%%%----------------------------------------------------------------------
%%% File    : mod_echo.erl
%%% Author  : Alexey Shchepin <alexey@process-one.net>
%%% Purpose : Simple ejabberd module.
%%% Created : 15 Jan 2003 by Alexey Shchepin <alexey@process-one.net>
%%%
%%%
%%% ejabberd, Copyright (C) 2002-2019   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(mod_echo).

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

-behaviour(gen_server).

-behaviour(gen_mod).

%% API
-export([start/2, stop/1, reload/3, do_client_version/3]).

-export([init/1, handle_call/3, handle_cast/2,
	 handle_info/2, terminate/2, code_change/3,
	 mod_opt_type/1, depends/2, mod_options/1]).

-include("logger.hrl").

-include("xmpp.hrl").

-record(state, {hosts = [] :: [binary()]}).

%%====================================================================
%% gen_mod API
%%====================================================================
start(Host, Opts) ->
    gen_mod:start_child(?MODULE, Host, Opts).

stop(Host) ->
    gen_mod:stop_child(?MODULE, Host).

reload(Host, NewOpts, OldOpts) ->
    Proc = gen_mod:get_module_proc(Host, ?MODULE),
    gen_server:cast(Proc, {reload, Host, NewOpts, OldOpts}).

depends(_Host, _Opts) ->
    [].

mod_opt_type(host) -> fun ejabberd_config:v_host/1;
mod_opt_type(hosts) -> fun ejabberd_config:v_hosts/1.

mod_options(_Host) ->
    [{host, <<"echo.@HOST@">>}, {hosts, []}].

%%====================================================================
%% gen_server callbacks
%%====================================================================

%%--------------------------------------------------------------------
%% Function: init(Args) -> {ok, State} |
%%                         {ok, State, Timeout} |
%%                         ignore               |
%%                         {stop, Reason}
%% Description: Initiates the server
%%--------------------------------------------------------------------
init([Host, Opts]) ->
    process_flag(trap_exit, true),
    Hosts = gen_mod:get_opt_hosts(Host, Opts),
    lists:foreach(
      fun(H) ->
	      ejabberd_router:register_route(H, Host)
      end, Hosts),
    {ok, #state{hosts = Hosts}}.

%%--------------------------------------------------------------------
%% Function: %% handle_call(Request, From, State) -> {reply, Reply, State} |
%%                                      {reply, Reply, State, Timeout} |
%%                                      {noreply, State} |
%%                                      {noreply, State, Timeout} |
%%                                      {stop, Reason, Reply, State} |
%%                                      {stop, Reason, State}
%% Description: Handling call messages
%%--------------------------------------------------------------------
handle_call(stop, _From, State) ->
    {stop, normal, ok, State}.

%%--------------------------------------------------------------------
%% Function: handle_cast(Msg, State) -> {noreply, State} |
%%                                      {noreply, State, Timeout} |
%%                                      {stop, Reason, State}
%% Description: Handling cast messages
%%--------------------------------------------------------------------
handle_cast({reload, Host, NewOpts, OldOpts}, State) ->
    NewMyHosts = gen_mod:get_opt_hosts(Host, NewOpts),
    OldMyHosts = gen_mod:get_opt_hosts(Host, OldOpts),
    lists:foreach(
      fun(H) ->
	      ejabberd_router:unregister_route(H)
      end, OldMyHosts -- NewMyHosts),
    lists:foreach(
      fun(H) ->
	      ejabberd_router:register_route(H, Host)
      end, NewMyHosts -- OldMyHosts),
    {noreply, State#state{hosts = NewMyHosts}};
handle_cast(Msg, State) ->
    ?WARNING_MSG("unexpected cast: ~p", [Msg]),
    {noreply, State}.

%%--------------------------------------------------------------------
%% Function: handle_info(Info, State) -> {noreply, State} |
%%                                       {noreply, State, Timeout} |
%%                                       {stop, Reason, State}
%% Description: Handling all non call/cast messages
%%--------------------------------------------------------------------
handle_info({route, Packet}, State) ->
    From = xmpp:get_from(Packet),
    To = xmpp:get_to(Packet),
    Packet2 = case From#jid.user of
		<<"">> ->
		    Lang = xmpp:get_lang(Packet),
		    Txt = <<"User part of JID in 'from' is empty">>,
		    xmpp:make_error(
		      Packet, xmpp:err_bad_request(Txt, Lang));
		_ ->
		    xmpp:set_from_to(Packet, To, From)
	      end,
    do_client_version(disabled, To, From),
    ejabberd_router:route(Packet2),
    {noreply, State};
handle_info(_Info, State) -> {noreply, State}.

%%--------------------------------------------------------------------
%% Function: terminate(Reason, State) -> void()
%% Description: This function is called by a gen_server when it is about to
%% terminate. It should be the opposite of Module:init/1 and do any necessary
%% cleaning up. When it returns, the gen_server terminates with Reason.
%% The return value is ignored.
%%--------------------------------------------------------------------
terminate(_Reason, State) ->
    lists:foreach(fun ejabberd_router:unregister_route/1, State#state.hosts).

%%--------------------------------------------------------------------
%% Func: code_change(OldVsn, State, Extra) -> {ok, NewState}
%% Description: Convert process state when code is changed
%%--------------------------------------------------------------------
code_change(_OldVsn, State, _Extra) -> {ok, State}.

%%--------------------------------------------------------------------
%% Example of routing XMPP packets using Erlang's message passing
%%--------------------------------------------------------------------

%% To enable this educational example, edit the function handle_info:
%% replace the argument 'disabled' with 'enabled' in the call to the
%% function do_client_version.

%% ejabberd provides a method to receive XMPP packets using Erlang's 
%% message passing mechanism. 
%%
%% The packets received by ejabberd are sent
%% to the local destination process by sending an Erlang message.
%% This means that you can receive XMPP stanzas in an Erlang process 
%% using Erlang's Receive, as long as this process is registered in
%% ejabberd as the process which handles the destination JID.
%%
%% This example function is called when a client queries the echo service.
%% This function then sends a query to the client, and waits 5 seconds to
%% receive an answer. The answer will only be accepted if it was sent
%% using exactly the same JID. We add a (mostly) random resource to
%% try to guarantee that the received response matches the request sent.
%% Finally, the received response is printed in the ejabberd log file.

%% THIS IS **NOT** HOW TO WRITE ejabberd CODE. THIS CODE IS RETARDED.

do_client_version(disabled, _From, _To) -> ok;
do_client_version(enabled, From, To) ->
    Random_resource = p1_rand:get_string(),
    From2 = From#jid{resource = Random_resource,
		     lresource = Random_resource},
    ID = p1_rand:get_string(),
    Packet = #iq{from = From2, to = To, type = get,
		 id = p1_rand:get_string(),
		 sub_els = [#version{}]},
    ejabberd_router:route(Packet),
    receive
	{route,
	 #iq{to = To, from = From2,
	     id = ID, type = result, sub_els = [#version{} = V]}} ->
	    ?INFO_MSG("Version of the client ~s:~n~s",
		      [jid:encode(To), xmpp:pp(V)])
    after 5000 -> % Timeout in miliseconds: 5 seconds
	    []
    end.
