%%%----------------------------------------------------------------------
%%% File : ejabberd_hooks.erl
%%% Author : Alexey Shchepin <alexey@process-one.net>
%%% Purpose : Manage hooks
%%% Created : 8 Aug 2004 by Alexey Shchepin <alexey@process-one.net>
%%%
%%%
%%% ejabberd, Copyright (C) 2002-2021 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.,
%%% 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
%%%
%%%----------------------------------------------------------------------
-module(ejabberd_hooks).
-author('alexey@process-one.net').
-behaviour(gen_server).
%% External exports
-export([start_link/0,
add/3,
add/4,
add/5,
delete/3,
delete/4,
delete/5,
run/2,
run/3,
run_fold/3,
run_fold/4]).
%% gen_server callbacks
-export([init/1,
handle_call/3,
handle_cast/2,
code_change/3,
handle_info/2,
terminate/2]).
-include("logger.hrl").
-include("ejabberd_stacktrace.hrl").
-record(state, {}).
-type hook() :: {Seq :: integer(), Module :: atom(), Function :: atom() | fun()}.
%%%----------------------------------------------------------------------
%%% API
%%%----------------------------------------------------------------------
start_link() ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
-spec add(atom(), fun(), integer()) -> ok.
%% @doc See add/4.
add(Hook, Function, Seq) when is_function(Function) ->
add(Hook, global, undefined, Function, Seq).
-spec add(atom(), HostOrModule :: binary() | atom(), fun() | atom() , integer()) -> ok.
add(Hook, Host, Function, Seq) when is_function(Function) ->
add(Hook, Host, undefined, Function, Seq);
%% @doc Add a module and function to this hook.
%% The integer sequence is used to sort the calls: low number is called before high number.
add(Hook, Module, Function, Seq) ->
add(Hook, global, Module, Function, Seq).
-spec add(atom(), binary() | global, atom(), atom() | fun(), integer()) -> ok.
add(Hook, Host, Module, Function, Seq) ->
gen_server:call(?MODULE, {add, Hook, Host, Module, Function, Seq}).
-spec delete(atom(), fun(), integer()) -> ok.
%% @doc See del/4.
delete(Hook, Function, Seq) when is_function(Function) ->
delete(Hook, global, undefined, Function, Seq).
-spec delete(atom(), binary() | atom(), atom() | fun(), integer()) -> ok.
delete(Hook, Host, Function, Seq) when is_function(Function) ->
delete(Hook, Host, undefined, Function, Seq);
%% @doc Delete a module and function from this hook.
%% It is important to indicate exactly the same information than when the call was added.
delete(Hook, Module, Function, Seq) ->
delete(Hook, global, Module, Function, Seq).
-spec delete(atom(), binary() | global, atom(), atom() | fun(), integer()) -> ok.
delete(Hook, Host, Module, Function, Seq) ->
gen_server:call(?MODULE, {delete, Hook, Host, Module, Function, Seq}).
-spec run(atom(), list()) -> ok.
%% @doc Run the calls of this hook in order, don't care about function results.
%% If a call returns stop, no more calls are performed.
run(Hook, Args) ->
run(Hook, global, Args).
-spec run(atom(), binary() | global, list()) -> ok.
run(Hook, Host, Args) ->
try ets:lookup(hooks, {Hook, Host}) of
[{_, Ls}] ->
run1(Ls, Hook, Args);
[] ->
ok
catch _:badarg ->
ok
end.
-spec run_fold(atom(), T, list()) -> T.
%% @doc Run the calls of this hook in order.
%% The arguments passed to the function are: [Val | Args].
%% The result of a call is used as Val for the next call.
%% If a call returns 'stop', no more calls are performed.
%% If a call returns {stop, NewVal}, no more calls are performed and NewVal is returned.
run_fold(Hook, Val, Args) ->
run_fold(Hook, global, Val, Args).
-spec run_fold(atom(), binary() | global, T, list()) -> T.
run_fold(Hook, Host, Val, Args) ->
try ets:lookup(hooks, {Hook, Host}) of
[{_, Ls}] ->
run_fold1(Ls, Hook, Val, Args);
[] ->
Val
catch _:badarg ->
Val
end.
%%%----------------------------------------------------------------------
%%% Callback functions from gen_server
%%%----------------------------------------------------------------------
init([]) ->
_ = ets:new(hooks, [named_table, {read_concurrency, true}]),
{ok, #state{}}.
handle_call({add, Hook, Host, Module, Function, Seq}, _From, State) ->
HookFormat = {Seq, Module, Function},
Reply = handle_add(Hook, Host, HookFormat),
{reply, Reply, State};
handle_call({delete, Hook, Host, Module, Function, Seq}, _From, State) ->
HookFormat = {Seq, Module, Function},
Reply = handle_delete(Hook, Host, HookFormat),
{reply, Reply, State};
handle_call(Request, From, State) ->
?WARNING_MSG("Unexpected call from ~p: ~p", [From, Request]),
{noreply, State}.
-spec handle_add(atom(), atom(), hook()) -> ok.
handle_add(Hook, Host, El) ->
case ets:lookup(hooks, {Hook, Host}) of
[{_, Ls}] ->
case lists:member(El, Ls) of
true ->
ok;
false ->
NewLs = lists:merge(Ls, [El]),
ets:insert(hooks, {{Hook, Host}, NewLs}),
ok
end;
[] ->
NewLs = [El],
ets:insert(hooks, {{Hook, Host}, NewLs}),
ok
end.
-spec handle_delete(atom(), atom(), hook()) -> ok.
handle_delete(Hook, Host, El) ->
case ets:lookup(hooks, {Hook, Host}) of
[{_, Ls}] ->
NewLs = lists:delete(El, Ls),
ets:insert(hooks, {{Hook, Host}, NewLs}),
ok;
[] ->
ok
end.
handle_cast(Msg, State) ->
?WARNING_MSG("Unexpected cast: ~p", [Msg]),
{noreply, State}.
handle_info(Info, State) ->
?WARNING_MSG("Unexpected info: ~p", [Info]),
{noreply, State}.
terminate(_Reason, _State) ->
ok.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
%%%----------------------------------------------------------------------
%%% Internal functions
%%%----------------------------------------------------------------------
-spec run1([hook()], atom(), list()) -> ok.
run1([], _Hook, _Args) ->
ok;
run1([{_Seq, Module, Function} | Ls], Hook, Args) ->
Res = safe_apply(Hook, Module, Function, Args),
case Res of
'EXIT' ->
run1(Ls, Hook, Args);
stop ->
ok;
_ ->
run1(Ls, Hook, Args)
end.
-spec run_fold1([hook()], atom(), T, list()) -> T.
run_fold1([], _Hook, Val, _Args) ->
Val;
run_fold1([{_Seq, Module, Function} | Ls], Hook, Val, Args) ->
Res = safe_apply(Hook, Module, Function, [Val | Args]),
case Res of
'EXIT' ->
run_fold1(Ls, Hook, Val, Args);
stop ->
Val;
{stop, NewVal} ->
NewVal;
NewVal ->
run_fold1(Ls, Hook, NewVal, Args)
end.
-spec safe_apply(atom(), atom(), atom() | fun(), list()) -> any().
safe_apply(Hook, Module, Function, Args) ->
?DEBUG("Running hook ~p: ~p:~p/~B",
[Hook, Module, Function, length(Args)]),
try if is_function(Function) ->
apply(Function, Args);
true ->
apply(Module, Function, Args)
end
catch ?EX_RULE(E, R, St) when E /= exit; R /= normal ->
Stack = ?EX_STACK(St),
?ERROR_MSG("Hook ~p crashed when running ~p:~p/~p:~n" ++
string:join(
["** ~ts"|
["** Arg " ++ integer_to_list(I) ++ " = ~p"
|| I <- lists:seq(1, length(Args))]],
"~n"),
[Hook, Module, Function, length(Args),
misc:format_exception(2, E, R, Stack)|Args]),
'EXIT'
end.
