%% Copyright (c) 2014, 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.

-module(cow_http_hd).

-export([parse_accept/1]).
-export([parse_accept_charset/1]).
-export([parse_accept_encoding/1]).
-export([parse_accept_language/1]).
-export([parse_connection/1]).
-export([parse_content_length/1]).
-export([parse_content_type/1]).
-export([parse_expect/1]).
-export([parse_if_modified_since/1]).
-export([parse_if_unmodified_since/1]).
-export([parse_max_forwards/1]).
-export([parse_transfer_encoding/1]).

-type media_type() :: {binary(), binary(), [{binary(), binary()}]}.
-export_type([media_type/0]).

-type qvalue() :: 0..1000.
-export_type([qvalue/0]).

-include("cow_inline.hrl").

-ifdef(TEST).
-include_lib("triq/include/triq.hrl").

ows() ->
	list(oneof([$\s, $\t])).

alpha_chars() -> "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".
alphanum_chars() -> "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".

alpha() ->
	oneof(alpha_chars()).

alphanum() ->
	oneof(alphanum_chars()).

tchar() ->
	frequency([
		{1, oneof([$!, $#, $$, $%, $&, $', $*, $+, $-, $., $^, $_, $`, $|, $~])},
		{99, oneof(alphanum_chars())}
	]).

token() ->
	?LET(T,
		non_empty(list(tchar())),
		list_to_binary(T)).

obs_text() ->
	[128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,
	146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,
	164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,
	182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,198,199,
	200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,216,217,
	218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,234,235,
	236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,252,253,
	254,255].

qdtext() ->
	frequency([
		{99, oneof("\t\s!#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^_`abcdefghijklmnopqrstuvwxyz{|}~")},
		{1, oneof(obs_text())}
	]).

quoted_pair() ->
	[$\\, frequency([
		{99, oneof("\t\s!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~")},
		{1, oneof(obs_text())}
	])].

quoted_string() ->
	[$", list(frequency([{100, qdtext()}, {1, quoted_pair()}])), $"].

%% Helper function for ( token / quoted-string ) values.
unquote([$", V, $"]) -> unquote(V, <<>>);
unquote(V) -> V.

unquote([], Acc) -> Acc;
unquote([[$\\, C]|Tail], Acc) -> unquote(Tail, << Acc/binary, C >>);
unquote([C|Tail], Acc) -> unquote(Tail, << Acc/binary, C >>).

parameter() ->
	?SUCHTHAT({K, _, _, _},
		{token(), oneof([token(), quoted_string()]), ows(), ows()},
		K =/= <<"q">>).

weight() ->
	frequency([
		{90, int(0, 1000)},
		{10, undefined}
	]).

%% Helper function for weight's qvalue formatting.
qvalue_to_iodata(0) -> <<"0">>;
qvalue_to_iodata(Q) when Q < 10 -> [<<"0.00">>, integer_to_binary(Q)];
qvalue_to_iodata(Q) when Q < 100 -> [<<"0.0">>, integer_to_binary(Q)];
qvalue_to_iodata(Q) when Q < 1000 -> [<<"0.">>, integer_to_binary(Q)];
qvalue_to_iodata(1000) -> <<"1">>.
-endif.

%% @doc Parse the Accept header.

-spec parse_accept(binary()) -> [{media_type(), qvalue(), [binary() | {binary(), binary()}]}].
parse_accept(<<"*/*">>) ->
	[{{<<"*">>, <<"*">>, []}, 1000, []}];
parse_accept(Accept) ->
	media_range_list(Accept, []).

media_range_list(<<>>, Acc) -> lists:reverse(Acc);
media_range_list(<< $\s, R/bits >>, Acc) -> media_range_list(R, Acc);
media_range_list(<< $\t, R/bits >>, Acc) -> media_range_list(R, Acc);
media_range_list(<< $,, R/bits >>, Acc) -> media_range_list(R, Acc);
media_range_list(<< C, R/bits >>, Acc) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(media_range_type, R, Acc, <<>>)
	end.

media_range_type(<< $/, R/bits >>, Acc, T) -> media_range_subtype(R, Acc, T, <<>>);
%% Special clause for badly behaving user agents that send * instead of */*.
media_range_type(<< $;, R/bits >>, Acc, <<"*">>) -> media_range_before_param(R, Acc, <<"*">>, <<"*">>, []);
media_range_type(<< C, R/bits >>, Acc, T) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(media_range_type, R, Acc, T)
	end.

media_range_subtype(<<>>, Acc, T, S) when S =/= <<>> -> lists:reverse([{{T, S, []}, 1000, []}|Acc]);
media_range_subtype(<< $,, R/bits >>, Acc, T, S) when S =/= <<>> -> media_range_list(R, [{{T, S, []}, 1000, []}|Acc]);
media_range_subtype(<< $;, R/bits >>, Acc, T, S) when S =/= <<>> -> media_range_before_param(R, Acc, T, S, []);
media_range_subtype(<< $\s, R/bits >>, Acc, T, S) when S =/= <<>> -> media_range_before_semicolon(R, Acc, T, S, []);
media_range_subtype(<< $\t, R/bits >>, Acc, T, S) when S =/= <<>> -> media_range_before_semicolon(R, Acc, T, S, []);
media_range_subtype(<< C, R/bits >>, Acc, T, S) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(media_range_subtype, R, Acc, T, S)
	end.

media_range_before_semicolon(<<>>, Acc, T, S, P) -> lists:reverse([{{T, S, lists:reverse(P)}, 1000, []}|Acc]);
media_range_before_semicolon(<< $,, R/bits >>, Acc, T, S, P) -> media_range_list(R, [{{T, S, lists:reverse(P)}, 1000, []}|Acc]);
media_range_before_semicolon(<< $;, R/bits >>, Acc, T, S, P) -> media_range_before_param(R, Acc, T, S, P);
media_range_before_semicolon(<< $\s, R/bits >>, Acc, T, S, P) -> media_range_before_semicolon(R, Acc, T, S, P);
media_range_before_semicolon(<< $\t, R/bits >>, Acc, T, S, P) -> media_range_before_semicolon(R, Acc, T, S, P).

media_range_before_param(<< $\s, R/bits >>, Acc, T, S, P) -> media_range_before_param(R, Acc, T, S, P);
media_range_before_param(<< $\t, R/bits >>, Acc, T, S, P) -> media_range_before_param(R, Acc, T, S, P);
%% Special clause for badly behaving user agents that send .123 instead of 0.123.
media_range_before_param(<< $q, $=, $., R/bits >>, Acc, T, S, P) -> media_range_broken_weight(R, Acc, T, S, P);
media_range_before_param(<< $q, $=, R/bits >>, Acc, T, S, P) -> media_range_weight(R, Acc, T, S, P);
media_range_before_param(<< C, R/bits >>, Acc, T, S, P) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(media_range_param, R, Acc, T, S, P, <<>>)
	end.

media_range_param(<< $=, $", R/bits >>, Acc, T, S, P, K) -> media_range_quoted(R, Acc, T, S, P, K, <<>>);
media_range_param(<< $=, R/bits >>, Acc, T, S, P, K) -> media_range_value(R, Acc, T, S, P, K, <<>>);
media_range_param(<< C, R/bits >>, Acc, T, S, P, K) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(media_range_param, R, Acc, T, S, P, K)
	end.

media_range_quoted(<< $", R/bits >>, Acc, T, S, P, K, V) -> media_range_before_semicolon(R, Acc, T, S, [{K, V}|P]);
media_range_quoted(<< $\\, C, R/bits >>, Acc, T, S, P, K, V) when ?IS_VCHAR(C) -> media_range_quoted(R, Acc, T, S, P, K, << V/binary, C >>);
media_range_quoted(<< C, R/bits >>, Acc, T, S, P, K, V) when ?IS_VCHAR(C) -> media_range_quoted(R, Acc, T, S, P, K, << V/binary, C >>).

media_range_value(<<>>, Acc, T, S, P, K, V) -> lists:reverse([{{T, S, lists:reverse([{K, V}|P])}, 1000, []}|Acc]);
media_range_value(<< $,, R/bits >>, Acc, T, S, P, K, V) -> media_range_list(R, [{{T, S, lists:reverse([{K, V}|P])}, 1000, []}|Acc]);
media_range_value(<< $;, R/bits >>, Acc, T, S, P, K, V) -> media_range_before_param(R, Acc, T, S, [{K, V}|P]);
media_range_value(<< $\s, R/bits >>, Acc, T, S, P, K, V) -> media_range_before_semicolon(R, Acc, T, S, [{K, V}|P]);
media_range_value(<< $\t, R/bits >>, Acc, T, S, P, K, V) -> media_range_before_semicolon(R, Acc, T, S, [{K, V}|P]);
media_range_value(<< C, R/bits >>, Acc, T, S, P, K, V) when ?IS_TOKEN(C) -> media_range_value(R, Acc, T, S, P, K, << V/binary, C >>).

%% Special function for badly behaving user agents that send .123 instead of 0.123.
media_range_broken_weight(<< A, B, C, R/bits >>, Acc, T, S, P)
	when A >= $0, A =< $9, B >= $0, B =< $9, C >= $0, C =< $9 ->
		accept_before_semicolon(R, Acc, T, S, P, (A - $0) * 100 + (B - $0) * 10 + (C - $0), []);
media_range_broken_weight(<< A, B, R/bits >>, Acc, T, S, P)
	when A >= $0, A =< $9, B >= $0, B =< $9 ->
		accept_before_semicolon(R, Acc, T, S, P, (A - $0) * 100 + (B - $0) * 10, []);
media_range_broken_weight(<< A, R/bits >>, Acc, T, S, P)
	when A >= $0, A =< $9 ->
		accept_before_semicolon(R, Acc, T, S, P, (A - $0) * 100, []).

media_range_weight(<< "1.000", R/bits >>, Acc, T, S, P) -> accept_before_semicolon(R, Acc, T, S, P, 1000, []);
media_range_weight(<< "1.00", R/bits >>, Acc, T, S, P) -> accept_before_semicolon(R, Acc, T, S, P, 1000, []);
media_range_weight(<< "1.0", R/bits >>, Acc, T, S, P) -> accept_before_semicolon(R, Acc, T, S, P, 1000, []);
media_range_weight(<< "1.", R/bits >>, Acc, T, S, P) -> accept_before_semicolon(R, Acc, T, S, P, 1000, []);
media_range_weight(<< "1", R/bits >>, Acc, T, S, P) -> accept_before_semicolon(R, Acc, T, S, P, 1000, []);
media_range_weight(<< "0.", A, B, C, R/bits >>, Acc, T, S, P)
	when A >= $0, A =< $9, B >= $0, B =< $9, C >= $0, C =< $9 ->
		accept_before_semicolon(R, Acc, T, S, P, (A - $0) * 100 + (B - $0) * 10 + (C - $0), []);
media_range_weight(<< "0.", A, B, R/bits >>, Acc, T, S, P)
	when A >= $0, A =< $9, B >= $0, B =< $9 ->
		accept_before_semicolon(R, Acc, T, S, P, (A - $0) * 100 + (B - $0) * 10, []);
media_range_weight(<< "0.", A, R/bits >>, Acc, T, S, P)
	when A >= $0, A =< $9 ->
		accept_before_semicolon(R, Acc, T, S, P, (A - $0) * 100, []);
media_range_weight(<< "0.", R/bits >>, Acc, T, S, P) -> accept_before_semicolon(R, Acc, T, S, P, 0, []);
media_range_weight(<< "0", R/bits >>, Acc, T, S, P) -> accept_before_semicolon(R, Acc, T, S, P, 0, []).

accept_before_semicolon(<<>>, Acc, T, S, P, Q, E) -> lists:reverse([{{T, S, lists:reverse(P)}, Q, lists:reverse(E)}|Acc]);
accept_before_semicolon(<< $,, R/bits >>, Acc, T, S, P, Q, E) -> media_range_list(R, [{{T, S, lists:reverse(P)}, Q, lists:reverse(E)}|Acc]);
accept_before_semicolon(<< $;, R/bits >>, Acc, T, S, P, Q, E) -> accept_before_ext(R, Acc, T, S, P, Q, E);
accept_before_semicolon(<< $\s, R/bits >>, Acc, T, S, P, Q, E) -> accept_before_semicolon(R, Acc, T, S, P, Q, E);
accept_before_semicolon(<< $\t, R/bits >>, Acc, T, S, P, Q, E) -> accept_before_semicolon(R, Acc, T, S, P, Q, E).

accept_before_ext(<< $\s, R/bits >>, Acc, T, S, P, Q, E) -> accept_before_ext(R, Acc, T, S, P, Q, E);
accept_before_ext(<< $\t, R/bits >>, Acc, T, S, P, Q, E) -> accept_before_ext(R, Acc, T, S, P, Q, E);
accept_before_ext(<< C, R/bits >>, Acc, T, S, P, Q, E) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(accept_ext, R, Acc, T, S, P, Q, E, <<>>)
	end.

accept_ext(<<>>, Acc, T, S, P, Q, E, K) -> lists:reverse([{{T, S, lists:reverse(P)}, Q, lists:reverse([K|E])}|Acc]);
accept_ext(<< $,, R/bits >>, Acc, T, S, P, Q, E, K) -> media_range_list(R, [{{T, S, lists:reverse(P)}, Q, lists:reverse([K|E])}|Acc]);
accept_ext(<< $;, R/bits >>, Acc, T, S, P, Q, E, K) -> accept_before_ext(R, Acc, T, S, P, Q, [K|E]);
accept_ext(<< $\s, R/bits >>, Acc, T, S, P, Q, E, K) -> accept_before_semicolon(R, Acc, T, S, P, Q, [K|E]);
accept_ext(<< $\t, R/bits >>, Acc, T, S, P, Q, E, K) -> accept_before_semicolon(R, Acc, T, S, P, Q, [K|E]);
accept_ext(<< $=, $", R/bits >>, Acc, T, S, P, Q, E, K) -> accept_quoted(R, Acc, T, S, P, Q, E, K, <<>>);
accept_ext(<< $=, R/bits >>, Acc, T, S, P, Q, E, K) -> accept_value(R, Acc, T, S, P, Q, E, K, <<>>);
accept_ext(<< C, R/bits >>, Acc, T, S, P, Q, E, K) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(accept_ext, R, Acc, T, S, P, Q, E, K)
	end.

accept_quoted(<< $", R/bits >>, Acc, T, S, P, Q, E, K, V) -> accept_before_semicolon(R, Acc, T, S, P, Q, [{K, V}|E]);
accept_quoted(<< $\\, C, R/bits >>, Acc, T, S, P, Q, E, K, V) when ?IS_VCHAR(C) -> accept_quoted(R, Acc, T, S, P, Q, E, K, << V/binary, C >>);
accept_quoted(<< C, R/bits >>, Acc, T, S, P, Q, E, K, V) when ?IS_VCHAR(C) -> accept_quoted(R, Acc, T, S, P, Q, E, K, << V/binary, C >>).

accept_value(<<>>, Acc, T, S, P, Q, E, K, V) -> lists:reverse([{{T, S, lists:reverse(P)}, Q, lists:reverse([{K, V}|E])}|Acc]);
accept_value(<< $,, R/bits >>, Acc, T, S, P, Q, E, K, V) -> media_range_list(R, [{{T, S, lists:reverse(P)}, Q, lists:reverse([{K, V}|E])}|Acc]);
accept_value(<< $;, R/bits >>, Acc, T, S, P, Q, E, K, V) -> accept_before_ext(R, Acc, T, S, P, Q, [{K, V}|E]);
accept_value(<< $\s, R/bits >>, Acc, T, S, P, Q, E, K, V) -> accept_before_semicolon(R, Acc, T, S, P, Q, [{K, V}|E]);
accept_value(<< $\t, R/bits >>, Acc, T, S, P, Q, E, K, V) -> accept_before_semicolon(R, Acc, T, S, P, Q, [{K, V}|E]);
accept_value(<< C, R/bits >>, Acc, T, S, P, Q, E, K, V) when ?IS_TOKEN(C) -> accept_value(R, Acc, T, S, P, Q, E, K, << V/binary, C >>).

-ifdef(TEST).
accept_ext() ->
	oneof([token(), parameter()]).

accept_params() ->
	frequency([
		{90, []},
		{10, list(accept_ext())}
	]).

accept() ->
	?LET({T, S, P, W, E},
		{token(), token(), list(parameter()), weight(), accept_params()},
		{T, S, P, W, E, iolist_to_binary([T, $/, S,
			[[OWS1, $;, OWS2, K, $=, V] || {K, V, OWS1, OWS2} <- P],
			case W of
				undefined -> [];
				_ -> [
					[<<";q=">>, qvalue_to_iodata(W)],
					[case Ext of
						{K, V, OWS1, OWS2} -> [OWS1, $;, OWS2, K, $=, V];
						K -> [$;, K]
					end || Ext <- E]]
			end])}
	).

prop_parse_accept() ->
	?FORALL(L,
		non_empty(list(accept())),
		begin
			<< _, Accept/binary >> = iolist_to_binary([[$,, A] || {_, _, _, _, _, A} <- L]),
			ResL = parse_accept(Accept),
			CheckedL = [begin
				ExpectedP = [{?INLINE_LOWERCASE_BC(K), unquote(V)} || {K, V, _, _} <- P],
				ExpectedE = [case Ext of
					{K, V, _, _} -> {?INLINE_LOWERCASE_BC(K), unquote(V)};
					K -> ?INLINE_LOWERCASE_BC(K)
				end || Ext <- E],
				ResT =:= ?INLINE_LOWERCASE_BC(T)
					andalso ResS =:= ?INLINE_LOWERCASE_BC(S)
					andalso ResP =:= ExpectedP
					andalso (ResW =:= W orelse (W =:= undefined andalso ResW =:= 1000))
					andalso ((W =:= undefined andalso ResE =:= []) orelse (W =/= undefined andalso ResE =:= ExpectedE))
			end || {{T, S, P, W, E, _}, {{ResT, ResS, ResP}, ResW, ResE}} <- lists:zip(L, ResL)],
			[true] =:= lists:usort(CheckedL)
		end
	).

parse_accept_test_() ->
	Tests = [
		{<<>>, []},
		{<<"   ">>, []},
		{<<"audio/*; q=0.2, audio/basic">>, [
			{{<<"audio">>, <<"*">>, []}, 200, []},
			{{<<"audio">>, <<"basic">>, []}, 1000, []}
		]},
		{<<"text/plain; q=0.5, text/html, "
		   "text/x-dvi; q=0.8, text/x-c">>, [
		   {{<<"text">>, <<"plain">>, []}, 500, []},
		   {{<<"text">>, <<"html">>, []}, 1000, []},
		   {{<<"text">>, <<"x-dvi">>, []}, 800, []},
		   {{<<"text">>, <<"x-c">>, []}, 1000, []}
		]},
		{<<"text/*, text/html, text/html;level=1, */*">>, [
			{{<<"text">>, <<"*">>, []}, 1000, []},
			{{<<"text">>, <<"html">>, []}, 1000, []},
			{{<<"text">>, <<"html">>, [{<<"level">>, <<"1">>}]}, 1000, []},
			{{<<"*">>, <<"*">>, []}, 1000, []}
		]},
		{<<"text/*;q=0.3, text/html;q=0.7, text/html;level=1, "
		   "text/html;level=2;q=0.4, */*;q=0.5">>, [
		   {{<<"text">>, <<"*">>, []}, 300, []},
		   {{<<"text">>, <<"html">>, []}, 700, []},
		   {{<<"text">>, <<"html">>, [{<<"level">>, <<"1">>}]}, 1000, []},
		   {{<<"text">>, <<"html">>, [{<<"level">>, <<"2">>}]}, 400, []},
		   {{<<"*">>, <<"*">>, []}, 500, []}
		]},
		{<<"text/html;level=1;quoted=\"hi hi hi\";"
		   "q=0.123;standalone;complex=gits, text/plain">>, [
			{{<<"text">>, <<"html">>,
				[{<<"level">>, <<"1">>}, {<<"quoted">>, <<"hi hi hi">>}]}, 123,
				[<<"standalone">>, {<<"complex">>, <<"gits">>}]},
			{{<<"text">>, <<"plain">>, []}, 1000, []}
		]},
		{<<"text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2">>, [
			{{<<"text">>, <<"html">>, []}, 1000, []},
			{{<<"image">>, <<"gif">>, []}, 1000, []},
			{{<<"image">>, <<"jpeg">>, []}, 1000, []},
			{{<<"*">>, <<"*">>, []}, 200, []},
			{{<<"*">>, <<"*">>, []}, 200, []}
		]}
	],
	[{V, fun() -> R = parse_accept(V) end} || {V, R} <- Tests].

parse_accept_error_test_() ->
	Tests = [
		<<"audio/basic, */;q=0.5">>,
		<<"audio/, audio/basic">>,
		<<"aud\tio/basic">>,
		<<"audio/basic;t=\"zero \\", 0, " woo\"">>
	],
	[{V, fun() -> {'EXIT', _} = (catch parse_accept(V)) end} || V <- Tests].
-endif.

-ifdef(PERF).
horse_parse_accept() ->
	horse:repeat(20000,
		parse_accept(<<"text/*;q=0.3, text/html;q=0.7, text/html;level=1, "
			"text/html;level=2;q=0.4, */*;q=0.5">>)
	).
-endif.

%% @doc Parse the Accept-Charset header.

-spec parse_accept_charset(binary()) -> [{binary(), qvalue()}].
parse_accept_charset(Charset) ->
	nonempty(conneg_list(Charset, [])).

conneg_list(<<>>, Acc) -> lists:reverse(Acc);
conneg_list(<< $\s, R/bits >>, Acc) -> conneg_list(R, Acc);
conneg_list(<< $\t, R/bits >>, Acc) -> conneg_list(R, Acc);
conneg_list(<< $\,, R/bits >>, Acc) -> conneg_list(R, Acc);
conneg_list(<< C, R/bits >>, Acc) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(conneg, R, Acc, <<>>)
	end.

conneg(<<>>, Acc, T) -> lists:reverse([{T, 1000}|Acc]);
conneg(<< $,, R/bits >>, Acc, T) -> conneg_list(R, [{T, 1000}|Acc]);
conneg(<< $;, R/bits >>, Acc, T) -> conneg_before_weight(R, Acc, T);
conneg(<< $\s, R/bits >>, Acc, T) -> conneg_before_semicolon(R, Acc, T);
conneg(<< $\t, R/bits >>, Acc, T) -> conneg_before_semicolon(R, Acc, T);
conneg(<< C, R/bits >>, Acc, T) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(conneg, R, Acc, T)
	end.

conneg_before_semicolon(<<>>, Acc, T) -> lists:reverse([{T, 1000}|Acc]);
conneg_before_semicolon(<< $,, R/bits >>, Acc, T) -> conneg_list(R, [{T, 1000}|Acc]);
conneg_before_semicolon(<< $;, R/bits >>, Acc, T) -> conneg_before_weight(R, Acc, T);
conneg_before_semicolon(<< $\s, R/bits >>, Acc, T) -> conneg_before_semicolon(R, Acc, T);
conneg_before_semicolon(<< $\t, R/bits >>, Acc, T) -> conneg_before_semicolon(R, Acc, T).

conneg_before_weight(<< $\s, R/bits >>, Acc, T) -> conneg_before_weight(R, Acc, T);
conneg_before_weight(<< $\t, R/bits >>, Acc, T) -> conneg_before_weight(R, Acc, T);
conneg_before_weight(<< $q, $=, R/bits >>, Acc, T) -> conneg_weight(R, Acc, T);
%% Special clause for broken user agents that confuse ; and , separators.
conneg_before_weight(<< C, R/bits >>, Acc, T) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(conneg, R, [{T, 1000}|Acc], <<>>)
	end.

conneg_weight(<< "1.000", R/bits >>, Acc, T) -> conneg_list_sep(R, [{T, 1000}|Acc]);
conneg_weight(<< "1.00", R/bits >>, Acc, T) -> conneg_list_sep(R, [{T, 1000}|Acc]);
conneg_weight(<< "1.0", R/bits >>, Acc, T) -> conneg_list_sep(R, [{T, 1000}|Acc]);
conneg_weight(<< "1.", R/bits >>, Acc, T) -> conneg_list_sep(R, [{T, 1000}|Acc]);
conneg_weight(<< "1", R/bits >>, Acc, T) -> conneg_list_sep(R, [{T, 1000}|Acc]);
conneg_weight(<< "0.", A, B, C, R/bits >>, Acc, T)
	when A >= $0, A =< $9, B >= $0, B =< $9, C >= $0, C =< $9 ->
		conneg_list_sep(R, [{T, (A - $0) * 100 + (B - $0) * 10 + (C - $0)}|Acc]);
conneg_weight(<< "0.", A, B, R/bits >>, Acc, T)
	when A >= $0, A =< $9, B >= $0, B =< $9 ->
		conneg_list_sep(R, [{T, (A - $0) * 100 + (B - $0) * 10}|Acc]);
conneg_weight(<< "0.", A, R/bits >>, Acc, T)
	when A >= $0, A =< $9 ->
		conneg_list_sep(R, [{T, (A - $0) * 100}|Acc]);
conneg_weight(<< "0.", R/bits >>, Acc, T) -> conneg_list_sep(R, [{T, 0}|Acc]);
conneg_weight(<< "0", R/bits >>, Acc, T) -> conneg_list_sep(R, [{T, 0}|Acc]).

conneg_list_sep(<<>>, Acc) -> lists:reverse(Acc);
conneg_list_sep(<< $\s, R/bits >>, Acc) -> conneg_list_sep(R, Acc);
conneg_list_sep(<< $\t, R/bits >>, Acc) -> conneg_list_sep(R, Acc);
conneg_list_sep(<< $,, R/bits >>, Acc) -> conneg_list(R, Acc).

-ifdef(TEST).
accept_charset() ->
	?LET({C, W},
		{token(), weight()},
		{C, W, iolist_to_binary([C, case W of
			undefined -> [];
			_ -> [<<";q=">>, qvalue_to_iodata(W)]
		end])}
	).

prop_parse_accept_charset() ->
	?FORALL(L,
		non_empty(list(accept_charset())),
		begin
			<< _, AcceptCharset/binary >> = iolist_to_binary([[$,, A] || {_, _, A} <- L]),
			ResL = parse_accept_charset(AcceptCharset),
			CheckedL = [begin
				ResC =:= ?INLINE_LOWERCASE_BC(Ch)
					andalso (ResW =:= W orelse (W =:= undefined andalso ResW =:= 1000))
			end || {{Ch, W, _}, {ResC, ResW}} <- lists:zip(L, ResL)],
			[true] =:= lists:usort(CheckedL)
		end).

parse_accept_charset_test_() ->
	Tests = [
		{<<"iso-8859-5, unicode-1-1;q=0.8">>, [
			{<<"iso-8859-5">>, 1000},
			{<<"unicode-1-1">>, 800}
		]},
		%% Some user agents send this invalid value for the Accept-Charset header
		{<<"ISO-8859-1;utf-8;q=0.7,*;q=0.7">>, [
			{<<"iso-8859-1">>, 1000},
			{<<"utf-8">>, 700},
			{<<"*">>, 700}
		]}
	],
	[{V, fun() -> R = parse_accept_charset(V) end} || {V, R} <- Tests].

parse_accept_charset_error_test_() ->
	Tests = [
		<<>>
	],
	[{V, fun() -> {'EXIT', _} = (catch parse_accept_charset(V)) end} || V <- Tests].
-endif.

-ifdef(PERF).
horse_parse_accept_charset() ->
	horse:repeat(20000,
		parse_accept_charset(<<"iso-8859-5, unicode-1-1;q=0.8">>)
	).
-endif.

%% @doc Parse the Accept-Encoding header.

-spec parse_accept_encoding(binary()) -> [{binary(), qvalue()}].
parse_accept_encoding(Encoding) ->
	conneg_list(Encoding, []).

-ifdef(TEST).
accept_encoding() ->
	?LET({E, W},
		{token(), weight()},
		{E, W, iolist_to_binary([E, case W of
			undefined -> [];
			_ -> [<<";q=">>, qvalue_to_iodata(W)]
		end])}
	).

prop_parse_accept_encoding() ->
	?FORALL(L,
		non_empty(list(accept_encoding())),
		begin
			<< _, AcceptEncoding/binary >> = iolist_to_binary([[$,, A] || {_, _, A} <- L]),
			ResL = parse_accept_encoding(AcceptEncoding),
			CheckedL = [begin
				ResE =:= ?INLINE_LOWERCASE_BC(E)
					andalso (ResW =:= W orelse (W =:= undefined andalso ResW =:= 1000))
			end || {{E, W, _}, {ResE, ResW}} <- lists:zip(L, ResL)],
			[true] =:= lists:usort(CheckedL)
		end).

parse_accept_encoding_test_() ->
	Tests = [
		{<<>>, []},
		{<<"*">>, [{<<"*">>, 1000}]},
		{<<"compress, gzip">>, [
			{<<"compress">>, 1000},
			{<<"gzip">>, 1000}
		]},
		{<<"compress;q=0.5, gzip;q=1.0">>, [
			{<<"compress">>, 500},
			{<<"gzip">>, 1000}
		]},
		{<<"gzip;q=1.0, identity; q=0.5, *;q=0">>, [
			{<<"gzip">>, 1000},
			{<<"identity">>, 500},
			{<<"*">>, 0}
		]}
	],
	[{V, fun() -> R = parse_accept_encoding(V) end} || {V, R} <- Tests].
-endif.

-ifdef(PERF).
horse_parse_accept_encoding() ->
	horse:repeat(20000,
		parse_accept_encoding(<<"gzip;q=1.0, identity; q=0.5, *;q=0">>)
	).
-endif.

%% @doc Parse the Accept-Language header.

-spec parse_accept_language(binary()) -> [{binary(), qvalue()}].
parse_accept_language(LanguageRange) ->
	nonempty(language_range_list(LanguageRange, [])).

language_range_list(<<>>, Acc) -> lists:reverse(Acc);
language_range_list(<< $\s, R/bits >>, Acc) -> language_range_list(R, Acc);
language_range_list(<< $\t, R/bits >>, Acc) -> language_range_list(R, Acc);
language_range_list(<< $\,, R/bits >>, Acc) -> language_range_list(R, Acc);
language_range_list(<< $*, R/bits >>, Acc) -> language_range_before_semicolon(R, Acc, <<"*">>);
language_range_list(<< C, R/bits >>, Acc) when ?IS_ALPHA(C) ->
	case C of
		?INLINE_LOWERCASE(language_range, R, Acc, 1, <<>>)
	end.

language_range(<<>>, Acc, _, T) -> lists:reverse([{T, 1000}|Acc]);
language_range(<< $,, R/bits >>, Acc, _, T) -> language_range_list(R, [{T, 1000}|Acc]);
language_range(<< $;, R/bits >>, Acc, _, T) -> language_range_before_weight(R, Acc, T);
language_range(<< $\s, R/bits >>, Acc, _, T) -> language_range_before_semicolon(R, Acc, T);
language_range(<< $\t, R/bits >>, Acc, _, T) -> language_range_before_semicolon(R, Acc, T);
language_range(<< $-, R/bits >>, Acc, _, T) -> language_range_sub(R, Acc, 0, << T/binary, $- >>);
language_range(<< _, _/bits >>, _, 8, _) -> error(badarg);
language_range(<< C, R/bits >>, Acc, N, T) when ?IS_ALPHA(C) ->
	case C of
		?INLINE_LOWERCASE(language_range, R, Acc, N + 1, T)
	end.

language_range_sub(<<>>, Acc, N, T) when N > 0 -> lists:reverse([{T, 1000}|Acc]);
language_range_sub(<< $,, R/bits >>, Acc, N, T) when N > 0 -> language_range_list(R, [{T, 1000}|Acc]);
language_range_sub(<< $;, R/bits >>, Acc, N, T) when N > 0 -> language_range_before_weight(R, Acc, T);
language_range_sub(<< $\s, R/bits >>, Acc, N, T) when N > 0 -> language_range_before_semicolon(R, Acc, T);
language_range_sub(<< $\t, R/bits >>, Acc, N, T) when N > 0 -> language_range_before_semicolon(R, Acc, T);
language_range_sub(<< $-, R/bits >>, Acc, N, T) when N > 0 -> language_range_sub(R, Acc, 0, << T/binary, $- >>);
language_range_sub(<< _, _/bits >>, _, 8, _) -> error(badarg);
language_range_sub(<< C, R/bits >>, Acc, N, T) when ?IS_ALPHA(C); ?IS_DIGIT(C) ->
	case C of
		?INLINE_LOWERCASE(language_range_sub, R, Acc, N + 1, T)
	end.

language_range_before_semicolon(<<>>, Acc, T) -> lists:reverse([{T, 1000}|Acc]);
language_range_before_semicolon(<< $,, R/bits >>, Acc, T) -> language_range_list(R, [{T, 1000}|Acc]);
language_range_before_semicolon(<< $;, R/bits >>, Acc, T) -> language_range_before_weight(R, Acc, T);
language_range_before_semicolon(<< $\s, R/bits >>, Acc, T) -> language_range_before_semicolon(R, Acc, T);
language_range_before_semicolon(<< $\t, R/bits >>, Acc, T) -> language_range_before_semicolon(R, Acc, T).

language_range_before_weight(<< $\s, R/bits >>, Acc, T) -> language_range_before_weight(R, Acc, T);
language_range_before_weight(<< $\t, R/bits >>, Acc, T) -> language_range_before_weight(R, Acc, T);
language_range_before_weight(<< $q, $=, R/bits >>, Acc, T) -> language_range_weight(R, Acc, T);
%% Special clause for broken user agents that confuse ; and , separators.
language_range_before_weight(<< C, R/bits >>, Acc, T) when ?IS_ALPHA(C) ->
	case C of
		?INLINE_LOWERCASE(language_range, R, [{T, 1000}|Acc], 1, <<>>)
	end.

language_range_weight(<< "1.000", R/bits >>, Acc, T) -> language_range_list_sep(R, [{T, 1000}|Acc]);
language_range_weight(<< "1.00", R/bits >>, Acc, T) -> language_range_list_sep(R, [{T, 1000}|Acc]);
language_range_weight(<< "1.0", R/bits >>, Acc, T) -> language_range_list_sep(R, [{T, 1000}|Acc]);
language_range_weight(<< "1.", R/bits >>, Acc, T) -> language_range_list_sep(R, [{T, 1000}|Acc]);
language_range_weight(<< "1", R/bits >>, Acc, T) -> language_range_list_sep(R, [{T, 1000}|Acc]);
language_range_weight(<< "0.", A, B, C, R/bits >>, Acc, T)
	when A >= $0, A =< $9, B >= $0, B =< $9, C >= $0, C =< $9 ->
		language_range_list_sep(R, [{T, (A - $0) * 100 + (B - $0) * 10 + (C - $0)}|Acc]);
language_range_weight(<< "0.", A, B, R/bits >>, Acc, T)
	when A >= $0, A =< $9, B >= $0, B =< $9 ->
		language_range_list_sep(R, [{T, (A - $0) * 100 + (B - $0) * 10}|Acc]);
language_range_weight(<< "0.", A, R/bits >>, Acc, T)
	when A >= $0, A =< $9 ->
		language_range_list_sep(R, [{T, (A - $0) * 100}|Acc]);
language_range_weight(<< "0.", R/bits >>, Acc, T) -> language_range_list_sep(R, [{T, 0}|Acc]);
language_range_weight(<< "0", R/bits >>, Acc, T) -> language_range_list_sep(R, [{T, 0}|Acc]).

language_range_list_sep(<<>>, Acc) -> lists:reverse(Acc);
language_range_list_sep(<< $\s, R/bits >>, Acc) -> language_range_list_sep(R, Acc);
language_range_list_sep(<< $\t, R/bits >>, Acc) -> language_range_list_sep(R, Acc);
language_range_list_sep(<< $,, R/bits >>, Acc) -> language_range_list(R, Acc).

-ifdef(TEST).
language_tag() ->
	oneof([
		[alpha()],
		[alpha(), alpha()],
		[alpha(), alpha(), alpha()],
		[alpha(), alpha(), alpha(), alpha()],
		[alpha(), alpha(), alpha(), alpha(), alpha()],
		[alpha(), alpha(), alpha(), alpha(), alpha(), alpha()],
		[alpha(), alpha(), alpha(), alpha(), alpha(), alpha(), alpha()],
		[alpha(), alpha(), alpha(), alpha(), alpha(), alpha(), alpha(), alpha()]
	]).

language_subtag() ->
	[$-, oneof([
		[alphanum()],
		[alphanum(), alphanum()],
		[alphanum(), alphanum(), alphanum()],
		[alphanum(), alphanum(), alphanum(), alphanum()],
		[alphanum(), alphanum(), alphanum(), alphanum(), alphanum()],
		[alphanum(), alphanum(), alphanum(), alphanum(), alphanum(), alphanum()],
		[alphanum(), alphanum(), alphanum(), alphanum(), alphanum(), alphanum(), alphanum()],
		[alphanum(), alphanum(), alphanum(), alphanum(), alphanum(), alphanum(), alphanum(), alphanum()]
	])].

language_range() ->
	[language_tag(), list(language_subtag())].

accept_language() ->
	?LET({R, W},
		{language_range(), weight()},
		{iolist_to_binary(R), W, iolist_to_binary([R, case W of
			undefined -> [];
			_ -> [<<";q=">>, qvalue_to_iodata(W)]
		end])}
	).

prop_parse_accept_language() ->
	?FORALL(L,
		non_empty(list(accept_language())),
		begin
			<< _, AcceptLanguage/binary >> = iolist_to_binary([[$,, A] || {_, _, A} <- L]),
			ResL = parse_accept_language(AcceptLanguage),
			CheckedL = [begin
				ResR =:= ?INLINE_LOWERCASE_BC(R)
					andalso (ResW =:= W orelse (W =:= undefined andalso ResW =:= 1000))
			end || {{R, W, _}, {ResR, ResW}} <- lists:zip(L, ResL)],
			[true] =:= lists:usort(CheckedL)
		end).

parse_accept_language_test_() ->
	Tests = [
		{<<"da, en-gb;q=0.8, en;q=0.7">>, [
			{<<"da">>, 1000},
			{<<"en-gb">>, 800},
			{<<"en">>, 700}
		]},
		{<<"en, en-US, en-cockney, i-cherokee, x-pig-latin, es-419">>, [
			{<<"en">>, 1000},
			{<<"en-us">>, 1000},
			{<<"en-cockney">>, 1000},
			{<<"i-cherokee">>, 1000},
			{<<"x-pig-latin">>, 1000},
			{<<"es-419">>, 1000}
		]}
	],
	[{V, fun() -> R = parse_accept_language(V) end} || {V, R} <- Tests].

parse_accept_language_error_test_() ->
	Tests = [
		<<>>,
		<<"loooooong">>,
		<<"en-us-loooooong">>,
		<<"419-en-us">>
	],
	[{V, fun() -> {'EXIT', _} = (catch parse_accept_language(V)) end} || V <- Tests].
-endif.

-ifdef(PERF).
horse_parse_accept_language() ->
	horse:repeat(20000,
		parse_accept_language(<<"da, en-gb;q=0.8, en;q=0.7">>)
	).
-endif.

%% @doc Parse the Connection header.

-spec parse_connection(binary()) -> [binary()].
parse_connection(<<"close">>) ->
	[<<"close">>];
parse_connection(<<"keep-alive">>) ->
	[<<"keep-alive">>];
parse_connection(Connection) ->
	nonempty(token_ci_list(Connection, [])).

-ifdef(TEST).
prop_parse_connection() ->
	?FORALL(L,
		non_empty(list(token())),
		begin
			<< _, Connection/binary >> = iolist_to_binary([[$,, C] || C <- L]),
			ResL = parse_connection(Connection),
			CheckedL = [?INLINE_LOWERCASE_BC(Co) =:= ResC || {Co, ResC} <- lists:zip(L, ResL)],
			[true] =:= lists:usort(CheckedL)
		end).

parse_connection_test_() ->
	Tests = [
		{<<"close">>, [<<"close">>]},
		{<<"ClOsE">>, [<<"close">>]},
		{<<"Keep-Alive">>, [<<"keep-alive">>]},
		{<<"keep-alive, Upgrade">>, [<<"keep-alive">>, <<"upgrade">>]}
	],
	[{V, fun() -> R = parse_connection(V) end} || {V, R} <- Tests].

parse_connection_error_test_() ->
	Tests = [
		<<>>
	],
	[{V, fun() -> {'EXIT', _} = (catch parse_connection(V)) end} || V <- Tests].
-endif.

-ifdef(PERF).
horse_parse_connection_close() ->
	horse:repeat(200000,
		parse_connection(<<"close">>)
	).

horse_parse_connection_keepalive() ->
	horse:repeat(200000,
		parse_connection(<<"keep-alive">>)
	).

horse_parse_connection_keepalive_upgrade() ->
	horse:repeat(200000,
		parse_connection(<<"keep-alive, upgrade">>)
	).
-endif.

%% @doc Parse the Content-Length header.
%%
%% The value has at least one digit, and may be followed by whitespace.

-spec parse_content_length(binary()) -> non_neg_integer().
parse_content_length(<< $0 >>) -> 0;
parse_content_length(<< $0, R/bits >>) -> number(R, 0);
parse_content_length(<< $1, R/bits >>) -> number(R, 1);
parse_content_length(<< $2, R/bits >>) -> number(R, 2);
parse_content_length(<< $3, R/bits >>) -> number(R, 3);
parse_content_length(<< $4, R/bits >>) -> number(R, 4);
parse_content_length(<< $5, R/bits >>) -> number(R, 5);
parse_content_length(<< $6, R/bits >>) -> number(R, 6);
parse_content_length(<< $7, R/bits >>) -> number(R, 7);
parse_content_length(<< $8, R/bits >>) -> number(R, 8);
parse_content_length(<< $9, R/bits >>) -> number(R, 9).

-ifdef(TEST).
prop_parse_content_length() ->
	?FORALL(
		X,
		non_neg_integer(),
		X =:= parse_content_length(integer_to_binary(X))
	).

parse_content_length_test_() ->
	Tests = [
		{<<"0">>, 0},
		{<<"42    ">>, 42},
		{<<"69\t">>, 69},
		{<<"1337">>, 1337},
		{<<"1234567890">>, 1234567890},
		{<<"1234567890     ">>, 1234567890}
	],
	[{V, fun() -> R = parse_content_length(V) end} || {V, R} <- Tests].

parse_content_length_error_test_() ->
	Tests = [
		<<>>,
		<<"123, 123">>,
		<<"4.17">>
	],
	[{V, fun() -> {'EXIT', _} = (catch parse_content_length(V)) end} || V <- Tests].
-endif.

-ifdef(PERF).
horse_parse_content_length_zero() ->
	horse:repeat(100000,
		parse_content_length(<<"0">>)
	).

horse_parse_content_length_giga() ->
	horse:repeat(100000,
		parse_content_length(<<"1234567890">>)
	).
-endif.

%% @doc Parse the Content-Type header.

-spec parse_content_type(binary()) -> media_type().
parse_content_type(<< C, R/bits >>) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(media_type, R, <<>>)
	end.

media_type(<< $/, C, R/bits >>, T) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(media_subtype, R, T, <<>>)
	end;
media_type(<< C, R/bits >>, T) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(media_type, R, T)
	end.

media_subtype(<<>>, T, S) -> {T, S, []};
media_subtype(<< $;, R/bits >>, T, S) -> media_before_param(R, T, S, []);
media_subtype(<< $\s, R/bits >>, T, S) -> media_before_semicolon(R, T, S, []);
media_subtype(<< $\t, R/bits >>, T, S) -> media_before_semicolon(R, T, S, []);
media_subtype(<< C, R/bits >>, T, S) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(media_subtype, R, T, S)
	end.

media_before_semicolon(<<>>, T, S, P) -> {T, S, lists:reverse(P)};
media_before_semicolon(<< $;, R/bits >>, T, S, P) -> media_before_param(R, T, S, P);
media_before_semicolon(<< $\s, R/bits >>, T, S, P) -> media_before_semicolon(R, T, S, P);
media_before_semicolon(<< $\t, R/bits >>, T, S, P) -> media_before_semicolon(R, T, S, P).

media_before_param(<< $\s, R/bits >>, T, S, P) -> media_before_param(R, T, S, P);
media_before_param(<< $\t, R/bits >>, T, S, P) -> media_before_param(R, T, S, P);
media_before_param(<< "charset=", $", R/bits >>, T, S, P) -> media_charset_quoted(R, T, S, P, <<>>);
media_before_param(<< "charset=", R/bits >>, T, S, P) -> media_charset(R, T, S, P, <<>>);
media_before_param(<< C, R/bits >>, T, S, P) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(media_param, R, T, S, P, <<>>)
	end.

media_charset_quoted(<< $", R/bits >>, T, S, P, V) ->
	media_before_semicolon(R, T, S, [{<<"charset">>, V}|P]);
media_charset_quoted(<< $\\, C, R/bits >>, T, S, P, V) when ?IS_VCHAR(C) ->
	case C of
		?INLINE_LOWERCASE(media_charset_quoted, R, T, S, P, V)
	end;
media_charset_quoted(<< C, R/bits >>, T, S, P, V) when ?IS_VCHAR(C) ->
	case C of
		?INLINE_LOWERCASE(media_charset_quoted, R, T, S, P, V)
	end.

media_charset(<<>>, T, S, P, V) -> {T, S, lists:reverse([{<<"charset">>, V}|P])};

media_charset(<< $;, R/bits >>, T, S, P, V) -> media_before_param(R, T, S, [{<<"charset">>, V}|P]);
media_charset(<< $\s, R/bits >>, T, S, P, V) -> media_before_semicolon(R, T, S, [{<<"charset">>, V}|P]);
media_charset(<< $\t, R/bits >>, T, S, P, V) -> media_before_semicolon(R, T, S, [{<<"charset">>, V}|P]);
media_charset(<< C, R/bits >>, T, S, P, V) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(media_charset, R, T, S, P, V)
	end.

media_param(<< $=, $", R/bits >>, T, S, P, K) -> media_quoted(R, T, S, P, K, <<>>);
media_param(<< $=, R/bits >>, T, S, P, K) -> media_value(R, T, S, P, K, <<>>);
media_param(<< C, R/bits >>, T, S, P, K) when ?IS_TOKEN(C) ->
	case C of
		?INLINE_LOWERCASE(media_param, R, T, S, P, K)
	end.

media_quoted(<< $", R/bits >>, T, S, P, K, V) -> media_before_semicolon(R, T, S, [{K, V}|P]);
media_quoted(<< $\\, C, R/bits >>, T, S, P, K, V) when ?IS_VCHAR(C) -> media_quoted(R, T, S, P, K, << V/binary, C >>);
media_quoted(<< C, R/bits >>, T, S, P, K, V) when ?IS_VCHAR(C) -> media_quoted(R, T, S, P, K, << V/binary, C >>).

media_value(<<>>, T, S, P, K, V) -> {T, S, lists:reverse([{K, V}|P])};
media_value(<< $;, R/bits >>, T, S, P, K, V) -> media_before_param(R, T, S, [{K, V}|P]);
media_value(<< $\s, R/bits >>, T, S, P, K, V) -> media_before_semicolon(R, T, S, [{K, V}|P]);
media_value(<< $\t, R/bits >>, T, S, P, K, V) -> media_before_semicolon(R, T, S, [{K, V}|P]);
media_value(<< C, R/bits >>, T, S, P, K, V) when ?IS_TOKEN(C) -> media_value(R, T, S, P, K, << V/binary, C >>).

-ifdef(TEST).
media_type_parameter() ->
	frequency([
		{90, parameter()},
		{10, {<<"charset">>, oneof([token(), quoted_string()]), <<>>, <<>>}}
	]).

media_type() ->
	?LET({T, S, P},
		{token(), token(), list(media_type_parameter())},
		{T, S, P, iolist_to_binary([T, $/, S, [[OWS1, $;, OWS2, K, $=, V] || {K, V, OWS1, OWS2} <- P]])}
	).

prop_parse_content_type() ->
	?FORALL({T, S, P, MediaType},
		media_type(),
		begin
			{ResT, ResS, ResP} = parse_content_type(MediaType),
			ExpectedP = [case ?INLINE_LOWERCASE_BC(K) of
				<<"charset">> -> {<<"charset">>, ?INLINE_LOWERCASE_BC(unquote(V))};
				LowK -> {LowK, unquote(V)}
			end || {K, V, _, _} <- P],
			ResT =:= ?INLINE_LOWERCASE_BC(T)
				andalso ResS =:= ?INLINE_LOWERCASE_BC(S)
				andalso ResP =:= ExpectedP
		end
	).

parse_content_type_test_() ->
	Tests = [
		{<<"text/html;charset=utf-8">>,
			{<<"text">>, <<"html">>, [{<<"charset">>, <<"utf-8">>}]}},
		{<<"text/html;charset=UTF-8">>,
			{<<"text">>, <<"html">>, [{<<"charset">>, <<"utf-8">>}]}},
		{<<"Text/HTML;Charset=\"utf-8\"">>,
			{<<"text">>, <<"html">>, [{<<"charset">>, <<"utf-8">>}]}},
		{<<"text/html; charset=\"utf-8\"">>,
			{<<"text">>, <<"html">>, [{<<"charset">>, <<"utf-8">>}]}},
		{<<"text/html; charset=ISO-8859-4">>,
			{<<"text">>, <<"html">>, [{<<"charset">>, <<"iso-8859-4">>}]}},
		{<<"text/plain; charset=iso-8859-4">>,
			{<<"text">>, <<"plain">>, [{<<"charset">>, <<"iso-8859-4">>}]}},
		{<<"multipart/form-data  \t;Boundary=\"MultipartIsUgly\"">>,
			{<<"multipart">>, <<"form-data">>, [
				{<<"boundary">>, <<"MultipartIsUgly">>}
			]}},
		{<<"foo/bar; one=FirstParam; two=SecondParam">>,
			{<<"foo">>, <<"bar">>, [
				{<<"one">>, <<"FirstParam">>},
				{<<"two">>, <<"SecondParam">>}
			]}}
	],
	[{V, fun() -> R = parse_content_type(V) end} || {V, R} <- Tests].
-endif.

-ifdef(PERF).
horse_parse_content_type() ->
	horse:repeat(200000,
		parse_content_type(<<"text/html;charset=utf-8">>)
	).
-endif.

%% @doc Parse the Expect header.

-spec parse_expect(binary()) -> continue.
parse_expect(<<"100-continue", Rest/bits >>) ->
	ws_end(Rest),
	continue;
parse_expect(<<"100-", C, O, N, T, I, M, U, E, Rest/bits >>)
	when C =:= $C orelse C =:= $c, O =:= $O orelse O =:= $o,
		N =:= $N orelse N =:= $n, T =:= $T orelse T =:= $t,
		I =:= $I orelse I =:= $i, M =:= $N orelse M =:= $n,
		U =:= $U orelse U =:= $u, E =:= $E orelse E =:= $e ->
	ws_end(Rest),
	continue.

-ifdef(TEST).
expect() ->
	?LET(E,
		[$1, $0, $0, $-,
			oneof([$c, $C]), oneof([$o, $O]), oneof([$n, $N]),
			oneof([$t, $T]), oneof([$i, $I]), oneof([$n, $N]),
			oneof([$u, $U]), oneof([$e, $E])],
		list_to_binary(E)).

prop_parse_expect() ->
	?FORALL(E, expect(), continue =:= parse_expect(E)).

parse_expect_test_() ->
	Tests = [
		<<"100-continue">>,
		<<"100-CONTINUE">>,
		<<"100-Continue">>,
		<<"100-CoNtInUe">>,
		<<"100-continue    ">>
	],
	[{V, fun() -> continue = parse_expect(V) end} || V <- Tests].

parse_expect_error_test_() ->
	Tests = [
		<<>>,
		<<"   ">>,
		<<"200-OK">>,
		<<"Cookies">>
	],
	[{V, fun() -> {'EXIT', _} = (catch parse_expect(V)) end} || V <- Tests].
-endif.

-ifdef(PERF).
horse_parse_expect() ->
	horse:repeat(200000,
		parse_expect(<<"100-continue">>)
	).
-endif.

%% @doc Parse the If-Modified-Since header.

-spec parse_if_modified_since(binary()) -> calendar:datetime().
parse_if_modified_since(IfModifiedSince) ->
	http_date(IfModifiedSince).

-ifdef(TEST).
parse_if_modified_since_test_() ->
	Tests = [
		{<<"Sat, 29 Oct 1994 19:43:31 GMT">>, {{1994, 10, 29}, {19, 43, 31}}}
	],
	[{V, fun() -> R = parse_if_modified_since(V) end} || {V, R} <- Tests].
-endif.

%% @doc Parse the If-Unmodified-Since header.

-spec parse_if_unmodified_since(binary()) -> calendar:datetime().
parse_if_unmodified_since(IfModifiedSince) ->
	http_date(IfModifiedSince).

-ifdef(TEST).
parse_if_unmodified_since_test_() ->
	Tests = [
		{<<"Sat, 29 Oct 1994 19:43:31 GMT">>, {{1994, 10, 29}, {19, 43, 31}}}
	],
	[{V, fun() -> R = parse_if_unmodified_since(V) end} || {V, R} <- Tests].
-endif.

%% @doc Parse the Max-Forwards header.

-spec parse_max_forwards(binary()) -> integer().
parse_max_forwards(<< $0, R/bits >>) -> number(R, 0);
parse_max_forwards(<< $1, R/bits >>) -> number(R, 1);
parse_max_forwards(<< $2, R/bits >>) -> number(R, 2);
parse_max_forwards(<< $3, R/bits >>) -> number(R, 3);
parse_max_forwards(<< $4, R/bits >>) -> number(R, 4);
parse_max_forwards(<< $5, R/bits >>) -> number(R, 5);
parse_max_forwards(<< $6, R/bits >>) -> number(R, 6);
parse_max_forwards(<< $7, R/bits >>) -> number(R, 7);
parse_max_forwards(<< $8, R/bits >>) -> number(R, 8);
parse_max_forwards(<< $9, R/bits >>) -> number(R, 9).

-ifdef(TEST).
prop_parse_max_forwards() ->
	?FORALL(
		X,
		non_neg_integer(),
		X =:= parse_max_forwards(integer_to_binary(X))
	).

parse_max_forwards_test_() ->
	Tests = [
		{<<"0">>, 0},
		{<<"42    ">>, 42},
		{<<"69\t">>, 69},
		{<<"1337">>, 1337},
		{<<"1234567890">>, 1234567890},
		{<<"1234567890     ">>, 1234567890}
	],
	[{V, fun() -> R = parse_max_forwards(V) end} || {V, R} <- Tests].

parse_max_forwards_error_test_() ->
	Tests = [
		<<>>,
		<<"123, 123">>,
		<<"4.17">>
	],
	[{V, fun() -> {'EXIT', _} = (catch parse_content_length(V)) end} || V <- Tests].
-endif.

%% @doc Parse the Transfer-Encoding header.
%%
%% @todo This function does not support parsing of transfer-parameter.

-spec parse_transfer_encoding(binary()) -> [binary()].
parse_transfer_encoding(<<"chunked">>) ->
	[<<"chunked">>];
parse_transfer_encoding(TransferEncoding) ->
	nonempty(token_ci_list(TransferEncoding, [])).

-ifdef(TEST).
prop_parse_transfer_encoding() ->
	?FORALL(L,
		non_empty(list(token())),
		begin
			<< _, TransferEncoding/binary >> = iolist_to_binary([[$,, C] || C <- L]),
			ResL = parse_transfer_encoding(TransferEncoding),
			CheckedL = [?INLINE_LOWERCASE_BC(Co) =:= ResC || {Co, ResC} <- lists:zip(L, ResL)],
			[true] =:= lists:usort(CheckedL)
		end).

parse_transfer_encoding_test_() ->
	Tests = [
		{<<"a , , , ">>, [<<"a">>]},
		{<<" , , , a">>, [<<"a">>]},
		{<<"a , , b">>, [<<"a">>, <<"b">>]},
		{<<"chunked">>, [<<"chunked">>]},
		{<<"chunked, something">>, [<<"chunked">>, <<"something">>]}
	],
	[{V, fun() -> R = parse_transfer_encoding(V) end} || {V, R} <- Tests].

parse_transfer_encoding_error_test_() ->
	Tests = [
		<<>>,
		<<" ">>,
		<<" , ">>,
		<<",,,">>,
		<<"a b">>
	],
	[{V, fun() -> {'EXIT', _} = (catch parse_transfer_encoding(V)) end}
		|| V <- Tests].
-endif.

-ifdef(PERF).
horse_parse_transfer_encoding_chunked() ->
	horse:repeat(200000,
		parse_transfer_encoding(<<"chunked">>)
	).

horse_parse_transfer_encoding_custom() ->
	horse:repeat(200000,
		parse_transfer_encoding(<<"chunked, something">>)
	).
-endif.

%% Internal.

%% Only return if the list is not empty.
nonempty(L) when L =/= [] -> L.

%% Parse a number optionally followed by whitespace.
number(<< $0, R/bits >>, Acc) -> number(R, Acc * 10);
number(<< $1, R/bits >>, Acc) -> number(R, Acc * 10 + 1);
number(<< $2, R/bits >>, Acc) -> number(R, Acc * 10 + 2);
number(<< $3, R/bits >>, Acc) -> number(R, Acc * 10 + 3);
number(<< $4, R/bits >>, Acc) -> number(R, Acc * 10 + 4);
number(<< $5, R/bits >>, Acc) -> number(R, Acc * 10 + 5);
number(<< $6, R/bits >>, Acc) -> number(R, Acc * 10 + 6);
number(<< $7, R/bits >>, Acc) -> number(R, Acc * 10 + 7);
number(<< $8, R/bits >>, Acc) -> number(R, Acc * 10 + 8);
number(<< $9, R/bits >>, Acc) -> number(R, Acc * 10 + 9);
number(<< $\s, R/bits >>, Acc) -> ws_end(R), Acc;
number(<< $\t, R/bits >>, Acc) -> ws_end(R), Acc;
number(<<>>, Acc) -> Acc.

ws_end(<< $\s, R/bits >>) -> ws_end(R);
ws_end(<< $\t, R/bits >>) -> ws_end(R);
ws_end(<<>>) -> ok.

%% Parse a list of case insensitive tokens.
token_ci_list(<<>>, Acc) -> lists:reverse(Acc);
token_ci_list(<< $\s, R/bits >>, Acc) -> token_ci_list(R, Acc);
token_ci_list(<< $\t, R/bits >>, Acc) -> token_ci_list(R, Acc);
token_ci_list(<< $,, R/bits >>, Acc) -> token_ci_list(R, Acc);
token_ci_list(<< C, R/bits >>, Acc) ->
	case C of
		?INLINE_LOWERCASE(token_ci_list, R, Acc, <<>>)
	end.

token_ci_list(<<>>, Acc, T) -> lists:reverse([T|Acc]);
token_ci_list(<< $\s, R/bits >>, Acc, T) -> token_ci_list_sep(R, Acc, T);
token_ci_list(<< $\t, R/bits >>, Acc, T) -> token_ci_list_sep(R, Acc, T);
token_ci_list(<< $,, R/bits >>, Acc, T) -> token_ci_list(R, [T|Acc]);
token_ci_list(<< C, R/bits >>, Acc, T) ->
	case C of
		?INLINE_LOWERCASE(token_ci_list, R, Acc, T)
	end.

token_ci_list_sep(<<>>, Acc, T) -> lists:reverse([T|Acc]);
token_ci_list_sep(<< $\s, R/bits >>, Acc, T) -> token_ci_list_sep(R, Acc, T);
token_ci_list_sep(<< $\t, R/bits >>, Acc, T) -> token_ci_list_sep(R, Acc, T);
token_ci_list_sep(<< $,, R/bits >>, Acc, T) -> token_ci_list(R, [T|Acc]).

-define(DIGITS(A, B), ((A - $0) * 10 + (B - $0))).
-define(DIGITS(A, B, C, D), ((A - $0) * 1000 + (B - $0) * 100 + (C - $0) * 10 + (D - $0))).

http_date(DateBin) ->
	Date = {{_, _, D}, {H, M, S}} = all_date(DateBin),
	true = D >= 0 andalso D =< 31,
	true = H >= 0 andalso H =< 23,
	true = M >= 0 andalso M =< 59,
	true = S >= 0 andalso S =< 60, %% Leap second.
	Date.

all_date(<<"Mon, ", D1, D2, " ", R/bits >>) -> fixdate(R, ?DIGITS(D1, D2));
all_date(<<"Tue, ", D1, D2, " ", R/bits >>) -> fixdate(R, ?DIGITS(D1, D2));
all_date(<<"Wed, ", D1, D2, " ", R/bits >>) -> fixdate(R, ?DIGITS(D1, D2));
all_date(<<"Thu, ", D1, D2, " ", R/bits >>) -> fixdate(R, ?DIGITS(D1, D2));
all_date(<<"Fri, ", D1, D2, " ", R/bits >>) -> fixdate(R, ?DIGITS(D1, D2));
all_date(<<"Sat, ", D1, D2, " ", R/bits >>) -> fixdate(R, ?DIGITS(D1, D2));
all_date(<<"Sun, ", D1, D2, " ", R/bits >>) -> fixdate(R, ?DIGITS(D1, D2));
all_date(<<"Monday, ", D1, D2, "-", R/bits >>) -> rfc850_date(R, ?DIGITS(D1, D2));
all_date(<<"Tuesday, ", D1, D2, "-", R/bits >>) -> rfc850_date(R, ?DIGITS(D1, D2));
all_date(<<"Wednesday, ", D1, D2, "-", R/bits >>) -> rfc850_date(R, ?DIGITS(D1, D2));
all_date(<<"Thursday, ", D1, D2, "-", R/bits >>) -> rfc850_date(R, ?DIGITS(D1, D2));
all_date(<<"Friday, ", D1, D2, "-", R/bits >>) -> rfc850_date(R, ?DIGITS(D1, D2));
all_date(<<"Saturday, ", D1, D2, "-", R/bits >>) -> rfc850_date(R, ?DIGITS(D1, D2));
all_date(<<"Sunday, ", D1, D2, "-", R/bits >>) -> rfc850_date(R, ?DIGITS(D1, D2));
all_date(<<"Mon ", R/bits >>) -> asctime_date(R);
all_date(<<"Tue ", R/bits >>) -> asctime_date(R);
all_date(<<"Wed ", R/bits >>) -> asctime_date(R);
all_date(<<"Thu ", R/bits >>) -> asctime_date(R);
all_date(<<"Fri ", R/bits >>) -> asctime_date(R);
all_date(<<"Sat ", R/bits >>) -> asctime_date(R);
all_date(<<"Sun ", R/bits >>) -> asctime_date(R).

fixdate(<<"Jan ", Y1, Y2, Y3, Y4, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 1, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
fixdate(<<"Feb ", Y1, Y2, Y3, Y4, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 2, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
fixdate(<<"Mar ", Y1, Y2, Y3, Y4, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 3, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
fixdate(<<"Apr ", Y1, Y2, Y3, Y4, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 4, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
fixdate(<<"May ", Y1, Y2, Y3, Y4, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 5, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
fixdate(<<"Jun ", Y1, Y2, Y3, Y4, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 6, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
fixdate(<<"Jul ", Y1, Y2, Y3, Y4, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 7, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
fixdate(<<"Aug ", Y1, Y2, Y3, Y4, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 8, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
fixdate(<<"Sep ", Y1, Y2, Y3, Y4, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 9, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
fixdate(<<"Oct ", Y1, Y2, Y3, Y4, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 10, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
fixdate(<<"Nov ", Y1, Y2, Y3, Y4, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 11, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
fixdate(<<"Dec ", Y1, Y2, Y3, Y4, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 12, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}}.

rfc850_date(<<"Jan-", Y1, Y2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{rfc850_year(?DIGITS(Y1, Y2)), 1, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
rfc850_date(<<"Feb-", Y1, Y2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{rfc850_year(?DIGITS(Y1, Y2)), 2, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
rfc850_date(<<"Mar-", Y1, Y2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{rfc850_year(?DIGITS(Y1, Y2)), 3, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
rfc850_date(<<"Apr-", Y1, Y2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{rfc850_year(?DIGITS(Y1, Y2)), 4, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
rfc850_date(<<"May-", Y1, Y2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{rfc850_year(?DIGITS(Y1, Y2)), 5, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
rfc850_date(<<"Jun-", Y1, Y2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{rfc850_year(?DIGITS(Y1, Y2)), 6, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
rfc850_date(<<"Jul-", Y1, Y2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{rfc850_year(?DIGITS(Y1, Y2)), 7, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
rfc850_date(<<"Aug-", Y1, Y2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{rfc850_year(?DIGITS(Y1, Y2)), 8, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
rfc850_date(<<"Sep-", Y1, Y2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{rfc850_year(?DIGITS(Y1, Y2)), 9, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
rfc850_date(<<"Oct-", Y1, Y2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{rfc850_year(?DIGITS(Y1, Y2)), 10, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
rfc850_date(<<"Nov-", Y1, Y2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{rfc850_year(?DIGITS(Y1, Y2)), 11, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
rfc850_date(<<"Dec-", Y1, Y2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " GMT">>, Day) ->
	{{rfc850_year(?DIGITS(Y1, Y2)), 12, Day}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}}.

rfc850_year(Y) when Y > 50 -> Y + 1900;
rfc850_year(Y) -> Y + 2000.

asctime_date(<<"Jan ", D1, D2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " ", Y1, Y2, Y3, Y4 >>) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 1, asctime_day(D1, D2)}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
asctime_date(<<"Feb ", D1, D2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " ", Y1, Y2, Y3, Y4 >>) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 2, asctime_day(D1, D2)}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
asctime_date(<<"Mar ", D1, D2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " ", Y1, Y2, Y3, Y4 >>) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 3, asctime_day(D1, D2)}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
asctime_date(<<"Apr ", D1, D2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " ", Y1, Y2, Y3, Y4 >>) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 4, asctime_day(D1, D2)}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
asctime_date(<<"May ", D1, D2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " ", Y1, Y2, Y3, Y4 >>) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 5, asctime_day(D1, D2)}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
asctime_date(<<"Jun ", D1, D2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " ", Y1, Y2, Y3, Y4 >>) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 6, asctime_day(D1, D2)}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
asctime_date(<<"Jul ", D1, D2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " ", Y1, Y2, Y3, Y4 >>) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 7, asctime_day(D1, D2)}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
asctime_date(<<"Aug ", D1, D2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " ", Y1, Y2, Y3, Y4 >>) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 8, asctime_day(D1, D2)}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
asctime_date(<<"Sep ", D1, D2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " ", Y1, Y2, Y3, Y4 >>) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 9, asctime_day(D1, D2)}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
asctime_date(<<"Oct ", D1, D2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " ", Y1, Y2, Y3, Y4 >>) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 10, asctime_day(D1, D2)}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
asctime_date(<<"Nov ", D1, D2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " ", Y1, Y2, Y3, Y4 >>) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 11, asctime_day(D1, D2)}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}};
asctime_date(<<"Dec ", D1, D2, " ", H1, H2, ":", M1, M2, ":", S1, S2, " ", Y1, Y2, Y3, Y4 >>) ->
	{{?DIGITS(Y1, Y2, Y3, Y4), 12, asctime_day(D1, D2)}, {?DIGITS(H1, H2), ?DIGITS(M1, M2), ?DIGITS(S1, S2)}}.

asctime_day($\s, D2) -> (D2 - $0);
asctime_day(D1, D2) -> (D1 - $0) * 10 + (D2 - $0).

-ifdef(TEST).
day_name() -> oneof(["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]).
day_name_l() -> oneof(["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"]).
year() -> int(1951, 2050).
month() -> int(1, 12).
day() -> int(1, 31).
hour() -> int(23).
minute() -> int(59).
second() -> int(60).

month(1) -> "Jan";
month(2) -> "Feb";
month(3) -> "Mar";
month(4) -> "Apr";
month(5) -> "May";
month(6) -> "Jun";
month(7) -> "Jul";
month(8) -> "Aug";
month(9) -> "Sep";
month(10) -> "Oct";
month(11) -> "Nov";
month(12) -> "Dec".

pad2(I) when I < 10 -> << $0, (I + $0) >>;
pad2(I) -> integer_to_binary(I).

pad2s(I) when I < 10 -> << $\s, (I + $0) >>;
pad2s(I) -> integer_to_binary(I).

fixdate_gen() ->
	?LET({DayName, Y, Mo, D, H, Mi, S},
		{day_name(), year(), month(), day(), hour(), minute(), second()},
		{{{Y, Mo, D}, {H, Mi, S}},
			list_to_binary([DayName, ", ", pad2(D), " ", month(Mo), " ", integer_to_binary(Y),
			" ", pad2(H), ":", pad2(Mi), ":", pad2(S), " GMT"])}).

rfc850_gen() ->
	?LET({DayName, Y, Mo, D, H, Mi, S},
		{day_name_l(), year(), month(), day(), hour(), minute(), second()},
		{{{Y, Mo, D}, {H, Mi, S}},
			list_to_binary([DayName, ", ", pad2(D), "-", month(Mo), "-", pad2(Y rem 100),
			" ", pad2(H), ":", pad2(Mi), ":", pad2(S), " GMT"])}).

asctime_gen() ->
	?LET({DayName, Y, Mo, D, H, Mi, S},
		{day_name(), year(), month(), day(), hour(), minute(), second()},
		{{{Y, Mo, D}, {H, Mi, S}},
			list_to_binary([DayName, " ", month(Mo), " ", pad2s(D),
			" ", pad2(H), ":", pad2(Mi), ":", pad2(S), " ", integer_to_binary(Y)])}).

prop_http_date() ->
	?FORALL({Date, DateBin},
		oneof([fixdate_gen(), rfc850_gen(), asctime_gen()]),
		Date =:= http_date(DateBin)).

http_date_test_() ->
	Tests = [
		{<<"Sun, 06 Nov 1994 08:49:37 GMT">>, {{1994, 11, 6}, {8, 49, 37}}},
		{<<"Sunday, 06-Nov-94 08:49:37 GMT">>, {{1994, 11, 6}, {8, 49, 37}}},
		{<<"Sun Nov  6 08:49:37 1994">>, {{1994, 11, 6}, {8, 49, 37}}}
	],
	[{V, fun() -> R = http_date(V) end} || {V, R} <- Tests].
-endif.

-ifdef(PERF).
horse_http_date_fixdate() ->
	horse:repeat(200000,
		http_date(<<"Sun, 06 Nov 1994 08:49:37 GMT">>)
	).

horse_http_date_rfc850() ->
	horse:repeat(200000,
		http_date(<<"Sunday, 06-Nov-94 08:49:37 GMT">>)
	).

horse_http_date_asctime() ->
	horse:repeat(200000,
		http_date(<<"Sun Nov  6 08:49:37 1994">>)
	).
-endif.