  Copyright ( c ) 2019 - 2023 ,   <  >
%%
%% Permission to use, copy, modify, and/or distribute this software for any
%% purpose with or without fee is hereby granted, provided that the above
%% copyright notice and this permission notice appear in all copies.
%%
  THE SOFTWARE IS PROVIDED " AS IS " AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  ANY SPECIAL , DIRECT , INDIRECT , OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER RESULTING FROM LOSS OF USE , DATA OR PROFITS , WHETHER IN AN
%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

  Intermediary process for proxying TLS connections . This process
%% is started by Gun when CONNECT request is issued and stays alive
%% while the proxy connection exists.
%%
%% Data comes in and out of this process, which is responsible for
%% passing incoming/outgoing data through the fake ssl socket process
%% it created to perform the decoding/encoding operations.
%%
%% Normal scenario:
%%   Gun process -> TLS socket
%%
  One proxy socket scenario :
%%   Gun process -> gun_tls_proxy (proxied socket) -> TLS socket
%%
%% N proxy socket scenario:
%%   Gun process -> gun_tls_proxy -> ... -> gun_tls_proxy -> TLS socket
%%
  The difficult part is the connection . Because ssl : connect/4 does
%% not return until the connection is setup, and we need to send and
  receive data for the TLS handshake , we need a temporary process
%% to call this function, and communicate with it. Once the connection
%% is setup the temporary process is gone and things go back to normal.
%% The send operations also require a temporary process in order to avoid
  blocking because the same gun_tls_proxy process must send twice ( first
%% to the fake ssl socket and then to the outgoing socket).

-module(gun_tls_proxy).
-behaviour(gen_statem).

%% Gun-specific interface.
-export([start_link/7]).

  gun_tls_proxy_cb interface .
-export([cb_controlling_process/2]).
-export([cb_send/2]).
-export([cb_setopts/2]).

%% Gun transport.
-export([name/0]).
-export([messages/0]).
-export([connect/3]).
-export([connect/4]).
-export([send/2]).
-export([setopts/2]).
-export([sockname/1]).
-export([close/1]).

%% Internals.
-export([callback_mode/0]).
-export([init/1]).
-export([connect_proc/5]).
-export([not_connected/3]).
-export([connected/3]).

-record(state, {
	%% The pid of the owner process. This is where we send active messages.
	owner_pid :: pid(),
	owner_active = false :: false | once | true | pos_integer(),
	owner_buffer = <<>> :: binary(),

	%% The host/port the fake ssl socket thinks it's connected to.
	host :: inet:ip_address() | inet:hostname(),
	port :: inet:port_number(),

	%% The fake ssl socket we are using in the proxy.
	proxy_socket :: any(),
	proxy_pid :: pid(),
	proxy_active = false :: false | once | true | pos_integer(),
	proxy_buffer = <<>> :: binary(),

	%% The socket or proxy process we are sending to.
	out_socket :: any(),
	out_transport :: module(),
	out_messages :: {atom(), atom(), atom()}, %% @todo Missing passive.

	%% Extra information to be sent to the owner when the handshake completes.
	extra :: any()
}).

%-define(DEBUG_PROXY,1).
-ifdef(DEBUG_PROXY).
-define(DEBUG_LOG(Format, Args),
	io:format(user, "(~p) ~p:~p/~p:" ++ Format ++ "~n",
		[self(), ?MODULE, ?FUNCTION_NAME, ?FUNCTION_ARITY] ++ Args)).
-else.
-define(DEBUG_LOG(Format, Args), _ = Format, _ = Args, ok).
-endif.

%% Gun-specific interface.

start_link(Host, Port, Opts, Timeout, OutSocket, OutTransport, Extra) ->
	?DEBUG_LOG("host ~0p port ~0p opts ~0p timeout ~0p out_socket ~0p out_transport ~0p",
		[Host, Port, Opts, Timeout, OutSocket, OutTransport]),
	case gen_statem:start_link(?MODULE,
			{self(), Host, Port, Opts, Timeout, OutSocket, OutTransport, Extra},
			[]) of
		{ok, Pid} when is_port(OutSocket) ->
			ok = gen_tcp:controlling_process(OutSocket, Pid),
			{ok, Pid};
		{ok, Pid} when is_map(OutSocket) ->
			{ok, Pid};
		{ok, Pid} when not is_pid(OutSocket) ->
			ok = ssl:controlling_process(OutSocket, Pid),
			{ok, Pid};
		Other ->
			Other
	end.

  gun_tls_proxy_cb interface .

cb_controlling_process(Pid, ControllingPid) ->
	?DEBUG_LOG("pid ~0p controlling_pid ~0p", [Pid, ControllingPid]),
	gen_statem:cast(Pid, {?FUNCTION_NAME, ControllingPid}).

cb_send(Pid, Data) ->
	?DEBUG_LOG("pid ~0p data ~0p", [Pid, Data]),
	try
		gen_statem:call(Pid, {?FUNCTION_NAME, Data})
	catch
		exit:{noproc, _} ->
			{error, closed}
	end.

cb_setopts(Pid, Opts) ->
	?DEBUG_LOG("pid ~0p opts ~0p", [Pid, Opts]),
	try
		gen_statem:call(Pid, {?FUNCTION_NAME, Opts})
	catch
		exit:{noproc, _} ->
			{error, einval}
	end.

%% Transport.

name() -> tls_proxy.

messages() -> {tls_proxy, tls_proxy_closed, tls_proxy_error}.

-spec connect(_, _, _) -> no_return().
connect(_, _, _) ->
	error(not_implemented).

-spec connect(_, _, _, _) -> no_return().
connect(_, _, _, _) ->
	error(not_implemented).

-spec send(pid(), iodata()) -> ok | {error, atom()}.
send(Pid, Data) ->
	?DEBUG_LOG("pid ~0p data ~0p", [Pid, Data]),
	gen_statem:call(Pid, {?FUNCTION_NAME, Data}).

-spec setopts(pid(), list()) -> ok.
setopts(Pid, Opts) ->
	?DEBUG_LOG("pid ~0p opts ~0p", [Pid, Opts]),
	gen_statem:cast(Pid, {?FUNCTION_NAME, Opts}).

-spec sockname(pid())
	-> {ok, {inet:ip_address(), inet:port_number()}} | {error, atom()}.
sockname(Pid) ->
	?DEBUG_LOG("pid ~0p", [Pid]),
	gen_statem:call(Pid, ?FUNCTION_NAME).

-spec close(pid()) -> ok.
close(Pid) ->
	?DEBUG_LOG("pid ~0p", [Pid]),
	try
		gen_statem:call(Pid, ?FUNCTION_NAME)
	catch
  May happen for example when the handshake fails .
		exit:{noproc, _} ->
			ok
	end.

%% gen_statem.

callback_mode() -> state_functions.

init({OwnerPid, Host, Port, Opts, Timeout, OutSocket, OutTransport, Extra}) ->
	if
		is_pid(OutSocket) ->
			gen_statem:cast(OutSocket, {set_owner, self()});
		true ->
			ok
	end,
	Messages = case OutTransport of
		gen_tcp -> {tcp, tcp_closed, tcp_error};
		ssl -> {ssl, ssl_closed, ssl_error};
		_ -> OutTransport:messages()
	end,
	ProxyPid = spawn_link(?MODULE, connect_proc, [self(), Host, Port, Opts, Timeout]),
	?DEBUG_LOG("owner_pid ~0p host ~0p port ~0p opts ~0p timeout ~0p"
		" out_socket ~0p out_transport ~0p proxy_pid ~0p",
		[OwnerPid, Host, Port, Opts, Timeout, OutSocket, OutTransport, ProxyPid]),
	{ok, not_connected, #state{owner_pid=OwnerPid, host=Host, port=Port, proxy_pid=ProxyPid,
		out_socket=OutSocket, out_transport=OutTransport, out_messages=Messages,
		extra=Extra}}.

connect_proc(ProxyPid, Host, Port, Opts, Timeout) ->
	?DEBUG_LOG("proxy_pid ~0p host ~0p port ~0p opts ~0p timeout ~0p",
		[ProxyPid, Host, Port, Opts, Timeout]),
	_ = case ssl:connect(Host, Port, [
		{active, false}, binary,
		{cb_info, {gun_tls_proxy_cb, tls_proxy, tls_proxy_closed, tls_proxy_error}},
		{?MODULE, ProxyPid}
	|Opts], Timeout) of
		{ok, Socket} ->
			?DEBUG_LOG("socket ~0p", [Socket]),
			ok = ssl:controlling_process(Socket, ProxyPid),
			gen_statem:cast(ProxyPid, {?FUNCTION_NAME, {ok, Socket}});
		Error ->
			?DEBUG_LOG("error ~0p", [Error]),
			gen_statem:cast(ProxyPid, {?FUNCTION_NAME, Error})
	end,
	ok.

  Postpone events that require the proxy socket to be up .
not_connected({call, _}, Msg={send, _}, State) ->
	?DEBUG_LOG("postpone ~0p state ~0p", [Msg, State]),
	{keep_state_and_data, postpone};
not_connected(cast, Msg={setopts, _}, State) ->
	?DEBUG_LOG("postpone ~0p state ~0p", [Msg, State]),
	{keep_state_and_data, postpone};
not_connected(cast, Msg={connect_proc, {ok, Socket}}, State=#state{owner_pid=OwnerPid, extra=Extra}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {?MODULE, self(), {ok, ssl:negotiated_protocol(Socket)}, Extra},
  We need to spawn this call before OTP-21.2 because it triggers
	%% a cb_setopts call that blocks us. Might be OK to just leave it
  like this once we support 21.2 + only .
	spawn(fun() -> ok = ssl:setopts(Socket, [{active, true}]) end),
	{next_state, connected, State#state{proxy_socket=Socket}};
not_connected(cast, Msg={connect_proc, Error}, State=#state{owner_pid=OwnerPid, extra=Extra}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {?MODULE, self(), Error, Extra},
	%% We unlink from the owner process to avoid taking it down with us.
	unlink(OwnerPid),
	{stop, {shutdown, Error}, State};
not_connected(Type, Event, State) ->
	handle_common(Type, Event, State).

%% Send data through the proxy socket.
connected({call, From}, Msg={send, Data}, State=#state{proxy_socket=Socket}) ->
	?DEBUG_LOG("msg ~0p from ~0p state ~0p", [Msg, From, State]),
	Self = self(),
	SpawnedPid = spawn(fun() ->
		gen_statem:cast(Self, {send_result, From, ssl:send(Socket, Data)})
	end),
	?DEBUG_LOG("spawned ~0p", [SpawnedPid]),
	keep_state_and_data;
%% Messages from the proxy socket.
%%
  When the out_socket is a # { stream_ref : = _ } map we know that processing
%% of the data isn't yet complete. We wrap the message in a handle_continue
  tuple and provide the StreamRef for further processing .
connected(info, Msg={ssl, Socket, Data}, State=#state{owner_pid=OwnerPid, proxy_socket=Socket,
		out_socket=#{handle_continue_stream_ref := StreamRef}}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {handle_continue, StreamRef, {tls_proxy, self(), Data}},
	keep_state_and_data;
connected(info, Msg={ssl_closed, Socket}, State=#state{owner_pid=OwnerPid, proxy_socket=Socket,
		out_socket=#{handle_continue_stream_ref := StreamRef}}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {handle_continue, StreamRef, {tls_proxy_closed, self()}},
	keep_state_and_data;
connected(info, Msg={ssl_error, Socket, Reason}, State=#state{owner_pid=OwnerPid, proxy_socket=Socket,
		out_socket=#{handle_continue_stream_ref := StreamRef}}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {handle_continue, StreamRef, {tls_proxy_error, self(), Reason}},
	keep_state_and_data;
%% When the out_socket is anything else then the data is sent like normal
%% socket data. It does not need to be handled specially.
connected(info, Msg={ssl, Socket, Data}, State=#state{owner_pid=OwnerPid, proxy_socket=Socket}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {tls_proxy, self(), Data},
	keep_state_and_data;
connected(info, Msg={ssl_closed, Socket}, State=#state{owner_pid=OwnerPid, proxy_socket=Socket}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {tls_proxy_closed, self()},
	keep_state_and_data;
connected(info, Msg={ssl_error, Socket, Reason}, State=#state{owner_pid=OwnerPid, proxy_socket=Socket}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {tls_proxy_error, self(), Reason},
	keep_state_and_data;
connected(Type, Event, State) ->
	handle_common(Type, Event, State).

handle_common({call, From}, Msg={cb_send, Data}, State=#state{
		out_socket=OutSocket, out_transport=OutTransport}) ->
	?DEBUG_LOG("msg ~0p from ~0p state ~0p", [Msg, From, State]),
	Self = self(),
	SpawnedPid = spawn(fun() ->
		gen_statem:cast(Self, {send_result, From, OutTransport:send(OutSocket, Data)})
	end),
	?DEBUG_LOG("spawned ~0p", [SpawnedPid]),
	keep_state_and_data;
handle_common({call, From}, Msg={cb_setopts, Opts}, State=#state{
		out_socket=OutSocket, out_transport=OutTransport0}) ->
	?DEBUG_LOG("msg ~0p from ~0p state ~0p", [Msg, From, State]),
	OutTransport = case OutTransport0 of
		gen_tcp -> inet;
		_ -> OutTransport0
	end,
	{keep_state, proxy_setopts(Opts, State),
		{reply, From, OutTransport:setopts(OutSocket, [{active, true}])}};
handle_common({call, From}, Msg=sockname, State=#state{
		out_socket=OutSocket, out_transport=OutTransport}) ->
	?DEBUG_LOG("msg ~0p from ~0p state ~0p", [Msg, From, State]),
	{keep_state, State,
		{reply, From, OutTransport:sockname(OutSocket)}};
handle_common({call, From}, Msg=close, State) ->
	?DEBUG_LOG("msg ~0p from ~0p state ~0p", [Msg, From, State]),
	{stop_and_reply, {shutdown, close}, {reply, From, ok}};
handle_common(cast, Msg={set_owner, OwnerPid}, State) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	{keep_state, State#state{owner_pid=OwnerPid}};
handle_common(cast, Msg={cb_controlling_process, ProxyPid}, State) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	{keep_state, State#state{proxy_pid=ProxyPid}};
handle_common(cast, Msg={setopts, Opts}, State) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	{keep_state, owner_setopts(Opts, State)};
handle_common(cast, Msg={send_result, From, Result}, State) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	gen_statem:reply(From, Result),
	keep_state_and_data;
%% Messages from the real socket.
%% @todo Make _Socket and __Socket match again.
handle_common(info, Msg={OK, _Socket, Data}, State=#state{proxy_pid=ProxyPid,
		out_socket=__Socket, out_messages={OK, _, _}}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	ProxyPid ! {tls_proxy, self(), Data},
	keep_state_and_data;
handle_common(info, Msg={Closed, Socket}, State=#state{proxy_pid=ProxyPid,
		out_socket=Socket, out_messages={_, Closed, _}}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	ProxyPid ! {tls_proxy_closed, self()},
	keep_state_and_data;
handle_common(info, Msg={Error, Socket, Reason}, State=#state{proxy_pid=ProxyPid,
		out_socket=Socket, out_messages={_, _, Error}}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	ProxyPid ! {tls_proxy_error, self(), Reason},
	keep_state_and_data;
%% Other messages.
handle_common(Type, Msg, State) ->
	?DEBUG_LOG("IGNORED type ~0p msg ~0p state ~0p", [Type, Msg, State]),
	case Type of
		{call, From} ->
			{keep_state, State, {reply, From, {error, bad_call}}};
		_ ->
			keep_state_and_data
	end.

  Internal .

owner_setopts(Opts, State0) ->
	case [A || {active, A} <- Opts] of
		[] -> State0;
		[false] -> State0#state{owner_active=false};
		 [ 0 ] - > OwnerPid ! { tls_proxy_passive , self ( ) } , State0#state{owner_active = false } ;
		[Active] -> owner_active(State0#state{owner_active=Active})
	end.

owner_active(State=#state{owner_buffer= <<>>}) ->
	State;
owner_active(State=#state{owner_active=false}) ->
	State;
owner_active(State=#state{owner_pid=OwnerPid, owner_active=Active0, owner_buffer=Buffer}) ->
	OwnerPid ! {tls_proxy, self(), Buffer},
	Active = case Active0 of
		true -> true;
		once -> false%;
		 1 - > OwnerPid ! { tls_proxy_passive , self ( ) } , false ;
%		N -> N - 1
	end,
	State#state{owner_active=Active, owner_buffer= <<>>}.

proxy_setopts(Opts, State0=#state{proxy_socket=ProxySocket, proxy_pid=ProxyPid}) ->
	case [A || {active, A} <- Opts] of
		[] -> State0;
		[false] -> State0#state{proxy_active=false};
		[0] -> ProxyPid ! {tls_proxy_passive, ProxySocket}, State0#state{proxy_active=false};
		[Active] -> proxy_active(State0#state{proxy_active=Active})
	end.

proxy_active(State=#state{proxy_buffer= <<>>}) ->
	State;
proxy_active(State=#state{proxy_active=false}) ->
	State;
proxy_active(State=#state{proxy_pid=ProxyPid, proxy_active=Active0, proxy_buffer=Buffer}) ->
	ProxyPid ! {tls_proxy, self(), Buffer},
	Active = case Active0 of
		true -> true;
		once -> false;
		%% Note that tcp_passive is hardcoded in ssl until OTP-21.3.1.
		1 -> ProxyPid ! {tcp_passive, self()}, false;
		N -> N - 1
	end,
	State#state{proxy_active=Active, proxy_buffer= <<>>}.

-ifdef(DISABLED_TEST).
proxy_test_() ->
	{timeout, 15000, [
		{"TCP proxy", fun proxy_tcp1_t/0},
		{"TLS proxy", fun proxy_ssl1_t/0},
		{"Double TLS proxy", fun proxy_ssl2_t/0}
	]}.

proxy_tcp1_t() ->
	ssl:start(),
	{ok, Socket} = gen_tcp:connect("google.com", 443, [binary, {active, false}]),
	{ok, ProxyPid1} = start_link("google.com", 443, [], 5000, Socket, gen_tcp, #{}),
	send(ProxyPid1, <<"GET / HTTP/1.1\r\nHost: google.com\r\n\r\n">>),
	receive {tls_proxy, ProxyPid1, <<"HTTP/1.1 ", _/bits>>} -> ok end.

proxy_ssl1_t() ->
	ssl:start(),
	_ = (catch ct_helper:make_certs_in_ets()),
	{ok, _, Port} = do_proxy_start("google.com", 443),
	{ok, Socket} = ssl:connect("localhost", Port, [binary, {active, false}]),
	{ok, ProxyPid1} = start_link("google.com", 443, [], 5000, Socket, ssl, #{}),
	send(ProxyPid1, <<"GET / HTTP/1.1\r\nHost: google.com\r\n\r\n">>),
	receive {tls_proxy, ProxyPid1, <<"HTTP/1.1 ", _/bits>>} -> ok end.

proxy_ssl2_t() ->
	ssl:start(),
	_ = (catch ct_helper:make_certs_in_ets()),
	{ok, _, Port1} = do_proxy_start("google.com", 443),
	{ok, _, Port2} = do_proxy_start("localhost", Port1),
	{ok, Socket} = ssl:connect("localhost", Port2, [binary, {active, false}]),
	{ok, ProxyPid1} = start_link("localhost", Port1, [], 5000, Socket, ssl, #{}),
	{ok, ProxyPid2} = start_link("google.com", 443, [], 5000, ProxyPid1, ?MODULE, #{}),
	send(ProxyPid2, <<"GET / HTTP/1.1\r\nHost: google.com\r\n\r\n">>),
	receive {tls_proxy, ProxyPid2, <<"HTTP/1.1 ", _/bits>>} -> ok end.

do_proxy_start(Host, Port) ->
	Self = self(),
	Pid = spawn_link(fun() -> do_proxy_init(Self, Host, Port) end),
	ListenPort = receive_from(Pid),
	{ok, Pid, ListenPort}.

do_proxy_init(Parent, Host, Port) ->
	Opts = ct_helper:get_certs_from_ets(),
	{ok, ListenSocket} = ssl:listen(0, [binary, {active, false}|Opts]),
	{ok, {_, ListenPort}} = ssl:sockname(ListenSocket),
	Parent ! {self(), ListenPort},
	{ok, ClientSocket0} = ssl:transport_accept(ListenSocket, 10000),
	{ok, ClientSocket} = ssl:handshake(ClientSocket0, 10000),
	{ok, OriginSocket} = gen_tcp:connect(
		Host, Port,
		[binary, {active, false}]),
	ssl:setopts(ClientSocket, [{active, true}]),
	inet:setopts(OriginSocket, [{active, true}]),
	do_proxy_loop(ClientSocket, OriginSocket).

do_proxy_loop(ClientSocket, OriginSocket) ->
	receive
		{ssl, ClientSocket, Data} ->
			ok = gen_tcp:send(OriginSocket, Data),
			do_proxy_loop(ClientSocket, OriginSocket);
		{tcp, OriginSocket, Data} ->
			ok = ssl:send(ClientSocket, Data),
			do_proxy_loop(ClientSocket, OriginSocket);
		{tcp_closed, _} ->
			ok;
		Msg ->
			error(Msg)
	end.

receive_from(Pid) ->
	receive_from(Pid, 5000).

receive_from(Pid, Timeout) ->
	receive
		{Pid, Msg} ->
			Msg
	after Timeout ->
		error(timeout)
	end.
-endif.


 Permission to use, copy, modify, and/or distribute this software for any
 purpose with or without fee is hereby granted, provided that the above
 copyright notice and this permission notice appear in all copies.

 WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 is started by Gun when CONNECT request is issued and stays alive
 while the proxy connection exists.

 Data comes in and out of this process, which is responsible for
 passing incoming/outgoing data through the fake ssl socket process
 it created to perform the decoding/encoding operations.

 Normal scenario:
   Gun process -> TLS socket

   Gun process -> gun_tls_proxy (proxied socket) -> TLS socket

 N proxy socket scenario:
   Gun process -> gun_tls_proxy -> ... -> gun_tls_proxy -> TLS socket

 not return until the connection is setup, and we need to send and
 to call this function, and communicate with it. Once the connection
 is setup the temporary process is gone and things go back to normal.
 The send operations also require a temporary process in order to avoid
 to the fake ssl socket and then to the outgoing socket).
 Gun-specific interface.
 Gun transport.
 Internals.
 The pid of the owner process. This is where we send active messages.
 The host/port the fake ssl socket thinks it's connected to.
 The fake ssl socket we are using in the proxy.
 The socket or proxy process we are sending to.
 @todo Missing passive.
 Extra information to be sent to the owner when the handshake completes.
-define(DEBUG_PROXY,1).
 Gun-specific interface.
 Transport.
 gen_statem.
 a cb_setopts call that blocks us. Might be OK to just leave it
 We unlink from the owner process to avoid taking it down with us.
 Send data through the proxy socket.
 Messages from the proxy socket.

 of the data isn't yet complete. We wrap the message in a handle_continue
 When the out_socket is anything else then the data is sent like normal
 socket data. It does not need to be handled specially.
 Messages from the real socket.
 @todo Make _Socket and __Socket match again.
 Other messages.
;
		N -> N - 1
 Note that tcp_passive is hardcoded in ssl until OTP-21.3.1.
  Copyright ( c ) 2019 - 2023 ,   <  >
  THE SOFTWARE IS PROVIDED " AS IS " AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  ANY SPECIAL , DIRECT , INDIRECT , OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER RESULTING FROM LOSS OF USE , DATA OR PROFITS , WHETHER IN AN

  Intermediary process for proxying TLS connections . This process
  One proxy socket scenario :
  The difficult part is the connection . Because ssl : connect/4 does
  receive data for the TLS handshake , we need a temporary process
  blocking because the same gun_tls_proxy process must send twice ( first

-module(gun_tls_proxy).
-behaviour(gen_statem).

-export([start_link/7]).

  gun_tls_proxy_cb interface .
-export([cb_controlling_process/2]).
-export([cb_send/2]).
-export([cb_setopts/2]).

-export([name/0]).
-export([messages/0]).
-export([connect/3]).
-export([connect/4]).
-export([send/2]).
-export([setopts/2]).
-export([sockname/1]).
-export([close/1]).

-export([callback_mode/0]).
-export([init/1]).
-export([connect_proc/5]).
-export([not_connected/3]).
-export([connected/3]).

-record(state, {
	owner_pid :: pid(),
	owner_active = false :: false | once | true | pos_integer(),
	owner_buffer = <<>> :: binary(),

	host :: inet:ip_address() | inet:hostname(),
	port :: inet:port_number(),

	proxy_socket :: any(),
	proxy_pid :: pid(),
	proxy_active = false :: false | once | true | pos_integer(),
	proxy_buffer = <<>> :: binary(),

	out_socket :: any(),
	out_transport :: module(),

	extra :: any()
}).

-ifdef(DEBUG_PROXY).
-define(DEBUG_LOG(Format, Args),
	io:format(user, "(~p) ~p:~p/~p:" ++ Format ++ "~n",
		[self(), ?MODULE, ?FUNCTION_NAME, ?FUNCTION_ARITY] ++ Args)).
-else.
-define(DEBUG_LOG(Format, Args), _ = Format, _ = Args, ok).
-endif.


start_link(Host, Port, Opts, Timeout, OutSocket, OutTransport, Extra) ->
	?DEBUG_LOG("host ~0p port ~0p opts ~0p timeout ~0p out_socket ~0p out_transport ~0p",
		[Host, Port, Opts, Timeout, OutSocket, OutTransport]),
	case gen_statem:start_link(?MODULE,
			{self(), Host, Port, Opts, Timeout, OutSocket, OutTransport, Extra},
			[]) of
		{ok, Pid} when is_port(OutSocket) ->
			ok = gen_tcp:controlling_process(OutSocket, Pid),
			{ok, Pid};
		{ok, Pid} when is_map(OutSocket) ->
			{ok, Pid};
		{ok, Pid} when not is_pid(OutSocket) ->
			ok = ssl:controlling_process(OutSocket, Pid),
			{ok, Pid};
		Other ->
			Other
	end.

  gun_tls_proxy_cb interface .

cb_controlling_process(Pid, ControllingPid) ->
	?DEBUG_LOG("pid ~0p controlling_pid ~0p", [Pid, ControllingPid]),
	gen_statem:cast(Pid, {?FUNCTION_NAME, ControllingPid}).

cb_send(Pid, Data) ->
	?DEBUG_LOG("pid ~0p data ~0p", [Pid, Data]),
	try
		gen_statem:call(Pid, {?FUNCTION_NAME, Data})
	catch
		exit:{noproc, _} ->
			{error, closed}
	end.

cb_setopts(Pid, Opts) ->
	?DEBUG_LOG("pid ~0p opts ~0p", [Pid, Opts]),
	try
		gen_statem:call(Pid, {?FUNCTION_NAME, Opts})
	catch
		exit:{noproc, _} ->
			{error, einval}
	end.


name() -> tls_proxy.

messages() -> {tls_proxy, tls_proxy_closed, tls_proxy_error}.

-spec connect(_, _, _) -> no_return().
connect(_, _, _) ->
	error(not_implemented).

-spec connect(_, _, _, _) -> no_return().
connect(_, _, _, _) ->
	error(not_implemented).

-spec send(pid(), iodata()) -> ok | {error, atom()}.
send(Pid, Data) ->
	?DEBUG_LOG("pid ~0p data ~0p", [Pid, Data]),
	gen_statem:call(Pid, {?FUNCTION_NAME, Data}).

-spec setopts(pid(), list()) -> ok.
setopts(Pid, Opts) ->
	?DEBUG_LOG("pid ~0p opts ~0p", [Pid, Opts]),
	gen_statem:cast(Pid, {?FUNCTION_NAME, Opts}).

-spec sockname(pid())
	-> {ok, {inet:ip_address(), inet:port_number()}} | {error, atom()}.
sockname(Pid) ->
	?DEBUG_LOG("pid ~0p", [Pid]),
	gen_statem:call(Pid, ?FUNCTION_NAME).

-spec close(pid()) -> ok.
close(Pid) ->
	?DEBUG_LOG("pid ~0p", [Pid]),
	try
		gen_statem:call(Pid, ?FUNCTION_NAME)
	catch
  May happen for example when the handshake fails .
		exit:{noproc, _} ->
			ok
	end.


callback_mode() -> state_functions.

init({OwnerPid, Host, Port, Opts, Timeout, OutSocket, OutTransport, Extra}) ->
	if
		is_pid(OutSocket) ->
			gen_statem:cast(OutSocket, {set_owner, self()});
		true ->
			ok
	end,
	Messages = case OutTransport of
		gen_tcp -> {tcp, tcp_closed, tcp_error};
		ssl -> {ssl, ssl_closed, ssl_error};
		_ -> OutTransport:messages()
	end,
	ProxyPid = spawn_link(?MODULE, connect_proc, [self(), Host, Port, Opts, Timeout]),
	?DEBUG_LOG("owner_pid ~0p host ~0p port ~0p opts ~0p timeout ~0p"
		" out_socket ~0p out_transport ~0p proxy_pid ~0p",
		[OwnerPid, Host, Port, Opts, Timeout, OutSocket, OutTransport, ProxyPid]),
	{ok, not_connected, #state{owner_pid=OwnerPid, host=Host, port=Port, proxy_pid=ProxyPid,
		out_socket=OutSocket, out_transport=OutTransport, out_messages=Messages,
		extra=Extra}}.

connect_proc(ProxyPid, Host, Port, Opts, Timeout) ->
	?DEBUG_LOG("proxy_pid ~0p host ~0p port ~0p opts ~0p timeout ~0p",
		[ProxyPid, Host, Port, Opts, Timeout]),
	_ = case ssl:connect(Host, Port, [
		{active, false}, binary,
		{cb_info, {gun_tls_proxy_cb, tls_proxy, tls_proxy_closed, tls_proxy_error}},
		{?MODULE, ProxyPid}
	|Opts], Timeout) of
		{ok, Socket} ->
			?DEBUG_LOG("socket ~0p", [Socket]),
			ok = ssl:controlling_process(Socket, ProxyPid),
			gen_statem:cast(ProxyPid, {?FUNCTION_NAME, {ok, Socket}});
		Error ->
			?DEBUG_LOG("error ~0p", [Error]),
			gen_statem:cast(ProxyPid, {?FUNCTION_NAME, Error})
	end,
	ok.

  Postpone events that require the proxy socket to be up .
not_connected({call, _}, Msg={send, _}, State) ->
	?DEBUG_LOG("postpone ~0p state ~0p", [Msg, State]),
	{keep_state_and_data, postpone};
not_connected(cast, Msg={setopts, _}, State) ->
	?DEBUG_LOG("postpone ~0p state ~0p", [Msg, State]),
	{keep_state_and_data, postpone};
not_connected(cast, Msg={connect_proc, {ok, Socket}}, State=#state{owner_pid=OwnerPid, extra=Extra}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {?MODULE, self(), {ok, ssl:negotiated_protocol(Socket)}, Extra},
  We need to spawn this call before OTP-21.2 because it triggers
  like this once we support 21.2 + only .
	spawn(fun() -> ok = ssl:setopts(Socket, [{active, true}]) end),
	{next_state, connected, State#state{proxy_socket=Socket}};
not_connected(cast, Msg={connect_proc, Error}, State=#state{owner_pid=OwnerPid, extra=Extra}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {?MODULE, self(), Error, Extra},
	unlink(OwnerPid),
	{stop, {shutdown, Error}, State};
not_connected(Type, Event, State) ->
	handle_common(Type, Event, State).

connected({call, From}, Msg={send, Data}, State=#state{proxy_socket=Socket}) ->
	?DEBUG_LOG("msg ~0p from ~0p state ~0p", [Msg, From, State]),
	Self = self(),
	SpawnedPid = spawn(fun() ->
		gen_statem:cast(Self, {send_result, From, ssl:send(Socket, Data)})
	end),
	?DEBUG_LOG("spawned ~0p", [SpawnedPid]),
	keep_state_and_data;
  When the out_socket is a # { stream_ref : = _ } map we know that processing
  tuple and provide the StreamRef for further processing .
connected(info, Msg={ssl, Socket, Data}, State=#state{owner_pid=OwnerPid, proxy_socket=Socket,
		out_socket=#{handle_continue_stream_ref := StreamRef}}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {handle_continue, StreamRef, {tls_proxy, self(), Data}},
	keep_state_and_data;
connected(info, Msg={ssl_closed, Socket}, State=#state{owner_pid=OwnerPid, proxy_socket=Socket,
		out_socket=#{handle_continue_stream_ref := StreamRef}}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {handle_continue, StreamRef, {tls_proxy_closed, self()}},
	keep_state_and_data;
connected(info, Msg={ssl_error, Socket, Reason}, State=#state{owner_pid=OwnerPid, proxy_socket=Socket,
		out_socket=#{handle_continue_stream_ref := StreamRef}}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {handle_continue, StreamRef, {tls_proxy_error, self(), Reason}},
	keep_state_and_data;
connected(info, Msg={ssl, Socket, Data}, State=#state{owner_pid=OwnerPid, proxy_socket=Socket}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {tls_proxy, self(), Data},
	keep_state_and_data;
connected(info, Msg={ssl_closed, Socket}, State=#state{owner_pid=OwnerPid, proxy_socket=Socket}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {tls_proxy_closed, self()},
	keep_state_and_data;
connected(info, Msg={ssl_error, Socket, Reason}, State=#state{owner_pid=OwnerPid, proxy_socket=Socket}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	OwnerPid ! {tls_proxy_error, self(), Reason},
	keep_state_and_data;
connected(Type, Event, State) ->
	handle_common(Type, Event, State).

handle_common({call, From}, Msg={cb_send, Data}, State=#state{
		out_socket=OutSocket, out_transport=OutTransport}) ->
	?DEBUG_LOG("msg ~0p from ~0p state ~0p", [Msg, From, State]),
	Self = self(),
	SpawnedPid = spawn(fun() ->
		gen_statem:cast(Self, {send_result, From, OutTransport:send(OutSocket, Data)})
	end),
	?DEBUG_LOG("spawned ~0p", [SpawnedPid]),
	keep_state_and_data;
handle_common({call, From}, Msg={cb_setopts, Opts}, State=#state{
		out_socket=OutSocket, out_transport=OutTransport0}) ->
	?DEBUG_LOG("msg ~0p from ~0p state ~0p", [Msg, From, State]),
	OutTransport = case OutTransport0 of
		gen_tcp -> inet;
		_ -> OutTransport0
	end,
	{keep_state, proxy_setopts(Opts, State),
		{reply, From, OutTransport:setopts(OutSocket, [{active, true}])}};
handle_common({call, From}, Msg=sockname, State=#state{
		out_socket=OutSocket, out_transport=OutTransport}) ->
	?DEBUG_LOG("msg ~0p from ~0p state ~0p", [Msg, From, State]),
	{keep_state, State,
		{reply, From, OutTransport:sockname(OutSocket)}};
handle_common({call, From}, Msg=close, State) ->
	?DEBUG_LOG("msg ~0p from ~0p state ~0p", [Msg, From, State]),
	{stop_and_reply, {shutdown, close}, {reply, From, ok}};
handle_common(cast, Msg={set_owner, OwnerPid}, State) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	{keep_state, State#state{owner_pid=OwnerPid}};
handle_common(cast, Msg={cb_controlling_process, ProxyPid}, State) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	{keep_state, State#state{proxy_pid=ProxyPid}};
handle_common(cast, Msg={setopts, Opts}, State) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	{keep_state, owner_setopts(Opts, State)};
handle_common(cast, Msg={send_result, From, Result}, State) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	gen_statem:reply(From, Result),
	keep_state_and_data;
handle_common(info, Msg={OK, _Socket, Data}, State=#state{proxy_pid=ProxyPid,
		out_socket=__Socket, out_messages={OK, _, _}}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	ProxyPid ! {tls_proxy, self(), Data},
	keep_state_and_data;
handle_common(info, Msg={Closed, Socket}, State=#state{proxy_pid=ProxyPid,
		out_socket=Socket, out_messages={_, Closed, _}}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	ProxyPid ! {tls_proxy_closed, self()},
	keep_state_and_data;
handle_common(info, Msg={Error, Socket, Reason}, State=#state{proxy_pid=ProxyPid,
		out_socket=Socket, out_messages={_, _, Error}}) ->
	?DEBUG_LOG("msg ~0p state ~0p", [Msg, State]),
	ProxyPid ! {tls_proxy_error, self(), Reason},
	keep_state_and_data;
handle_common(Type, Msg, State) ->
	?DEBUG_LOG("IGNORED type ~0p msg ~0p state ~0p", [Type, Msg, State]),
	case Type of
		{call, From} ->
			{keep_state, State, {reply, From, {error, bad_call}}};
		_ ->
			keep_state_and_data
	end.

  Internal .

owner_setopts(Opts, State0) ->
	case [A || {active, A} <- Opts] of
		[] -> State0;
		[false] -> State0#state{owner_active=false};
		 [ 0 ] - > OwnerPid ! { tls_proxy_passive , self ( ) } , State0#state{owner_active = false } ;
		[Active] -> owner_active(State0#state{owner_active=Active})
	end.

owner_active(State=#state{owner_buffer= <<>>}) ->
	State;
owner_active(State=#state{owner_active=false}) ->
	State;
owner_active(State=#state{owner_pid=OwnerPid, owner_active=Active0, owner_buffer=Buffer}) ->
	OwnerPid ! {tls_proxy, self(), Buffer},
	Active = case Active0 of
		true -> true;
		 1 - > OwnerPid ! { tls_proxy_passive , self ( ) } , false ;
	end,
	State#state{owner_active=Active, owner_buffer= <<>>}.

proxy_setopts(Opts, State0=#state{proxy_socket=ProxySocket, proxy_pid=ProxyPid}) ->
	case [A || {active, A} <- Opts] of
		[] -> State0;
		[false] -> State0#state{proxy_active=false};
		[0] -> ProxyPid ! {tls_proxy_passive, ProxySocket}, State0#state{proxy_active=false};
		[Active] -> proxy_active(State0#state{proxy_active=Active})
	end.

proxy_active(State=#state{proxy_buffer= <<>>}) ->
	State;
proxy_active(State=#state{proxy_active=false}) ->
	State;
proxy_active(State=#state{proxy_pid=ProxyPid, proxy_active=Active0, proxy_buffer=Buffer}) ->
	ProxyPid ! {tls_proxy, self(), Buffer},
	Active = case Active0 of
		true -> true;
		once -> false;
		1 -> ProxyPid ! {tcp_passive, self()}, false;
		N -> N - 1
	end,
	State#state{proxy_active=Active, proxy_buffer= <<>>}.

-ifdef(DISABLED_TEST).
proxy_test_() ->
	{timeout, 15000, [
		{"TCP proxy", fun proxy_tcp1_t/0},
		{"TLS proxy", fun proxy_ssl1_t/0},
		{"Double TLS proxy", fun proxy_ssl2_t/0}
	]}.

proxy_tcp1_t() ->
	ssl:start(),
	{ok, Socket} = gen_tcp:connect("google.com", 443, [binary, {active, false}]),
	{ok, ProxyPid1} = start_link("google.com", 443, [], 5000, Socket, gen_tcp, #{}),
	send(ProxyPid1, <<"GET / HTTP/1.1\r\nHost: google.com\r\n\r\n">>),
	receive {tls_proxy, ProxyPid1, <<"HTTP/1.1 ", _/bits>>} -> ok end.

proxy_ssl1_t() ->
	ssl:start(),
	_ = (catch ct_helper:make_certs_in_ets()),
	{ok, _, Port} = do_proxy_start("google.com", 443),
	{ok, Socket} = ssl:connect("localhost", Port, [binary, {active, false}]),
	{ok, ProxyPid1} = start_link("google.com", 443, [], 5000, Socket, ssl, #{}),
	send(ProxyPid1, <<"GET / HTTP/1.1\r\nHost: google.com\r\n\r\n">>),
	receive {tls_proxy, ProxyPid1, <<"HTTP/1.1 ", _/bits>>} -> ok end.

proxy_ssl2_t() ->
	ssl:start(),
	_ = (catch ct_helper:make_certs_in_ets()),
	{ok, _, Port1} = do_proxy_start("google.com", 443),
	{ok, _, Port2} = do_proxy_start("localhost", Port1),
	{ok, Socket} = ssl:connect("localhost", Port2, [binary, {active, false}]),
	{ok, ProxyPid1} = start_link("localhost", Port1, [], 5000, Socket, ssl, #{}),
	{ok, ProxyPid2} = start_link("google.com", 443, [], 5000, ProxyPid1, ?MODULE, #{}),
	send(ProxyPid2, <<"GET / HTTP/1.1\r\nHost: google.com\r\n\r\n">>),
	receive {tls_proxy, ProxyPid2, <<"HTTP/1.1 ", _/bits>>} -> ok end.

do_proxy_start(Host, Port) ->
	Self = self(),
	Pid = spawn_link(fun() -> do_proxy_init(Self, Host, Port) end),
	ListenPort = receive_from(Pid),
	{ok, Pid, ListenPort}.

do_proxy_init(Parent, Host, Port) ->
	Opts = ct_helper:get_certs_from_ets(),
	{ok, ListenSocket} = ssl:listen(0, [binary, {active, false}|Opts]),
	{ok, {_, ListenPort}} = ssl:sockname(ListenSocket),
	Parent ! {self(), ListenPort},
	{ok, ClientSocket0} = ssl:transport_accept(ListenSocket, 10000),
	{ok, ClientSocket} = ssl:handshake(ClientSocket0, 10000),
	{ok, OriginSocket} = gen_tcp:connect(
		Host, Port,
		[binary, {active, false}]),
	ssl:setopts(ClientSocket, [{active, true}]),
	inet:setopts(OriginSocket, [{active, true}]),
	do_proxy_loop(ClientSocket, OriginSocket).

do_proxy_loop(ClientSocket, OriginSocket) ->
	receive
		{ssl, ClientSocket, Data} ->
			ok = gen_tcp:send(OriginSocket, Data),
			do_proxy_loop(ClientSocket, OriginSocket);
		{tcp, OriginSocket, Data} ->
			ok = ssl:send(ClientSocket, Data),
			do_proxy_loop(ClientSocket, OriginSocket);
		{tcp_closed, _} ->
			ok;
		Msg ->
			error(Msg)
	end.

receive_from(Pid) ->
	receive_from(Pid, 5000).

receive_from(Pid, Timeout) ->
	receive
		{Pid, Msg} ->
			Msg
	after Timeout ->
		error(timeout)
	end.
-endif.
