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%% 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/3]).
%% gen_statem.
-export([callback_mode/0]).
-export([init/1]).
-export([connected/3]).
-export([terminate/3]).
-export([code_change/4]).
-define(TIMEOUT, 60000).
-record(state, {ref, transport, socket}).
%% API.
start_link(Ref, Transport, Opts) ->
gen_statem:start_link(?MODULE, {Ref, Transport, Opts}, []).
%% gen_statem.
callback_mode() ->
[state_functions, state_enter].
init({Ref, Transport, _Opts = []}) ->
{ok, connected, #state{ref=Ref, transport=Transport}, ?TIMEOUT}.
connected(enter, connected, StateData=#state{
ref=Ref, transport=Transport}) ->
{ok, Socket} = ranch:handshake(Ref),
ok = Transport:setopts(Socket, [{active, once}, {packet, line}]),
{keep_state, StateData#state{socket=Socket}};
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, 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(B0) when is_binary(B0) ->
Size = bit_size(B0),
<<B1:Size/integer-little>> = B0,
case <<B1:Size/integer-big>> of
%% Take care of different possible line terminators.
<<$\n, $\r, B2/binary>> ->
%% CR/LF (Windows)
<<B2/binary, $\r, $\n>>;
<<$\n, B2/binary>> ->
%% LF (Linux, Mac OS X and later)
<<B2/binary, $\n>>;
<<$\r, B2/binary>> ->
%% CR (Mac Classic, ie prior to Mac OS X)
<<B2/binary, $\r>>
end.
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