path: root/src/gun_http.erl

%% Copyright (c) 2014-2019, Loïc Hoguin <[email protected]>
%%
%% 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.

-module(gun_http).

-export([check_options/1]).
-export([name/0]).
-export([opts_name/0]).
-export([has_keepalive/0]).
-export([default_keepalive/0]).
-export([init/4]).
-export([switch_transport/3]).
-export([handle/4]).
-export([update_flow/4]).
-export([closing/4]).
-export([close/4]).
-export([keepalive/1]).
-export([headers/11]).
-export([request/12]).
-export([data/7]).
-export([connect/6]).
-export([cancel/5]).
-export([stream_info/2]).
-export([down/1]).
-export([ws_upgrade/9]).

%% Functions shared with gun_http2.
-export([host_header/3]).

-type io() :: head | {body, non_neg_integer()} | body_close | body_chunked | body_trailer.

%% @todo Make that a record.
-type connect_info() :: {connect, reference(), gun:connect_destination()}.

%% @todo Make that a record.
-type websocket_info() :: {websocket, reference(), binary(), [binary()], gun:ws_opts()}. %% key, extensions, options

-record(stream, {
	ref :: reference() | connect_info() | websocket_info(),
	reply_to :: pid(),
	flow :: integer() | infinity,
	method :: binary(),
	is_alive :: boolean(),
	handler_state :: undefined | gun_content_handler:state()
}).

-record(http_state, {
	owner :: pid(),
	socket :: inet:socket() | ssl:sslsocket(),
	transport :: module(),
	opts = #{} :: map(), %% @todo
	version = 'HTTP/1.1' :: cow_http:version(),
	content_handlers :: gun_content_handler:opt(),
	connection = keepalive :: keepalive | close,
	buffer = <<>> :: binary(),
	streams = [] :: [#stream{}],
	in = head :: io(),
	in_state = {0, 0} :: {non_neg_integer(), non_neg_integer()},
	out = head :: io(),
	transform_header_name :: fun((binary()) -> binary())
}).

check_options(Opts) ->
	do_check_options(maps:to_list(Opts)).

do_check_options([]) ->
	ok;
do_check_options([{closing_timeout, infinity}|Opts]) ->
	do_check_options(Opts);
do_check_options([{closing_timeout, T}|Opts]) when is_integer(T), T > 0 ->
	do_check_options(Opts);
do_check_options([Opt={content_handlers, Handlers}|Opts]) ->
	case gun_content_handler:check_option(Handlers) of
		ok -> do_check_options(Opts);
		error -> {error, {options, {http, Opt}}}
	end;
do_check_options([{flow, InitialFlow}|Opts]) when is_integer(InitialFlow), InitialFlow > 0 ->
	do_check_options(Opts);
do_check_options([{keepalive, infinity}|Opts]) ->
	do_check_options(Opts);
do_check_options([{keepalive, K}|Opts]) when is_integer(K), K > 0 ->
	do_check_options(Opts);
do_check_options([{transform_header_name, F}|Opts]) when is_function(F) ->
	do_check_options(Opts);
do_check_options([{version, V}|Opts]) when V =:= 'HTTP/1.1'; V =:= 'HTTP/1.0' ->
	do_check_options(Opts);
do_check_options([Opt|_]) ->
	{error, {options, {http, Opt}}}.

name() -> http.
opts_name() -> http_opts.
has_keepalive() -> true.
default_keepalive() -> infinity.

init(Owner, Socket, Transport, Opts) ->
	%% @todo If we keep the opts we don't need to add these to the state.
	Version = maps:get(version, Opts, 'HTTP/1.1'),
	Handlers = maps:get(content_handlers, Opts, [gun_data_h]),
	TransformHeaderName = maps:get(transform_header_name, Opts, fun (N) -> N end),
	{connected, #http_state{owner=Owner, socket=Socket, transport=Transport, opts=Opts,
		version=Version, content_handlers=Handlers, transform_header_name=TransformHeaderName}}.

switch_transport(Transport, Socket, State) ->
	State#http_state{socket=Socket, transport=Transport}.

%% Stop looping when we got no more data.
handle(<<>>, State, _, EvHandlerState) ->
	{{state, State}, EvHandlerState};
%% Close when server responds and we don't have any open streams.
handle(_, #http_state{streams=[]}, _, EvHandlerState) ->
	{close, EvHandlerState};
%% Wait for the full response headers before trying to parse them.
handle(Data, State=#http_state{in=head, buffer=Buffer,
		streams=[#stream{ref=StreamRef, reply_to=ReplyTo}|_]}, EvHandler, EvHandlerState0) ->
	%% Send the event only if there was no data in the buffer.
	%% If there is data in the buffer then we already sent the event.
	EvHandlerState = case Buffer of
		<<>> ->
			EvHandler:response_start(#{
				stream_ref => stream_ref(StreamRef),
				reply_to => ReplyTo
			}, EvHandlerState0);
		_ ->
			EvHandlerState0
	end,
	Data2 = << Buffer/binary, Data/binary >>,
	case binary:match(Data2, <<"\r\n\r\n">>) of
		nomatch -> {{state, State#http_state{buffer=Data2}}, EvHandlerState};
		{_, _} -> handle_head(Data2, State#http_state{buffer= <<>>}, EvHandler, EvHandlerState)
	end;
%% Everything sent to the socket until it closes is part of the response body.
handle(Data, State=#http_state{in=body_close}, _, EvHandlerState) ->
	{send_data(Data, State, nofin), EvHandlerState};
%% Chunked transfer-encoding may contain both data and trailers.
handle(Data, State=#http_state{in=body_chunked, in_state=InState,
		buffer=Buffer, streams=[#stream{ref=StreamRef, reply_to=ReplyTo}|_],
		connection=Conn}, EvHandler, EvHandlerState0) ->
	Buffer2 = << Buffer/binary, Data/binary >>,
	case cow_http_te:stream_chunked(Buffer2, InState) of
		more ->
			{{state, State#http_state{buffer=Buffer2}}, EvHandlerState0};
		{more, Data2, InState2} ->
			{send_data(Data2, State#http_state{buffer= <<>>, in_state=InState2}, nofin), EvHandlerState0};
		{more, Data2, Length, InState2} when is_integer(Length) ->
			%% @todo See if we can recv faster than one message at a time.
			{send_data(Data2, State#http_state{buffer= <<>>, in_state=InState2}, nofin), EvHandlerState0};
		{more, Data2, Rest, InState2} ->
			%% @todo See if we can recv faster than one message at a time.
			{send_data(Data2, State#http_state{buffer=Rest, in_state=InState2}, nofin), EvHandlerState0};
		{done, HasTrailers, Rest} ->
			%% @todo response_end should be called AFTER send_data
			{IsFin, EvHandlerState} = case HasTrailers of
				trailers ->
					{nofin, EvHandlerState0};
				no_trailers ->
					EvHandlerState1 = EvHandler:response_end(#{
						stream_ref => StreamRef,
						reply_to => ReplyTo
					}, EvHandlerState0),
					{fin, EvHandlerState1}
			end,
			%% I suppose it doesn't hurt to append an empty binary.
			%% We ignore the active command because the stream ended.
			[{state, State1}|_] = send_data(<<>>, State, IsFin),
			case {HasTrailers, Conn} of
				{trailers, _} ->
					handle(Rest, State1#http_state{buffer = <<>>, in=body_trailer}, EvHandler, EvHandlerState);
				{no_trailers, keepalive} ->
					handle(Rest, end_stream(State1#http_state{buffer= <<>>}), EvHandler, EvHandlerState);
				{no_trailers, close} ->
					{[{state, end_stream(State1)}, close], EvHandlerState}
			end;
		{done, Data2, HasTrailers, Rest} ->
			%% @todo response_end should be called AFTER send_data
			{IsFin, EvHandlerState} = case HasTrailers of
				trailers ->
					{nofin, EvHandlerState0};
				no_trailers ->
					EvHandlerState1 = EvHandler:response_end(#{
						stream_ref => StreamRef,
						reply_to => ReplyTo
					}, EvHandlerState0),
					{fin, EvHandlerState1}
			end,
			%% We ignore the active command because the stream ended.
			[{state, State1}|_] = send_data(Data2, State, IsFin),
			case {HasTrailers, Conn} of
				{trailers, _} ->
					handle(Rest, State1#http_state{buffer = <<>>, in=body_trailer}, EvHandler, EvHandlerState);
				{no_trailers, keepalive} ->
					handle(Rest, end_stream(State1#http_state{buffer= <<>>}), EvHandler, EvHandlerState);
				{no_trailers, close} ->
					{[{state, end_stream(State1)}, close], EvHandlerState}
			end
	end;
handle(Data, State=#http_state{in=body_trailer, buffer=Buffer, connection=Conn,
		streams=[#stream{ref=StreamRef, reply_to=ReplyTo}|_]}, EvHandler, EvHandlerState0) ->
	Data2 = << Buffer/binary, Data/binary >>,
	case binary:match(Data2, <<"\r\n\r\n">>) of
		nomatch ->
			{{state, State#http_state{buffer=Data2}}, EvHandlerState0};
		{_, _} ->
			{Trailers, Rest} = cow_http:parse_headers(Data2),
			%% @todo We probably want to pass this to gun_content_handler?
			ReplyTo ! {gun_trailers, self(), stream_ref(StreamRef), Trailers},
			ResponseEvent = #{
				stream_ref => StreamRef,
				reply_to => ReplyTo
			},
			EvHandlerState1 = EvHandler:response_trailers(ResponseEvent#{headers => Trailers}, EvHandlerState0),
			EvHandlerState = EvHandler:response_end(ResponseEvent, EvHandlerState1),
			case Conn of
				keepalive ->
					handle(Rest, end_stream(State#http_state{buffer= <<>>}), EvHandler, EvHandlerState);
				close ->
					{[{state, end_stream(State)}, close], EvHandlerState}
			end
	end;
%% We know the length of the rest of the body.
handle(Data, State=#http_state{in={body, Length}, connection=Conn,
		streams=[#stream{ref=StreamRef, reply_to=ReplyTo}|_]},
		EvHandler, EvHandlerState0) ->
	DataSize = byte_size(Data),
	if
		%% More data coming.
		DataSize < Length ->
			{send_data(Data, State#http_state{in={body, Length - DataSize}}, nofin), EvHandlerState0};
		%% Stream finished, no rest.
		DataSize =:= Length ->
			%% We ignore the active command because the stream ended.
			[{state, State1}|_] = send_data(Data, State, fin),
			EvHandlerState = EvHandler:response_end(#{
				stream_ref => StreamRef,
				reply_to => ReplyTo
			}, EvHandlerState0),
			case Conn of
				keepalive -> {[{state, end_stream(State1)}, {active, true}], EvHandlerState};
				close -> {[{state, end_stream(State1)}, close], EvHandlerState}
			end;
		%% Stream finished, rest.
		true ->
			<< Body:Length/binary, Rest/bits >> = Data,
			%% We ignore the active command because the stream ended.
			[{state, State1}|_] = send_data(Body, State, fin),
			EvHandlerState = EvHandler:response_end(#{
				stream_ref => StreamRef,
				reply_to => ReplyTo
			}, EvHandlerState0),
			case Conn of
				keepalive -> handle(Rest, end_stream(State1), EvHandler, EvHandlerState);
				close -> {[{state, end_stream(State1)}, close], EvHandlerState}
			end
	end.

handle_head(Data, State=#http_state{version=ClientVersion, content_handlers=Handlers0,
		connection=Conn, streams=[Stream=#stream{ref=StreamRef, reply_to=ReplyTo,
			method=Method, is_alive=IsAlive}|Tail]},
		EvHandler, EvHandlerState0) ->
	{Version, Status, _, Rest} = cow_http:parse_status_line(Data),
	{Headers, Rest2} = cow_http:parse_headers(Rest),
	case {Status, StreamRef} of
		{101, {websocket, RealStreamRef, WsKey, WsExtensions, WsOpts}} ->
			EvHandlerState = EvHandler:response_inform(#{
				stream_ref => RealStreamRef,
				reply_to => ReplyTo,
				status => 101,
				headers => Headers
			}, EvHandlerState0),
			{ws_handshake(Rest2, State, RealStreamRef, Headers, WsKey, WsExtensions, WsOpts),
				EvHandlerState};
		%% @todo If the stream is cancelled we probably shouldn't finish the CONNECT setup.
		{_, {connect, RealStreamRef, Destination}} when Status >= 200, Status < 300 ->
			case IsAlive of
				false ->
					ok;
				true ->
					ReplyTo ! {gun_response, self(), RealStreamRef,
						fin, Status, Headers},
					ok
			end,
			%% @todo Figure out whether the event should trigger if the stream was cancelled.
			EvHandlerState1 = EvHandler:response_headers(#{
				stream_ref => RealStreamRef,
				reply_to => ReplyTo,
				status => Status,
				headers => Headers
			}, EvHandlerState0),
			%% We expect there to be no additional data after the CONNECT response.
			<<>> = Rest2,
			_ = end_stream(State#http_state{streams=[Stream|Tail]}),
			NewHost = maps:get(host, Destination),
			NewPort = maps:get(port, Destination),
			case Destination of
				#{transport := tls} ->
					HandshakeEvent = #{
						stream_ref => RealStreamRef,
						reply_to => ReplyTo,
						tls_opts => maps:get(tls_opts, Destination, []),
						timeout => maps:get(tls_handshake_timeout, Destination, infinity)
					},
					Protocols = maps:get(protocols, Destination, [http2, http]),
					{[{origin, <<"https">>, NewHost, NewPort, connect},
						{tls_handshake, HandshakeEvent, Protocols}], EvHandlerState1};
				_ ->
					[Protocol] = maps:get(protocols, Destination, [http]),
					{[{origin, <<"http">>, NewHost, NewPort, connect},
						{switch_protocol, Protocol}], EvHandlerState1}
			end;
		{_, _} when Status >= 100, Status =< 199 ->
			ReplyTo ! {gun_inform, self(), stream_ref(StreamRef), Status, Headers},
			EvHandlerState = EvHandler:response_inform(#{
				stream_ref => StreamRef,
				reply_to => ReplyTo,
				status => Status,
				headers => Headers
			}, EvHandlerState0),
			handle(Rest2, State, EvHandler, EvHandlerState);
		_ ->
			In = response_io_from_headers(Method, Version, Status, Headers),
			IsFin = case In of head -> fin; _ -> nofin end,
			%% @todo Figure out whether the event should trigger if the stream was cancelled.
			{Handlers, EvHandlerState2} = case IsAlive of
				false ->
					{undefined, EvHandlerState0};
				true ->
					ReplyTo ! {gun_response, self(), stream_ref(StreamRef),
						IsFin, Status, Headers},
					EvHandlerState1 = EvHandler:response_headers(#{
						stream_ref => StreamRef,
						reply_to => ReplyTo,
						status => Status,
						headers => Headers
					}, EvHandlerState0),
					case IsFin of
						fin -> {undefined, EvHandlerState1};
						nofin ->
							{gun_content_handler:init(ReplyTo, stream_ref(StreamRef),
								Status, Headers, Handlers0), EvHandlerState1}
					end
			end,
			EvHandlerState = case IsFin of
				nofin ->
					EvHandlerState2;
				fin ->
					EvHandler:response_end(#{
						stream_ref => StreamRef,
						reply_to => ReplyTo
					}, EvHandlerState2)
			end,
			Conn2 = if
				Conn =:= close -> close;
				Version =:= 'HTTP/1.0' -> close;
				ClientVersion =:= 'HTTP/1.0' -> close;
				true -> conn_from_headers(Version, Headers)
			end,
			%% We always reset in_state even if not chunked.
			if
				IsFin =:= fin, Conn2 =:= close ->
					{close, EvHandlerState};
				IsFin =:= fin ->
					handle(Rest2, end_stream(State#http_state{in=In,
						in_state={0, 0}, connection=Conn2,
						streams=[Stream#stream{handler_state=Handlers}|Tail]}),
						EvHandler, EvHandlerState);
				true ->
					handle(Rest2, State#http_state{in=In,
						in_state={0, 0}, connection=Conn2,
						streams=[Stream#stream{handler_state=Handlers}|Tail]},
						EvHandler, EvHandlerState)
			end
	end.

stream_ref({connect, StreamRef, _}) -> StreamRef;
stream_ref({websocket, StreamRef, _, _, _}) -> StreamRef;
stream_ref(StreamRef) -> StreamRef.

%% The state must be first in order to retrieve it when the stream ended.
send_data(<<>>, State, nofin) ->
	[{state, State}, {active, true}];
%% @todo What if we receive data when the HEAD method was used?
send_data(Data, State=#http_state{streams=[Stream=#stream{
		flow=Flow0, is_alive=true, handler_state=Handlers0}|Tail]}, IsFin) ->
	{ok, Dec, Handlers} = gun_content_handler:handle(IsFin, Data, Handlers0),
	Flow = case Flow0 of
		infinity -> infinity;
		_ -> Flow0 - Dec
	end,
	[
		{state, State#http_state{streams=[Stream#stream{flow=Flow, handler_state=Handlers}|Tail]}},
		{active, Flow > 0}
	];
send_data(_, State, _) ->
	[{state, State}, {active, true}].

%% We only update the active state when the current stream is being updated.
update_flow(State=#http_state{streams=[Stream=#stream{ref=StreamRef, flow=Flow0}|Tail]},
		_ReplyTo, StreamRef, Inc) ->
	Flow = case Flow0 of
		infinity -> infinity;
		_ -> Flow0 + Inc
	end,
	[
		{state, State#http_state{streams=[Stream#stream{flow=Flow}|Tail]}},
		{active, Flow > 0}
	];
update_flow(State=#http_state{streams=Streams0}, _ReplyTo, StreamRef, Inc) ->
	Streams = [case Ref of
		StreamRef when Flow =/= infinity ->
			Tuple#stream{flow=Flow + Inc};
		_ ->
			Tuple
	end || Tuple = #stream{ref=Ref, flow=Flow} <- Streams0],
	{state, State#http_state{streams=Streams}}.

%% We can immediately close the connection when there's no streams.
closing(_, #http_state{streams=[]}, _, EvHandlerState) ->
	{close, EvHandlerState};
%% Otherwise we set connection: close (even if the header was not sent)
%% and close any pipelined streams, only keeping the active stream.
closing(Reason, State=#http_state{streams=[LastStream|Tail]}, _, EvHandlerState) ->
	close_streams(Tail, {closing, Reason}),
	{[
		{state, State#http_state{connection=close, streams=[LastStream]}},
		closing(State)
	], EvHandlerState}.

closing(#http_state{opts=Opts}) ->
	Timeout = maps:get(closing_timeout, Opts, 15000),
	{closing, Timeout}.

close(Reason, State=#http_state{in=body_close,
		streams=[#stream{ref=StreamRef, reply_to=ReplyTo}|Tail]},
		EvHandler, EvHandlerState) ->
	%% We may have more than one stream in case we somehow close abruptly.
	close_streams(Tail, close_reason(Reason)),
	_ = send_data(<<>>, State, fin),
	EvHandler:response_end(#{
		stream_ref => StreamRef,
		reply_to => ReplyTo
	}, EvHandlerState);
close(Reason, #http_state{streams=Streams}, _, EvHandlerState) ->
	close_streams(Streams, close_reason(Reason)),
	EvHandlerState.

close_reason(closed) -> closed;
close_reason(Reason) -> {closed, Reason}.

%% @todo Do we want an event for this?
close_streams([], _) ->
	ok;
close_streams([#stream{is_alive=false}|Tail], Reason) ->
	close_streams(Tail, Reason);
close_streams([#stream{ref=StreamRef, reply_to=ReplyTo}|Tail], Reason) ->
	ReplyTo ! {gun_error, self(), StreamRef, Reason},
	close_streams(Tail, Reason).

%% We don't send a keep-alive when a CONNECT request was initiated.
keepalive(State=#http_state{streams=[#stream{ref={connect, _, _}}]}) ->
	State;
%% We can only keep-alive by sending an empty line in-between streams.
keepalive(State=#http_state{socket=Socket, transport=Transport, out=head}) ->
	Transport:send(Socket, <<"\r\n">>),
	State;
keepalive(State) ->
	State.

headers(State=#http_state{opts=Opts, out=head},
		StreamRef, ReplyTo, Method, Host, Port, Path, Headers,
		InitialFlow0, EvHandler, EvHandlerState0) ->
	{Conn, Out, EvHandlerState} = send_request(State, StreamRef, ReplyTo,
		Method, Host, Port, Path, Headers, undefined,
		EvHandler, EvHandlerState0, ?FUNCTION_NAME),
	InitialFlow = initial_flow(InitialFlow0, Opts),
	{new_stream(State#http_state{connection=Conn, out=Out}, StreamRef, ReplyTo, Method, InitialFlow),
		EvHandlerState}.

request(State=#http_state{opts=Opts, out=head}, StreamRef, ReplyTo,
		Method, Host, Port, Path, Headers, Body,
		InitialFlow0, EvHandler, EvHandlerState0) ->
	{Conn, Out, EvHandlerState} = send_request(State, StreamRef, ReplyTo,
		Method, Host, Port, Path, Headers, Body,
		EvHandler, EvHandlerState0, ?FUNCTION_NAME),
	InitialFlow = initial_flow(InitialFlow0, Opts),
	{new_stream(State#http_state{connection=Conn, out=Out}, StreamRef, ReplyTo, Method, InitialFlow),
		EvHandlerState}.

initial_flow(infinity, #{flow := InitialFlow}) -> InitialFlow;
initial_flow(InitialFlow, _) -> InitialFlow.

send_request(State=#http_state{socket=Socket, transport=Transport, version=Version},
		StreamRef, ReplyTo, Method, Host, Port, Path, Headers0, Body,
		EvHandler, EvHandlerState0, Function) ->
	Headers1 = lists:keydelete(<<"transfer-encoding">>, 1, Headers0),
	Headers2 = case Body of
		undefined -> Headers1;
		_ -> lists:keydelete(<<"content-length">>, 1, Headers1)
	end,
	%% We use Headers2 because this is the smallest list.
	Conn = conn_from_headers(Version, Headers2),
	Out = case Body of
		undefined when Function =:= ws_upgrade -> head;
		undefined -> request_io_from_headers(Headers2);
		_ -> head
	end,
	Authority0 = host_header(Transport, Host, Port),
	{Authority, Headers3} = case lists:keyfind(<<"host">>, 1, Headers2) of
		false -> {Authority0, [{<<"host">>, Authority0}|Headers2]};
		{_, Authority1} -> {Authority1, Headers2}
	end,
	Headers4 = transform_header_names(State, Headers3),
	Headers = case {Body, Out} of
		{undefined, body_chunked} when Version =:= 'HTTP/1.0' -> Headers4;
		{undefined, body_chunked} -> [{<<"transfer-encoding">>, <<"chunked">>}|Headers4];
		{undefined, _} -> Headers4;
		_ -> [{<<"content-length">>, integer_to_binary(iolist_size(Body))}|Headers4]
	end,
	RequestEvent = #{
		stream_ref => StreamRef,
		reply_to => ReplyTo,
		function => Function,
		method => Method,
		authority => Authority,
		path => Path,
		headers => Headers
	},
	EvHandlerState1 = EvHandler:request_start(RequestEvent, EvHandlerState0),
	Transport:send(Socket, [
		cow_http:request(Method, Path, Version, Headers),
		[Body || Body =/= undefined]]),
	EvHandlerState2 = EvHandler:request_headers(RequestEvent, EvHandlerState1),
	EvHandlerState = case Out of
		head ->
			RequestEndEvent = #{
				stream_ref => StreamRef,
				reply_to => ReplyTo
			},
			EvHandler:request_end(RequestEndEvent, EvHandlerState2);
		_ ->
			EvHandlerState2
	end,
	{Conn, Out, EvHandlerState}.

host_header(Transport, Host0, Port) ->
	Host = case Host0 of
		{local, _SocketPath} -> <<>>;
		Tuple when is_tuple(Tuple) -> inet:ntoa(Tuple);
		Atom when is_atom(Atom) -> atom_to_list(Atom);
		_ -> Host0
	end,
	case {Transport:name(), Port} of
		{tcp, 80} -> Host;
		{tls, 443} -> Host;
		_ -> [Host, $:, integer_to_binary(Port)]
	end.

transform_header_names(#http_state{transform_header_name = Fun}, Headers) ->
	lists:keymap(Fun, 1, Headers).

%% We are expecting a new stream.
data(State=#http_state{out=head}, StreamRef, ReplyTo, _, _, _, EvHandlerState) ->
	{error_stream_closed(State, StreamRef, ReplyTo), EvHandlerState};
%% There are no active streams.
data(State=#http_state{streams=[]}, StreamRef, ReplyTo, _, _, _, EvHandlerState) ->
	{error_stream_not_found(State, StreamRef, ReplyTo), EvHandlerState};
%% We can only send data on the last created stream.
data(State=#http_state{socket=Socket, transport=Transport, version=Version,
		out=Out, streams=Streams}, StreamRef, ReplyTo, IsFin, Data,
		EvHandler, EvHandlerState0) ->
	case lists:last(Streams) of
		#stream{ref=StreamRef, is_alive=true} ->
			DataLength = iolist_size(Data),
			case Out of
				body_chunked when Version =:= 'HTTP/1.1', IsFin =:= fin ->
					case Data of
						<<>> ->
							Transport:send(Socket, cow_http_te:last_chunk());
						_ ->
							Transport:send(Socket, [
								cow_http_te:chunk(Data),
								cow_http_te:last_chunk()
							])
					end,
					RequestEndEvent = #{
						stream_ref => StreamRef,
						reply_to => ReplyTo
					},
					EvHandlerState = EvHandler:request_end(RequestEndEvent, EvHandlerState0),
					{State#http_state{out=head}, EvHandlerState};
				body_chunked when Version =:= 'HTTP/1.1' ->
					Transport:send(Socket, cow_http_te:chunk(Data)),
					{State, EvHandlerState0};
				{body, Length} when DataLength =< Length ->
					Transport:send(Socket, Data),
					Length2 = Length - DataLength,
					if
						Length2 =:= 0, IsFin =:= fin ->
							RequestEndEvent = #{
								stream_ref => StreamRef,
								reply_to => ReplyTo
							},
							EvHandlerState = EvHandler:request_end(RequestEndEvent, EvHandlerState0),
							{State#http_state{out=head}, EvHandlerState};
						Length2 > 0, IsFin =:= nofin ->
							{State#http_state{out={body, Length2}}, EvHandlerState0}
					end;
				body_chunked -> %% HTTP/1.0
					Transport:send(Socket, Data),
					{State, EvHandlerState0}
			end;
		_ ->
			{error_stream_not_found(State, StreamRef, ReplyTo), EvHandlerState0}
	end.

connect(State=#http_state{streams=Streams}, StreamRef, ReplyTo, _, _, _) when Streams =/= [] ->
	ReplyTo ! {gun_error, self(), StreamRef, {badstate,
		"CONNECT can only be used with HTTP/1.1 when no other streams are active."}},
	State;
connect(State=#http_state{socket=Socket, transport=Transport, opts=Opts, version=Version},
		StreamRef, ReplyTo, Destination=#{host := Host0}, Headers0, InitialFlow0) ->
	Host = case Host0 of
		Tuple when is_tuple(Tuple) -> inet:ntoa(Tuple);
		_ -> Host0
	end,
	Port = maps:get(port, Destination, 1080),
	Authority = [Host, $:, integer_to_binary(Port)],
	Headers1 = lists:keydelete(<<"content-length">>, 1,
		lists:keydelete(<<"transfer-encoding">>, 1, Headers0)),
	Headers2 = case lists:keymember(<<"host">>, 1, Headers1) of
		false -> [{<<"host">>, Authority}|Headers1];
		true -> Headers1
	end,
	HasProxyAuthorization = lists:keymember(<<"proxy-authorization">>, 1, Headers2),
	Headers3 = case {HasProxyAuthorization, Destination} of
		{false, #{username := UserID, password := Password}} ->
			[{<<"proxy-authorization">>, [
					<<"Basic ">>,
					base64:encode(iolist_to_binary([UserID, $:, Password]))]}
				|Headers2];
		_ ->
			Headers2
	end,
	Headers = transform_header_names(State, Headers3),
	Transport:send(Socket, [
		cow_http:request(<<"CONNECT">>, Authority, Version, Headers)
	]),
	InitialFlow = initial_flow(InitialFlow0, Opts),
	new_stream(State, {connect, StreamRef, Destination}, ReplyTo, <<"CONNECT">>, InitialFlow).

%% We can't cancel anything, we can just stop forwarding messages to the owner.
cancel(State0, StreamRef, ReplyTo, EvHandler, EvHandlerState0) ->
	case is_stream(State0, StreamRef) of
		true ->
			State = cancel_stream(State0, StreamRef),
			EvHandlerState = EvHandler:cancel(#{
				stream_ref => StreamRef,
				reply_to => ReplyTo,
				endpoint => local,
				reason => cancel
			}, EvHandlerState0),
			{State, EvHandlerState};
		false ->
			{error_stream_not_found(State0, StreamRef, ReplyTo), EvHandlerState0}
	end.

stream_info(#http_state{streams=Streams}, StreamRef) ->
	case lists:keyfind(StreamRef, #stream.ref, Streams) of
		#stream{reply_to=ReplyTo, is_alive=IsAlive} ->
			{ok, #{
				ref => StreamRef,
				reply_to => ReplyTo,
				state => case IsAlive of
					true -> running;
					false -> stopping
				end
			}};
		false ->
			{ok, undefined}
	end.

%% HTTP does not provide any way to figure out what streams are unprocessed.
down(#http_state{streams=Streams}) ->
	KilledStreams = [case Ref of
		{connect, Ref2, _} -> Ref2;
		{websocket, Ref2, _, _, _} -> Ref2;
		_ -> Ref
	end || #stream{ref=Ref} <- Streams],
	{KilledStreams, []}.

error_stream_closed(State, StreamRef, ReplyTo) ->
	ReplyTo ! {gun_error, self(), StreamRef, {badstate,
		"The stream has already been closed."}},
	State.

error_stream_not_found(State, StreamRef, ReplyTo) ->
	ReplyTo ! {gun_error, self(), StreamRef, {badstate,
		"The stream cannot be found."}},
	State.

%% Headers information retrieval.

conn_from_headers(Version, Headers) ->
	case lists:keyfind(<<"connection">>, 1, Headers) of
		false when Version =:= 'HTTP/1.0' ->
			close;
		false ->
			keepalive;
		{_, ConnHd} ->
			conn_from_header(cow_http_hd:parse_connection(ConnHd))
	end.

conn_from_header([]) -> close;
conn_from_header([<<"keep-alive">>|_]) -> keepalive;
conn_from_header([<<"upgrade">>|_]) -> keepalive;
conn_from_header([_|Tail]) -> conn_from_header(Tail).

request_io_from_headers(Headers) ->
	case lists:keyfind(<<"content-length">>, 1, Headers) of
		{_, Length} ->
			{body, cow_http_hd:parse_content_length(Length)};
		_ ->
			body_chunked
	end.

response_io_from_headers(<<"HEAD">>, _, _, _) ->
	head;
response_io_from_headers(_, _, Status, _) when (Status =:= 204) or (Status =:= 304) ->
	head;
response_io_from_headers(_, Version, _Status, Headers) ->
	case lists:keyfind(<<"transfer-encoding">>, 1, Headers) of
		{_, TE} when Version =:= 'HTTP/1.1' ->
			case cow_http_hd:parse_transfer_encoding(TE) of
				[<<"chunked">>] -> body_chunked;
				[<<"identity">>] -> body_close
			end;
		_ ->
			case lists:keyfind(<<"content-length">>, 1, Headers) of
				{_, <<"0">>} ->
					head;
				{_, Length} ->
					{body, cow_http_hd:parse_content_length(Length)};
				_ ->
					body_close
			end
	end.

%% Streams.

new_stream(State=#http_state{streams=Streams}, StreamRef, ReplyTo, Method, InitialFlow) ->
	State#http_state{streams=Streams
		++ [#stream{ref=StreamRef, reply_to=ReplyTo, flow=InitialFlow,
			method=iolist_to_binary(Method), is_alive=true}]}.

is_stream(#http_state{streams=Streams}, StreamRef) ->
	lists:keymember(StreamRef, #stream.ref, Streams).

cancel_stream(State=#http_state{streams=Streams}, StreamRef) ->
	Streams2 = [case Ref of
		StreamRef ->
			Tuple#stream{is_alive=false};
		_ ->
			Tuple
	end || Tuple = #stream{ref=Ref} <- Streams],
	State#http_state{streams=Streams2}.

end_stream(State=#http_state{streams=[_|Tail]}) ->
	State#http_state{in=head, streams=Tail}.

%% Websocket upgrade.

%% Ensure version is 1.1.
ws_upgrade(#http_state{version='HTTP/1.0'}, _, _, _, _, _, _, _, _) ->
	error; %% @todo Probably don't error out here, have a protocol function/command.
ws_upgrade(State=#http_state{owner=ReplyTo, out=head},
		StreamRef, Host, Port, Path, Headers0, WsOpts,
		EvHandler, EvHandlerState0) ->
	{Headers1, GunExtensions} = case maps:get(compress, WsOpts, false) of
		true -> {[{<<"sec-websocket-extensions">>,
				<<"permessage-deflate; client_max_window_bits; server_max_window_bits=15">>}
			|Headers0],
			[<<"permessage-deflate">>]};
		false -> {Headers0, []}
	end,
	Headers2 = case maps:get(protocols, WsOpts, []) of
		[] -> Headers1;
		ProtoOpt ->
			<< _, _, Proto/bits >> = iolist_to_binary([[<<", ">>, P] || {P, _} <- ProtoOpt]),
			[{<<"sec-websocket-protocol">>, Proto}|Headers1]
	end,
	Key = cow_ws:key(),
	Headers = [
		{<<"connection">>, <<"upgrade">>},
		{<<"upgrade">>, <<"websocket">>},
		{<<"sec-websocket-version">>, <<"13">>},
		{<<"sec-websocket-key">>, Key}
		|Headers2
	],
	{Conn, Out, EvHandlerState} = send_request(State, StreamRef, ReplyTo,
		<<"GET">>, Host, Port, Path, Headers, undefined,
		EvHandler, EvHandlerState0, ?FUNCTION_NAME),
	InitialFlow = maps:get(flow, WsOpts, infinity),
	{new_stream(State#http_state{connection=Conn, out=Out},
		{websocket, StreamRef, Key, GunExtensions, WsOpts}, ReplyTo, <<"GET">>, InitialFlow),
		EvHandlerState}.

ws_handshake(Buffer, State, StreamRef, Headers, Key, GunExtensions, Opts) ->
	%% @todo check upgrade, connection
	case lists:keyfind(<<"sec-websocket-accept">>, 1, Headers) of
		false ->
			close;
		{_, Accept} ->
			case cow_ws:encode_key(Key) of
				Accept ->
					ws_handshake_extensions(Buffer, State, StreamRef,
						Headers, GunExtensions, Opts);
				_ ->
					close
			end
	end.

ws_handshake_extensions(Buffer, State, StreamRef, Headers, GunExtensions, Opts) ->
	case lists:keyfind(<<"sec-websocket-extensions">>, 1, Headers) of
		false ->
			ws_handshake_protocols(Buffer, State, StreamRef, Headers, #{}, Opts);
		{_, ExtHd} ->
			case ws_validate_extensions(cow_http_hd:parse_sec_websocket_extensions(ExtHd), GunExtensions, #{}, Opts) of
				close ->
					close;
				Extensions ->
					ws_handshake_protocols(Buffer, State, StreamRef, Headers, Extensions, Opts)
			end
	end.

ws_validate_extensions([], _, Acc, _) ->
	Acc;
ws_validate_extensions([{Name = <<"permessage-deflate">>, Params}|Tail], GunExts, Acc, Opts) ->
	case lists:member(Name, GunExts) of
		true ->
			case cow_ws:validate_permessage_deflate(Params, Acc, Opts) of
				{ok, Acc2} -> ws_validate_extensions(Tail, GunExts, Acc2, Opts);
				error -> close
			end;
		%% Fail the connection if extension was not requested.
		false ->
			close
	end;
%% Fail the connection on unknown extension.
ws_validate_extensions(_, _, _, _) ->
	close.

%% @todo Validate protocols.
ws_handshake_protocols(Buffer, State, StreamRef, Headers, Extensions, Opts) ->
	case lists:keyfind(<<"sec-websocket-protocol">>, 1, Headers) of
		false ->
			ws_handshake_end(Buffer, State, StreamRef, Headers, Extensions,
				maps:get(default_protocol, Opts, gun_ws_h), Opts);
		{_, Proto} ->
			ProtoOpt = maps:get(protocols, Opts, []),
			case lists:keyfind(Proto, 1, ProtoOpt) of
				{_, Handler} ->
					ws_handshake_end(Buffer, State, StreamRef,
						Headers, Extensions, Handler, Opts);
				false ->
					close
			end
	end.

%% We know that the most recent stream is the Websocket one.
ws_handshake_end(Buffer, #http_state{owner=Owner, socket=Socket, transport=Transport,
		streams=[#stream{flow=InitialFlow}|_]}, StreamRef, Headers, Extensions, Handler, Opts) ->
	%% Send ourselves the remaining buffer, if any.
	_ = case Buffer of
		<<>> ->
			ok;
		_ ->
			{OK, _, _} = Transport:messages(),
			self() ! {OK, Socket, Buffer}
	end,
	%% Inform the user that the upgrade was successful and switch the protocol.
	Owner ! {gun_upgrade, self(), StreamRef, [<<"websocket">>], Headers},
	{switch_protocol, {ws, #{
		stream_ref => StreamRef,
		headers => Headers,
		extensions => Extensions,
		flow => InitialFlow,
		handler => Handler,
		opts => Opts
	}}}.