Add meta/2 and meta/3 to cowboy_http_req to save useful protocol information

* cowboy_http_protocol now defines 'websocket_version' as metadata.
* cowboy_http_rest now defines 'media_type', 'language', 'charset' as metadata.

include/http.hrl

@@ -60,6 +60,7 @@
 	headers    = []        :: http_headers(),
 	p_headers  = []        :: [any()], %% @todo Improve those specs.
 	cookies    = undefined :: undefined | http_cookies(),
+	meta       = []        :: [{atom(), any()}],
 
 	%% Request body.
 	body_state = waiting   :: waiting | done,

src/cowboy_http_req.erl

@@ -29,7 +29,8 @@
 	binding/2, binding/3, bindings/1,
 	header/2, header/3, headers/1,
 	parse_header/2, parse_header/3,
-	cookie/2, cookie/3, cookies/1
+	cookie/2, cookie/3, cookies/1,
+	meta/2, meta/3
 ]). %% Request API.
 
 -export([
@@ -341,6 +342,23 @@ cookies(Req=#http_req{cookies=undefined}) ->
 cookies(Req=#http_req{cookies=Cookies}) ->
 	{Cookies, Req}.
 
+%% @equiv meta(Name, Req, undefined)
+-spec meta(atom(), #http_req{}) -> {any() | undefined, #http_req{}}.
+meta(Name, Req) ->
+	meta(Name, Req, undefined).
+
+%% @doc Return metadata information about the request.
+%%
+%% Metadata information varies from one protocol to another. Websockets
+%% would define the protocol version here, while REST would use it to
+%% indicate which media type, language and charset were retained.
+-spec meta(atom(), #http_req{}, any()) -> {any(), #http_req{}}.
+meta(Name, Req, Default) ->
+	case lists:keyfind(Name, 1, Req#http_req.meta) of
+		{Name, Value} -> {Value, Req};
+		false -> {Default, Req}
+	end.
+
 %% Request Body API.
 
 %% @doc Return the full body sent with the request, or <em>{error, badarg}</em>

src/cowboy_http_rest.erl

@@ -182,7 +182,7 @@ options(Req, State) ->
 %% resources a little more readable, this is a lot less efficient. An example
 %% of such a return value would be:
 %%    {<<"text/html">>, to_html}
-content_types_provided(Req, State) ->
+content_types_provided(Req=#http_req{meta=Meta}, State) ->
 	case call(Req, State, content_types_provided) of
 		no_call ->
 			not_acceptable(Req, State);
@@ -195,8 +195,10 @@ content_types_provided(Req, State) ->
 			{Accept, Req3} = cowboy_http_req:parse_header('Accept', Req2),
 			case Accept of
 				undefined ->
-					languages_provided(Req3,
-						State2#state{content_type_a=hd(CTP2)});
+					{PMT, _Fun} = HeadCTP = hd(CTP2),
+					languages_provided(
+						Req3#http_req{meta=[{media_type, PMT}|Meta]},
+						State2#state{content_type_a=HeadCTP});
 				Accept ->
 					Accept2 = prioritize_accept(Accept),
 					choose_media_type(Req3, State2, Accept2)
@@ -258,12 +260,13 @@ match_media_type(Req, State, Accept,
 match_media_type(Req, State, Accept, [_Any|Tail], MediaType) ->
 	match_media_type(Req, State, Accept, Tail, MediaType).
 
-match_media_type_params(Req, State, Accept,
-		[Provided = {{_TP, _STP, Params_P}, _Fun}|Tail],
+match_media_type_params(Req=#http_req{meta=Meta}, State, Accept,
+		[Provided = {PMT = {_TP, _STP, Params_P}, _Fun}|Tail],
 		MediaType = {{_TA, _STA, Params_A}, _QA, _APA}) ->
 	case lists:sort(Params_P) =:= lists:sort(Params_A) of
 		true ->
-			languages_provided(Req, State#state{content_type_a=Provided});
+			languages_provided(Req#http_req{meta=[{media_type, PMT}|Meta]},
+				State#state{content_type_a=Provided});
 		false ->
 			match_media_type(Req, State, Accept, Tail, MediaType)
 	end.
@@ -327,10 +330,10 @@ match_language(Req, State, Accept, [Provided|Tail],
 			match_language(Req, State, Accept, Tail, Language)
 	end.
 
-set_language(Req, State=#state{language_a=Language}) ->
+set_language(Req=#http_req{meta=Meta}, State=#state{language_a=Language}) ->
 	{ok, Req2} = cowboy_http_req:set_resp_header(
 		<<"Content-Language">>, Language, Req),
-	charsets_provided(Req2, State).
+	charsets_provided(Req2#http_req{meta=[{language, Language}|Meta]}, State).
 
 %% charsets_provided should return a list of binary values indicating
 %% which charsets are accepted by the resource.
@@ -382,7 +385,7 @@ match_charset(Req, State, _Accept, [Provided|_Tail],
 match_charset(Req, State, Accept, [_Provided|Tail], Charset) ->
 	match_charset(Req, State, Accept, Tail, Charset).
 
-set_content_type(Req, State=#state{
+set_content_type(Req=#http_req{meta=Meta}, State=#state{
 		content_type_a={{Type, SubType, Params}, _Fun},
 		charset_a=Charset}) ->
 	ParamsBin = set_content_type_build_params(Params, []),
@@ -393,7 +396,7 @@ set_content_type(Req, State=#state{
 	end,
 	{ok, Req2} = cowboy_http_req:set_resp_header(
 		<<"Content-Type">>, ContentType2, Req),
-	encodings_provided(Req2, State).
+	encodings_provided(Req2#http_req{meta=[{charset, Charset}|Meta]}, State).
 
 set_content_type_build_params([], []) ->
 	<<>>;

src/cowboy_http_websocket.erl

@@ -30,9 +30,9 @@
 %%  <li>Firefox 6</li>
 %% </ul>
 %%
-%% Version 8 is supported by the following browsers:
+%% Version 8+ is supported by the following browsers:
 %% <ul>
-%%  <li>Firefox 7</li>
+%%  <li>Firefox 7+</li>
 %%  <li>Chrome 14+</li>
 %% </ul>
 -module(cowboy_http_websocket).
@@ -95,23 +95,24 @@ websocket_upgrade(State, Req) ->
 %% third part of the challenge key, because proxies will wait for
 %% a reply before sending it. Therefore we calculate the challenge
 %% key only in websocket_handshake/3.
-websocket_upgrade(undefined, State, Req) ->
+websocket_upgrade(undefined, State, Req=#http_req{meta=Meta}) ->
 	{Origin, Req2} = cowboy_http_req:header(<<"Origin">>, Req),
 	{Key1, Req3} = cowboy_http_req:header(<<"Sec-Websocket-Key1">>, Req2),
 	{Key2, Req4} = cowboy_http_req:header(<<"Sec-Websocket-Key2">>, Req3),
 	false = lists:member(undefined, [Origin, Key1, Key2]),
 	EOP = binary:compile_pattern(<< 255 >>),
 	{ok, State#state{version=0, origin=Origin, challenge={Key1, Key2},
-		eop=EOP}, Req4};
+		eop=EOP}, Req4#http_req{meta=[{websocket_version, 0}|Meta]}};
 %% Versions 7 and 8. Implementation follows the hybi 7 through 17 drafts.
-websocket_upgrade(Version, State, Req)
+websocket_upgrade(Version, State, Req=#http_req{meta=Meta})
 		when Version =:= <<"7">>; Version =:= <<"8">>;
 			Version =:= <<"13">> ->
 	{Key, Req2} = cowboy_http_req:header(<<"Sec-Websocket-Key">>, Req),
 	false = Key =:= undefined,
 	Challenge = hybi_challenge(Key),
 	IntVersion = list_to_integer(binary_to_list(Version)),
-	{ok, State#state{version=IntVersion, challenge=Challenge}, Req2}.
+	{ok, State#state{version=IntVersion, challenge=Challenge},
+		Req2#http_req{meta=[{websocket_version, IntVersion}|Meta]}}.
 
 -spec handler_init(#state{}, #http_req{}) -> closed | none().
 handler_init(State=#state{handler=Handler, opts=Opts},