http_parameters.pl

/*  $Id$

    Part of SWI-Prolog

    Author:        Jan Wielemaker
    E-mail:        J.Wielemaker@cs.vu.nl
    WWW:           http://www.swi-prolog.org
    Copyright (C): 2004-2009, 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., 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_parameters,
	  [ http_parameters/2,		% +Request, -Params
	    http_parameters/3,		% +Request, -Params, +TypeG
	    http_convert_parameter/4	% +Options, +FieldName, +ValIn, -ValOut
	  ]).
:- use_module(http_client).
:- use_module(http_mime_plugin).
:- use_module(http_hook).
:- use_module(library(debug)).
:- use_module(library(option)).
:- use_module(library(lists)).
:- use_module(library(error)).

:- predicate_options(http_parameters/3, 3,
		     [ form_data(-list),
		       attribute_declarations(callable)
		     ]).

/** <module> Extract parameters (GET and POST) from HTTP requests
@ingroup http

This module is used to extract the value  of GET or POST parameters from
an HTTP request. The typical usage is e.g.,

    ==
    :- http_handler('/register_user', register_user, []).

    register_user(Request) :-
	http_parameters(Request,
			[ name(Name, []),
			  sex(Sex, [oneof([male,female])]),
			  birth_year(BY, [between(1850,10000)])
			]),
	register_user(Name, Sex, BY),
	html_reply_page(title('New user added'),
			...).
    ==

@see http_dispatch.pl dispatches requests to predicates.
*/

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

%%	http_parameters(+Request, ?Parms) is det.
%%	http_parameters(+Request, ?Parms, :Options) is det.
%
%	Get HTTP GET  or  POST   form-data,  applying  type  validation,
%	default values, etc.  Provided options are:
%
%		* attribute_declarations(:Goal)
%		Causes the declarations for an attributed named A to be
%		fetched using call(Goal, A, Declarations).
%
%		* form_data(-Data)
%		Return the data read from the GET por POST request as a
%		list Name = Value.  All data, including name/value pairs
%		used for Parms, is unified with Data.
%
%	The attribute_declarations hook allows   sharing the declaration
%	of attribute-properties between many http_parameters/3 calls. In
%	this form, the requested attribute takes   only one argument and
%	the options are acquired by calling the hook. For example:
%
%	    ==
%		...,
%		http_parameters(Request,
%				[ sex(Sex)
%				],
%				[ attribute_declarations(http_param)
%				]),
%		...
%
%	    http_param(sex, [ oneof(male, female),
%			      description('Sex of the person')
%			    ]).
%	    ==

http_parameters(Request, Params) :-
	http_parameters(Request, Params, []).

http_parameters(Request, Params, Options) :-
	must_be(list, Params),
	meta_options(is_meta, Options, QOptions),
	option(attribute_declarations(DeclGoal), QOptions, -),
	http_parms(Request, Params, DeclGoal, Form),
	(   memberchk(form_data(RForm), QOptions)
	->  RForm = Form
	;   true
	).

is_meta(attribute_declarations).


http_parms(Request, Params, DeclGoal, Data) :-
	memberchk(method(post), Request),
	memberchk(content_type(Content), Request),
	form_data_content_type(Content), !,
	debug(post_request, 'POST Request: ~p', [Request]),
	http_read_data(Request, Data, []),
	debug(post, 'POST Data: ~p', [Data]),
	fill_parameters(Params, Data, DeclGoal).
http_parms(Request, Params, DeclGoal, Search) :-
	(   memberchk(search(Search), Request)
	->  true
	;   Search = []
	),
	fill_parameters(Params, Search, DeclGoal).

:- multifile
	form_data_content_type/1.

form_data_content_type('application/x-www-form-urlencoded') :- !.
form_data_content_type(ContentType) :-
	sub_atom(ContentType, 0, _, _, 'application/x-www-form-urlencoded;').

%%	fill_parameters(+ParamDecls, +FormData, +DeclGoal)
%
%	Fill values from the parameter list

fill_parameters([], _, _).
fill_parameters([H|T], FormData, DeclGoal) :-
	fill_parameter(H, FormData, DeclGoal),
	fill_parameters(T, FormData, DeclGoal).

fill_parameter(H, _, _) :-
	var(H), !,
	instantiation_error(H).
fill_parameter(group(Members, _Options), FormData, DeclGoal) :-
	is_list(Members), !,
	fill_parameters(Members, FormData, DeclGoal).
fill_parameter(H, FormData, _) :-
	H =.. [Name,Value,Options], !,
	fill_param(Name, Value, Options, FormData).
fill_parameter(H, FormData, DeclGoal) :-
	H =.. [Name,Value],
	(   DeclGoal \== (-),
	    call(DeclGoal, Name, Options)
	->  true
	;   throw(error(existence_error(attribute_declaration, Name), _))
	),
	fill_param(Name, Value, Options, FormData).

fill_param(Name, Values, Options, FormData) :-
	memberchk(zero_or_more, Options), !,
	fill_param_list(FormData, Name, Values, Options).
fill_param(Name, Values, Options, FormData) :-
	memberchk(list(Type), Options), !,
	fill_param_list(FormData, Name, Values, [Type|Options]).
fill_param(Name, Value, Options, FormData) :-
	(   memberchk(Name=Value0, FormData),
	    Value0 \== ''		% Not sure
	->  http_convert_parameter(Options, Name, Value0, Value)
	;   memberchk(default(Value), Options)
	->  true
	;   memberchk(optional(true), Options)
	->  true
	;   throw(error(existence_error(form_data, Name), _))
	).


fill_param_list([], _, [], _).
fill_param_list([Name=Value0|Form], Name, [Value|VT], Options) :- !,
	http_convert_parameter(Options, Name, Value0, Value),
	fill_param_list(Form, Name, VT, Options).
fill_param_list([_|Form], Name, VT, Options) :-
	fill_param_list(Form, Name, VT, Options).


%%	http_convert_parameter(+Options, +FieldName, +ValueIn, -ValueOut) is det.
%
%	Conversion of an HTTP form value. First tries the multifile hook
%	http:convert_parameter/3 and next the built-in checks.
%
%	@param Option		List as provided with the parameter
%	@param FieldName	Name of the HTTP field (for better message)
%	@param ValueIn		Atom value as received from HTTP layer
%	@param ValueOut		Possibly converted final value
%	@error type_error(Type, Value)

http_convert_parameter([], _, Value, Value).
http_convert_parameter([H|T], Field, Value0, Value) :-
	(   check_type_no_error(H, Value0, Value1)
	->  http_convert_parameter(T, Field, Value1, Value)
	;   format(string(Msg), 'HTTP parameter ~w', [Field]),
	    throw(error(type_error(H, Value0),
			context(_, Msg)))
	).

check_type_no_error(Type, In, Out) :-
	http:convert_parameter(Type, In, Out), !.
check_type_no_error(Type, In, Out) :-
	check_type3(Type, In, Out).

%%	check_type3(+Type, +ValueIn, -ValueOut) is semidet.
%
%	HTTP parameter type-check for types that need converting.

check_type3((T1;T2), In, Out) :- !,
	(   check_type_no_error(T1, In, Out)
	->  true
	;   check_type_no_error(T2, In, Out)
	).
check_type3(number, Atom, Number) :- !,
	to_number(Atom, Number).
check_type3(integer, Atom, Integer) :- !,
	to_number(Atom, Integer),
	integer(Integer).
check_type3(nonneg, Atom, Integer) :- !,
	to_number(Atom, Integer),
	integer(Integer),
	Integer >= 0.
check_type3(float, Atom, Float) :- !,
	to_number(Atom, Number),
	Float is float(Number).
check_type3(between(Low, High), Atom, Value) :- !,
	to_number(Atom, Number),
	(   (float(Low) ; float(High))
	->  Value is float(Number)
	;   Value = Number
	),
	must_be(between(Low, High), Value).
check_type3(boolean, Atom, Bool) :- !,
	truth(Atom, Bool).
check_type3(Type, Atom, Atom) :-
	check_type2(Type, Atom).

to_number(In, Number) :-
	number(In), !, Number = In.
to_number(In, Number) :-
	atom(In),
	catch(atom_number(In, Number), _, fail).

%%	check_type2(+Type, +ValueIn) is semidet.
%
%	HTTP parameter type-check for types that need no conversion.

check_type2(oneof(Set), Value) :- !,
	memberchk(Value, Set).
check_type2(length > N, Value) :- !,
	atom_length(Value, Len),
	Len > N.
check_type2(length >= N, Value) :- !,
	atom_length(Value, Len),
	Len >= N.
check_type2(length < N, Value) :- !,
	atom_length(Value, Len),
	Len < N.
check_type2(length =< N, Value) :- !,
	atom_length(Value, Len),
	Len =< N.
check_type2(_, _).

%%	truth(+In, -Boolean) is semidet.
%
%	Translate some commonly used textual   representations  for true
%	and false into their canonical representation.

truth(true,    true).
truth('TRUE',  true).
truth(yes,     true).
truth('YES',   true).
truth(on,      true).
truth('ON',    true).			% IE7
truth('1',     true).

truth(false,   false).
truth('FALSE', false).
truth(no,      false).
truth('NO',    false).
truth(off,     false).
truth('OFF',   false).
truth('0',     false).


		 /*******************************
		 *	   XREF SUPPORT		*
		 *******************************/

:- multifile
	prolog:called_by/2,
	emacs_prolog_colours:goal_colours/2.

prolog:called_by(http_parameters(_,_,Options), [G+2]) :-
	option(attribute_declarations(G), Options, _),
	callable(G), !.

emacs_prolog_colours:goal_colours(http_parameters(_,_,Options),
				  built_in-[classify, classify, Colours]) :-
	option_list_colours(Options, Colours).

option_list_colours(Var, error) :-
	var(Var), !.
option_list_colours([], classify) :- !.
option_list_colours(Term, list-Elements) :-
	Term = [_|_], !,
	option_list_colours_2(Term, Elements).
option_list_colours(_, error).

option_list_colours_2(Var, classify) :-
	var(Var).
option_list_colours_2([], []).
option_list_colours_2([H0|T0], [H|T]) :-
	option_colours(H0, H),
	option_list_colours_2(T0, T).

option_colours(Var,  classify) :-
	var(Var), !.
option_colours(_=_,  built_in-[classify,classify]) :- !.
option_colours(attribute_declarations(_),		% DCG = is a hack!
	       option(attribute_declarations)-[dcg]) :- !.
option_colours(Term, option(Name)-[classify]) :-
	compound(Term),
	Term =.. [Name,_Value], !.
option_colours(_, error).