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cowboy/src/cowboy_rest.erl
Loïc Hoguin a45813c60f
Allow passing options to sub protocols 
Before this commit we had an issue where configuring a
Websocket connection was simply not possible without
doing magic, adding callbacks or extra return values.
The init/2 function only allowed setting hibernate
and timeout options.

After this commit, when switching to a different
type of handler you can either return

  {module, Req, State}

or

  {module, Req, State, Opts}

where Opts is any value (as far as the sub protocol
interface is concerned) and is ultimately checked
by the custom handlers.

A large protocol like Websocket would accept only
a map there, with many different options, while a
small interface like loop handlers would allow
passing hibernate and nothing else.

For Websocket, hibernate must be set from the
websocket_init/1 callback, because init/2 executes
in a separate process.

Sub protocols now have two callbacks: one with the
Opts value, one without.

The loop handler code was largely reworked and
simplified. It does not need to manage a timeout
or read from the socket anymore, it's the job of
the protocol code. A lot of unnecessary stuff was
therefore removed.

Websocket compression must now be enabled from
the handler options instead of per listener. This
means that a project can have two separate Websocket
handlers with different options. Compression is
still disabled by default, and the idle_timeout
value was changed from inifnity to 60000 (60 seconds),
as that's safer and is also a good value for mobile
devices.
2017-02-18 18:26:20 +01:00

1158 lines
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%% Copyright (c) 2011-2017, Loïc Hoguin <essen@ninenines.eu>
%%
%% 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.
%% Originally based on the Webmachine Diagram from Alan Dean and
%% Justin Sheehy.
-module(cowboy_rest).
-behaviour(cowboy_sub_protocol).
-export([upgrade/4]).
-export([upgrade/5]).
%% Common handler callbacks.
-callback init(Req, any())
-> {ok | module(), Req, any()}
| {module(), Req, any(), any()}
when Req::cowboy_req:req().
-callback terminate(any(), cowboy_req:req(), any()) -> ok.
-optional_callbacks([terminate/3]).
%% REST handler callbacks.
-callback allowed_methods(Req, State)
-> {[binary()], Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([allowed_methods/2]).
-callback allow_missing_post(Req, State)
-> {boolean(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([allow_missing_post/2]).
-callback charsets_provided(Req, State)
-> {[binary()], Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([charsets_provided/2]).
-callback content_types_accepted(Req, State)
-> {[{binary() | {binary(), binary(), '*' | [{binary(), binary()}]}, atom()}], Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([content_types_accepted/2]).
-callback content_types_provided(Req, State)
-> {[{binary() | {binary(), binary(), '*' | [{binary(), binary()}]}, atom()}], Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([content_types_provided/2]).
-callback delete_completed(Req, State)
-> {boolean(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([delete_completed/2]).
-callback delete_resource(Req, State)
-> {boolean(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([delete_resource/2]).
-callback expires(Req, State)
-> {calendar:datetime() | binary() | undefined, Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([expires/2]).
-callback forbidden(Req, State)
-> {boolean(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([forbidden/2]).
-callback generate_etag(Req, State)
-> {binary() | {weak | strong, binary()}, Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([generate_etag/2]).
-callback is_authorized(Req, State)
-> {true | {false, iodata()}, Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([is_authorized/2]).
-callback is_conflict(Req, State)
-> {boolean(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([is_conflict/2]).
-callback known_methods(Req, State)
-> {[binary()], Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([known_methods/2]).
-callback languages_provided(Req, State)
-> {[binary()], Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([languages_provided/2]).
-callback last_modified(Req, State)
-> {calendar:datetime(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([last_modified/2]).
-callback malformed_request(Req, State)
-> {boolean(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([malformed_request/2]).
-callback moved_permanently(Req, State)
-> {{true, iodata()} | false, Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([moved_permanently/2]).
-callback moved_temporarily(Req, State)
-> {{true, iodata()} | false, Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([moved_temporarily/2]).
-callback multiple_choices(Req, State)
-> {boolean(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([multiple_choices/2]).
-callback options(Req, State)
-> {ok, Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([options/2]).
-callback previously_existed(Req, State)
-> {boolean(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([previously_existed/2]).
-callback resource_exists(Req, State)
-> {boolean(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([resource_exists/2]).
-callback service_available(Req, State)
-> {boolean(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([service_available/2]).
-callback uri_too_long(Req, State)
-> {boolean(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([uri_too_long/2]).
-callback valid_content_headers(Req, State)
-> {boolean(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([valid_content_headers/2]).
-callback valid_entity_length(Req, State)
-> {boolean(), Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([valid_entity_length/2]).
-callback variances(Req, State)
-> {[binary()], Req, State}
| {stop, Req, State}
when Req::cowboy_req:req(), State::any().
-optional_callbacks([variances/2]).
%% End of REST callbacks. Whew!
-record(state, {
method = undefined :: binary(),
%% Handler.
handler :: atom(),
handler_state :: any(),
%% Allowed methods. Only used for OPTIONS requests.
allowed_methods :: [binary()] | undefined,
%% Media type.
content_types_p = [] ::
[{binary() | {binary(), binary(), [{binary(), binary()}] | '*'},
atom()}],
content_type_a :: undefined
| {binary() | {binary(), binary(), [{binary(), binary()}] | '*'},
atom()},
%% Language.
languages_p = [] :: [binary()],
language_a :: undefined | binary(),
%% Charset.
charsets_p = [] :: [binary()],
charset_a :: undefined | binary(),
%% Whether the resource exists.
exists = false :: boolean(),
%% Cached resource calls.
etag :: undefined | no_call | {strong | weak, binary()},
last_modified :: undefined | no_call | calendar:datetime(),
expires :: undefined | no_call | calendar:datetime() | binary()
}).
-spec upgrade(Req, Env, module(), any())
-> {ok, Req, Env} when Req::cowboy_req:req(), Env::cowboy_middleware:env().
upgrade(Req0, Env, Handler, HandlerState) ->
Method = cowboy_req:method(Req0),
{ok, Req, Result} = service_available(Req0, #state{method=Method,
handler=Handler, handler_state=HandlerState}),
{ok, Req, Env#{result => Result}}.
-spec upgrade(Req, Env, module(), any(), any())
-> {ok, Req, Env} when Req::cowboy_req:req(), Env::cowboy_middleware:env().
%% cowboy_rest takes no options.
upgrade(Req, Env, Handler, HandlerState, _Opts) ->
upgrade(Req, Env, Handler, HandlerState).
service_available(Req, State) ->
expect(Req, State, service_available, true, fun known_methods/2, 503).
%% known_methods/2 should return a list of binary methods.
known_methods(Req, State=#state{method=Method}) ->
case call(Req, State, known_methods) of
no_call when Method =:= <<"HEAD">>; Method =:= <<"GET">>;
Method =:= <<"POST">>; Method =:= <<"PUT">>;
Method =:= <<"PATCH">>; Method =:= <<"DELETE">>;
Method =:= <<"OPTIONS">> ->
next(Req, State, fun uri_too_long/2);
no_call ->
next(Req, State, 501);
{stop, Req2, HandlerState} ->
terminate(Req2, State#state{handler_state=HandlerState});
{List, Req2, HandlerState} ->
State2 = State#state{handler_state=HandlerState},
case lists:member(Method, List) of
true -> next(Req2, State2, fun uri_too_long/2);
false -> next(Req2, State2, 501)
end
end.
uri_too_long(Req, State) ->
expect(Req, State, uri_too_long, false, fun allowed_methods/2, 414).
%% allowed_methods/2 should return a list of binary methods.
allowed_methods(Req, State=#state{method=Method}) ->
case call(Req, State, allowed_methods) of
no_call when Method =:= <<"HEAD">>; Method =:= <<"GET">> ->
next(Req, State, fun malformed_request/2);
no_call when Method =:= <<"OPTIONS">> ->
next(Req, State#state{allowed_methods=
[<<"HEAD">>, <<"GET">>, <<"OPTIONS">>]},
fun malformed_request/2);
no_call ->
method_not_allowed(Req, State,
[<<"HEAD">>, <<"GET">>, <<"OPTIONS">>]);
{stop, Req2, HandlerState} ->
terminate(Req2, State#state{handler_state=HandlerState});
{List, Req2, HandlerState} ->
State2 = State#state{handler_state=HandlerState},
case lists:member(Method, List) of
true when Method =:= <<"OPTIONS">> ->
next(Req2, State2#state{allowed_methods=List},
fun malformed_request/2);
true ->
next(Req2, State2, fun malformed_request/2);
false ->
method_not_allowed(Req2, State2, List)
end
end.
method_not_allowed(Req, State, []) ->
Req2 = cowboy_req:set_resp_header(<<"allow">>, <<>>, Req),
respond(Req2, State, 405);
method_not_allowed(Req, State, Methods) ->
<< ", ", Allow/binary >> = << << ", ", M/binary >> || M <- Methods >>,
Req2 = cowboy_req:set_resp_header(<<"allow">>, Allow, Req),
respond(Req2, State, 405).
malformed_request(Req, State) ->
expect(Req, State, malformed_request, false, fun is_authorized/2, 400).
%% is_authorized/2 should return true or {false, WwwAuthenticateHeader}.
is_authorized(Req, State) ->
case call(Req, State, is_authorized) of
no_call ->
forbidden(Req, State);
{stop, Req2, HandlerState} ->
terminate(Req2, State#state{handler_state=HandlerState});
{true, Req2, HandlerState} ->
forbidden(Req2, State#state{handler_state=HandlerState});
{{false, AuthHead}, Req2, HandlerState} ->
Req3 = cowboy_req:set_resp_header(
<<"www-authenticate">>, AuthHead, Req2),
respond(Req3, State#state{handler_state=HandlerState}, 401)
end.
forbidden(Req, State) ->
expect(Req, State, forbidden, false, fun valid_content_headers/2, 403).
valid_content_headers(Req, State) ->
expect(Req, State, valid_content_headers, true,
fun valid_entity_length/2, 501).
valid_entity_length(Req, State) ->
expect(Req, State, valid_entity_length, true, fun options/2, 413).
%% If you need to add additional headers to the response at this point,
%% you should do it directly in the options/2 call using set_resp_headers.
options(Req, State=#state{allowed_methods=Methods, method= <<"OPTIONS">>}) ->
case call(Req, State, options) of
no_call when Methods =:= [] ->
Req2 = cowboy_req:set_resp_header(<<"allow">>, <<>>, Req),
respond(Req2, State, 200);
no_call ->
<< ", ", Allow/binary >>
= << << ", ", M/binary >> || M <- Methods >>,
Req2 = cowboy_req:set_resp_header(<<"allow">>, Allow, Req),
respond(Req2, State, 200);
{stop, Req2, HandlerState} ->
terminate(Req2, State#state{handler_state=HandlerState});
{ok, Req2, HandlerState} ->
respond(Req2, State#state{handler_state=HandlerState}, 200)
end;
options(Req, State) ->
content_types_provided(Req, State).
%% content_types_provided/2 should return a list of content types and their
%% associated callback function as a tuple: {{Type, SubType, Params}, Fun}.
%% Type and SubType are the media type as binary. Params is a list of
%% Key/Value tuple, with Key and Value a binary. Fun is the name of the
%% callback that will be used to return the content of the response. It is
%% given as an atom.
%%
%% An example of such return value would be:
%% {{<<"text">>, <<"html">>, []}, to_html}
%%
%% Note that it is also possible to return a binary content type that will
%% then be parsed by Cowboy. However note that while this may make your
%% resources a little more readable, this is a lot less efficient.
%%
%% An example of such return value would be:
%% {<<"text/html">>, to_html}
content_types_provided(Req, State) ->
case call(Req, State, content_types_provided) of
no_call ->
State2 = State#state{
content_types_p=[{{<<"text">>, <<"html">>, '*'}, to_html}]},
try cowboy_req:parse_header(<<"accept">>, Req) of
undefined ->
languages_provided(
Req#{media_type => {<<"text">>, <<"html">>, []}},
State2#state{content_type_a={{<<"text">>, <<"html">>, []}, to_html}});
Accept ->
choose_media_type(Req, State2, prioritize_accept(Accept))
catch _:_ ->
respond(Req, State2, 400)
end;
{stop, Req2, HandlerState} ->
terminate(Req2, State#state{handler_state=HandlerState});
{[], Req2, HandlerState} ->
not_acceptable(Req2, State#state{handler_state=HandlerState});
{CTP, Req2, HandlerState} ->
CTP2 = [normalize_content_types(P) || P <- CTP],
State2 = State#state{
handler_state=HandlerState, content_types_p=CTP2},
try cowboy_req:parse_header(<<"accept">>, Req2) of
undefined ->
{PMT, _Fun} = HeadCTP = hd(CTP2),
languages_provided(
Req2#{media_type => PMT},
State2#state{content_type_a=HeadCTP});
Accept ->
choose_media_type(Req2, State2, prioritize_accept(Accept))
catch _:_ ->
respond(Req2, State2, 400)
end
end.
normalize_content_types({ContentType, Callback})
when is_binary(ContentType) ->
{cow_http_hd:parse_content_type(ContentType), Callback};
normalize_content_types(Normalized) ->
Normalized.
prioritize_accept(Accept) ->
lists:sort(
fun ({MediaTypeA, Quality, _AcceptParamsA},
{MediaTypeB, Quality, _AcceptParamsB}) ->
%% Same quality, check precedence in more details.
prioritize_mediatype(MediaTypeA, MediaTypeB);
({_MediaTypeA, QualityA, _AcceptParamsA},
{_MediaTypeB, QualityB, _AcceptParamsB}) ->
%% Just compare the quality.
QualityA > QualityB
end, Accept).
%% Media ranges can be overridden by more specific media ranges or
%% specific media types. If more than one media range applies to a given
%% type, the most specific reference has precedence.
%%
%% We always choose B over A when we can't decide between the two.
prioritize_mediatype({TypeA, SubTypeA, ParamsA}, {TypeB, SubTypeB, ParamsB}) ->
case TypeB of
TypeA ->
case SubTypeB of
SubTypeA -> length(ParamsA) > length(ParamsB);
<<"*">> -> true;
_Any -> false
end;
<<"*">> -> true;
_Any -> false
end.
%% Ignoring the rare AcceptParams. Not sure what should be done about them.
choose_media_type(Req, State, []) ->
not_acceptable(Req, State);
choose_media_type(Req, State=#state{content_types_p=CTP},
[MediaType|Tail]) ->
match_media_type(Req, State, Tail, CTP, MediaType).
match_media_type(Req, State, Accept, [], _MediaType) ->
choose_media_type(Req, State, Accept);
match_media_type(Req, State, Accept, CTP,
MediaType = {{<<"*">>, <<"*">>, _Params_A}, _QA, _APA}) ->
match_media_type_params(Req, State, Accept, CTP, MediaType);
match_media_type(Req, State, Accept,
CTP = [{{Type, SubType_P, _PP}, _Fun}|_Tail],
MediaType = {{Type, SubType_A, _PA}, _QA, _APA})
when SubType_P =:= SubType_A; SubType_A =:= <<"*">> ->
match_media_type_params(Req, State, Accept, CTP, MediaType);
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, '*'}, _Fun}|_Tail],
{{_TA, _STA, Params_A}, _QA, _APA}) ->
PMT = {TP, STP, Params_A},
languages_provided(Req#{media_type => PMT},
State#state{content_type_a=Provided});
match_media_type_params(Req, 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#{media_type => PMT},
State#state{content_type_a=Provided});
false ->
match_media_type(Req, State, Accept, Tail, MediaType)
end.
%% languages_provided should return a list of binary values indicating
%% which languages are accepted by the resource.
%%
%% @todo I suppose we should also ask the resource if it wants to
%% set a language itself or if it wants it to be automatically chosen.
languages_provided(Req, State) ->
case call(Req, State, languages_provided) of
no_call ->
charsets_provided(Req, State);
{stop, Req2, HandlerState} ->
terminate(Req2, State#state{handler_state=HandlerState});
{[], Req2, HandlerState} ->
not_acceptable(Req2, State#state{handler_state=HandlerState});
{LP, Req2, HandlerState} ->
State2 = State#state{handler_state=HandlerState, languages_p=LP},
case cowboy_req:parse_header(<<"accept-language">>, Req2) of
undefined ->
set_language(Req2, State2#state{language_a=hd(LP)});
AcceptLanguage ->
AcceptLanguage2 = prioritize_languages(AcceptLanguage),
choose_language(Req2, State2, AcceptLanguage2)
end
end.
%% A language-range matches a language-tag if it exactly equals the tag,
%% or if it exactly equals a prefix of the tag such that the first tag
%% character following the prefix is "-". The special range "*", if
%% present in the Accept-Language field, matches every tag not matched
%% by any other range present in the Accept-Language field.
%%
%% @todo The last sentence probably means we should always put '*'
%% at the end of the list.
prioritize_languages(AcceptLanguages) ->
lists:sort(
fun ({_TagA, QualityA}, {_TagB, QualityB}) ->
QualityA > QualityB
end, AcceptLanguages).
choose_language(Req, State, []) ->
not_acceptable(Req, State);
choose_language(Req, State=#state{languages_p=LP}, [Language|Tail]) ->
match_language(Req, State, Tail, LP, Language).
match_language(Req, State, Accept, [], _Language) ->
choose_language(Req, State, Accept);
match_language(Req, State, _Accept, [Provided|_Tail], {'*', _Quality}) ->
set_language(Req, State#state{language_a=Provided});
match_language(Req, State, _Accept, [Provided|_Tail], {Provided, _Quality}) ->
set_language(Req, State#state{language_a=Provided});
match_language(Req, State, Accept, [Provided|Tail],
Language = {Tag, _Quality}) ->
Length = byte_size(Tag),
case Provided of
<< Tag:Length/binary, $-, _Any/bits >> ->
set_language(Req, State#state{language_a=Provided});
_Any ->
match_language(Req, State, Accept, Tail, Language)
end.
set_language(Req, State=#state{language_a=Language}) ->
Req2 = cowboy_req:set_resp_header(<<"content-language">>, Language, Req),
charsets_provided(Req2#{language => Language}, State).
%% charsets_provided should return a list of binary values indicating
%% which charsets are accepted by the resource.
charsets_provided(Req, State) ->
case call(Req, State, charsets_provided) of
no_call ->
set_content_type(Req, State);
{stop, Req2, HandlerState} ->
terminate(Req2, State#state{handler_state=HandlerState});
{[], Req2, HandlerState} ->
not_acceptable(Req2, State#state{handler_state=HandlerState});
{CP, Req2, HandlerState} ->
State2 = State#state{handler_state=HandlerState, charsets_p=CP},
case cowboy_req:parse_header(<<"accept-charset">>, Req2) of
undefined ->
set_content_type(Req2, State2#state{charset_a=hd(CP)});
AcceptCharset ->
AcceptCharset2 = prioritize_charsets(AcceptCharset),
choose_charset(Req2, State2, AcceptCharset2)
end
end.
%% The special value "*", if present in the Accept-Charset field,
%% matches every character set (including ISO-8859-1) which is not
%% mentioned elsewhere in the Accept-Charset field. If no "*" is present
%% in an Accept-Charset field, then all character sets not explicitly
%% mentioned get a quality value of 0, except for ISO-8859-1, which gets
%% a quality value of 1 if not explicitly mentioned.
prioritize_charsets(AcceptCharsets) ->
AcceptCharsets2 = lists:sort(
fun ({_CharsetA, QualityA}, {_CharsetB, QualityB}) ->
QualityA > QualityB
end, AcceptCharsets),
case lists:keymember(<<"*">>, 1, AcceptCharsets2) of
true -> AcceptCharsets2;
false ->
case lists:keymember(<<"iso-8859-1">>, 1, AcceptCharsets2) of
true -> AcceptCharsets2;
false -> [{<<"iso-8859-1">>, 1000}|AcceptCharsets2]
end
end.
choose_charset(Req, State, []) ->
not_acceptable(Req, State);
choose_charset(Req, State=#state{charsets_p=CP}, [Charset|Tail]) ->
match_charset(Req, State, Tail, CP, Charset).
match_charset(Req, State, Accept, [], _Charset) ->
choose_charset(Req, State, Accept);
match_charset(Req, State, _Accept, [Provided|_], {Provided, _}) ->
set_content_type(Req, State#state{charset_a=Provided});
match_charset(Req, State, Accept, [_|Tail], Charset) ->
match_charset(Req, State, Accept, Tail, Charset).
set_content_type(Req, State=#state{
content_type_a={{Type, SubType, Params}, _Fun},
charset_a=Charset}) ->
ParamsBin = set_content_type_build_params(Params, []),
ContentType = [Type, <<"/">>, SubType, ParamsBin],
ContentType2 = case Charset of
undefined -> ContentType;
Charset -> [ContentType, <<"; charset=">>, Charset]
end,
Req2 = cowboy_req:set_resp_header(<<"content-type">>, ContentType2, Req),
encodings_provided(Req2#{charset => Charset}, State).
set_content_type_build_params('*', []) ->
<<>>;
set_content_type_build_params([], []) ->
<<>>;
set_content_type_build_params([], Acc) ->
lists:reverse(Acc);
set_content_type_build_params([{Attr, Value}|Tail], Acc) ->
set_content_type_build_params(Tail, [[Attr, <<"=">>, Value], <<";">>|Acc]).
%% @todo Match for identity as we provide nothing else for now.
%% @todo Don't forget to set the Content-Encoding header when we reply a body
%% and the found encoding is something other than identity.
encodings_provided(Req, State) ->
variances(Req, State).
not_acceptable(Req, State) ->
respond(Req, State, 406).
%% variances/2 should return a list of headers that will be added
%% to the Vary response header. The Accept, Accept-Language,
%% Accept-Charset and Accept-Encoding headers do not need to be
%% specified.
%%
%% @todo Do Accept-Encoding too when we handle it.
%% @todo Does the order matter?
variances(Req, State=#state{content_types_p=CTP,
languages_p=LP, charsets_p=CP}) ->
Variances = case CTP of
[] -> [];
[_] -> [];
[_|_] -> [<<"accept">>]
end,
Variances2 = case LP of
[] -> Variances;
[_] -> Variances;
[_|_] -> [<<"accept-language">>|Variances]
end,
Variances3 = case CP of
[] -> Variances2;
[_] -> Variances2;
[_|_] -> [<<"accept-charset">>|Variances2]
end,
try variances(Req, State, Variances3) of
{Variances4, Req2, State2} ->
case [[<<", ">>, V] || V <- Variances4] of
[] ->
resource_exists(Req2, State2);
[[<<", ">>, H]|Variances5] ->
Req3 = cowboy_req:set_resp_header(
<<"vary">>, [H|Variances5], Req2),
resource_exists(Req3, State2)
end
catch Class:Reason ->
error_terminate(Req, State, Class, Reason)
end.
variances(Req, State, Variances) ->
case unsafe_call(Req, State, variances) of
no_call ->
{Variances, Req, State};
{HandlerVariances, Req2, HandlerState} ->
{Variances ++ HandlerVariances, Req2,
State#state{handler_state=HandlerState}}
end.
resource_exists(Req, State) ->
expect(Req, State, resource_exists, true,
fun if_match_exists/2, fun if_match_must_not_exist/2).
if_match_exists(Req, State) ->
State2 = State#state{exists=true},
case cowboy_req:parse_header(<<"if-match">>, Req) of
undefined ->
if_unmodified_since_exists(Req, State2);
'*' ->
if_unmodified_since_exists(Req, State2);
ETagsList ->
if_match(Req, State2, ETagsList)
end.
if_match(Req, State, EtagsList) ->
try generate_etag(Req, State) of
%% Strong Etag comparison: weak Etag never matches.
{{weak, _}, Req2, State2} ->
precondition_failed(Req2, State2);
{Etag, Req2, State2} ->
case lists:member(Etag, EtagsList) of
true -> if_none_match_exists(Req2, State2);
%% Etag may be `undefined' which cannot be a member.
false -> precondition_failed(Req2, State2)
end
catch Class:Reason ->
error_terminate(Req, State, Class, Reason)
end.
if_match_must_not_exist(Req, State) ->
case cowboy_req:header(<<"if-match">>, Req) of
undefined -> is_put_to_missing_resource(Req, State);
_ -> precondition_failed(Req, State)
end.
if_unmodified_since_exists(Req, State) ->
try cowboy_req:parse_header(<<"if-unmodified-since">>, Req) of
undefined ->
if_none_match_exists(Req, State);
IfUnmodifiedSince ->
if_unmodified_since(Req, State, IfUnmodifiedSince)
catch _:_ ->
if_none_match_exists(Req, State)
end.
%% If LastModified is the atom 'no_call', we continue.
if_unmodified_since(Req, State, IfUnmodifiedSince) ->
try last_modified(Req, State) of
{LastModified, Req2, State2} ->
case LastModified > IfUnmodifiedSince of
true -> precondition_failed(Req2, State2);
false -> if_none_match_exists(Req2, State2)
end
catch Class:Reason ->
error_terminate(Req, State, Class, Reason)
end.
if_none_match_exists(Req, State) ->
case cowboy_req:parse_header(<<"if-none-match">>, Req) of
undefined ->
if_modified_since_exists(Req, State);
'*' ->
precondition_is_head_get(Req, State);
EtagsList ->
if_none_match(Req, State, EtagsList)
end.
if_none_match(Req, State, EtagsList) ->
try generate_etag(Req, State) of
{Etag, Req2, State2} ->
case Etag of
undefined ->
precondition_failed(Req2, State2);
Etag ->
case is_weak_match(Etag, EtagsList) of
true -> precondition_is_head_get(Req2, State2);
false -> method(Req2, State2)
end
end
catch Class:Reason ->
error_terminate(Req, State, Class, Reason)
end.
%% Weak Etag comparison: only check the opaque tag.
is_weak_match(_, []) ->
false;
is_weak_match({_, Tag}, [{_, Tag}|_]) ->
true;
is_weak_match(Etag, [_|Tail]) ->
is_weak_match(Etag, Tail).
precondition_is_head_get(Req, State=#state{method=Method})
when Method =:= <<"HEAD">>; Method =:= <<"GET">> ->
not_modified(Req, State);
precondition_is_head_get(Req, State) ->
precondition_failed(Req, State).
if_modified_since_exists(Req, State) ->
try cowboy_req:parse_header(<<"if-modified-since">>, Req) of
undefined ->
method(Req, State);
IfModifiedSince ->
if_modified_since_now(Req, State, IfModifiedSince)
catch _:_ ->
method(Req, State)
end.
if_modified_since_now(Req, State, IfModifiedSince) ->
case IfModifiedSince > erlang:universaltime() of
true -> method(Req, State);
false -> if_modified_since(Req, State, IfModifiedSince)
end.
if_modified_since(Req, State, IfModifiedSince) ->
try last_modified(Req, State) of
{undefined, Req2, State2} ->
method(Req2, State2);
{LastModified, Req2, State2} ->
case LastModified > IfModifiedSince of
true -> method(Req2, State2);
false -> not_modified(Req2, State2)
end
catch Class:Reason ->
error_terminate(Req, State, Class, Reason)
end.
not_modified(Req, State) ->
Req2 = cowboy_req:delete_resp_header(<<"content-type">>, Req),
try set_resp_etag(Req2, State) of
{Req3, State2} ->
try set_resp_expires(Req3, State2) of
{Req4, State3} ->
respond(Req4, State3, 304)
catch Class:Reason ->
error_terminate(Req, State2, Class, Reason)
end
catch Class:Reason ->
error_terminate(Req, State, Class, Reason)
end.
precondition_failed(Req, State) ->
respond(Req, State, 412).
is_put_to_missing_resource(Req, State=#state{method= <<"PUT">>}) ->
moved_permanently(Req, State, fun is_conflict/2);
is_put_to_missing_resource(Req, State) ->
previously_existed(Req, State).
%% moved_permanently/2 should return either false or {true, Location}
%% with Location the full new URI of the resource.
moved_permanently(Req, State, OnFalse) ->
case call(Req, State, moved_permanently) of
{{true, Location}, Req2, HandlerState} ->
Req3 = cowboy_req:set_resp_header(
<<"location">>, Location, Req2),
respond(Req3, State#state{handler_state=HandlerState}, 301);
{false, Req2, HandlerState} ->
OnFalse(Req2, State#state{handler_state=HandlerState});
{stop, Req2, HandlerState} ->
terminate(Req2, State#state{handler_state=HandlerState});
no_call ->
OnFalse(Req, State)
end.
previously_existed(Req, State) ->
expect(Req, State, previously_existed, false,
fun (R, S) -> is_post_to_missing_resource(R, S, 404) end,
fun (R, S) -> moved_permanently(R, S, fun moved_temporarily/2) end).
%% moved_temporarily/2 should return either false or {true, Location}
%% with Location the full new URI of the resource.
moved_temporarily(Req, State) ->
case call(Req, State, moved_temporarily) of
{{true, Location}, Req2, HandlerState} ->
Req3 = cowboy_req:set_resp_header(
<<"location">>, Location, Req2),
respond(Req3, State#state{handler_state=HandlerState}, 307);
{false, Req2, HandlerState} ->
is_post_to_missing_resource(Req2, State#state{handler_state=HandlerState}, 410);
{stop, Req2, HandlerState} ->
terminate(Req2, State#state{handler_state=HandlerState});
no_call ->
is_post_to_missing_resource(Req, State, 410)
end.
is_post_to_missing_resource(Req, State=#state{method= <<"POST">>}, OnFalse) ->
allow_missing_post(Req, State, OnFalse);
is_post_to_missing_resource(Req, State, OnFalse) ->
respond(Req, State, OnFalse).
allow_missing_post(Req, State, OnFalse) ->
expect(Req, State, allow_missing_post, true, fun accept_resource/2, OnFalse).
method(Req, State=#state{method= <<"DELETE">>}) ->
delete_resource(Req, State);
method(Req, State=#state{method= <<"PUT">>}) ->
is_conflict(Req, State);
method(Req, State=#state{method=Method})
when Method =:= <<"POST">>; Method =:= <<"PATCH">> ->
accept_resource(Req, State);
method(Req, State=#state{method=Method})
when Method =:= <<"GET">>; Method =:= <<"HEAD">> ->
set_resp_body_etag(Req, State);
method(Req, State) ->
multiple_choices(Req, State).
%% delete_resource/2 should start deleting the resource and return.
delete_resource(Req, State) ->
expect(Req, State, delete_resource, false, 500, fun delete_completed/2).
%% delete_completed/2 indicates whether the resource has been deleted yet.
delete_completed(Req, State) ->
expect(Req, State, delete_completed, true, fun has_resp_body/2, 202).
is_conflict(Req, State) ->
expect(Req, State, is_conflict, false, fun accept_resource/2, 409).
%% content_types_accepted should return a list of media types and their
%% associated callback functions in the same format as content_types_provided.
%%
%% The callback will then be called and is expected to process the content
%% pushed to the resource in the request body.
%%
%% content_types_accepted SHOULD return a different list
%% for each HTTP method.
accept_resource(Req, State) ->
case call(Req, State, content_types_accepted) of
no_call ->
respond(Req, State, 415);
{stop, Req2, HandlerState} ->
terminate(Req2, State#state{handler_state=HandlerState});
{CTA, Req2, HandlerState} ->
CTA2 = [normalize_content_types(P) || P <- CTA],
State2 = State#state{handler_state=HandlerState},
try cowboy_req:parse_header(<<"content-type">>, Req2) of
ContentType ->
choose_content_type(Req2, State2, ContentType, CTA2)
catch _:_ ->
respond(Req2, State2, 415)
end
end.
%% The special content type '*' will always match. It can be used as a
%% catch-all content type for accepting any kind of request content.
%% Note that because it will always match, it should be the last of the
%% list of content types, otherwise it'll shadow the ones following.
choose_content_type(Req, State, _ContentType, []) ->
respond(Req, State, 415);
choose_content_type(Req, State, ContentType, [{Accepted, Fun}|_Tail])
when Accepted =:= '*'; Accepted =:= ContentType ->
process_content_type(Req, State, Fun);
%% The special parameter '*' will always match any kind of content type
%% parameters.
%% Note that because it will always match, it should be the last of the
%% list for specific content type, otherwise it'll shadow the ones following.
choose_content_type(Req, State, {Type, SubType, Param},
[{{Type, SubType, AcceptedParam}, Fun}|_Tail])
when AcceptedParam =:= '*'; AcceptedParam =:= Param ->
process_content_type(Req, State, Fun);
choose_content_type(Req, State, ContentType, [_Any|Tail]) ->
choose_content_type(Req, State, ContentType, Tail).
process_content_type(Req, State=#state{method=Method, exists=Exists}, Fun) ->
try case call(Req, State, Fun) of
{stop, Req2, HandlerState2} ->
terminate(Req2, State#state{handler_state=HandlerState2});
{true, Req2, HandlerState2} when Exists ->
State2 = State#state{handler_state=HandlerState2},
next(Req2, State2, fun has_resp_body/2);
{true, Req2, HandlerState2} ->
State2 = State#state{handler_state=HandlerState2},
next(Req2, State2, fun maybe_created/2);
{false, Req2, HandlerState2} ->
State2 = State#state{handler_state=HandlerState2},
respond(Req2, State2, 400);
{{true, ResURL}, Req2, HandlerState2} when Method =:= <<"POST">> ->
State2 = State#state{handler_state=HandlerState2},
Req3 = cowboy_req:set_resp_header(
<<"location">>, ResURL, Req2),
if
Exists -> respond(Req3, State2, 303);
true -> respond(Req3, State2, 201)
end
end catch Class:Reason = {case_clause, no_call} ->
error_terminate(Req, State, Class, Reason)
end.
%% If PUT was used then the resource has been created at the current URL.
%% Otherwise, if a location header has been set then the resource has been
%% created at a new URL. If not, send a 200 or 204 as expected from a
%% POST or PATCH request.
maybe_created(Req, State=#state{method= <<"PUT">>}) ->
respond(Req, State, 201);
maybe_created(Req, State) ->
case cowboy_req:has_resp_header(<<"location">>, Req) of
true -> respond(Req, State, 201);
false -> has_resp_body(Req, State)
end.
has_resp_body(Req, State) ->
case cowboy_req:has_resp_body(Req) of
true -> multiple_choices(Req, State);
false -> respond(Req, State, 204)
end.
%% Set the Etag header if any for the response provided.
set_resp_body_etag(Req, State) ->
try set_resp_etag(Req, State) of
{Req2, State2} ->
set_resp_body_last_modified(Req2, State2)
catch Class:Reason ->
error_terminate(Req, State, Class, Reason)
end.
%% Set the Last-Modified header if any for the response provided.
set_resp_body_last_modified(Req, State) ->
try last_modified(Req, State) of
{LastModified, Req2, State2} ->
case LastModified of
LastModified when is_atom(LastModified) ->
set_resp_body_expires(Req2, State2);
LastModified ->
LastModifiedBin = cowboy_clock:rfc1123(LastModified),
Req3 = cowboy_req:set_resp_header(
<<"last-modified">>, LastModifiedBin, Req2),
set_resp_body_expires(Req3, State2)
end
catch Class:Reason ->
error_terminate(Req, State, Class, Reason)
end.
%% Set the Expires header if any for the response provided.
set_resp_body_expires(Req, State) ->
try set_resp_expires(Req, State) of
{Req2, State2} ->
set_resp_body(Req2, State2)
catch Class:Reason ->
error_terminate(Req, State, Class, Reason)
end.
%% Set the response headers and call the callback found using
%% content_types_provided/2 to obtain the request body and add
%% it to the response.
set_resp_body(Req, State=#state{content_type_a={_, Callback}}) ->
try case call(Req, State, Callback) of
{stop, Req2, HandlerState2} ->
terminate(Req2, State#state{handler_state=HandlerState2});
{Body, Req2, HandlerState2} ->
State2 = State#state{handler_state=HandlerState2},
Req3 = cowboy_req:set_resp_body(Body, Req2),
multiple_choices(Req3, State2)
end catch Class:Reason = {case_clause, no_call} ->
error_terminate(Req, State, Class, Reason)
end.
multiple_choices(Req, State) ->
expect(Req, State, multiple_choices, false, 200, 300).
%% Response utility functions.
set_resp_etag(Req, State) ->
{Etag, Req2, State2} = generate_etag(Req, State),
case Etag of
undefined ->
{Req2, State2};
Etag ->
Req3 = cowboy_req:set_resp_header(
<<"etag">>, encode_etag(Etag), Req2),
{Req3, State2}
end.
-spec encode_etag({strong | weak, binary()}) -> iolist().
encode_etag({strong, Etag}) -> [$",Etag,$"];
encode_etag({weak, Etag}) -> ["W/\"",Etag,$"].
set_resp_expires(Req, State) ->
{Expires, Req2, State2} = expires(Req, State),
case Expires of
Expires when is_atom(Expires) ->
{Req2, State2};
Expires when is_binary(Expires) ->
Req3 = cowboy_req:set_resp_header(
<<"expires">>, Expires, Req2),
{Req3, State2};
Expires ->
ExpiresBin = cowboy_clock:rfc1123(Expires),
Req3 = cowboy_req:set_resp_header(
<<"expires">>, ExpiresBin, Req2),
{Req3, State2}
end.
%% Info retrieval. No logic.
generate_etag(Req, State=#state{etag=no_call}) ->
{undefined, Req, State};
generate_etag(Req, State=#state{etag=undefined}) ->
case unsafe_call(Req, State, generate_etag) of
no_call ->
{undefined, Req, State#state{etag=no_call}};
{Etag, Req2, HandlerState} when is_binary(Etag) ->
Etag2 = cow_http_hd:parse_etag(Etag),
{Etag2, Req2, State#state{handler_state=HandlerState, etag=Etag2}};
{Etag, Req2, HandlerState} ->
{Etag, Req2, State#state{handler_state=HandlerState, etag=Etag}}
end;
generate_etag(Req, State=#state{etag=Etag}) ->
{Etag, Req, State}.
last_modified(Req, State=#state{last_modified=no_call}) ->
{undefined, Req, State};
last_modified(Req, State=#state{last_modified=undefined}) ->
case unsafe_call(Req, State, last_modified) of
no_call ->
{undefined, Req, State#state{last_modified=no_call}};
{LastModified, Req2, HandlerState} ->
{LastModified, Req2, State#state{handler_state=HandlerState,
last_modified=LastModified}}
end;
last_modified(Req, State=#state{last_modified=LastModified}) ->
{LastModified, Req, State}.
expires(Req, State=#state{expires=no_call}) ->
{undefined, Req, State};
expires(Req, State=#state{expires=undefined}) ->
case unsafe_call(Req, State, expires) of
no_call ->
{undefined, Req, State#state{expires=no_call}};
{Expires, Req2, HandlerState} ->
{Expires, Req2, State#state{handler_state=HandlerState,
expires=Expires}}
end;
expires(Req, State=#state{expires=Expires}) ->
{Expires, Req, State}.
%% REST primitives.
expect(Req, State, Callback, Expected, OnTrue, OnFalse) ->
case call(Req, State, Callback) of
no_call ->
next(Req, State, OnTrue);
{stop, Req2, HandlerState} ->
terminate(Req2, State#state{handler_state=HandlerState});
{Expected, Req2, HandlerState} ->
next(Req2, State#state{handler_state=HandlerState}, OnTrue);
{_Unexpected, Req2, HandlerState} ->
next(Req2, State#state{handler_state=HandlerState}, OnFalse)
end.
call(Req, State=#state{handler=Handler, handler_state=HandlerState},
Callback) ->
case erlang:function_exported(Handler, Callback, 2) of
true ->
try
Handler:Callback(Req, HandlerState)
catch Class:Reason ->
error_terminate(Req, State, Class, Reason)
end;
false ->
no_call
end.
unsafe_call(Req, #state{handler=Handler, handler_state=HandlerState},
Callback) ->
case erlang:function_exported(Handler, Callback, 2) of
true -> Handler:Callback(Req, HandlerState);
false -> no_call
end.
next(Req, State, Next) when is_function(Next) ->
Next(Req, State);
next(Req, State, StatusCode) when is_integer(StatusCode) ->
respond(Req, State, StatusCode).
respond(Req, State, StatusCode) ->
terminate(cowboy_req:reply(StatusCode, Req), State).
-spec error_terminate(cowboy_req:req(), #state{}, atom(), any()) -> no_return().
error_terminate(Req, #state{handler=Handler, handler_state=HandlerState}, Class, Reason) ->
cowboy_handler:terminate({crash, Class, Reason}, Req, HandlerState, Handler),
erlang:raise(Class, Reason, erlang:get_stacktrace()).
terminate(Req, #state{handler=Handler, handler_state=HandlerState}) ->
Result = cowboy_handler:terminate(normal, Req, HandlerState, Handler),
{ok, Req, Result}.
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