/*  $Id: pce_expansion.pl,v 1.45 2006/08/04 14:24:01 jan Exp $

    Part of XPCE --- The SWI-Prolog GUI toolkit

    Author:        Jan Wielemaker and Anjo Anjewierden
    E-mail:        jan@swi.psy.uva.nl
    WWW:           http://www.swi.psy.uva.nl/projects/xpce/
    Copyright (C): 1985-2002, 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(pce_expansion,
	[ pce_term_expansion/2,		% +In, -Out
	  pce_compiling/1,		% -ClassName
	  pce_compiling/2,		% -ClassName, -Path
	  pce_begin_recording/1,	% +- source|documentation
	  pce_end_recording/0
	]).
:- use_module(pce_boot(pce_principal)).
:- require([ pce_error/1
	   , pce_info/1
	   , pce_warn/1
	   , string/1
	   , concat_atom/2
	   , expand_goal/2
	   , flatten/2
	   , forall/2
	   , reverse/2
	   , source_location/2
	   , string_to_list/2
	   , append/3
	   , atom_concat/3
	   , between/3
	   , genarg/3
	   , maplist/3
	   , sub_atom/5
	   , push_operators/1
	   , pop_operators/0
	   ]).

:- dynamic
	compiling/2,			% -ClassName
	attribute/3,			% ClassName, Attribute, Value
	verbose/0,
	recording/2.			% items recorded

pce_ifhostproperty(prolog(swi), (:- index(attribute(1,1,0)))).

		 /*******************************
		 *	     OPERATORS		*
		 *******************************/

%	push_compile_operators.
%	
%	Push operator definitions  that  are   specific  to  XPCE  class
%	definitions.

:- module_transparent
	push_compile_operators/0.

push_compile_operators :-
	context_module(M),
	push_compile_operators(M).

push_compile_operators(M) :-
	push_operators(M:
		[ op(1200, xfx, :->)
		, op(1200, xfx, :<-)
		, op(910,  xfy, ::)	% above \+
		, op(100,  xf,  *)
		, op(125,  xf,  ?)
		, op(150,  xf,  ...)
		, op(100,  xfx, ..)
		]).

pop_compile_operators :-
	pop_operators.

:- op(100, fx, @).			% standard XPCE operators
:- op(150, yfx, ?).
:- op(990, xfx, :=).
:- push_compile_operators.

%verbose.

pce_term_expansion(In, Out) :-
	pce_pre_expand(In, In0),
	(   list(In0)
	->  maplist(map_term_expand, In0, In1),
	    flatten(In1, Out0),
	    (	Out0 = [X]
	    ->	Out = X
	    ;	Out = Out0
	    )
	;   do_term_expand(In0, Out)
	).

list([]).
list([_|_]).

map_term_expand(X, X) :-
	var(X), !.
map_term_expand(X, Y) :-
	do_term_expand(X, Y), !.
map_term_expand(X, X).


do_term_expand(In0, Out) :-
	pce_expandable(In0),
	(   do_expand(In0, Out0)
	->  (   pce_post_expand(Out0, Out)
	    ->	true
	    ;	Out = Out0
	    )
	;   pce_error(expand_failed(In0)),
	    Out = []
	), !.
do_term_expand((Head :- Body), _) :-	% check for :- instead of :-> or :<-
	pce_compiling,
	(   Body = ::(Doc, _Body),	% TBD
	    is_string(Doc)
	;   typed_head(Head)
	),
	pce_error(context_error((Head :- Body), nomethod, clause)),
	fail.

	
is_string(0) :- !, fail.		% catch variables
is_string([]).
is_string([H|T]) :-
	integer(H),
	between(0, 255, H),
	is_string(T).

typed_head(T) :-
	functor(T, _, Arity),
	Arity > 1,
	forall(genarg(N, T, A), head_arg(N, A)).

head_arg(1, A) :- !,
	var(A).
head_arg(_, A) :-
	nonvar(A),
	(   A = (_:TP)
	->  true
	;   A = (_:Name=TP),
	    atom(Name)
	),
	ground(TP).

%%	pce_pre_expand(+In, -Out)
%
%	First step of the XPCE class compiler, calling the supported
%	hook pce_pre_expansion_hook/2.

:- multifile user:pce_pre_expansion_hook/2.
:- dynamic user:pce_pre_expansion_hook/2.
:- multifile user:pce_post_expansion_hook/2.
:- dynamic user:pce_post_expansion_hook/2.

pce_pre_expand(X, Y) :-
	user:pce_pre_expansion_hook(X, X1), !,
	(   list(X1)
	->  maplist(do_pce_pre_expand, X1, Y)
	;   do_pce_pre_expand(X1, Y)
	).
pce_pre_expand(X, Y) :-
	do_pce_pre_expand(X, Y).

do_pce_pre_expand((:- pce_begin_class(Class, Super)),
		  (:- pce_begin_class(Class, Super, @default))).
do_pce_pre_expand(variable(Name, Type, Access),
		  variable(Name, Type, Access, @default)) :-
	pce_compiling.
do_pce_pre_expand(class_variable(Name, Type, Default),
		  class_variable(Name, Type, Default, @default)) :-
	pce_compiling.
do_pce_pre_expand(handle(X, Y, Kind),
		  handle(X, Y, Kind, @default)) :-
	pce_compiling.
do_pce_pre_expand((:- ClassDirective), D) :-
	functor(ClassDirective, send, _),
	arg(1, ClassDirective, @class), !,
	D = (:- pce_class_directive(ClassDirective)).
do_pce_pre_expand(pce_ifhostproperty(Prop, Clause), TheClause) :-
	(   pce_host:property(Prop)
	->  TheClause = Clause
	;   TheClause = []
	).
do_pce_pre_expand(pce_ifhostproperty(Prop, If, Else), Clause) :-
	(   pce_host:property(Prop)
	->  Clause = If
	;   Clause = Else
	).
do_pce_pre_expand(X, X).


%%	pce_post_expand(In, Out)

pce_post_expand([], []).
pce_post_expand([H0|T0], [H|T]) :-
	user:pce_post_expansion_hook(H0, H), !,
	pce_post_expand(T0, T).
pce_post_expand([H|T0], [H|T]) :-
	pce_post_expand(T0, T).
pce_post_expand(T0, T) :-
	user:pce_post_expansion_hook(T0, T), !.
pce_post_expand(T, T).


%%	pce_expandable(+Term)
%	Quick test whether we can expand this.

pce_expandable((:- pce_begin_class(_Class, _Super, _Doc))).
pce_expandable((:- pce_extend_class(_Class))).
pce_expandable((:- pce_end_class)).
pce_expandable((:- pce_end_class(_))).
pce_expandable((:- use_class_template(_TemplateClass))).
pce_expandable((:- pce_group(_))).
pce_expandable((:- pce_class_directive(_))).
pce_expandable(variable(_Name, _Type, _Access, _Doc)) :-
	pce_compiling.
pce_expandable(class_variable(_Name, _Type, _Default, _Doc)) :-
	pce_compiling.
pce_expandable(delegate_to(_VarName)) :-
	pce_compiling.
pce_expandable(handle(_X, _Y, _Kind, _Name)) :-
	pce_compiling.
pce_expandable((_Head :-> _Body)).
pce_expandable((_Head :<- _Body)).


%%	do_expand(In, Out)
%
%	The XPCE kernel expansion.

do_expand((:- pce_begin_class(Spec, Super, Doc)),
	  (:- pce_begin_class_definition(ClassName, MetaClass, Super, Doc))) :-
	break_class_specification(Spec, ClassName, MetaClass, TermArgs),
	can_define_class(ClassName, Super),
	push_class(ClassName),
	set_attribute(ClassName, super, Super),
	set_attribute(ClassName, meta, MetaClass),
	class_summary(ClassName, Doc),
	class_source(ClassName),
	term_names(ClassName, TermArgs).
do_expand((:- pce_extend_class(ClassName)), []) :-
	push_class(ClassName),
	set_attribute(ClassName, extending, true).
do_expand((:- pce_end_class(Class)), Expansion) :-
	(   pce_compiling(ClassName),
	    (   Class == ClassName
	    ->  do_expand((:- pce_end_class), Expansion)
	    ;   pce_error(end_class_mismatch(Class, ClassName))
	    )
	;   pce_error(no_class_to_end)
	).
do_expand((:- pce_end_class),
	  [ pce_principal:pce_class(ClassName, MetaClass, Super,
				    Variables,
				    Resources,
				    Directs),
	    RegisterDecl
	  ]) :-
	pce_compiling(ClassName), !,
	findall(V, retract(attribute(ClassName, variable, V)),  Variables),
	findall(R, retract(attribute(ClassName, classvar, R)),  Resources),
	findall(D, retract(attribute(ClassName, directive, D)), Directs),
	(   attribute(ClassName, extending, true)
	->  MetaClass = '-',
	    Super = '-',
	    expand_term((:- initialization(pce_extended_class(ClassName))),
			RegisterDecl)
	;   retract(attribute(ClassName, super, Super)),
	    retract(attribute(ClassName, meta, MetaClass)),
	    expand_term((:- initialization(pce_register_class(ClassName))),
			RegisterDecl)
	),
	pop_class.
do_expand((:- pce_end_class), []) :-
	pce_error(no_class_to_end).
do_expand((:- use_class_template(Template)), []) :-
	used_class_template(Template), !.
do_expand((:- use_class_template(Template)),
	  [ pce_principal:pce_uses_template(ClassName, Template)
	  | LinkClauses
	  ]) :-
	pce_compiling(ClassName),
	use_template_class_attributes(Template),
	use_template_send_methods(Template, SendClauses),
	use_template_get_methods(Template, GetClauses),
	append(SendClauses, GetClauses, LinkClauses).
do_expand((:- pce_group(Group)), []) :-
	pce_compiling(ClassName),
	set_attribute(ClassName, group, Group).
do_expand(variable(Name, Type, Access, Doc), []) :-
	pce_compiling(ClassName),
	current_group(ClassName, Group),
	pce_access(Access),
	var_type(Type, PceType, Initial),
	pce_summary(Doc, PceDoc),
	strip_defaults([Initial, Group, PceDoc], Defs),
	Var =.. [variable, Name, PceType, Access | Defs],
	add_attribute(ClassName, variable, Var).
do_expand(class_variable(Name, Type, Default, Doc), []) :-
	pce_compiling(ClassName),
	prolog_load_context(module, M),
	pce_type(Type, PceType),
	pce_summary(Doc, PceDoc),
	add_attribute(ClassName, classvar,
		      M:class_variable(Name, Default, PceType, PceDoc)).
do_expand(handle(X, Y, Kind, Name), []) :-
	pce_compiling(ClassName),
	add_attribute(ClassName, directive,
		      send(@class, handle, handle(X, Y, Kind, Name))).
do_expand(delegate_to(Var), []) :-
	pce_compiling(ClassName),
	add_attribute(ClassName, directive,
		      send(@class, delegate, Var)).
do_expand((:- pce_class_directive(Goal)),
	  (:- initialization((send(@class, assign, Class),
			      Goal)))) :-
	pce_compiling(ClassName),
	realised_class(ClassName),
	attribute(ClassName, extending, true), !,
	get(@classes, member, ClassName, Class).
do_expand((:- pce_class_directive(Goal)), (:- Goal)) :-
	pce_compiling(ClassName),
	realised_class(ClassName), !.
do_expand((:- pce_class_directive(Goal)), []) :-
	pce_compiling(ClassName),
	prolog_load_context(module, M),
	add_attribute(ClassName, directive, M:Goal).
do_expand(:->(Head, DocBody),
	  [ pce_principal:pce_lazy_send_method(Selector, ClassName, LSM)
	  | Clauses
	  ]) :-
	extract_documentation(DocBody, Doc, Body),
	source_location_term(Loc),
	pce_compiling(ClassName),
	current_group(ClassName, Group),
	prolog_head(send, Id, Head, Selector, Types, PlHead),
	strip_defaults([Group, Loc, Doc], NonDefArgs),
	LSM =.. [bind_send, Id, Types | NonDefArgs],
	Clause = (PlHead :- Body),
	gen_method_id((->), ClassName, Selector, Id),
	(   attribute(ClassName, super, template)
	->  template_clause(Clause, Clauses)
	;   Clauses = [Clause]
	),
	(   realised_class(ClassName)	% force a reload (TBD: move to realise)
	->  send(@class, delete_send_method, Selector)
	;   true
	),
	feedback(expand_send(ClassName, Selector)).
do_expand(:<-(Head, DocBody),
	  [ pce_principal:pce_lazy_get_method(Selector, ClassName, LGM)
	  | Clauses
	  ]) :-
	extract_documentation(DocBody, Doc, Body),
	source_location_term(Loc),
	pce_compiling(ClassName),
	current_group(ClassName, Group),
	return_type(Head, RType),
	prolog_head(get, Id, Head, Selector, Types, PlHead),
	strip_defaults([Group, Loc, Doc], NonDefArgs),
	LGM =.. [bind_get, Id, RType, Types | NonDefArgs],
	Clause = (PlHead :- Body),
	gen_method_id((<-), ClassName, Selector, Id),
	(   attribute(ClassName, super, template)
	->  template_clause(Clause, Clauses)
	;   Clauses = [Clause]
	),
	(   realised_class(ClassName)	% force a reload
	->  send(@class, delete_get_method, Selector)
	;   true
	),
	feedback(expand_get(ClassName, Selector)).

strip_defaults([@default|T0], T) :- !,
	strip_defaults(T0, T).
strip_defaults(L, LV) :-
	reverse(L, LV).

break_class_specification(Meta:Term, ClassName, Meta, TermArgs) :- !,
	Term =.. [ClassName|TermArgs].
break_class_specification(Term, ClassName, @default, TermArgs) :-
	Term =.. [ClassName|TermArgs].

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
gen_method_id(+SendGet, +Class, +Selector, -Identifier)

Generate a unique identifier for the method,  used as the first argument
of send_implementation/3 or get_implementation/4.  The identifier should
be an atom or integer. The  value  is   not  relevant,  as long as it is
unique.

This  suggests  simple  counting:  always    unique   and  integers  are
considerably cheaper than atoms. Unfortunately, there  is a problem with
this. If methods appear in pre-compiled files, they cannot be joined. It
is hard to see a good and workable  solution to this problem. Grant each
file a domain? How do we associate a unique domain to each file?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

gen_method_id(SG, Class, Selector, Id) :-
	attribute(Class, extending, true), !,
	concat_atom([Class, '$+$', SG, Selector], Id).
gen_method_id(SG, Class, Selector, Id) :-
	concat_atom([Class, SG, Selector], Id).

%gen_method_id(_, _, _, Id) :-
%%	flag(pce_method_id, Id, Id+1).

		 /*******************************
		 *       TEMPLATE SUPPORT	*
		 *******************************/

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
When compiling a template, calls to   send_class/3 and get_class/4 refer
to the template  classes.  This  is   not  correct.  Therefore,  we will
translate  the  method  implementation   into    a   parameterized  real
implementation and a normal implementation  that calls the parameterized
one. On method instantiation, we create additional clauses for the class
to which we attach the method.

Importing the template (pce_use_class_template/1):

	+ Put binding in bind_lazy by searching the templates.
	+ Expand the directive itself into the wrapper-implementations.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

template_clause((M:send_implementation(Id, Msg, R) :- Body),
		[ (M:send_implementation(Tid, ClassMsg, R) :- ClassBody),
		  (M:(send_implementation(Id, Msg, R) :-
		  	send_implementation(Tid, IClassMsg, R)))
		]) :- !,
	atom_concat('T-', Id, Tid),
	Msg =.. Args,
	append(Args, [Class], Args2),
	ClassMsg =.. Args2,
	append(Args, [template], Args3),
	IClassMsg =.. Args3,
	template_body(Body, template, Class, ClassBody).
template_clause((M:get_implementation(Id, Msg, R, V) :- Body),
		[ (M:get_implementation(Tid, ClassMsg, R, V) :- ClassBody),
		  (M:(get_implementation(Id, Msg, R, V) :-
		  	get_implementation(Tid, IClassMsg, R, V)))
		]) :- !,
	atom_concat('T-', Id, Tid),
	Msg =.. Args,
	append(Args, [Class], Args2),
	ClassMsg =.. Args2,
	append(Args, [template], Args3),
	IClassMsg =.. Args3,
	template_body(Body, template, Class, ClassBody).
template_clause(Clause, Clause).

template_body(G0, T, C, G) :-
	compound(G0),
	functor(G0, Name, Arity),
	functor(M, Name, Arity),
	meta(M), !,
	functor(G, Name, Arity),
	convert_meta(0, Arity, G0, M, T, C, G).
template_body(G, T, C, send_class(R, C, Msg)) :-
	expand_goal(G, send_class(R, T, Msg)), !.
template_body(G, T, C, get_class(R, C, Msg, V)) :-
	expand_goal(G, get_class(R, T, Msg, V)), !.
template_body(G, _, _, G).

convert_meta(A, A, _, _, _, _, _) :- !.
convert_meta(I, Arity, G0, M, T, C, G) :-
	A is I + 1,
	arg(A, M, :), !,
	arg(A, G0, GA0),
	arg(A, G,  GA),
	template_body(GA0, T, C, GA),
	convert_meta(A, Arity, G0, M, T, C, G).
convert_meta(I, Arity, G0, M, T, C, G) :-
	A is I + 1,
	arg(A, G0, GA),
	arg(A, G,  GA),
	convert_meta(A, Arity, G0, M, T, C, G).

meta(','(:, :)).			% TBD: synchronise with boot/init.pl
meta(;(:, :)).	
meta(->(:, :)).	
meta(*->(:, :)).	
meta(\+(:)).	
meta(not(:)).	
meta(call(:)).
meta(once(:)).
meta(ignore(:)).
meta(forall(:, :)).	
meta(findall(-, :, -)).
meta(bagof(-, :, -)).
meta(setof(-, :, -)).
meta(^(-,:)).

%%	use_template_class_attributes(+Template)
%
%	Insert variables, class-variables and directives as if they appeared
%	in the current class definition.

use_template_class_attributes(Template) :-
	pce_class(Template, _, template, Variables, ClassVars, Directs),
	assert_attributes(Variables, variable),
	assert_attributes(ClassVars, classvar),
	assert_attributes(Directs,   directive).

assert_attributes([], _).
assert_attributes([H|T], Att) :-
	pce_compiling(ClassName),
	(   H = send(@class, source, _Source)
	->  true
	;   add_attribute(ClassName, Att, H)
	),
	assert_attributes(T, Att).

use_template_send_methods(Template, Clauses) :-
	findall(C, use_template_send_method(Template, C), Clauses).

use_template_send_method(Template, pce_principal:Clause) :-
	pce_compiling(ClassName),
	pce_lazy_send_method(Sel, Template, Binder),
	Binder =.. [Functor, Id | RestBinder],
	gen_method_id('$T$->', ClassName, Sel, NewId),
	(   Clause = pce_lazy_send_method(Sel, ClassName, NewBinder),
	    NewBinder =.. [Functor, NewId | RestBinder]
	;   Clause = (send_implementation(NewId, Msg, R) :-
		     	send_implementation(Tid, IClassMsg, R)),
	    attribute(ClassName, super, SuperClass), % TBD: pce_extend_class/1
	    arg(2, Binder, Types),
	    type_arity(Types, Arity),
	    functor(Msg, Sel, Arity),
	    Msg =.. Args,
	    append(Args, [SuperClass], Args1),
	    IClassMsg =.. Args1,
	    atom_concat('T-', Id, Tid)
	).
	  
use_template_get_methods(Template, Clauses) :-
	findall(C, use_template_get_method(Template, C), Clauses).

use_template_get_method(Template, pce_principal:Clause) :-
	pce_compiling(ClassName),
	pce_lazy_get_method(Sel, Template, Binder),
	Binder =.. [Functor, Id | RestBinder],
	gen_method_id('$T$<-', ClassName, Sel, NewId),
	(   Clause = pce_lazy_get_method(Sel, ClassName, NewBinder),
	    NewBinder =.. [Functor, NewId | RestBinder]
	;   Clause = (get_implementation(NewId, Msg, R, V) :-
		     	get_implementation(Tid, IClassMsg, R, V)),
	    attribute(ClassName, super, SuperClass), % TBD: pce_extend_class/1
	    arg(3, Binder, Types),
	    type_arity(Types, Arity),
	    functor(Msg, Sel, Arity),
	    Msg =.. Args,
	    append(Args, [SuperClass], Args1),
	    IClassMsg =.. Args1,
	    atom_concat('T-', Id, Tid)
	).

type_arity(@default, 0) :- !.
type_arity(Atom, 1) :-
	atom(Atom), !.
type_arity(Vector, A) :-
	functor(Vector, _, A).

%%	used_class_template(+Template)
%
%	Succeeds if any of my (Prolog-defined) super classes
%	has imported the named template.

used_class_template(Template) :-
	pce_compiling(Class),
	isa_prolog_class(Class, Super),
	Super \== Class,
	pce_uses_template(Super, Template), !.

isa_prolog_class(Class, Class).
isa_prolog_class(Class, Super) :-
	attribute(Class, super, Super0), !,	% Prolog class being loaded
	isa_prolog_class(Super0, Super).
isa_prolog_class(Class, Super) :-		% Loaded Prolog class
	pce_class(Class, _, Super0, _, _, _), !,
	isa_prolog_class(Super0, Super).


		 /*******************************
		 *	      CHECKING		*
		 *******************************/

%%	can_define_class(+Name, +Super)
%	
%	Check whether we can define Name as   a  subclass of Super. This
%	cannot be done of Name  is  a   builtin  class  or it is already
%	defined at another location.

can_define_class(Name, _Super) :-
	get(@classes, member, Name, Class),
	get(Class, creator, built_in), !,
	throw(error(permission_error(modify, pce(built_in_class), Name), _)).
can_define_class(Name, _Super) :-
	flag('$compilation_level', Level, Level),
	Level > 0,			% SWI: we are running consult
	pce_class(Name, _Meta, _OldSuper, _Vars, _ClassVars, _Dirs),
	throw(error(permission_error(modify, pce(class), Name), _)).
can_define_class(Name, _Super) :-
	get(@types, member, Name, Type),
	\+ get(Type, kind, class),
	throw(error(permission_error(define, pce(class), Name),
		    context(pce_begin_class/3,
			    'Already defined as a type'))).
can_define_class(_, _).


		 /*******************************
		 *   PUSH/POP CLASS STRUCTURE	*
		 *******************************/

%%	push_class(+ClassName)
%	Start compiling the argument class.

push_class(ClassName) :-
	compiling(ClassName, _), !,
	pce_error(recursive_loading_class(ClassName)),
	fail.
push_class(ClassName) :-
	prolog_load_context(module, M),
	push_compile_operators(M),
	(   source_location(Path, _Line)
	->  true
	;   Path = []
	),
	asserta(compiling(ClassName, Path)),
	(   realised_class(ClassName)
	->  get(@class, '_value', OldClassVal),
	    asserta(attribute(ClassName, old_class_val, OldClassVal)),
	    get(@classes, member, ClassName, Class),
	    send(@class, assign, Class, global)
	;   true
	).

%	pop_class
%	End class compilation.

pop_class :-
	retract(compiling(ClassName, _)), !,
	(   attribute(ClassName, old_class_val, OldClassVal)
	->  send(@class, assign, OldClassVal, global)
	;   true
	),
	retractall(attribute(ClassName, _, _)),
	pop_compile_operators.
pop_class :-
	pce_error(no_class_to_end),
	fail.
	
		 /*******************************
		 *	     ATTRIBUTES		*
		 *******************************/

set_attribute(Class, Name, Value) :-
	retractall(attribute(Class, Name, _)),
	asserta(attribute(Class, Name, Value)).

add_attribute(Class, Name, Value) :-
	assert(attribute(Class, Name, Value)).


		 /*******************************
		 *	  CONTEXT VALUES	*
		 *******************************/

source_location_term(source_location(File, Line)) :-
	pce_recording(source),
	source_location(File, Line), !.
source_location_term(@default).

current_group(Class, Group) :-
	attribute(Class, group, Group), !.
current_group(_, @default).

class_source(ClassName) :-
	pce_recording(source),
	source_location_term(Term),
	Term \== @default, !,
	add_attribute(ClassName, directive,
		      send(@class, source, Term)).
class_source(_).
	

		 /*******************************
		 *	     RECORDING		*
		 *******************************/

pce_begin_recording(+Topic) :-
	asserta(recording(Topic, true)).
pce_begin_recording(-Topic) :-
	asserta(recording(Topic, fail)).

pce_end_recording :-
	retract(recording(_, _)), !.

pce_recording(Topic) :-
	recording(Topic, X), !,
	X == true.
pce_recording(_).			% default recording all


		 /*******************************
		 *	  SUMMARY HANDLING	*
		 *******************************/

class_summary(ClassName, Summary) :-
	pce_summary(Summary, PceSummary),
	(   PceSummary \== @default
	->  add_attribute(ClassName, directive,
			  send(@class, summary, PceSummary))
	;   true
	).


pce_summary(@X, @X) :- !.
pce_summary(_, @default) :-
	\+ pce_recording(documentation), !.
pce_summary(Atomic, Atomic) :-
	atomic(Atomic), !.
pce_ifhostproperty(string, [
(pce_summary(String, String) :-
	string(String), !),
(pce_summary(List, String) :-
	string_to_list(String, List))]).
pce_summary(List, string(List)).


		 /*******************************
		 *	 TERM DESCRIPTION	*
		 *******************************/

term_names(_, []) :- !.
term_names(Class, Selectors) :-
	check_term_selectors(Selectors),
	VectorTerm =.. [vector|Selectors],
	add_attribute(Class, directive,
		      send(@class, term_names, new(VectorTerm))).


check_term_selectors([]).
check_term_selectors([H|T]) :-
	(   atom(H)
	->  true
	;   pce_error(bad_term_argument(H)),
	    fail
	),
	check_term_selectors(T).


		 /*******************************
		 *	       ACCESS		*
		 *******************************/

pce_access(both) :- !.
pce_access(get)  :- !.
pce_access(send) :- !.
pce_access(none) :- !.
pce_access(X) :-
	pce_error(invalid_access(X)),
	fail.


		 /*******************************
		 *	       TYPES		*
		 *******************************/

%%	pce_type(+Spec, -PceTypeName)
%	Convert type specification into legal PCE type-name

pce_type(Prolog, Pce) :-
	to_atom(Prolog, RawPce),
	canonise_type(RawPce, Pce).

canonise_type(T0, T0) :-
	sub_atom(T0, _, _, 0, ' ...'), !.
canonise_type(T0, T) :-
	atom_concat(T1, '...', T0), !,
	atom_concat(T1, ' ...', T).
canonise_type(T, T).

to_atom(Atom, Atom) :-
	atom(Atom), !.
to_atom(Term, Atom) :-
	ground(Term), !,
	phrase(pce_type_description(Term), Chars, []),
	atom_chars(Atom, Chars).
to_atom(Term, any) :-
	pce_error(type_error(to_atom(Term, any), 1, ground, Term)).

pce_type_description(Atom, Chars, Tail) :-
	atomic(Atom), !,
	name(Atom, C0),
	append(C0, Tail, Chars).
pce_type_description([X]) -->
	"[", pce_type_description(X), "]".
pce_type_description([X|Y]) -->
	"[", pce_type_description(X), "|", pce_type_description(Y), "]".
pce_type_description({}(Words)) -->
	"{", word_list(Words), "}".
pce_type_description(=(Name, Type)) -->
	pce_type_description(Name), "=", pce_type_description(Type).
pce_type_description(*(T)) -->
	pce_type_description(T), "*".
pce_type_description(...(T)) -->
	pce_type_description(T), " ...".

word_list((A,B)) --> !,
	pce_type_description(A), ",", word_list(B).
word_list(A) -->
	pce_type_description(A).


var_type(Type := new(Term), PceType, Initial) :- !,
	pce_type(Type, PceType),
	Term =.. L,
	Initial =.. [create|L].
var_type(Type := Initial, PceType, Initial) :- !,
	pce_type(Type, PceType).
var_type(Type, PceType, @default) :-
	pce_type(Type, PceType).


		 /*******************************
		 *	  METHOD SUPPORT	*
		 *******************************/

extract_documentation(Body0, Summary, Body) :-
	ex_documentation(Body0, Summary, Body), !.
extract_documentation(Body, @default, Body).

ex_documentation(::(DocText, Body), Summary, Body) :- !,
	pce_summary(DocText, Summary).
ex_documentation((::(DocText, A), B), Summary, (A,B)) :- !,
	pce_summary(DocText, Summary).
ex_documentation((A0 ; B), Summary, (A;B)) :-
	ex_documentation(A0, Summary, A), !.
ex_documentation((A0->B), Summary, (A->B)) :- !,
	ex_documentation(A0, Summary, A), !.
ex_documentation((A0*->B), Summary, (A*->B)) :- !,
	ex_documentation(A0, Summary, A), !.

return_type(Term, RType) :-
	functor(Term, _, Arity),
	arg(Arity, Term, Last),
	(   nonvar(Last),
	    Last = _:Type
	->  pce_type(Type, RType)
	;   RType = @default
	).

prolog_head(send, MethodId, Head, Selector,
	    TypeVector, pce_principal:PlHead) :- !,
	Head =.. [Selector, Receiver | Args],
	prolog_send_arguments(Args, Types, PlArgs),
	create_type_vector(Types, TypeVector),
	CallArgs =.. [Selector | PlArgs],
	PlHead =.. [send_implementation, MethodId, CallArgs, Receiver].
prolog_head(get, MethodId, Head, Selector,
	    TypeVector, pce_principal:PlHead) :- !,
	Head =.. [Selector, Receiver | Args],
	prolog_get_arguments(Args, Types, PlArgs, Rval),
	create_type_vector(Types, TypeVector),
	CallArgs =.. [Selector | PlArgs],
	PlHead =.. [get_implementation, MethodId, CallArgs, Receiver, Rval].

create_type_vector([],      @default) :- !.
create_type_vector(List,    VectorTerm) :-
	VectorTerm =.. [vector|List].

prolog_send_arguments([], [], []) :- !.
prolog_send_arguments([ArgAndType|RA], [T|RT], [Arg|TA]) :- !,
	head_arg(ArgAndType, Arg, Type),
	pce_type(Type, T),
	prolog_send_arguments(RA, RT, TA).

prolog_get_arguments([Return], [], [], ReturnVar) :- !,
	(   var(Return)
	->  ReturnVar = Return
	;   Return = ReturnVar:_Type
	).
prolog_get_arguments([ArgAndType|RA], [T|RT], [Arg|TA], ReturnVar) :- !,
	head_arg(ArgAndType, Arg, Type),
	pce_type(Type, T),
	prolog_get_arguments(RA, RT, TA, ReturnVar).


head_arg(Var, Var, any) :-
	var(Var), !.
head_arg(Arg:Type, Arg, Type).
head_arg(Arg:Name=Type, Arg, Name=Type).

	
		 /*******************************
		 *	  PUBLIC METHODS	*
		 *******************************/

%%	pce_compiling(-ClassName)
%	External function to get the current classname

pce_compiling(ClassName, Path) :-
	compiling(X, Y), !,
	X = ClassName,
	Y = Path.

pce_compiling(ClassName) :-
	compiling(X, _), !,
	X = ClassName.

pce_compiling :-
	compiling(_, _), !.


		 /*******************************
		 *	      CHECKS		*
		 *******************************/

%	If we are expanding on behalf of cross-referencing tool, never
%	send messages anywhere!

pce_ifhostproperty(qpc,
(realised_class(_ClassName) :- fail),
(realised_class(ClassName) :-
	\+ current_prolog_flag(xref, true),
	get(@classes, member, ClassName, Class),
	get(Class, realised, @on))).


		/********************************
		*           UTILITIES		*
		********************************/

term_member(El, Term) :-
	El == Term.
term_member(El, Term) :-
	functor(Term, _, Arity),
	term_member(Arity, El, Term).

term_member(0, _, _) :- !,
	fail.
term_member(N, El, Term) :-
	arg(N, Term, Sub),
	term_member(El, Sub).
term_member(N, El, Term) :-
	NN is N - 1,
	term_member(NN, El, Term).

%%	feedback(+Term)
%	Only print if verbose is asserted (basically debugging).

feedback(Term) :-
	(   verbose
	->  pce_info(Term)
	;   true
	).


		/********************************
		*         TERM EXPANSION	*
		********************************/

:- multifile
	user:term_expansion/2.
:- dynamic
	user:term_expansion/2.

user:term_expansion(A, B) :-
	pce_term_expansion(A, B).

:- pop_compile_operators.
