/* $Id$
Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: wielemak@science.uva.nl
WWW: http://www.swi-prolog.org
Copyright (C): 1985-2007, 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 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(settings,
[ setting/4, % :Name, +Type, +Default, +Comment
setting/2, % :Name, ?Value
set_setting/2, % :Name, +Value
set_setting_default/2, % :Name, +Value
restore_setting/1, % :Name
load_settings/1, % +File
load_settings/2, % +File, +Options
save_settings/0,
save_settings/1, % +File
current_setting/1, % Module:Name
setting_property/2, % ?Setting, ?Property
list_settings/0,
convert_setting_text/3 % +Type, +Text, -Value
]).
:- use_module(library(error)).
:- use_module(library(broadcast)).
:- use_module(library(debug)).
:- use_module(library(option)).
/** <module> Setting management
@ingroup swi
This library allows management of configuration settings for Prolog
applications. Applications define settings in one or multiple files
using the directive setting/4 as illustrated below:
==
:- use_module(library(setting)).
:- setting(version, atom, '1.0', 'Current version').
:- setting(timeout, number, 20, 'Timeout in seconds').
==
The directive is subject to term_expansion/2, which guarantees proper
synchronisation of the database if source-files are reloaded. This
implies it is *not* possible to call setting/4 as a predicate.
Settings are local to a module. This implies they are defined in a
two-level namespace. Managing settings per module greatly simplifies
assembling large applications from multiple modules that configuration
through settings. This settings management library ensures proper
access, loading and saving of settings.
@see library(config) distributed with XPCE provides an alternative
aimed at graphical applications.
@author Jan Wielemaker
*/
:- dynamic
st_value/3, % Name, Module, Value
st_default/3, % Name, Module, Value
local_file/1. % Path
:- multifile
current_setting/6. % Name, Module, Type, Default, Comment, Source
:- meta_predicate
setting(:, +, +, +),
setting(:, ?),
set_setting(:, +),
set_setting_default(:, +),
current_setting(:),
restore_setting(:).
curr_setting(Name, Module, Type, Default, Comment) :-
current_setting(Name, Module, Type, Default0, Comment, _Src),
( st_default(Name, Module, Default1)
-> Default = Default1
; Default = Default0
).
%% setting(Name, Type, Default, Comment) is det.
%
% Define a setting. Name denotes the name of the setting, Type its
% type. Default is the value before it is modified. Default refer
% to environment variables and use arithmetic expressions as
% defined by eval_default/4.
%
% @param Name Name of the setting (an atom)
% @param Type Type for setting. One of =any= or a type defined
% by must_be/2.
% @param Default Default value for the setting.
% @param Comment Atom containing a (short) descriptive note.
setting(Name, Type, Default, Comment) :-
throw(error(context_error(nodirective,
setting(Name, Type, Default, Comment)),
_)).
:- multifile
system:term_expansion/2.
system:term_expansion((:- setting(QName, Type, Default, Comment)),
Expanded) :-
prolog_load_context(module, M0),
strip_module(M0:QName, Module, Name),
must_be(atom, Name),
to_atom(Comment, CommentAtom),
eval_default(Default, Module, Type, Value),
check_type(Type, Value),
( current_setting(Name, Module, _, _, _, OldLoc)
-> format(string(Message),
'Already defined at: ~w', [OldLoc]),
throw(error(permission_error(redefine, setting, Module:Name),
context(Message, _)))
; source_location(File, Line)
-> Expanded = settings:current_setting(Name, Module, Type, Default,
CommentAtom, File:Line)
).
to_atom(Atom, Atom) :-
atom(Atom), !.
to_atom(String, Atom) :-
format(atom(Atom), '~s', String).
%% setting(:Name, ?Value) is nondet.
%
% True if Name is a currently defined setting with Value.
%
% @error existence_error(setting, Name)
setting(QName, Value) :-
strip_module(QName, Module, Name),
( ground(Name)
-> ( st_value(Name, Module, Value0)
-> Value = Value0
; curr_setting(Name, Module, Type, Default, _)
-> eval_default(Default, Module, Type, Value)
; existence_error(setting, Module:Name)
)
; current_setting(Name, Module, _, _, _, _),
setting(Module:Name, Value)
).
:- dynamic
setting_cache/3.
:- volatile
setting_cache/3.
%% clear_setting_cache is det.
%
% Clear the cache for evaluation of default values.
clear_setting_cache :-
retractall(setting_cache(_,_,_)).
%% eval_default(+Default, +Module, +Type, -Value) is det.
%
% Convert the settings default value. The notation allows for some
% `function-style' notations to make the library more generic:
%
% * env(Name)
% Get value from the given environment variable. The value
% is handed to convert_setting_text/3 to convert the
% textual representation into a Prolog term. Raises an
% existence_error of the variable is not defined.
%
% * env(Name, Default)
% As env(Name), but uses the value Default if the variable
% is not defined.
%
% * setting(Name)
% Ask the value of another setting.
%
% * Expression
% If Type is numeric, evaluate the expression. env(Var)
% evaluates to the value of an environment variable.
% If Type is =atom=, concatenate A+B+.... Elements of the
% expression can be env(Name).
:- multifile
eval_default/3. % +Default, +Type, -Value
eval_default(Default, _, Type, Value) :-
eval_default(Default, Type, Val), !,
Value = Val.
eval_default(Default, _, _, Value) :-
atomic(Default), !,
Value = Default.
eval_default(Default, _, Type, Value) :-
setting_cache(Default, Type, Val), !,
Value = Val.
eval_default(env(Name), _, Type, Value) :- !,
( getenv(Name, TextValue)
-> convert_setting_text(Type, TextValue, Val),
assert(setting_cache(env(Name), Type, Val)),
Value = Val
; existence_error(environment_variable, Name)
).
eval_default(env(Name, Default), _, Type, Value) :- !,
( getenv(Name, TextValue)
-> convert_setting_text(Type, TextValue, Val)
; Value = Default
),
assert(setting_cache(env(Name), Type, Val)),
Value = Val.
eval_default(setting(Name), Module, Type, Value) :- !,
strip_module(Module:Name, M, N),
setting(M:N, Value),
must_be(Type, Value).
eval_default(Expr, _, Type, Value) :-
numeric_type(Type, Basic), !,
Val0 is Expr,
( Basic == float
-> Val is float(Val0)
; Basic = integer
-> Val is round(Val0)
; Val = Val0
),
assert(setting_cache(Expr, Type, Val)),
Value = Val.
eval_default(A+B, Module, atom, Value) :- !,
phrase(expr_to_list(A+B, Module), L),
atomic_list_concat(L, Val),
assert(setting_cache(A+B, atom, Val)),
Value = Val.
eval_default(List, Module, list(Type), Value) :- !,
eval_list_default(List, Module, Type, Val),
assert(setting_cache(List, list(Type), Val)),
Value = Val.
eval_default(Default, _, _, Default).
%% eval_list_default(+List, +Module, +ElementType, -DefaultList)
%
% Evaluate the default for a list of values.
eval_list_default([], _, _, []).
eval_list_default([H0|T0], Module, Type, [H|T]) :-
eval_default(H0, Module, Type, H),
eval_list_default(T0, Module, Type, T).
%% expr_to_list(+Expression, +Module)// is det.
%
% Process the components to create an atom. Atom concatenation is
% expressed as A+B. Components may refer to envrionment variables.
expr_to_list(A+B, Module) --> !,
expr_to_list(A, Module),
expr_to_list(B, Module).
expr_to_list(env(Name), _) --> !,
( { getenv(Name, Text) }
-> [Text]
; { existence_error(environment_variable, Name) }
).
expr_to_list(env(Name, Default), _) --> !,
( { getenv(Name, Text) }
-> [Text]
; [Default]
).
expr_to_list(setting(Name), Module) --> !,
{ strip_module(Module:Name, M, N),
setting(M:N, Value)
},
[ Value ].
expr_to_list(A, _) -->
[A].
:- if((\+ current_prolog_flag(version_data,yap(_,_,_,_)))).
%% env(+Name:atom, -Value:number) is det.
%% env(+Name:atom, +Default:number, -Value:number) is det
%
% Evaluate environment variables on behalf of arithmetic
% expressions.
:- arithmetic_function(env/1).
:- arithmetic_function(env/2).
env(Name, Value) :-
( getenv(Name, Text)
-> convert_setting_text(number, Text, Value)
; existence_error(environment_variable, Name)
).
env(Name, Default, Value) :-
( getenv(Name, Text)
-> convert_setting_text(number, Text, Value)
; Value = Default
).
:- endif.
%% numeric_type(+Type, -BaseType)
%
% True if Type is a numeric type and BaseType is the associated
% basic Prolog type. BaseType is one of =integer=, =float= or
% =number=.
numeric_type(integer, integer).
numeric_type(nonneg, integer).
numeric_type(float, float).
numeric_type(between(L,_), Type) :-
( integer(L) -> Type = integer ; Type = float ).
%% set_setting(:Name, +Value) is det.
%
% Change a setting. Performs existence and type-checking for the
% setting. If the effective value of the setting is changed it
% broadcasts the event below.
%
% settings(changed(Module:Name, Old, New))
%
% @error existence_error(setting, Name)
% @error type_error(Type, Value)
set_setting(QName, Value) :-
strip_module(QName, Module, Name),
must_be(atom, Name),
( curr_setting(Name, Module, Type, Default0, _Comment),
eval_default(Default0, Module, Type, Default)
-> ( Value == Default
-> retract_setting(Module:Name)
; st_value(Name, Module, Value)
-> true
; check_type(Type, Value)
-> setting(Module:Name, Old),
retract_setting(Module:Name),
assert_setting(Module:Name, Value),
broadcast(settings(changed(Module:Name, Old, Value))),
clear_setting_cache % might influence dependent settings.
)
; existence_error(setting, Name)
).
retract_setting(Module:Name) :-
retractall(st_value(Name, Module, _)).
assert_setting(Module:Name, Value) :-
assert(st_value(Name, Module, Value)).
%% restore_setting(:Name) is det.
%
% Restore the value of setting Name to its default. Broadcast a
% change like set_setting/2 if the current value is not the
% default.
restore_setting(QName) :-
strip_module(QName, Module, Name),
must_be(atom, Name),
( st_value(Name, Module, Old)
-> retract_setting(Module:Name),
setting(Module:Name, Value),
( Old \== Value
-> broadcast(settings(changed(Module:Name, Old, Value)))
; true
)
; true
).
%% set_setting_default(:Name, +Default) is det.
%
% Change the default for a setting. The effect is the same as
% set_setting/2, but the new value is considered the default when
% saving and restoring a setting. It is intended to change
% application defaults in a particular context.
set_setting_default(QName, Default) :-
strip_module(QName, Module, Name),
must_be(atom, Name),
( current_setting(Name, Module, Type, Default0, _Comment, _Src)
-> retractall(settings:st_default(Name, Module, _)),
retract_setting(Module:Name),
( Default == Default0
-> true
; assert(settings:st_default(Name, Module, Default))
),
eval_default(Default, Module, Type, Value),
set_setting(Module:Name, Value)
; existence_error(setting, Module:Name)
).
/*******************************
* TYPES *
*******************************/
%% check_type(+Type, +Term)
%
% Type checking for settings. Currently simply forwarded to
% must_be/2.
check_type(Type, Term) :-
must_be(Type, Term).
/*******************************
* FILE *
*******************************/
%% load_settings(File) is det.
%% load_settings(File, +Options) is det.
%
% Load local settings from File. Succeeds if File does not exist,
% setting the default save-file to File. Options are:
%
% * undefined(+Action)
% Define how to handle settings that are not defined. When
% =error=, an error is printed and the setting is ignored.
% when =load=, the setting is loaded anyway, waiting for a
% definition.
load_settings(File) :-
load_settings(File, []).
load_settings(File, Options) :-
absolute_file_name(File, Path,
[ access(read),
file_errors(fail)
]), !,
assert(local_file(Path)),
open(Path, read, In, [encoding(utf8)]),
read_setting(In, T0),
call_cleanup(load_settings(T0, In, Options), close(In)),
clear_setting_cache.
load_settings(File, _) :-
absolute_file_name(File, Path,
[ access(write),
file_errors(fail)
]), !,
assert(local_file(Path)).
load_settings(_, _).
load_settings(end_of_file, _, _) :- !.
load_settings(Setting, In, Options) :-
catch(store_setting(Setting, Options), E,
print_message(warning, E)),
read_setting(In, Next),
load_settings(Next, In, Options).
read_setting(In, Term) :-
read_term(In, Term,
[ errors(dec10)
]).
%% store_setting(Term, +Options)
%
% Store setting loaded from file in the Prolog database.
store_setting(setting(Module:Name, Value), _) :-
curr_setting(Name, Module, Type, Default0, _Commentm), !,
eval_default(Default0, Module, Type, Default),
( Value == Default
-> true
; check_type(Type, Value)
-> retractall(st_value(Name, Module, _)),
assert(st_value(Name, Module, Value)),
broadcast(settings(changed(Module:Name, Default, Value)))
).
store_setting(setting(Module:Name, Value), Options) :- !,
( option(undefined(load), Options, load)
-> retractall(st_value(Name, Module, _)),
assert(st_value(Name, Module, Value))
; existence_error(setting, Module:Name)
).
store_setting(Term, _) :-
type_error(setting, Term).
%% save_settings is det.
%% save_settings(+File) is det.
%
% Save modified settings to File.
save_settings :-
local_file(File), !,
save_settings(File).
save_settings(File) :-
absolute_file_name(File, Path,
[ access(write)
]), !,
open(Path, write, Out,
[ encoding(utf8),
bom(true)
]),
write_setting_header(Out),
forall(current_setting(Name, Module, _, _, _, _),
save_setting(Out, Module:Name)),
close(Out).
write_setting_header(Out) :-
get_time(Now),
format_time(string(Date), '%+', Now),
format(Out, '/* Saved settings~n', []),
format(Out, ' Date: ~w~n', [Date]),
format(Out, '*/~n~n', []).
save_setting(Out, Module:Name) :-
curr_setting(Name, Module, Type, Default, Comment),
( st_value(Name, Module, Value),
\+ ( eval_default(Default, Module, Type, DefValue),
debug(setting, '~w <-> ~w~n', [DefValue, Value]),
DefValue =@= Value
)
-> format(Out, '~n% ~w~n', [Comment]),
format(Out, 'setting(~q:~q, ~q).~n', [Module, Name, Value])
; true
).
%% current_setting(?Setting) is nondet.
%
% True if Setting is a currently defined setting
current_setting(Setting) :-
ground(Setting), !,
strip_module(Setting, Module, Name),
current_setting(Name, Module, _, _, _, _).
current_setting(Module:Name) :-
current_setting(Name, Module, _, _, _, _).
%% setting_property(+Setting, +Property) is det.
%% setting_property(?Setting, ?Property) is nondet.
%
% Query currently defined settings. Property is one of
%
% * comment(-Atom)
% * type(-Type)
% Type of the setting.
% * default(-Default)
% Default value. If this is an expression, it is
% evaluated.
setting_property(Setting, Property) :-
ground(Setting), !,
Setting = Module:Name,
curr_setting(Name, Module, Type, Default, Comment), !,
setting_property(Property, Module, Type, Default, Comment).
setting_property(Setting, Property) :-
Setting = Module:Name,
curr_setting(Name, Module, Type, Default, Comment),
setting_property(Property, Module, Type, Default, Comment).
setting_property(type(Type), _, Type, _, _).
setting_property(default(Default), M, Type, Default0, _) :-
eval_default(Default0, M, Type, Default).
setting_property(comment(Comment), _, _, _, Comment).
%% list_settings
%
% List settings to =current_output=.
list_settings :-
format('~`=t~72|~n'),
format('~w~t~20| ~w~w~t~40| ~w~n', ['Name', 'Value (*=modified)', '', 'Comment']),
format('~`=t~72|~n'),
forall(current_setting(Module:Setting),
list_setting(Module:Setting)).
list_setting(Module:Name) :-
curr_setting(Name, Module, Type, Default0, Comment),
eval_default(Default0, Module, Type, Default),
setting(Module:Name, Value),
( Value \== Default
-> Modified = (*)
; Modified = ''
),
format('~w~t~20| ~q~w~t~40| ~w~n', [Module:Name, Value, Modified, Comment]).
/*******************************
* TYPES *
*******************************/
%% convert_setting_text(+Type, +Text, -Value)
%
% Converts from textual form to Prolog Value. Used to convert
% values obtained from the environment. Public to provide support
% in user-interfaces to this library.
%
% @error type_error(Type, Value)
:- multifile
convert_text/3. % +Type, +Text, -Value
convert_setting_text(Type, Text, Value) :-
convert_text(Type, Text, Value), !.
convert_setting_text(atom, Value, Value) :- !,
must_be(atom, Value).
convert_setting_text(boolean, Value, Value) :- !,
must_be(boolean, Value).
convert_setting_text(integer, Atom, Number) :- !,
term_to_atom(Term, Atom),
Number is round(Term).
convert_setting_text(float, Atom, Number) :- !,
term_to_atom(Term, Atom),
Number is float(Term).
convert_setting_text(between(L,U), Atom, Number) :- !,
( integer(L)
-> convert_setting_text(integer, Atom, Number)
; convert_setting_text(float, Atom, Number)
),
must_be(between(L,U), Number).
convert_setting_text(Type, Atom, Term) :-
term_to_atom(Term, Atom),
must_be(Type, Term).