/*  $Id$

    Part of SWI-Prolog

    Author:        Jan Wielemaker
    E-mail:        wielemak@science.uva.nl
    WWW:           http://www.swi-prolog.org
    Copyright (C): 1985-2005, University of Amsterdam

    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
    as published by the Free Software Foundation; either version 2
    of the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    As a special exception, if you link this library with other files,
    compiled with a Free Software compiler, to produce an executable, this
    library does not by itself cause the resulting executable to be covered
    by the GNU General Public License. This exception does not however
    invalidate any other reasons why the executable file might be covered by
    the GNU General Public License.
*/

:- module(xpce_httpd,
	  [ http_current_server/2,	% ?:Goal, ?Port
	    http_server/2		% :Goal, :Options
	  ]).
:- use_module(library(pce)).
:- use_module(http_header).
:- use_module(library(debug)).
:- use_module(http_wrapper).
:- use_module(library(lists)).

:- meta_predicate
	http_server(:, ?),
	http_server(:, ?, +).

%	@http_servers: keep track of them and avoid the servers being
%	garbage collected.

:- pce_global(@http_servers, new(chain)).

%:- debug(connection).

http_current_server(Goal, Port) :-
	object(@open_sockets),
	chain_list(@open_sockets, Sockets),
	member(Socket, Sockets),
	send(Socket, instance_of, interactive_httpd),
	get(Socket, goal, Goal),
	get(Socket, address, Port).

%%	http_server(:Goal, +Options) is det.
%
%	Start server at given or arbitrary port.

http_server(Goal, Options) :-
	select(port(Port), Options, Options1), !,
	http_server(Goal, Port, Options1).
http_server(_Goal, _Options) :-
	throw(error(existence_error(option, port), _)).

http_server(Goal, Port, _Options) :-
	strip_module(Goal, M, PlainGoal),
	(   var(Port)
	->  new(X, interactive_httpd(M:PlainGoal)),
	    get(X, address, Port)
	;   new(X, interactive_httpd(M:PlainGoal, Port))
	).

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
XPCE based socket handling for   generic HTTP interface infra-structure.
This module acts as a replacement for inetd_httpd, which allows a Prolog
process to acts as an inet-driven HTTP server.

Using this module the user can easily  debug HTTP connections or provide
services while running the XPCE GUI.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

:- pce_begin_class(interactive_httpd, socket,
		   "Prolog HTTP debugger").

variable(allowed_hosts,	chain*,	 both, "Chain of regex with acceptable peers").
variable(goal,		prolog,	 get,  "Goal to use for processing").
variable(out_stream,	prolog,	 get,  "Stream for output").
variable(peer,		name,	 get,  "Peer connection (host only)").
variable(request,	string*, get,  "Data for first line").
variable(data,		string*, get,  "Data for POST request").
variable(chunk_data,	string*, get,  "Collect chunked input").
variable(mode,
	 {request,header,post_content_length,chunked} := request,
				 get,  "Mode of operation").

:- pce_global(@http_end_header_regex,
	      new(regex('\n\r?\n\r?'))).
:- pce_global(@http_end_line_regex,
	      new(regex('\n\r?'))).
:- pce_global(@http_has_header_regex,
	      new(regex('[^\n]*HTTP/'))).

initialise(S, Goal:prolog, Port:[int]) :->
	default(Port, 0, ThePort),	% anonymous
	send_super(S, initialise, ThePort),
	send(S, slot, goal, Goal),
	send(S, record_separator, @http_end_line_regex),
	send(S, input_message, message(@receiver, input, @arg1)),
	send(S, accept_message, message(@arg1, accepted)),
	send(S, listen, reuse := @on),
	send(@http_servers, append, S).

unlink(S) :->
	send(@http_servers, delete_all, S),
	send_super(S, unlink).

:- pce_group(connection).

accepted(S) :->
	"A new connection is established on this socket"::
	(   pce_catch_error(_, get(S, peer_name, tuple(Peer, _Port)))
	->  send(S, slot, peer, Peer),
	    send(S, authorise),
	    debug(connection, 'New connection from ~w', [Peer]),
	    pce_open(S, append, Fd),
	    send(S, slot, out_stream, Fd)
	;   debug(connection, 'Cannot get peer: closing.', []),
	    free(S)
	).

authorise(S) :->
	"See whether we will proceeed with this connection"::
	get(S, allowed_hosts, Allowed),
	(   Allowed == @nil
	->  true
	;   get(S, peer, Peer),
	    get(Allowed, find,
		message(@arg1, match, Peer),
		_)
	->  true
	;   debug(connection, 'Refused connection from ~w', [Peer]),
	    free(S),
	    fail
	).

unlink(S) :->
	(   debugging(connection)
	->  get(S, peer, Peer),
	    debug(connection, 'Closed connection from ~w', [Peer])
	;   true
	),
	(   get(S, slot, out_stream, Fd),
	    Fd \== @nil
	->  catch(close(Fd), _, true)
	;   true
	),
	send_super(S, unlink).

:- pce_group(request).

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
->input collects input from  the  stream   until  an  entire  request is
complete. A request consists of one of the following:

	<Request>	::= <Action> <Path>\n
			  | <Action> <Path> HTTP/<Version>\n
			    <Header>
			    <Post Data>?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

input(S, Input:string) :->
	"Process input.  The argument is the header"::
	get(S, mode, Mode),
	(   debugging(input)
	->  send(@pce, format, 'GOT (mode %s): "%s"\n', Mode, Input)
	;   true
	),
	(   Mode == request		% got first line
	->  (   send(@http_has_header_regex, match, Input)
	    ->	send(S, slot, request, Input),
		send(S, slot, mode, header),
		send(S, record_separator, @http_end_header_regex)
	    ;	send(S, dispatch, Input)
	    )
	;   Mode == header
	->  send(Input, prepend, S?request),
	    send(S, slot, request, @nil),
	    (	send(S, collect_post_data, Input)
	    ->	true
	    ;	send(S, dispatch, Input)
	    )
	;   Mode == post_content_length
	->  send(S, slot, mode, request),
	    send(S, record_separator, @http_end_line_regex),
	    get(S, data, Header),
	    send(Header, append, Input),
	    send(Header, lock_object, @on),
	    send(S, slot, data, @nil),
	    send(S, dispatch, Header),
	    send(Header, lock_object, @off)
	;   Mode == chunked
	->  get(S, chunk_data, ChunkData),
	    (   get(S, record_separator, Bytes),
	        integer(Bytes)
	    ->  send(ChunkData, append, Input),
		send(S, record_separator, '\n')
	    ;	send(Input, prepend, '0x'),
		get(Input, value, HexAtom),
		term_to_atom(Bytes, HexAtom),
		(   Bytes == 0
		->  get(S, data, Header),
		    get(ChunkData, size, ContentLength),
		    send(@http_chunked_regex, search, Header),
		    send(@http_chunked_regex, register_value, 0, Header,
			 string('Content-Length: %d', ContentLength)),
		    send(Header, append, ChunkData),
		    send(S, slot, chunk_data, @nil),
		    send(S, slot, mode, request),
		    send(S, record_separator, @http_end_line_regex),
		    send(S, dispatch, Header)
		;   send(S, record_separator, Bytes)
		)
	    )
	).


dispatch(S, Input:string) :->
	"Hand complete input for dispatching"::
	(   debugging(dispatch)
	->  send(@pce, write_ln, Input)
	;   true
	),
	pce_open(Input, read, In),
	get(S, goal, Goal),
	get(S, out_stream, Out),
	(   catch(http_wrapper(Goal, In, Out, Close, []),
		  E, wrapper_error(E))
	->  close(In),
	    (   downcase_atom(Close, 'keep-alive')
	    ->  send(S, slot, mode, request), % prepare for next
		send(S, record_separator, @http_end_line_regex),
		send(S, slot, data, @nil)
	    ;   free(S)
	    )
	;   close(In),			% exception or failure
	    free(S)
	).

wrapper_error(Error) :-
	(   debugging(connection)
	->  print_message(error, Error)
	;   true
	),
	fail.

:- pce_group(post).


:- pce_global(@http_content_length_regex,
	      new(regex('^Content-Length:[[:blank:]]*([0-9]+)', @off))).
:- pce_global(@http_chunked_regex,
	      new(regex('^Transfer-encoding:[[:blank:]]*chunked', @off))).


collect_post_data(S, Header:string) :->
	(   send(@http_content_length_regex, search, Header)
	->  get(@http_content_length_regex, register_value, Header,
		1, int, Len),
	    debug(dispatch, '[POST] Content-length: ~w~n', [Len]),
	    send(S, slot, mode, post_content_length),
	    send(S, slot, data, Header),
	    send(S, record_separator, Len)
	;   send(@http_chunked_regex, search, Header)
	->  send(S, slot, mode, chunked),
	    send(S, slot, chunk_data, new(string)),
	    send(S, record_separator, '\n')
	).

:- pce_end_class(interactive_httpd).

