//===========================================================================
/*!
 * 
 *
 * \brief       abstract super class of all metrics
 * 
 * 
 *
 * \author      O. Krause
 * \date        2015
 *
 *
 * \par Copyright 1995-2015 Shark Development Team
 * 
 * <BR><HR>
 * This file is part of Shark.
 * <http://image.diku.dk/shark/>
 * 
 * Shark is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published 
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * Shark 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 Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with Shark.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
//===========================================================================

#ifndef SHARK_MODELS_KERNELS_ABSTRACTMETRIC_H
#define SHARK_MODELS_KERNELS_ABSTRACTMETRIC_H

#include <shark/Data/BatchInterface.h>
#include <shark/Core/IParameterizable.h>

#include <shark/Core/INameable.h>
#include <shark/Core/Traits/ProxyReferenceTraits.h>
namespace shark {
        
        
template<class InputTypeT>
class AbstractMetric: public INameable, public IParameterizable{
public:
        /// \brief  Input type of the Kernel.
        typedef InputTypeT InputType;
        /// \brief batch input type of the kernel
        typedef typename Batch<InputTypeT>::type BatchInputType;
        /// \brief Const references to InputType
        typedef typename ConstProxyReference<InputType const>::type ConstInputReference;
        /// \brief Const references to BatchInputType
        typedef typename ConstProxyReference<BatchInputType const>::type ConstBatchInputReference;

        AbstractMetric() { }
        virtual ~AbstractMetric() { }
                
        /// \brief From ISerializable, reads a metric from an archive.
        /// \brief From ISerializable, writes a metric to an archive.
        ///
        /// The default implementation just saves the parameters.
        /// Computes the squared distance in the kernel induced feature space.
        virtual double featureDistanceSqr(ConstInputReference x1, ConstInputReference x2) const=0;
        
        virtual RealMatrix featureDistanceSqr(
                ConstBatchInputReference batchX1,
                ConstBatchInputReference batchX2
        ) const = 0;
        

        /// \brief Computes the distance in the kernel induced feature space.
        double featureDistance(ConstInputReference x1, ConstInputReference x2) const {
                return std::sqrt(featureDistanceSqr(x1, x2));
        }
};
}
#endif
