//
// Copyright 2005-2007 Adobe Systems Incorporated
//
// Distributed under the Boost Software License, Version 1.0
// See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt
//
#ifndef BOOST_GIL_EXTENSION_NUMERIC_KERNEL_HPP
#define BOOST_GIL_EXTENSION_NUMERIC_KERNEL_HPP

#include <boost/gil/utilities.hpp>

#include <boost/assert.hpp>

#include <algorithm>
#include <array>
#include <cstddef>
#include <memory>
#include <vector>

namespace boost { namespace gil {

// Definitions of 1D fixed-size and variable-size kernels and related operations

namespace detail {

/// \brief kernel adaptor for one-dimensional cores
/// Core needs to provide size(),begin(),end(),operator[],
///                       value_type,iterator,const_iterator,reference,const_reference
template <typename Core>
class kernel_1d_adaptor : public Core {
private:
    std::size_t _center;
public:
    kernel_1d_adaptor() : _center(0) {}

    explicit kernel_1d_adaptor(std::size_t center_in)
        : _center(center_in)
    {
        BOOST_ASSERT(_center < this->size());
    }

    kernel_1d_adaptor(std::size_t size_in, std::size_t center_in)
        : Core(size_in)
        , _center(center_in)
    {
        BOOST_ASSERT(_center < this->size());
    }

    kernel_1d_adaptor(kernel_1d_adaptor const& k_in) : Core(k_in), _center(k_in._center) {}

    kernel_1d_adaptor& operator=(const kernel_1d_adaptor& k_in) {
        Core::operator=(k_in);
        _center=k_in._center;
        return *this;
    }

    std::size_t left_size() const
    {
        BOOST_ASSERT(_center < this->size());
        return _center;
    }

    std::size_t right_size() const
    {
        BOOST_ASSERT(_center < this->size());
        return this->size() - _center - 1;
    }

    std::size_t& center()       {return _center;}
    const std::size_t& center() const {return _center;}
};

} // namespace detail

/// \brief variable-size kernel
template <typename T, typename Alloc = std::allocator<T> >
class kernel_1d : public detail::kernel_1d_adaptor<std::vector<T,Alloc>>
{
    using parent_t = detail::kernel_1d_adaptor<std::vector<T,Alloc>>;
public:
    kernel_1d() {}
    kernel_1d(std::size_t size_in,std::size_t center_in) : parent_t(size_in,center_in) {}
    template <typename FwdIterator>
    kernel_1d(FwdIterator elements, std::size_t size_in, std::size_t center_in) : parent_t(size_in,center_in) {
        detail::copy_n(elements,size_in,this->begin());
    }
    kernel_1d(const kernel_1d& k_in)                     : parent_t(k_in) {}
};

/// \brief static-size kernel
template <typename T,std::size_t Size>
class kernel_1d_fixed : public detail::kernel_1d_adaptor<std::array<T,Size>>
{
    using parent_t = detail::kernel_1d_adaptor<std::array<T,Size>>;
public:
    kernel_1d_fixed() {}
    explicit kernel_1d_fixed(std::size_t center_in) : parent_t(center_in) {}

    template <typename FwdIterator>
    explicit kernel_1d_fixed(FwdIterator elements, std::size_t center_in) : parent_t(center_in) {
        detail::copy_n(elements,Size,this->begin());
    }
    kernel_1d_fixed(const kernel_1d_fixed& k_in)    : parent_t(k_in) {}
};

/// \brief reverse a kernel
template <typename Kernel>
inline Kernel reverse_kernel(const Kernel& kernel) {
    Kernel result(kernel);
    result.center()=kernel.right_size();
    std::reverse(result.begin(), result.end());
    return result;
}

}} // namespace boost::gil

#endif
