Factory.h

/*
 * (C) Copyright 2013 ECMWF.
 *
 * This software is licensed under the terms of the Apache Licence Version 2.0
 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
 * In applying this licence, ECMWF does not waive the privileges and immunities
 * granted to it by virtue of its status as an intergovernmental organisation
 * nor does it submit to any jurisdiction.
 */

#pragma once

#include <map>
#include <memory>
#include <mutex>
#include <string>
#include <vector>

namespace eckit {
class Parametrisation;
}

namespace atlas {
namespace util {

class FactoryBase;

class FactoryRegistry {
protected:
    FactoryRegistry( const std::string& factory );
    virtual ~FactoryRegistry();

private:
    mutable std::mutex mutex_;
    std::string factory_;
    std::map<std::string, FactoryBase*> factories_;

public:
    const std::string& factory() const { return factory_; }
    std::vector<std::string> keys() const;
    void list( std::ostream& ) const;
    bool has( const std::string& builder ) const;
    void add( const std::string& builder, FactoryBase* );
    void remove( const std::string& builder );
    FactoryBase* get( const std::string& builder ) const;
};

template <typename T>
struct FactoryRegistryT : public FactoryRegistry {
public:
    static std::shared_ptr<FactoryRegistryT<T>> instance() {
        static std::shared_ptr<FactoryRegistryT<T>> env( new FactoryRegistryT<T>( T::className() ) );
        return env;
    }
    virtual ~FactoryRegistryT() {}

protected:
    FactoryRegistryT( const std::string& factory ) : FactoryRegistry( factory ) {}
};

class FactoryBase {
private:
    FactoryRegistry& registry_;
    std::string builder_;
    std::shared_ptr<FactoryRegistry> attached_registry_;

protected:
    FactoryBase( FactoryRegistry&, const std::string& builder );
    virtual ~FactoryBase();
    void attach_registry( const std::shared_ptr<FactoryRegistry>& registry ) { attached_registry_ = registry; }
    friend class FactoryRegistry;

public:
    const std::string& factoryBuilder() const { return builder_; }
    const std::string& factoryName() const { return registry_.factory(); }
};

template <typename T>
class Factory : public FactoryBase {
public:
    static std::vector<std::string> keys() { return registry().keys(); }
    static void list( std::ostream& out ) { return registry().list( out ); }
    static bool has( const std::string& builder ) { return registry().has( builder ); }
    static T* get( const std::string& builder ) { return dynamic_cast<T*>( registry().get( builder ) ); }

    Factory( const std::string& builder = "" ) : FactoryBase( registry(), builder ) {
        if ( not builder.empty() ) {
            attach_registry( FactoryRegistryT<T>::instance() );
        }
    }

protected:
    virtual ~Factory(){};
    static FactoryRegistry& registry() { return *FactoryRegistryT<T>::instance().get(); }
};

//----------------------------------------------------------------------------------------------------------------------

}  // namespace util
}  // namespace atlas