231 lines
8.5 KiB
C++
231 lines
8.5 KiB
C++
/*
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CONFIG-RULES.hpp - interface for rule based configuration
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Copyright (C) Lumiera.org
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2008, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/** @file config-rules.hpp
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** Interface for accessing rule based configuration.
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** By using the Query template, you can pose a query in prolog syntax and get some
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** existing or newly created object fulfilling the requested predicates. The actual
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** implementation is hidden behind the #instance (Singleton factory). As of 1/2008,
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** it is \e planned to use an embedded YAP Prolog system at some point in the future,
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** for now we use a \link MockConfigRules mock implementation \endlink employing a
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** preconfigured Map.
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**
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** Fully implementing this facility would require the participating objects to register capabilities
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** they want to provide, together with functors carrying out the necessary configuration steps.
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** All details and consequences of this approach still have to be worked out...
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**
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** \par relation to Query and QueryResolver
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** The ConfigRules resolver is just a special kind of QueryResolver, able to handle specific kinds
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** of queries. Clients using the ConfigRules directly get a more easy to use point-and-shot style
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** interface, allowing just to retrieve some \em suitable solution, instead of having to iterate
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** through a result set.
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**
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** @todo right now (12/2012) the above paragraph is a lie.
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** ConfigQuery is way older than QueryResolver and will be retrofitted step by step.
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** Not much of a problem, since the currently utilised mock implementation isn't able to
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** deal with a real query anyway.
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**
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** @note this is rather a concept draft and left as such for now... don't take this code too literal!
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** @todo clarify the relation of config query and query-for-defaults ///////////////TICKET #705
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**
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** @see lumiera::Query
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** @see mobject::session::DefsManager
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** @see asset::StructFactory
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** @see config-resolver.hpp specialised setup for the Proc-Layer
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** @see fake-configrules.hpp currently used dummy-implementation
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** @see
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**
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*/
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#ifndef LUMIERA_CONFIG_RULES_H
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#define LUMIERA_CONFIG_RULES_H
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#include "lib/p.hpp"
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#include "lib/symbol.hpp"
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#include "lib/meta/generator.hpp"
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#include "common/query.hpp"
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#include <string>
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namespace lumiera {
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using std::string;
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using lib::P;
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/////////////////////////////////////////////////////////////////////TICKET #705 this is draft/preview code; a real resolution system needs to be integrated
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namespace query {
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// The intention is to support the following style of Prolog code
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//
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// resolve(O, Cap) :- find(O), capabilities(Cap).
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// resolve(O, Cap) :- make(O), capabilities(Cap).
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// capabilities(Q) :- call(Q).
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//
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// stream(T, mpeg) :- type(T, track), type(P, pipe), resolve(P, stream(P,mpeg)), placed_to(P, T).
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//
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// The type guard is inserted automatically, while the predicate implementations for
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// find/1, make/1, stream/2, and placed_to/2 are to be provided by the target types.
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//
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// As a example, the goal ":-retrieve(T, stream(T,mpeg))." would search a Track object, try to
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// retrieve a pipe object with stream-type=mpeg and associate the track with this Pipe. The
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// predicate "stream(P,mpeg)" needs to be implemented (natively) for the pipe object.
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class Resolver
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{
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///////////////////////////////////////////////////////////////TICKET #705 a real resolution system needs to be integrated
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};
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using lib::Symbol;
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using lib::Literal;
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using lumiera::Query;
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/** placeholder definition for later.
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* @todo intention is to integrate with lib::Symbol
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*/
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#define SYMBOL uint
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template
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< SYMBOL SYM, // Predicate symbol
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typename SIG = bool(string) // Signature
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>
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class Pred
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{ };
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/**
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* the "back side" interface towards the classes participating
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* in the configuration system (the config system will be
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* delivering instances of these classes for a given query).
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* This one currently is just brainstorming. The idea is that
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* a participating class would provide such and TypeHandler
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* implementing the predicates which make sense for this special
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* type of object. Registering such a TypeHandler should create
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* the necessary handler functions to be installed into
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* the Prolog system.
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* @todo it can't be done exactly this way, but I leave it in
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* as a reminder for later, to show the intention
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*/
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template<class TY>
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class TypeHandler
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{
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static const TY NIL;
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template<SYMBOL SYM, typename SIG>
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TY find (Pred<SYM,SIG> capability);
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template<SYMBOL SYM, typename SIG>
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TY make (Pred<SYM,SIG> capability, TY& refObj =NIL);
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};
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/**
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* the "front side" interface: the Proc-Layer code can
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* use this QueryHandler to retrieve instances of the
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* type TY fulfilling the given Query. To start with,
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* we use a mock implementation.
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* (this code works and is already used 2/2008)
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* @todo retrofit this to install and use a QueryResolver
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* @see lumiera::query::LookupPreconfigured
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* @see lumiera::query::MockTable
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*/
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template<class TY>
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class QueryHandler
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{
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protected:
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virtual ~QueryHandler() { }
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public:
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/** try to find or create an object of type TY
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* fulfilling the given query.
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* @param solution object fulfilling the query. Will be bound or
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* unified (in case it's already bound) with the first solution.
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* @query any goals to be fulfilled by the solution.
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* @return false if resolution failed. In this case, solution ptr is empty.
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*/
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virtual bool resolve (P<TY>& solution, const Query<TY>& q) = 0;
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};
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// TODO: the Idea is to provide specialisations for the concrete types
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// we want to participate in the ConfigRules system....
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// Thus we get the possibility to create a specific return type,
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// e.g. return a P<Pipe> but a Placement<Track>, using the appropriate factory.
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// Of course then the definitions need to be split up in separate headers.
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/**
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* Generic query interface for retrieving objects matching
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* some capability query. To be instantiated using a typelist,
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* thus inheriting from the Handler classes for each type. In
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* the (future) version using YAP Prolog, this will drive the
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* generation and registration of the necessary predicate
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* implementations for each concrete type, using the specialisations
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* given alongside with the types. For now it just serves to generate
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* the necessary resolve(Query<TY>) virtual functions (implemented
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* by MockConfigRules)
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*/
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template<typename TYPES>
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class ConfigRules
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: public lib::meta::InstantiateForEach<TYPES, QueryHandler>
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{
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protected:
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ConfigRules () {}
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virtual ~ConfigRules() {}
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public:
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// TODO: find out what operations we need to support here for the »real solution« (using Prolog)
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};
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LUMIERA_ERROR_DECLARE (CAPABILITY_QUERY); ///< unresolvable capability query.
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} // namespace query
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namespace query {
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/** backdoor for tests: the next config query with this query string
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* will magically succeed with every candidate object provided. This
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* is currently necessary to get objects into the defaults manager,
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* as the query system is not able to do real query resolution */
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void setFakeBypass(string const& q);
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bool isFakeBypass (string const& q);
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/////////////////////////////////////////////////////////////////////////////TICKET 710
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} // namespace query
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} // namespace lumiera
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#endif
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