//
// Copyright 2013 Christian Henning
//
// 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_TEST_EXTENSION_IO_MANDEL_VIEW_HPP
#define BOOST_GIL_TEST_EXTENSION_IO_MANDEL_VIEW_HPP

#include <boost/gil.hpp>

#include <cmath>
#include <cstdint>

namespace gil = boost::gil;

// Models a Unary Function
template <typename P>  // Models PixelValueConcept
struct mandelbrot_fn
{
    using point_t                    = gil::point_t;
    using const_t                    = mandelbrot_fn;
    using value_type                 = P;
    using reference                  = value_type;
    using const_reference            = value_type;
    using argument_type              = point_t;
    using result_type                = reference;
    static constexpr bool is_mutable = false;

    value_type in_color_;
    value_type out_color_;
    point_t img_size_;
    static const int MAX_ITER = 100;  // max number of iterations

    mandelbrot_fn() = default;
    mandelbrot_fn(gil::point_t const& sz, value_type const& in_color, value_type const& out_color)
        : in_color_(in_color), out_color_(out_color), img_size_(sz)
    {
    }

    std::ptrdiff_t width()
    {
        return img_size_.x;
    }
    std::ptrdiff_t height()
    {
        return img_size_.y;
    }

    result_type operator()(gil::point_t const& p) const
    {
        // normalize the coords to (-2..1, -1.5..1.5)
        // (actually make y -1.0..2 so it is asymmetric, so we can verify some view factory methods)
        gil::point<double> const n{
            static_cast<double>(p.x) / static_cast<double>(img_size_.x) * 3 - 2,
            static_cast<double>(p.y) / static_cast<double>(img_size_.y) * 3 - 1.0f};  //1.5f}
        double t = get_num_iter(n);
        t        = std::pow(t, 0.2);

        value_type ret;
        for (std::size_t k = 0; k < gil::num_channels<P>::value; ++k)
            ret[k] =
                (typename gil::channel_type<P>::type)(in_color_[k] * t + out_color_[k] * (1 - t));
        return ret;
    }

    private:
    double get_num_iter(boost::gil::point<double> const& p) const
    {
        gil::point<double> z(0, 0);
        for (int i = 0; i < MAX_ITER; ++i)
        {
            z = gil::point<double>(z.x * z.x - z.y * z.y + p.x, 2 * z.x * z.y + p.y);
            if (z.x * z.x + z.y * z.y > 4)
                return i / (double)MAX_ITER;
        }
        return 0;
    }
};

template <typename Pixel>
struct mandel_view
{
    using deref_t        = mandelbrot_fn<Pixel>;
    using locator_t      = gil::virtual_2d_locator<deref_t, false>;
    using my_virt_view_t = gil::image_view<locator_t>;
    using type           = my_virt_view_t;
};

template <typename Pixel>
auto create_mandel_view(unsigned int width, unsigned int height, Pixel const& in, Pixel const& out)
    -> typename mandel_view<Pixel>::type
{
    using view_t    = typename mandel_view<Pixel>::type;
    using deref_t   = typename mandel_view<Pixel>::deref_t;
    using locator_t = typename mandel_view<Pixel>::locator_t;

    gil::point_t dims(width, height);
    return view_t(dims, locator_t(gil::point_t(0, 0), gil::point_t(1, 1), deref_t(dims, in, out)));
}

#endif // BOOST_GIL_TEST_EXTENSION_IO_MANDEL_VIEW_HPP