/src/middleware/ewgi_stream_file/ewgi_stream_file.erl

%% @author Hunter Morris <hunter.morris@smarkets.com>
%% @author Filippo Pacini <filippo.pacini@gmail.com>

%% @doc ewgi stream file application
-module(ewgi_stream_file).

-export([run/2]).

%%
%% Files opened in raw mode cannot be read in processes distinct
%% from the one that opened the file! So we need to make sure 
%% that both the open and read operations are done in the same
%% process. 
%% 
%% Since a webserver might need to spawn a new process to handle
%% our stream (Yaws and the old Inets implementation did)
%% we'll get around that by delaying the open operation to the
%% head of the stream.
%% 
run(Ctx, [File]) ->
    case file:read_file_info(File) of
	{ok, _} ->
	    Mime = guess_mime(File),
	    LoadIoDevice = {open, File, [raw, binary]},
 	    %% Set ChunkSize to an optimal value
 	    ChunkSize = 1024,
	    Stream = iodevice_stream(LoadIoDevice, ChunkSize),
	    ewgi_api:response_status(
	      {200, "OK"}, 
	      ewgi_api:response_headers(
		[{"Content-type", Mime}], 
		ewgi_api:response_message_body(Stream, Ctx)
	       )
	     );
	_ ->
	    %% Respond with 404...
	    ewgi_api:response_message_body(
	      "404 NOT FOUND", 
	      ewgi_api:response_status({404, "NOT FOUND"}, Ctx)
	     )
    end.	

iodevice_stream({open, File, Modes}, ChunkSize) ->
    fun() ->
	    case file:open(File, Modes) of
		{ok, IoDevice} ->
		    {<<>>, iodevice_stream(IoDevice, ChunkSize)};
		_ ->
		    {}
	    end
    end;
iodevice_stream(IoDevice, ChunkSize) ->
    fun() ->
            case file:read(IoDevice, ChunkSize) of
                eof ->
                    file:close(IoDevice),
                    {};
                {ok, Data} ->
                    {Data, iodevice_stream(IoDevice, ChunkSize)};
		{error, Reason} ->
		    io:format("got error: ~p~n", [Reason]),
		    {}
            end
    end.


%% @spec guess_mime(string()) -> string()
%% @doc  Guess the mime type of a file by the extension of its filename.
guess_mime(File) -> 
    %% Taken from webmachine.
    case filename:extension(File) of
	".html" ->
	    "text/html";
	".xhtml" ->
	    "application/xhtml+xml";
	".xml" ->
	    "application/xml";
	".css" ->
	    "text/css";
	".js" ->
	    "application/x-javascript";
	".jpg" ->
	    "image/jpeg";
	".jpeg" ->
	    "image/jpeg";
	".gif" ->
	    "image/gif";
	".png" ->
	    "image/png";
	".ico" ->
	    "image/x-icon";
	".swf" ->
	    "application/x-shockwave-flash";
	".zip" ->
	    "application/zip";
	".bz2" ->
	    "application/x-bzip2";
	".gz" ->
	    "application/x-gzip";
	".tar" ->
	    "application/x-tar";
	".tgz" ->
	    "application/x-gzip";
        ".htc" ->
            "text/x-component";
        _ ->
	    "text/plain"
    end.