%% 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.
