/*  Part of SWI-Prolog

    Author:        Jan Wielemaker
    E-mail:        J.Wielemaker@cs.vu.nl
    WWW:           http://www.swi-prolog.org
    Copyright (C): 2007-2011, VU University 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 General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  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(http_cookie,
	  [ cookie_remove_client/1,	% +ClientId
	    cookie_remove_all_clients/0,
	    cookie_current_cookie/4	% ?ClientId, ?Name, ?Value, ?Options
	  ]).
:- use_module(library(http/http_header)).
:- use_module(library(option)).
:- use_module(library(debug)).

/** <module> HTTP client cookie handling

This module implements the cookie hooks  called from http_open/3, adding
cookie handling to the client.

This library supports a notion of _clients_. A client is a (ground) term
to which a cookie database is  connected.   This  allows a single Prolog
process to act  as  multiple  clients.   The  default  client  is called
=default=. Use the option client(+ClientId) to select another client.

The client and cookie database can be  inspected and cleared using these
predicates.

  * cookie_remove_client/1
  * cookie_remove_all_clients/0
  * cookie_current_cookie/4

@tbd add hooks to http_get/3 and http_post/4
*/

:- multifile
	http:write_cookies/3,		% +Out, +Parts, +Options
	http:update_cookies/3.		% +CookieData, +Parts, +Options

:- dynamic
	client_cookie/5.		% Id, CanName, Name, Value, Options

%%	http:write_cookies(+Out, +Parts, +Options) is det.
%
%	Emit a cookie header for the current request.

http:write_cookies(Out, Parts, Options) :-
	option(client(ClientId), Options, default),
	cookie(ClientId, Parts, Cookie),
	format(Out, 'Cookie: ~s\r\n', [Cookie]).

%%	cookie(+ClientId, +Parts, -Cookie) is semidet.
%
%	Cookie is the cookie for Parts for the given ClientId

cookie(ClientId, Parts, Cookie) :-
	request_host(Parts, Host),
	request_path(Parts, Path),
	findall(N=V, current_cookie(ClientId, Host, Path, N, V), Cookies),
	Cookies \== [], !,
	debug(http(cookie), 'Cookies for ~w at ~w~w: ~p',
	      [ClientId, Host, Path, Cookies]),
	cookie_value(Cookies, Cookie).

request_host(Parts, Host) :-
	memberchk(host(Host), Parts).

request_path(Parts, Path) :-
	(   memberchk(path(Path), Parts)
	->  true
	;   Path = (/)
	).

%%	cookie_value(+NameValueList, -CookieString) is det.
%
%	Create a cookie value string with name=value, seperated by ";".

cookie_value(List, Cookie) :-
	with_output_to(string(Cookie),
		       write_cookies(List)).

write_cookies([]).
write_cookies([Name=Value|T]) :-
	format('~w=~w', [Name, Value]),
	(   T == []
	->  true
	;   format('; ', []),
	    write_cookies(T)
	).

%%	http:update_cookies(+CookieData, +Parts, +Options) is semidet.
%
%	Update the client  cookie  database.

http:update_cookies(CookieData, Parts, Options) :-
	http_parse_header_value(set_cookie, CookieData,
				set_cookie(Name, Value, COptions)), !,
	option(client(ClientId), Options, default),
	request_host(Parts, Host),
	request_path(Parts, Path),
	with_mutex(http_cookie,
		   update_cookie(ClientId, Host, Path, Name, Value, COptions)).

update_cookie(ClientId, Host, Path, Name, Value, Options) :-
	downcase_atom(Name, CName),
	remove_cookies(ClientId, Host, Path, CName, Options),
	debug(http(cookie), 'New for ~w: ~w=~p', [ClientId, Name, Value]),
	assert(client_cookie(ClientId, CName, Name, Value, [host=Host|Options])).

%%	remove_cookies(+ClientId, +Host, +Path, +Name, +SetOptions) is det.
%
%	Remove all cookies that conflict with the new set-cookie
%	command.

remove_cookies(ClientId, Host, Path, CName, SetOptions) :-
	(   client_cookie(ClientId, CName, Name, Value, OldOptions),
	    cookie_match_host(Host, SetOptions, OldOptions),
	    cookie_match_path(Path, SetOptions, OldOptions),
	    debug(cookie, 'Del for ~w: ~w=~p', [ClientId, Name, Value]),
	    retract(client_cookie(ClientId, CName, Name, Value, OldOptions)),
	    fail
	;   true
	).

cookie_match_host(Host, SetOptions, OldOptions) :-
	(   memberchk(domain=Domain, SetOptions)
	->  cookie_match_host(Domain, OldOptions)
	;   cookie_match_host(Host, OldOptions)
	).

cookie_match_path(Path, SetOptions, OldOptions) :-
	(   memberchk(path=PathO, SetOptions)
	->  cookie_match_path(PathO, OldOptions)
	;   cookie_match_path(Path, OldOptions)
	).

%%	current_cookie(+ClientId, +Host, +Path, -Name, -Value) is nondet.
%
%	Find cookies that match the given request.

current_cookie(ClientId, Host, Path, Name, Value) :-
	client_cookie(ClientId, _CName, Name, Value, Options),
	cookie_match_host(Host, Options),
	cookie_match_path(Path, Options),
	cookie_match_expire(Options).

cookie_match_host(Host, Options) :-
	(   memberchk(domain=Domain, Options)
	->  downcase_atom(Host, LHost),
	    downcase_atom(Domain, LDomain),
	    sub_atom(LHost, _, _, 0, LDomain) 	% TBD: check '.'?
	;   memberchk(host=CHost, Options),
	    downcase_atom(Host, LHost),
	    downcase_atom(CHost, LHost)
	).

cookie_match_path(Path, Options) :-
	(   memberchk(path=Root, Options)
	->  sub_atom(Path, 0, _, _, Root)	% TBD: check '/'?
	;   true
	).

cookie_match_expire(Options) :-
	(   memberchk(expire=Expire, Options)
	->  get_time(Now),
	    Now =< Expire
	;   true
	).

%%	cookie_remove_client(+ClientId) is det.
%
%	Fake user quitting a browser.   Removes all cookies that do
%	not have an expire date.

cookie_remove_client(ClientId) :-
	var(ClientId), !,
	throw(error(instantiation_error, _)).
cookie_remove_client(ClientId) :-
	(   client_cookie(ClientId, CName, Name, Value, Options),
	    \+ memberchk(expire=_, Options),
	    retract(client_cookie(ClientId, CName, Name, Value, Options)),
	    fail
	;   true
	).

%%	cookie_remove_all_clients is det.
%
%	Simply logout all clients.  See http_remove_client/1.

cookie_remove_all_clients :-
	forall(current_client(ClientId),
	       cookie_remove_client(ClientId)).

%%	current_client(?ClientId) is nondet.
%
%	True if ClientId is the identifier of a client.

current_client(ClientId) :-
	client_cookie(ClientId, _CName, _Name, _Value, _Options).

%%	http_current_cookie(?ClientId, ?Name, ?Value, ?Options) is nondet.
%
%	Query current cookie database. If Name   is given, it is matched
%	case insensitive against the known cookies.   If  it is unbound,
%	the  cookie  name  is  returned  in    its  oiginal  case  (case
%	preserving).

cookie_current_cookie(ClientId, Name, Value, Options) :-
	nonvar(Name), !,
	downcase_atom(Name, CName),
	client_cookie(ClientId, CName, Name, Value, Options).
cookie_current_cookie(ClientId, Name, Value, Options) :-
	client_cookie(ClientId, _CName, Name, Value, Options).
