Add cow_sse module which implements parsing of SSE

Building of events will be implemented at a later time.

1 files changed, 214 insertions, 0 deletions

diff --git a/src/cow_sse.erl b/src/cow_sse.erl
new file mode 100644
index 0000000..710e9b3
--- /dev/null
+++ b/src/cow_sse.erl
@@ -0,0 +1,214 @@
+%% Copyright (c) 2017, Loïc Hoguin <[email protected]>
+%%
+%% Permission to use, copy, modify, and/or distribute this software for any
+%% purpose with or without fee is hereby granted, provided that the above
+%% copyright notice and this permission notice appear in all copies.
+%%
+%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+-module(cow_sse).
+
+-export([init/0]).
+-export([parse/2]).
+
+-record(state, {
+	state_name = bom :: bom | events,
+	buffer = <<>> :: binary(),
+	last_event_id = <<>> :: binary(),
+	event_type = <<>> :: binary(),
+	data = [] :: iolist(),
+	retry = undefined :: undefined | non_neg_integer()
+}).
+-type state() :: #state{}.
+-export_type([state/0]).
+
+-type event() :: #{
+	last_event_id := binary(),
+	event_type := binary(),
+	data := iolist()
+}.
+
+-spec init() -> state().
+init() ->
+	#state{}.
+
+%% @todo Add a function to retrieve the retry value from the state.
+
+-spec parse(binary(), state())
+	-> {event, event(), State} | {more, State}.
+parse(Data0, State=#state{state_name=bom, buffer=Buffer}) ->
+	Data1 = case Buffer of
+		<<>> -> Data0;
+		_ -> << Buffer/binary, Data0/binary >>
+	end,
+	case Data1 of
+		%% Skip the BOM.
+		<< 16#fe, 16#ff, Data/bits >> ->
+			parse_event(Data, State#state{state_name=events, buffer= <<>>});
+		%% Not enough data to know wether we have a BOM.
+		<< 16#fe >> ->
+			{more, State#state{buffer=Data1}};
+		<<>> ->
+			{more, State};
+		%% No BOM.
+		_ ->
+			parse_event(Data1, State#state{state_name=events, buffer= <<>>})
+	end;
+%% Try to process data from the buffer if there is no new input.
+parse(<<>>, State=#state{buffer=Buffer}) ->
+	parse_event(Buffer, State#state{buffer= <<>>});
+%% Otherwise process the input data as-is.
+parse(Data, State) ->
+	parse_event(Data, State).
+
+parse_event(Data0, State0=#state{buffer=Buffer}) ->
+	Data = case Buffer of
+		<<>> -> Data0;
+		_ -> << Buffer/binary, Data0/binary >>
+	end,
+	case binary:split(Data, [<<"\r\n">>, <<"\r">>, <<"\n">>]) of
+		[Line, Rest] ->
+			case parse_line(Line, State0) of
+				{ok, State} ->
+					parse_event(Rest, State);
+				{event, Event, State} ->
+					{event, Event, State#state{buffer=Rest}}
+			end;
+		[_] ->
+			{more, State0#state{buffer=Data}}
+	end.
+
+%% Dispatch events on empty line.
+parse_line(<<>>, State) ->
+	dispatch_event(State);
+%% Ignore comments.
+parse_line(<< $:, _/bits >>, State) ->
+	{ok, State};
+%% Normal line.
+parse_line(Line, State) ->
+	case binary:split(Line, [<<":\s">>, <<":">>]) of
+		[Field, Value] ->
+			process_field(Field, Value, State);
+		[Field] ->
+			process_field(Field, <<>>, State)
+	end.
+
+process_field(<<"event">>, Value, State) ->
+	{ok, State#state{event_type=Value}};
+process_field(<<"data">>, Value, State=#state{data=Data}) ->
+	{ok, State#state{data=[<<$\n>>, Value|Data]}};
+process_field(<<"id">>, Value, State) ->
+	{ok, State#state{last_event_id=Value}};
+process_field(<<"retry">>, Value, State) ->
+	try
+		{ok, State#state{retry=binary_to_integer(Value)}}
+	catch _:_ ->
+		{ok, State}
+	end;
+process_field(_, _, State) ->
+	{ok, State}.
+
+%% Data is an empty string; abort.
+dispatch_event(State=#state{data=[]}) ->
+	{ok, State#state{event_type= <<>>}};
+%% Dispatch the event.
+%%
+%% Always remove the last linebreak from the data.
+dispatch_event(State=#state{last_event_id=LastEventID,
+		event_type=EventType, data=[_|Data]}) ->
+	{event, #{
+		last_event_id => LastEventID,
+		event_type => case EventType of
+			<<>> -> <<"message">>;
+			_ -> EventType
+		end,
+		data => lists:reverse(Data)
+	}, State#state{event_type= <<>>, data=[]}}.
+
+-ifdef(TEST).
+
+parse_example1_test() ->
+	{event, #{
+		event_type := <<"message">>,
+		last_event_id := <<>>,
+		data := Data
+	}, State} = parse(<<
+		"data: YHOO\n"
+		"data: +2\n"
+		"data: 10\n"
+		"\n">>, init()),
+	<<"YHOO\n+2\n10">> = iolist_to_binary(Data),
+	{more, _} = parse(<<>>, State),
+	ok.
+
+parse_example2_test() ->
+	{event, #{
+		event_type := <<"message">>,
+		last_event_id := <<"1">>,
+		data := Data1
+	}, State0} = parse(<<
+		": test stream\n"
+		"\n"
+		"data: first event\n"
+		"id: 1\n"
+		"\n"
+		"data:second event\n"
+		"id\n"
+		"\n"
+		"data:  third event\n"
+		"\n">>, init()),
+	<<"first event">> = iolist_to_binary(Data1),
+	{event, #{
+		event_type := <<"message">>,
+		last_event_id := <<>>,
+		data := Data2
+	}, State1} = parse(<<>>, State0),
+	<<"second event">> = iolist_to_binary(Data2),
+	{event, #{
+		event_type := <<"message">>,
+		last_event_id := <<>>,
+		data := Data3
+	}, State} = parse(<<>>, State1),
+	<<" third event">> = iolist_to_binary(Data3),
+	{more, _} = parse(<<>>, State),
+	ok.
+
+parse_example3_test() ->
+	{event, #{
+		event_type := <<"message">>,
+		last_event_id := <<>>,
+		data := Data1
+	}, State0} = parse(<<
+		"data\n"
+		"\n"
+		"data\n"
+		"data\n"
+		"\n"
+		"data:\n">>, init()),
+	<<>> = iolist_to_binary(Data1),
+	{event, #{
+		event_type := <<"message">>,
+		last_event_id := <<>>,
+		data := Data2
+	}, State} = parse(<<>>, State0),
+	<<"\n">> = iolist_to_binary(Data2),
+	{more, _} = parse(<<>>, State),
+	ok.
+
+parse_example4_test() ->
+	{event, Event, State0} = parse(<<
+		"data:test\n"
+		"\n"
+		"data: test\n"
+		"\n">>, init()),
+	{event, Event, State} = parse(<<>>, State0),
+	{more, _} = parse(<<>>, State),
+	ok.
+
+-endif.