%% Feel free to use, reuse and abuse the code in this file.
-module(reverse_protocol).
-behaviour(gen_statem).
-behaviour(ranch_protocol).
%% API.
-export([start_link/4]).
%% gen_statem.
-export([callback_mode/0]).
-export([init/1]).
-export([connected/3]).
-export([terminate/3]).
-export([code_change/4]).
-define(TIMEOUT, 5000).
-record(state, {socket, transport}).
%% API.
start_link(Ref, Socket, Transport, Opts) ->
{ok, proc_lib:spawn_link(?MODULE, init, [{Ref, Socket, Transport, Opts}])}.
%% gen_statem.
callback_mode() ->
state_functions.
init({Ref, Socket, Transport, _Opts = []}) ->
ok = ranch:accept_ack(Ref),
ok = Transport:setopts(Socket, [{active, once}, {packet, line}]),
gen_statem:enter_loop(?MODULE, [], connected,
#state{socket=Socket, transport=Transport},
[?TIMEOUT]).
connected(info, {tcp, Socket, Data}, _StateData=#state{
socket=Socket, transport=Transport})
when byte_size(Data) > 1 ->
Transport:setopts(Socket, [{active, once}]),
Transport:send(Socket, reverse_binary(Data)),
{keep_state_and_data, ?TIMEOUT};
connected(info, {tcp_closed, _Socket}, _StateData) ->
{stop, normal};
connected(info, {tcp_error, _, Reason}, _StateData) ->
{stop, Reason};
connected({call, From}, _Request, _StateData) ->
gen_statem:reply(From, ok),
keep_state_and_data;
connected(cast, _Msg, _StateData) ->
keep_state_and_data;
connected(timeout, _Msg, _StateData) ->
{stop, normal};
connected(_EventType, _Msg, _StateData) ->
{stop, normal}.
terminate(Reason, StateName, StateData=#state{
socket=Socket, transport=Transport})
when Socket=/=undefined andalso Transport=/=undefined ->
catch Transport:close(Socket),
terminate(Reason, StateName,
StateData#state{socket=undefined, transport=undefined});
terminate(_Reason, _StateName, _StateData) ->
ok.
code_change(_OldVsn, StateName, StateData, _Extra) ->
{ok, StateName, StateData}.
%% Internal.
reverse_binary(B) when is_binary(B) ->
[list_to_binary(lists:reverse(binary_to_list(
binary:part(B, {0, byte_size(B)-2})
))), "\r\n"].
