// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
#ifndef DUNE_GEOMETRY_TOPOLOGYFACTORY_HH
#define DUNE_GEOMETRY_TOPOLOGYFACTORY_HH

#include <vector>
#include <map>

#include <dune/common/array.hh>

#include <dune/geometry/type.hh>

namespace Dune
{

  /**
   * @brief Provide a factory over the generic topologies
   *
   * This class can be used to dynamically create objects
   * statically bound by their generic topologies.
   * The method create() returns a pointer to an object depending
   * on the topology id and a key; the dimension corresponding
   * to the topology id is static and is provided by the
   * Traits class. A static method (taking the Topology as template
   * argument) is also provided.
   * The Traits class must provide the space dimension,
   * the types for the key (Key),
   * the objects returned (Object), and the underlying factory
   * (Factory). This class must have a template method
   * createObject taking a key and returning a pointer to
   * the newly create Object - for destruction call the release
   * method.
   **/
  template <class Traits>
  struct TopologyFactory
  {
    // extract types from Traits class
    static const unsigned int dimension = Traits::dimension;
    typedef typename Traits::Key Key;
    typedef typename Traits::Object Object;
    typedef typename Traits::Factory Factory;

    //! dynamically create objects
    static Object *create ( const Dune::GeometryType &gt, const Key &key )
    {
      return Impl::IfTopology< Maker, dimension >::apply( gt.id(), key );
    }

    //! statically create objects
    template< class Topology >
    static Object *create ( const Key &key )
    {
      return Factory::template createObject< Topology >( key );
    }

    //! release the object returned by the create methods
    static void release( Object *object ) { delete object; }

  private:
    // Internal maker class used in ifTopology helper
    template< class Topology >
    struct Maker
    {
      static Object *apply ( const Key &key )
      {
        return create< Topology >( key );
      };
    };
  };



  /** @brief A wrapper for a TopologyFactory providing
   *         singleton storage. Same usage as TopologyFactory
   *         but with empty release method an internal storage.
   **/
  template <class Factory>
  struct TopologySingletonFactory
  {
    static const unsigned int dimension = Factory::dimension;
    typedef typename Factory::Key Key;
    typedef const typename Factory::Object Object;

    //! @copydoc TopologyFactory::create(const Dune::GeometryType &gt,const Key &key)
    static Object *create ( const Dune::GeometryType &gt, const Key &key )
    {
      assert( gt.id() < numTopologies );
      return instance().getObject( gt, key );
    }
    //! @copydoc TopologyFactory::create(const Key &key)
    template< class Topology >
    static Object *create ( const Key &key )
    {
      static_assert((Topology::dimension == dimension),
                    "Topology with incompatible dimension used");
      return instance().template getObject< Topology >( key );
    }
    //! @copydoc TopologyFactory::release
    static void release ( Object *object )
    {}
  private:
    static TopologySingletonFactory &instance ()
    {
      static TopologySingletonFactory instance;
      return instance;
    }

    static const unsigned int numTopologies = (1 << dimension);
    typedef std::array< Object *, numTopologies > Array;
    typedef std::map< Key, Array > Storage;

    TopologySingletonFactory ()
    {}
    ~TopologySingletonFactory ()
    {
      const typename Storage::iterator end = storage_.end();
      for( typename Storage::iterator it = storage_.begin(); it != end; ++it )
      {
        for( unsigned int topologyId = 0; topologyId < numTopologies; ++topologyId )
        {
          Object *&object = it->second[ topologyId ];
          if( object != 0 )
            Factory::release( object );
          object = 0;
        }
      }
    }

    Object *&find( const unsigned int topologyId, const Key &key )
    {
      typename Storage::iterator it = storage_.find( key );
      if( it == storage_.end() )
        it = storage_.insert( std::make_pair( key, fill_array<Object*, numTopologies>( nullptr ) ) ).first;
      return it->second[ topologyId ];
    }

    Object *getObject ( const Dune::GeometryType &gt, const Key &key )
    {
      Object *&object = find( gt.id(), key );
      if( object == 0 )
        object = Factory::create( gt, key );
      return object;
    }

    template< class Topology >
    Object *getObject ( const Key &key )
    {
      Object *&object = find(Topology::id,key);
      if( object == 0 )
        object = Factory::template create< Topology >( key );
      return object;
    }
    Storage storage_;
  };

}

#endif // #ifndef DUNE_GEOMETRY_TOPOLOGYFACTORY_HH
