===================================================================
 %%% Internal functions
 %%%===================================================================