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+%% 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.