%%%----------------------------------------------------------------------
%%% File    : mod_proxy65_stream.erl
%%% Author  : Evgeniy Khramtsov <xram@jabber.ru>
%%% Purpose : Bytestream process.
%%% Created : 12 Oct 2006 by Evgeniy Khramtsov <xram@jabber.ru>
%%%
%%% 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_proxy65_stream).

-author('xram@jabber.ru').

-behaviour(p1_fsm).
-behaviour(ejabberd_listener).

%% gen_fsm callbacks.
-export([init/1, handle_event/3, handle_sync_event/4,
	 code_change/4, handle_info/3, terminate/3]).

%% gen_fsm states.
-export([accepting/2, wait_for_init/2, wait_for_auth/2,
	 wait_for_request/2, wait_for_activation/2,
	 stream_established/2]).

-export([start/3, stop/1, start_link/3, activate/2,
	 relay/3, accept/1, listen_options/0]).

-include("mod_proxy65.hrl").

-include("logger.hrl").

-define(WAIT_TIMEOUT, 60000).

-record(state,
	{socket :: inet:socket(),
         timer = make_ref() :: reference(),
         sha1 = <<"">> :: binary(),
         host = <<"">> :: binary(),
         auth_type = anonymous :: plain | anonymous,
         shaper = none :: ejabberd_shaper:shaper()}).

%% Unused callbacks
handle_event(_Event, StateName, StateData) ->
    {next_state, StateName, StateData}.

code_change(_OldVsn, StateName, StateData, _Extra) ->
    {ok, StateName, StateData}.

%%-------------------------------

start(gen_tcp, Socket, Opts) ->
    Host = proplists:get_value(server_host, Opts),
    p1_fsm:start(?MODULE, [Socket, Host], []).

start_link(gen_tcp, Socket, Opts) ->
    Host = proplists:get_value(server_host, Opts),
    p1_fsm:start_link(?MODULE, [Socket, Host], []).

init([Socket, Host]) ->
    process_flag(trap_exit, true),
    AuthType = mod_proxy65_opt:auth_type(Host),
    Shaper = mod_proxy65_opt:shaper(Host),
    RecvBuf = mod_proxy65_opt:recbuf(Host),
    SendBuf = mod_proxy65_opt:sndbuf(Host),
    TRef = erlang:send_after(?WAIT_TIMEOUT, self(), stop),
    inet:setopts(Socket, [{recbuf, RecvBuf}, {sndbuf, SendBuf}]),
    {ok, accepting,
     #state{host = Host, auth_type = AuthType,
	    socket = Socket, shaper = Shaper, timer = TRef}}.

terminate(_Reason, StateName, #state{sha1 = SHA1}) ->
    Mod = gen_mod:ram_db_mod(global, mod_proxy65),
    Mod:unregister_stream(SHA1),
    if StateName == stream_established ->
	   ?INFO_MSG("(~w) Bytestream terminated", [self()]);
       true -> ok
    end.

%%%------------------------------
%%% API.
%%%------------------------------
accept(StreamPid) ->
    p1_fsm:send_event(StreamPid, accept).

stop(StreamPid) -> StreamPid ! stop.

activate({P1, J1}, {P2, J2}) ->
    case catch {p1_fsm:sync_send_all_state_event(P1,
						  get_socket),
		p1_fsm:sync_send_all_state_event(P2, get_socket)}
	of
      {S1, S2} when is_port(S1), is_port(S2) ->
	  P1 ! {activate, P2, S2, J1, J2},
	  P2 ! {activate, P1, S1, J1, J2},
	  JID1 = jid:encode(J1),
	  JID2 = jid:encode(J2),
	  ?INFO_MSG("(~w:~w) Activated bytestream for ~ts "
		    "-> ~ts",
		    [P1, P2, JID1, JID2]),
	  ok;
      _ -> error
    end.

%%%-----------------------
%%% States
%%%-----------------------
accepting(accept, State) ->
    inet:setopts(State#state.socket, [{active, true}]),
    {next_state, wait_for_init, State}.

wait_for_init(Packet,
	      #state{socket = Socket, auth_type = AuthType} =
		  StateData) ->
    case mod_proxy65_lib:unpack_init_message(Packet) of
      {ok, AuthMethods} ->
	  Method = select_auth_method(AuthType, AuthMethods),
	  gen_tcp:send(Socket,
		       mod_proxy65_lib:make_init_reply(Method)),
	  case Method of
	    ?AUTH_ANONYMOUS ->
		{next_state, wait_for_request, StateData};
	    ?AUTH_PLAIN -> {next_state, wait_for_auth, StateData};
	    ?AUTH_NO_METHODS -> {stop, normal, StateData}
	  end;
      error -> {stop, normal, StateData}
    end.

wait_for_auth(Packet,
	      #state{socket = Socket, host = Host} = StateData) ->
    case mod_proxy65_lib:unpack_auth_request(Packet) of
      {User, Pass} ->
	  Result = ejabberd_auth:check_password(User, <<"">>, Host, Pass),
	  gen_tcp:send(Socket,
		       mod_proxy65_lib:make_auth_reply(Result)),
	  case Result of
	    true -> {next_state, wait_for_request, StateData};
	    false -> {stop, normal, StateData}
	  end;
      _ -> {stop, normal, StateData}
    end.

wait_for_request(Packet,
		 #state{socket = Socket} = StateData) ->
    Request = mod_proxy65_lib:unpack_request(Packet),
    case Request of
      #s5_request{sha1 = SHA1, cmd = connect} ->
	  Mod = gen_mod:ram_db_mod(global, mod_proxy65),
	  case Mod:register_stream(SHA1, self()) of
	    ok ->
		inet:setopts(Socket, [{active, false}]),
		gen_tcp:send(Socket,
			     mod_proxy65_lib:make_reply(Request)),
		{next_state, wait_for_activation,
		 StateData#state{sha1 = SHA1}};
	    _ ->
		Err = mod_proxy65_lib:make_error_reply(Request),
		gen_tcp:send(Socket, Err),
		{stop, normal, StateData}
	  end;
      #s5_request{cmd = udp} ->
	  Err = mod_proxy65_lib:make_error_reply(Request,
						 ?ERR_COMMAND_NOT_SUPPORTED),
	  gen_tcp:send(Socket, Err),
	  {stop, normal, StateData};
      _ -> {stop, normal, StateData}
    end.

wait_for_activation(_Data, StateData) ->
    {next_state, wait_for_activation, StateData}.

stream_established(_Data, StateData) ->
    {next_state, stream_established, StateData}.

%%%-----------------------
%%% Callbacks processing
%%%-----------------------

%% SOCKS5 packets.
handle_info({tcp, _S, Data}, StateName, StateData)
    when StateName /= wait_for_activation ->
    misc:cancel_timer(StateData#state.timer),
    TRef = erlang:send_after(?WAIT_TIMEOUT, self(), stop),
    p1_fsm:send_event(self(), Data),
    {next_state, StateName, StateData#state{timer = TRef}};
%% Activation message.
handle_info({activate, PeerPid, PeerSocket, IJid, TJid},
	    wait_for_activation, StateData) ->
    erlang:monitor(process, PeerPid),
    misc:cancel_timer(StateData#state.timer),
    MySocket = StateData#state.socket,
    Shaper = StateData#state.shaper,
    Host = StateData#state.host,
    MaxRate = find_maxrate(Shaper, IJid, TJid, Host),
    spawn_link(?MODULE, relay,
	       [MySocket, PeerSocket, MaxRate]),
    {next_state, stream_established, StateData};
%% Socket closed
handle_info({tcp_closed, _Socket}, _StateName,
	    StateData) ->
    {stop, normal, StateData};
handle_info({tcp_error, _Socket, _Reason}, _StateName,
	    StateData) ->
    {stop, normal, StateData};
%% Got stop message.
handle_info(stop, _StateName, StateData) ->
    {stop, normal, StateData};
%% Either linked process or peer process died.
handle_info({'EXIT', _, _}, _StateName, StateData) ->
    {stop, normal, StateData};
handle_info({'DOWN', _, _, _, _}, _StateName,
	    StateData) ->
    {stop, normal, StateData};
%% Packets of no interest
handle_info(_Info, StateName, StateData) ->
    {next_state, StateName, StateData}.

%% Socket request.
handle_sync_event(get_socket, _From,
		  wait_for_activation, StateData) ->
    Socket = StateData#state.socket,
    {reply, Socket, wait_for_activation, StateData};
handle_sync_event(_Event, _From, StateName,
		  StateData) ->
    {reply, error, StateName, StateData}.

%%%-------------------------------------------------
%%% Relay Process.
%%%-------------------------------------------------
relay(MySocket, PeerSocket, Shaper) ->
    case gen_tcp:recv(MySocket, 0) of
	{ok, Data} ->
	    case gen_tcp:send(PeerSocket, Data) of
		ok ->
		    {NewShaper, Pause} = ejabberd_shaper:update(Shaper, byte_size(Data)),
		    if Pause > 0 -> timer:sleep(Pause);
		       true -> pass
		    end,
		    relay(MySocket, PeerSocket, NewShaper);
		{error, _} = Err ->
		    Err
	    end;
	{error, _} = Err ->
	    Err
    end.

%%%------------------------
%%% Auxiliary functions
%%%------------------------
select_auth_method(plain, AuthMethods) ->
    case lists:member(?AUTH_PLAIN, AuthMethods) of
      true -> ?AUTH_PLAIN;
      false -> ?AUTH_NO_METHODS
    end;
select_auth_method(anonymous, AuthMethods) ->
    case lists:member(?AUTH_ANONYMOUS, AuthMethods) of
      true -> ?AUTH_ANONYMOUS;
      false -> ?AUTH_NO_METHODS
    end.

%% Obviously, we must use shaper with maximum rate.
find_maxrate(Shaper, JID1, JID2, Host) ->
    R1 = ejabberd_shaper:match(Host, Shaper, JID1),
    R2 = ejabberd_shaper:match(Host, Shaper, JID2),
    R = case ejabberd_shaper:get_max_rate(R1) >= ejabberd_shaper:get_max_rate(R2) of
	    true -> R1;
	    false -> R2
	end,
    ejabberd_shaper:new(R).

listen_options() ->
    [].
