From 3f0b598edff1f411e31aca18ea96562b0d724257 Mon Sep 17 00:00:00 2001
From: Gustaf Sjoberg <gs@pipsq.com>
Date: Wed, 22 Mar 2017 09:18:43 +0100
Subject: Add transform_header_name http option.

---
 doc/src/manual/gun.asciidoc |  6 ++++++
 src/gun_http.erl            | 17 +++++++++++++----
 src/gun_http2.erl           |  2 +-
 test/gun_SUITE.erl          | 13 +++++++++++++
 4 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/doc/src/manual/gun.asciidoc b/doc/src/manual/gun.asciidoc
index 7b9ddd0..7c794ee 100644
--- a/doc/src/manual/gun.asciidoc
+++ b/doc/src/manual/gun.asciidoc
@@ -61,6 +61,12 @@ keepalive => pos_integer()::
 	empty line when the connection is idle. Gun only makes a best
 	effort here as servers usually have configurable limits to drop
 	idle connections. Defaults to 5000.
+transform_header_name => fun((LowercaseName :: binary()) -> TransformedName :: binary()) | undefined::
+	A function that will be applied to all header names before they
+	are sent to the server. Gun assumes that all header names are in
+	lower case. This function is useful if you, for example, need to
+	re-case header names in the event that the server incorrectly
+	considers header name case to be significant.
 version => 'HTTP/1.1' | 'HTTP/1.0'::
 	HTTP version to use. Defaults to 'HTTP/1.1'.
 
diff --git a/src/gun_http.erl b/src/gun_http.erl
index 2388182..3766ca5 100644
--- a/src/gun_http.erl
+++ b/src/gun_http.erl
@@ -51,7 +51,8 @@
 	streams = [] :: [#stream{}],
 	in = head :: io(),
 	in_state = {0, 0} :: {non_neg_integer(), non_neg_integer()},
-	out = head :: io()
+	out = head :: io(),
+	transform_header_name :: fun((binary()) -> binary())
 }).
 
 check_options(Opts) ->
@@ -68,6 +69,8 @@ do_check_options([Opt={content_handlers, Handlers}|Opts]) ->
 		ok -> do_check_options(Opts);
 		error -> {error, {options, {http, Opt}}}
 	end;
+do_check_options([{transform_header_name, F}|Opts]) when is_function(F) ->
+	do_check_options(Opts);
 do_check_options([Opt|_]) ->
 	{error, {options, {http, Opt}}}.
 
@@ -76,8 +79,9 @@ name() -> http.
 init(Owner, Socket, Transport, Opts) ->
 	Version = maps:get(version, Opts, 'HTTP/1.1'),
 	Handlers = maps:get(content_handlers, Opts, [gun_data]),
+	TransformHeaderName = maps:get(transform_header_name, Opts, fun (N) -> N end),
 	#http_state{owner=Owner, socket=Socket, transport=Transport, version=Version,
-		content_handlers=Handlers}.
+		content_handlers=Handlers, transform_header_name=TransformHeaderName}.
 
 %% Stop looping when we got no more data.
 handle(<<>>, State) ->
@@ -255,7 +259,8 @@ request(State=#http_state{socket=Socket, transport=Transport, version=Version,
 		body_chunked -> [{<<"transfer-encoding">>, <<"chunked">>}|Headers3];
 		_ -> Headers3
 	end,
-	Transport:send(Socket, cow_http:request(Method, Path, Version, Headers4)),
+	Headers5 = transform_header_names(State, Headers4),
+	Transport:send(Socket, cow_http:request(Method, Path, Version, Headers5)),
 	new_stream(State#http_state{connection=Conn, out=Out}, StreamRef, ReplyTo, Method).
 
 request(State=#http_state{socket=Socket, transport=Transport, version=Version,
@@ -266,15 +271,19 @@ request(State=#http_state{socket=Socket, transport=Transport, version=Version,
 		false -> [{<<"host">>, [Host, $:, integer_to_binary(Port)]}|Headers2];
 		true -> Headers2
 	end,
+	Headers4 = transform_header_names(State, Headers3),
 	%% We use Headers2 because this is the smallest list.
 	Conn = conn_from_headers(Version, Headers2),
 	Transport:send(Socket, [
 		cow_http:request(Method, Path, Version, [
 			{<<"content-length">>, integer_to_binary(iolist_size(Body))}
-		|Headers3]),
+		|Headers4]),
 		Body]),
 	new_stream(State#http_state{connection=Conn}, StreamRef, ReplyTo, Method).
 
+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, _, _) ->
 	error_stream_closed(State, StreamRef, ReplyTo);
diff --git a/src/gun_http2.erl b/src/gun_http2.erl
index 6073119..2195037 100644
--- a/src/gun_http2.erl
+++ b/src/gun_http2.erl
@@ -173,7 +173,7 @@ frame(settings_ack, State) -> %% @todo =#http2_state{next_settings=_NextSettings
 %% PUSH_PROMISE frame.
 %% @todo Continuation.
 frame({push_promise, StreamID, head_fin, PromisedStreamID, HeaderBlock},
-		State=#http2_state{owner=Owner, decode_state=DecodeState0}) ->
+		State=#http2_state{decode_state=DecodeState0}) ->
 	case get_stream_by_id(PromisedStreamID, State) of
 		false ->
 			case get_stream_by_id(StreamID, State) of
diff --git a/test/gun_SUITE.erl b/test/gun_SUITE.erl
index 171c874..505f365 100644
--- a/test/gun_SUITE.erl
+++ b/test/gun_SUITE.erl
@@ -139,3 +139,16 @@ retry_timeout(_) ->
 	after 400 ->
 		error(gone_too_late)
 	end.
+
+transform_header_name(_) ->
+	doc("The reply_to option allows using a separate process for requests."),
+	{ok, Pid} = gun:open("google.com", 443, #{
+		protocols => [http],
+		http_opts => #{
+			transform_header_name => fun(<<"host">>) -> <<"HOST">>; (N) -> N end
+		}
+	}),
+	{ok, http} = gun:await_up(Pid),
+	Ref = gun:get(Pid, "/", [{<<"host">>, <<"google.com">>}]),
+	{response, _, _, _} = gun:await(Pid, Ref),
+	ok.
-- 
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