%%%----------------------------------------------------------------------
%%% File    : mod_offline.erl
%%% Author  : Alexey Shchepin <alexey@process-one.net>
%%% Purpose : Store and manage offline messages in Mnesia database.
%%% Created :  5 Jan 2003 by Alexey Shchepin <alexey@process-one.net>
%%%
%%%
%%% ejabberd, Copyright (C) 2002-2010   ProcessOne
%%%
%%% This program is free software; you can redistribute it and/or
%%% modify it under the terms of the GNU General Public License as
%%% published by the Free Software Foundation; either version 2 of the
%%% License, or (at your option) any later version.
%%%
%%% This program is distributed in the hope that it will be useful,
%%% but WITHOUT ANY WARRANTY; without even the implied warranty of
%%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
%%% General Public License for more details.
%%%
%%% You should have received a copy of the GNU General Public License
%%% along with this program; if not, write to the Free Software
%%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
%%% 02111-1307 USA
%%%
%%%----------------------------------------------------------------------

-module(mod_offline).
-author('alexey@process-one.net').

-behaviour(gen_mod).

-export([start/2,
	 loop/1,
	 stop/1,
	 store_packet/3,
	 resend_offline_messages/2,
	 pop_offline_messages/3,
	 get_sm_features/5,
	 remove_expired_messages/0,
	 remove_old_messages/1,
	 remove_user/2,
	 get_queue_length/2,
	 webadmin_page/3,
	 webadmin_user/4,
	 webadmin_user_parse_query/5]).

-include_lib("exmpp/include/exmpp.hrl").

-include("ejabberd.hrl").
-include("web/ejabberd_http.hrl").
-include("web/ejabberd_web_admin.hrl").

-record(offline_msg, {us, timestamp, expire, from, to, packet}).

-define(PROCNAME, ejabberd_offline).
-define(OFFLINE_TABLE_LOCK_THRESHOLD, 1000).

% These are the namespace already declared by the stream opening. This is
% used at serialization time.
-define(DEFAULT_NS, ?NS_JABBER_CLIENT).
-define(PREFIXED_NS, [{?NS_XMPP, ?NS_XMPP_pfx}]).

%% default value for the maximum number of user messages
-define(MAX_USER_MESSAGES, infinity).

start(Host, Opts) ->
    HostB = list_to_binary(Host),
    mnesia:create_table(offline_msg,
			[{disc_only_copies, [node()]},
			 {type, bag},
			 {attributes, record_info(fields, offline_msg)}]),
    update_table(),
    ejabberd_hooks:add(offline_message_hook, HostB,
		       ?MODULE, store_packet, 50),
    ejabberd_hooks:add(resend_offline_messages_hook, HostB,
		       ?MODULE, pop_offline_messages, 50),
    ejabberd_hooks:add(remove_user, HostB,
		       ?MODULE, remove_user, 50),
    ejabberd_hooks:add(anonymous_purge_hook, HostB,
		       ?MODULE, remove_user, 50),
    ejabberd_hooks:add(disco_sm_features, HostB,
		       ?MODULE, get_sm_features, 50),
    ejabberd_hooks:add(disco_local_features, HostB,
		       ?MODULE, get_sm_features, 50),
    ejabberd_hooks:add(webadmin_page_host, HostB,
		       ?MODULE, webadmin_page, 50),
    ejabberd_hooks:add(webadmin_user, HostB,
		       ?MODULE, webadmin_user, 50),
    ejabberd_hooks:add(webadmin_user_parse_query, HostB,
                       ?MODULE, webadmin_user_parse_query, 50),
    AccessMaxOfflineMsgs = gen_mod:get_opt(access_max_user_messages, Opts, max_user_offline_messages),
    register(gen_mod:get_module_proc(Host, ?PROCNAME),
	     spawn(?MODULE, loop, [AccessMaxOfflineMsgs])).

loop(AccessMaxOfflineMsgs) ->
    receive
	#offline_msg{us=US} = Msg ->
	    Msgs = receive_all(US, [Msg]),
	    Len = length(Msgs),
	    {User, Host} = US,
	    MaxOfflineMsgs = get_max_user_messages(AccessMaxOfflineMsgs,
						   User, Host),
	    F = fun() ->
			%% Only count messages if needed:
			Count = if MaxOfflineMsgs =/= infinity ->
					Len + p1_mnesia:count_records(
						offline_msg, 
						#offline_msg{us=US, _='_'});
				   true -> 
					0
				end,
			if
			    Count > MaxOfflineMsgs ->
				discard_warn_sender(Msgs);
			    true ->
				if
				    Len >= ?OFFLINE_TABLE_LOCK_THRESHOLD ->
					mnesia:write_lock_table(offline_msg);
				    true ->
					ok
				end,
				lists:foreach(fun(M) ->
						      mnesia:write(M)
					      end, Msgs)
			end
		end,
	    mnesia:transaction(F),
	    loop(AccessMaxOfflineMsgs);
	_ ->
	    loop(AccessMaxOfflineMsgs)
    end.

%% Function copied from ejabberd_sm.erl:
get_max_user_messages(AccessRule, LUser, Host) ->
    case acl:match_rule(
	   Host, AccessRule, exmpp_jid:make(LUser, Host, "")) of
	Max when is_integer(Max) -> Max;
	infinity -> infinity;
	_ -> ?MAX_USER_MESSAGES
    end.

receive_all(US, Msgs) ->
    receive
	#offline_msg{us=US} = Msg ->
	    receive_all(US, [Msg | Msgs])
    after 0 ->
	    Msgs
    end.


stop(Host) ->
    HostB = list_to_binary(Host),
    ejabberd_hooks:delete(offline_message_hook, HostB,
			  ?MODULE, store_packet, 50),
    ejabberd_hooks:delete(resend_offline_messages_hook, HostB,
			  ?MODULE, pop_offline_messages, 50),
    ejabberd_hooks:delete(remove_user, HostB,
			  ?MODULE, remove_user, 50),
    ejabberd_hooks:delete(anonymous_purge_hook, HostB,
			  ?MODULE, remove_user, 50),
    ejabberd_hooks:delete(disco_sm_features, HostB, ?MODULE, get_sm_features, 50),
    ejabberd_hooks:delete(disco_local_features, HostB, ?MODULE, get_sm_features, 50),
    ejabberd_hooks:delete(webadmin_page_host, HostB,
			  ?MODULE, webadmin_page, 50),
    ejabberd_hooks:delete(webadmin_user, HostB,
			  ?MODULE, webadmin_user, 50),
    ejabberd_hooks:delete(webadmin_user_parse_query, HostB,
                          ?MODULE, webadmin_user_parse_query, 50),
    Proc = gen_mod:get_module_proc(Host, ?PROCNAME),
    exit(whereis(Proc), stop),
    {wait, Proc}.

get_sm_features(Acc, _From, _To, <<>>, _Lang) ->
    Feats = case Acc of
		{result, I} -> I;
		_ -> []
	    end,
    {result, Feats ++ [?NS_MSGOFFLINE]};

get_sm_features(_Acc, _From, _To, ?NS_MSGOFFLINE, _Lang) ->
    %% override all lesser features...
    {result, []};

get_sm_features(Acc, _From, _To, _Node, _Lang) ->
    Acc.


store_packet(From, To, Packet) ->
    Type = exmpp_stanza:get_type(Packet),
    if
	(Type /= <<"error">>) and (Type /= <<"groupchat">>) and
	(Type /= <<"headline">>) ->
	    case check_event_chatstates(From, To, Packet) of
		true ->
            LUser = exmpp_jid:prep_node_as_list(To),
            LServer = exmpp_jid:prep_domain_as_list(To),
		    TimeStamp = now(),
		    Expire = find_x_expire(TimeStamp, Packet#xmlel.children),
		    gen_mod:get_module_proc(LServer, ?PROCNAME) !
			#offline_msg{us = {LUser, LServer},
				     timestamp = TimeStamp,
				     expire = Expire,
				     from = From,
				     to = To,
				     packet = Packet},
		    stop;
		_ ->
		    ok
	    end;
	true ->
	    ok
    end.

%% Check if the packet has any content about XEP-0022 or XEP-0085
check_event_chatstates(From, To, Packet) ->
    case find_x_event_chatstates(Packet#xmlel.children, {false, false, false}) of
	%% There wasn't any x:event or chatstates subelements
	{false, false, _} ->
	    true;
	%% There a chatstates subelement and other stuff, but no x:event
	{false, CEl, true} when CEl /= false ->
  	    true;
	%% There was only a subelement: a chatstates
	{false, CEl, false} when CEl /= false ->
	    %% Don't allow offline storage
	    false;
	%% There was an x:event element, and maybe also other stuff
	{El, _, _} when El /= false->
	    case exmpp_xml:get_element(El, 'id') of
		undefined ->
		    case exmpp_xml:get_element(El, 'offline') of
			undefined ->
			    true;
			_ ->
			    ID = case exmpp_stanza:get_id(Packet) of
				     undefined ->
					 #xmlel{ns = ?NS_MESSAGE_EVENT, name = 'id'};
				     S ->
					 #xmlel{ns = ?NS_MESSAGE_EVENT, name = 'id',
					   children = [#xmlcdata{cdata =
					       S}]}
				 end,
			    X = #xmlel{ns = ?NS_MESSAGE_EVENT, name = 'x', children =
			      [ID, #xmlel{ns = ?NS_MESSAGE_EVENT, name = 'offline'}]},
			    ejabberd_router:route(
			      To, From, exmpp_xml:set_children(Packet, [X])),
			    true
		    end;
		_ ->
		    false
	    end
    end.

%% Check if the packet has subelements about XEP-0022, XEP-0085 or other
find_x_event_chatstates([], Res) ->
    Res;
find_x_event_chatstates([#xmlel{ns = ?NS_MESSAGE_EVENT} = El | Els], {_, B, C}) ->
    find_x_event_chatstates(Els, {El, B, C});
find_x_event_chatstates([#xmlel{ns = ?NS_CHATSTATES} = El | Els], {A, _, C}) ->
    find_x_event_chatstates(Els, {A, El, C});
find_x_event_chatstates([#xmlcdata{} = _ | Els], {A, B, C}) ->
    find_x_event_chatstates(Els, {A, B, C});
find_x_event_chatstates([_ | Els], {A, B, _}) ->
    find_x_event_chatstates(Els, {A, B, true}).

find_x_expire(_, []) ->
    never;
find_x_expire(TimeStamp, [#xmlel{ns = ?NS_MESSAGE_EXPIRE} = El | _Els]) ->
    Val = exmpp_xml:get_attribute_as_list(El, 'seconds', ""),
    case catch list_to_integer(Val) of
	{'EXIT', _} ->
	    never;
	Int when Int > 0 ->
	    {MegaSecs, Secs, MicroSecs} = TimeStamp,
	    S = MegaSecs * 1000000 + Secs + Int,
	    MegaSecs1 = S div 1000000,
	    Secs1 = S rem 1000000,
	    {MegaSecs1, Secs1, MicroSecs};
	_ ->
	    never
    end;
find_x_expire(TimeStamp, [_ | Els]) ->
    find_x_expire(TimeStamp, Els).


resend_offline_messages(User, Server) ->
    try
	LUser = exmpp_stringprep:nodeprep(User),
	LServer = exmpp_stringprep:nameprep(Server),
	US = {LUser, LServer},
	F = fun() ->
		    Rs = mnesia:wread({offline_msg, US}),
		    mnesia:delete({offline_msg, US}),
		    Rs
	    end,
	case mnesia:transaction(F) of
	    {atomic, Rs} ->
		lists:foreach(
		  fun(R) ->
			  Packet = R#offline_msg.packet,
			  ejabberd_sm !
			      {route,
			       R#offline_msg.from,
			       R#offline_msg.to,
			       exmpp_xml:append_children(
				 Packet,
				 [jlib:timestamp_to_xml(
				    calendar:now_to_universal_time(R#offline_msg.timestamp),
				    utc,
				    exmpp_jid:make("", Server, ""),
				    "Offline Storage"),
				  %% TODO: Delete the next three lines once XEP-0091 is Obsolete
				  jlib:timestamp_to_xml(
				    calendar:now_to_universal_time(
				      R#offline_msg.timestamp))
				 ]
				)}
		  end,
		  lists:keysort(#offline_msg.timestamp, Rs));
	    _ ->
		ok
	end
    catch
	_ ->
	    ok
    end.

pop_offline_messages(Ls, User, Server)
        when is_binary(User), is_binary(Server) ->
    try
	LUser = binary_to_list(User),
	LServer = binary_to_list(Server),
	US = {LUser, LServer},
	F = fun() ->
		    Rs = mnesia:wread({offline_msg, US}),
		    mnesia:delete({offline_msg, US}),
		    Rs
	    end,
	case mnesia:transaction(F) of
	    {atomic, Rs} ->
		TS = now(),
		Ls ++ lists:map(
			fun(R) ->
				Packet = R#offline_msg.packet,
				{route,
				 R#offline_msg.from,
				 R#offline_msg.to,
			       exmpp_xml:append_children(
				 Packet,
				 [jlib:timestamp_to_xml(
				    calendar:now_to_universal_time(
				      R#offline_msg.timestamp),
				    utc,
				    exmpp_jid:make("", Server, ""),
				    "Offline Storage"),
				  %% TODO: Delete the next three lines once XEP-0091 is Obsolete
				  jlib:timestamp_to_xml(
				    calendar:now_to_universal_time(
				      R#offline_msg.timestamp))]
				)}
			end,
			lists:filter(
			  fun(R) ->
				case R#offline_msg.expire of
				    never ->
					true;
				    TimeStamp ->
					TS < TimeStamp
				end
			  end,
			  lists:keysort(#offline_msg.timestamp, Rs)));
	    _ ->
		Ls
	end
    catch
	_ ->
	    Ls
    end.


remove_expired_messages() ->
    TimeStamp = now(),
    F = fun() ->
		mnesia:write_lock_table(offline_msg),
		mnesia:foldl(
		  fun(Rec, _Acc) ->
			  case Rec#offline_msg.expire of
			      never ->
				  ok;
			      TS ->
				  if
				      TS < TimeStamp ->
					  mnesia:delete_object(Rec);
				      true ->
					  ok
				  end
			  end
		  end, ok, offline_msg)
	end,
    mnesia:transaction(F).

remove_old_messages(Days) ->
    {MegaSecs, Secs, _MicroSecs} = now(),
    S = MegaSecs * 1000000 + Secs - 60 * 60 * 24 * Days,
    MegaSecs1 = S div 1000000,
    Secs1 = S rem 1000000,
    TimeStamp = {MegaSecs1, Secs1, 0},
    F = fun() ->
		mnesia:write_lock_table(offline_msg),
		mnesia:foldl(
		  fun(#offline_msg{timestamp = TS} = Rec, _Acc)
		     when TS < TimeStamp ->
			  mnesia:delete_object(Rec);
		     (_Rec, _Acc) -> ok
		  end, ok, offline_msg)
	end,
    mnesia:transaction(F).

remove_user(User, Server) when is_binary(User), is_binary(Server) ->
    try
	LUser = exmpp_stringprep:nodeprep(User),
	LServer = exmpp_stringprep:nameprep(Server),
	US = {LUser, LServer},
	F = fun() ->
		    mnesia:delete({offline_msg, US})
	    end,
	mnesia:transaction(F)
    catch
	_ ->
	    ok
    end.

update_table() ->
    Fields = record_info(fields, offline_msg),
    case mnesia:table_info(offline_msg, attributes) of
	Fields ->
	    convert_to_exmpp();
	[user, timestamp, expire, from, to, packet] ->
	    ?INFO_MSG("Converting offline_msg table from "
		      "{user, timestamp, expire, from, to, packet} format", []),
	    Host = ?MYNAME,
	    {atomic, ok} = mnesia:create_table(
			     mod_offline_tmp_table,
			     [{disc_only_copies, [node()]},
			      {type, bag},
			      {local_content, true},
			      {record_name, offline_msg},
			      {attributes, record_info(fields, offline_msg)}]),
	    mnesia:transform_table(offline_msg, ignore, Fields),
	    F1 = fun() ->
			 mnesia:write_lock_table(mod_offline_tmp_table),
			 mnesia:foldl(
			   fun(#offline_msg{us = U, from = F, to = T, packet = P} = R, _) ->
				   U1 = convert_jid_to_exmpp(U),
				   F1 = jlib:from_old_jid(F),
				   T1 = jlib:from_old_jid(T),
				   P1 = exmpp_xml:xmlelement_to_xmlel(
				     P,
				     [?DEFAULT_NS],
				     ?PREFIXED_NS),
				   New_R = R#offline_msg{
				     us = {U1, Host},
				     from = F1,
				     to = T1,
				     packet = P1
				   },
				   mnesia:dirty_write(
				     mod_offline_tmp_table,
				     New_R)
			   end, ok, offline_msg)
		 end,
	    mnesia:transaction(F1),
	    mnesia:clear_table(offline_msg),
	    F2 = fun() ->
			 mnesia:write_lock_table(offline_msg),
			 mnesia:foldl(
			   fun(R, _) ->
				   mnesia:dirty_write(R)
			   end, ok, mod_offline_tmp_table)
		 end,
	    mnesia:transaction(F2),
	    mnesia:delete_table(mod_offline_tmp_table);
	[user, timestamp, from, to, packet] ->
	    ?INFO_MSG("Converting offline_msg table from "
		      "{user, timestamp, from, to, packet} format", []),
	    Host = ?MYNAME,
	    {atomic, ok} = mnesia:create_table(
			     mod_offline_tmp_table,
			     [{disc_only_copies, [node()]},
			      {type, bag},
			      {local_content, true},
			      {record_name, offline_msg},
			      {attributes, record_info(fields, offline_msg)}]),
	    mnesia:transform_table(
	      offline_msg,
	      fun({_, U, TS, F, T, P}) ->
		      Expire = find_x_expire(TS, P#xmlelement.children),
		      U1 = convert_jid_to_exmpp(U),
		      F1 = jlib:from_old_jid(F),
		      T1 = jlib:from_old_jid(T),
		      P1 = exmpp_xml:xmlelement_to_xmlel(
			P,
			[?DEFAULT_NS],
			?PREFIXED_NS),
		      #offline_msg{us = U1,
				   timestamp = TS,
				   expire = Expire,
				   from = F1,
				   to = T1,
				   packet = P1}
	      end, Fields),
	    F1 = fun() ->
			 mnesia:write_lock_table(mod_offline_tmp_table),
			 mnesia:foldl(
			   fun(#offline_msg{us = U} = R, _) ->
				   mnesia:dirty_write(
				     mod_offline_tmp_table,
				     R#offline_msg{us = {U, Host}})
			   end, ok, offline_msg)
		 end,
	    mnesia:transaction(F1),
	    mnesia:clear_table(offline_msg),
	    F2 = fun() ->
			 mnesia:write_lock_table(offline_msg),
			 mnesia:foldl(
			   fun(R, _) ->
				   mnesia:dirty_write(R)
			   end, ok, mod_offline_tmp_table)
		 end,
	    mnesia:transaction(F2),
	    mnesia:delete_table(mod_offline_tmp_table);
	_ ->
	    ?INFO_MSG("Recreating offline_msg table", []),
	    mnesia:transform_table(offline_msg, ignore, Fields)
    end.

convert_to_exmpp() ->
    Fun = fun() ->
	case mnesia:first(offline_msg) of
	    '$end_of_table' ->
		none;
	    Key ->
		case mnesia:read({offline_msg, Key}) of
		    [#offline_msg{packet = #xmlel{}} | _] ->
			none;
		    [#offline_msg{packet = #xmlelement{}} | _] ->
			mnesia:foldl(fun convert_to_exmpp2/2,
			  done, offline_msg, write)
		end
	end
    end,
    mnesia:transaction(Fun).

convert_to_exmpp2(#offline_msg{
  us = {US_U, US_S},
  from = From,
  to = To,
  packet = Packet} = R, Acc) ->
    % Remove old entry.
    mnesia:delete_object(R),
    % Convert "" to undefined in JIDs.
    US_U1 = convert_jid_to_exmpp(US_U),
    US_S1 = convert_jid_to_exmpp(US_S),
    From1 = jlib:from_old_jid(From),
    To1 = jlib:from_old_jid(To),
    % Convert stanza.
    Packet1 = exmpp_xml:xmlelement_to_xmlel(Packet,
      [?DEFAULT_NS], ?PREFIXED_NS),
    % Prepare the new record.
    New_R = R#offline_msg{
      us = {US_U1, US_S1},
      from = From1,
      to = To1,
      packet = Packet1},
    % Write the new record.
    mnesia:write(New_R),
    Acc.

convert_jid_to_exmpp("") -> undefined;
convert_jid_to_exmpp(V)  -> V.

%% Helper functions:

%% Warn senders that their messages have been discarded:
discard_warn_sender(Msgs) ->
    lists:foreach(
      fun(#offline_msg{from=From, to=To, packet=Packet}) ->
	      ErrText = "Your contact offline message queue is full. The message has been discarded.",
	      Error = exmpp_stanza:error('resource-constraint',
		{"en", ErrText}),
	      Err = exmpp_stanza:reply_with_error(Packet, Error),
	      ejabberd_router:route(
		To,
		From, Err)
      end, Msgs).


webadmin_page(_, Host,
	      #request{us = _US,
		       path = ["user", U, "queue"],
		       q = Query,
		       lang = Lang} = _Request) ->
    Res = user_queue(U, Host, Query, Lang),
    {stop, Res};

webadmin_page(Acc, _, _) -> Acc.

user_queue(User, Server, Query, Lang) ->
    {US, MsgsAll, Res} = try
	US0 = {
	  exmpp_stringprep:nodeprep(User),
	  exmpp_stringprep:nameprep(Server)
	},
	{
	  US0,
	  lists:keysort(#offline_msg.timestamp,
			mnesia:dirty_read({offline_msg, US0})),
	  user_queue_parse_query(US0, Query)
	}
    catch
	_ ->
	    {{"invalid", "invalid"}, [], nothing}
    end,
    Msgs = get_messages_subset(User, Server, MsgsAll),
    FMsgs =
	lists:map(
	  fun(#offline_msg{timestamp = TimeStamp, from = From, to = To,
			   packet = Packet} = Msg) ->
		  ID = jlib:encode_base64(binary_to_list(term_to_binary(Msg))),
		  {{Year, Month, Day}, {Hour, Minute, Second}} =
		      calendar:now_to_local_time(TimeStamp),
		  Time = lists:flatten(
			   io_lib:format(
			     "~w-~.2.0w-~.2.0w ~.2.0w:~.2.0w:~.2.0w",
			     [Year, Month, Day, Hour, Minute, Second])),
		  SFrom = exmpp_jid:to_list(From),
		  STo = exmpp_jid:to_list(To),
		  Packet1 = exmpp_stanza:set_jids(Packet, SFrom, STo),
		  FPacket = exmpp_xml:node_to_list(
		    exmpp_xml:indent_document(Packet1, <<"  ">>),
		    [?DEFAULT_NS], ?PREFIXED_NS),
		  ?XE("tr",
		      [?XAE("td", [?XMLATTR('class', <<"valign">>)], [?INPUT("checkbox", "selected", ID)]),
		       ?XAC("td", [?XMLATTR('class', <<"valign">>)], Time),
		       ?XAC("td", [?XMLATTR('class', <<"valign">>)], SFrom),
		       ?XAC("td", [?XMLATTR('class', <<"valign">>)], STo),
		       ?XAE("td", [?XMLATTR('class', <<"valign">>)], [?XC("pre", FPacket)])]
		     )
	  end, Msgs),
    [?XC("h1", io_lib:format(?T("~s's Offline Messages Queue"),
			     [us_to_list(US)]))] ++
	case Res of
	    ok -> [?XREST("Submitted")];
	    nothing -> []
	end ++
	[?XAE("form", [?XMLATTR('action', <<"">>), ?XMLATTR('method', <<"post">>)],
	      [?XE("table",
		   [?XE("thead",
			[?XE("tr",
			     [?X("td"),
			      ?XCT("td", "Time"),
			      ?XCT("td", "From"),
			      ?XCT("td", "To"),
			      ?XCT("td", "Packet")
			     ])]),
		    ?XE("tbody",
			if
			    FMsgs == [] ->
				[?XE("tr",
				     [?XAC("td", [?XMLATTR('colspan', <<"4">>)], " ")]
				    )];
			    true ->
				FMsgs
			end
		       )]),
	       ?BR,
	       ?INPUTT("submit", "delete", "Delete Selected")
	      ])].

user_queue_parse_query(US, Query) ->
    case lists:keysearch("delete", 1, Query) of
	{value, _} ->
	    Msgs = lists:keysort(#offline_msg.timestamp,
				 mnesia:dirty_read({offline_msg, US})),
	    F = fun() ->
			lists:foreach(
			  fun(Msg) ->
				  ID = jlib:encode_base64(
					 binary_to_list(term_to_binary(Msg))),
				  case lists:member({"selected", ID}, Query) of
				      true ->
					  mnesia:delete_object(Msg);
				      false ->
					  ok
				  end
			  end, Msgs)
		end,
	    mnesia:transaction(F),
	    ok;
	false ->
	    nothing
    end.

us_to_list({User, Server}) ->
    exmpp_jid:to_list(User, Server).

get_queue_length(User, Server) ->
    length(mnesia:dirty_read({offline_msg, {User, Server}})).

get_messages_subset(User, Host, MsgsAll) ->
    Access = gen_mod:get_module_opt(Host, ?MODULE, access_max_user_messages,
				    max_user_offline_messages),
    MaxOfflineMsgs = case get_max_user_messages(Access, User, Host) of
			 Number when is_integer(Number) -> Number;
			 _ -> 100
		     end,
    Length = length(MsgsAll),
    get_messages_subset2(MaxOfflineMsgs, Length, MsgsAll).

get_messages_subset2(Max, Length, MsgsAll) when Length =< Max*2 ->
    MsgsAll;
get_messages_subset2(Max, Length, MsgsAll) ->
    FirstN = Max,
    {MsgsFirstN, Msgs2} = lists:split(FirstN, MsgsAll),
    MsgsLastN = lists:nthtail(Length - FirstN - FirstN, Msgs2),
    NoJID = exmpp_jid:make("...", "...", ""),
    IntermediateMsg = #offline_msg{timestamp = now(), from = NoJID, to = NoJID,
				   packet = exmpp_xml:element("...")},
    MsgsFirstN ++ [IntermediateMsg] ++ MsgsLastN.

webadmin_user(Acc, User, Server, Lang) ->
    QueueLen = get_queue_length(exmpp_stringprep:nodeprep(User), exmpp_stringprep:nameprep(Server)),
    FQueueLen = [?AC("queue/", integer_to_list(QueueLen))],
    Acc ++ [?XCT("h3", "Offline Messages:")] ++ FQueueLen ++ [?C(" "), ?INPUTT("submit", "removealloffline", "Remove All Offline Messages")].

webadmin_user_parse_query(_, "removealloffline", User, Server, _Query) ->
    US = {User, Server},
    F = fun() ->
            mnesia:write_lock_table(offline_msg),
            lists:foreach(
              fun(Msg) ->
                      mnesia:delete_object(Msg)
              end, mnesia:dirty_read({offline_msg, US}))
        end,
    case mnesia:transaction(F) of
         {aborted, Reason} ->
            ?ERROR_MSG("Failed to remove offline messages: ~p", [Reason]),
            {stop, error};
         {atomic, ok} ->
            ?INFO_MSG("Removed all offline messages for ~s@~s", [User, Server]),
            {stop, ok}
    end;
webadmin_user_parse_query(Acc, _Action, _User, _Server, _Query) ->
    Acc.