%% @author Davide Marquês <nesrait@gmail.com>

%% @copyright 2009 Davide Marquês <nesrait@gmail.com>

%%

%% @doc ewgi Push streams middleware.

%% The difference for regular [pull-]streams is that those are synchronously polled

%% by the ewgi server for more data. With pull streams the ewgi server is notified

%% when there is more data available.

%% @end

%%

%% Licensed under the MIT license:

%% http://www.opensource.org/licenses/mit-license.php

%%

-module(ewgi_push_stream).

-author('Davide Marquês <nesrait@gmail.com>').



-define(STREAM_INIT_TIMEOUT, 5000).



-define(EX_STREAM_DATA, ["ini\r\n", "mini\r\n", "mini\r\n", "mo\r\n"]).



%% Ewgi Application API

-export([run/2]).



%% Usage examples

-export([

		chunked_stream_example/1,

		non_chunked_stream_example/1,

		ewgi_free_stream_example/1

	]).



%% The body field is used to specify which process will be producing data.

%% The various headers and data are all send asynchronously to the

%% ewgi gateway when available.

%% The given timeout defines how long to want before issuing a 504 response.

run(Ctx, [StreamPid]) when is_pid(StreamPid) ->

	PS = {push_stream, StreamPid, ?STREAM_INIT_TIMEOUT},

	ewgi_api:response_message_body(PS, Ctx);

	

run(Ctx, [StreamPid, Timeout]) when is_pid(StreamPid) ->

	PS = {push_stream, StreamPid, Timeout},

	ewgi_api:response_message_body(PS, Ctx).



%%--------------------------------------------------------------------

%% Chunked stream example

%%--------------------------------------------------------------------

%% N.B.: there's no point in setting headers in the ewgi_context

%% passed to ewgi_push_stream:run/2. Those headers will be ignore!

chunked_stream_example(Ctx) ->

	StreamPid = spawn(fun() -> chunked_stream(Ctx) end),

    ?MODULE:run(Ctx, [StreamPid]).



%% The ewgi_context that is passed to ewgi_api:stream_process_init/2 is 

%% the one from where the status code and headers are read from.

%% The default is a chunked response (see below for non-chunked responses).

chunked_stream(Ctx0) ->

	Status = {200, "OK"},

	H = ewgi_api:response_headers(Ctx0),

	CTHeader = {"Content-type", "text/plain"},

	Ctx = ewgi_api:response_headers([CTHeader|H],

					ewgi_api:response_status(Status, Ctx0)),

	

	CSEnd = "chunked_stream_end",

	case ewgi_api:stream_process_init(Ctx, chunked) of

	{ok, Connection} ->

		lists:foreach(fun(Word) ->

			ewgi_api:stream_process_deliver_chunk(Connection, Word),

			timer:sleep(1000)

			end, ?EX_STREAM_DATA),

		ewgi_api:stream_process_deliver_final_chunk(Connection, CSEnd),

		ewgi_api:stream_process_end(Connection);

	_ -> ok

	end.

	

%%--------------------------------------------------------------------

%% Non-Chunked stream example

%%--------------------------------------------------------------------

%% N.B.: there's no point in setting headers in the ewgi_context

%% passed to ewgi_push_stream:run/2. Those headers will be ignore!

non_chunked_stream_example(Ctx) ->

	StreamPid = spawn(fun() -> non_chunked_stream(Ctx) end),

    ?MODULE:run(Ctx, [StreamPid]).



%% The ewgi_context that is passed to ewgi_api:stream_process_init/2 is 

%% the one from where the status code and headers are read from.

%% By passing a content-length we specify that this woun't be a chunked response.

non_chunked_stream(Ctx0) ->

	Status = {200, "OK"},

	H = ewgi_api:response_headers(Ctx0),

	CTHeader = {"Content-type", "text/plain"},

	Ctx = ewgi_api:response_headers([CTHeader|H],

					ewgi_api:response_status(Status, Ctx0)),



	NCSEnd = "non_chunked_stream_end",

	ContentLength = iolist_size(?EX_STREAM_DATA) + iolist_size(NCSEnd),

	case ewgi_api:stream_process_init(Ctx, ContentLength) of

	{ok, Connection} ->

		lists:foreach(fun(Word) ->

			ewgi_api:stream_process_deliver(Connection, Word),

			timer:sleep(1000)

			end, ?EX_STREAM_DATA),

		ewgi_api:stream_process_deliver(Connection, NCSEnd),

		ewgi_api:stream_process_end(Connection);

	_ -> ok

	end.



%%--------------------------------------------------------------------

%% Ewgi-free stream

%% Just showing off that any process can serve as a push stream

%%--------------------------------------------------------------------

ewgi_free_stream_example(Ctx) ->

	StreamPid = spawn(fun ewgi_free_stream/0),

    ?MODULE:run(Ctx, [StreamPid]).

	

ewgi_free_stream() ->

	EFSEnd = "ewgi_free_stream_end",

	StatusCode = 200,

	Headers = [{"Content-type", "text/plain"}],

	case ewgi_api:stream_process_init(StatusCode, Headers, chunked) of

	{ok, Connection} ->

		lists:foreach(fun(Word) ->

			ewgi_api:stream_process_deliver_chunk(Connection, Word),

			timer:sleep(1000)

			end, ?EX_STREAM_DATA),

		ewgi_api:stream_process_deliver_final_chunk(Connection, EFSEnd),

		ewgi_api:stream_process_end(Connection);

	_ -> ok

	end.