//----------------------------------------------------------------------------
// Anti-Grain Geometry - Version 2.4
// Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
//
// Permission to copy, use, modify, sell and distribute this software
// is granted provided this copyright notice appears in all copies.
// This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.
//
//----------------------------------------------------------------------------
// Contact: mcseem@antigrain.com
//          mcseemagg@yahoo.com
//          http://www.antigrain.com
//----------------------------------------------------------------------------

#ifndef AGG_SPAN_GRADIENT_INCLUDED
#define AGG_SPAN_GRADIENT_INCLUDED

#include <cmath>
#include <cstdlib>
#include "agg_basics.h"
#include "agg_math.h"
#include "agg_array.h"

namespace agg
{

    enum gradient_subpixel_scale_e
    {
        gradient_subpixel_shift = 4, //-----gradient_subpixel_shift
        gradient_subpixel_scale =
            1 << gradient_subpixel_shift, //-----gradient_subpixel_scale
        gradient_subpixel_mask =
            gradient_subpixel_scale - 1 //-----gradient_subpixel_mask
    };

    //==========================================================span_gradient
    template <class ColorT, class Interpolator, class GradientF, class ColorF>
    class span_gradient
    {
    public:
        typedef Interpolator interpolator_type;
        typedef ColorT color_type;

        enum downscale_shift_e
        {
            downscale_shift =
                interpolator_type::subpixel_shift - gradient_subpixel_shift
        };

        //--------------------------------------------------------------------
        span_gradient() {}

        //--------------------------------------------------------------------
        span_gradient(interpolator_type& inter,
            GradientF& gradient_function,
            ColorF& color_function,
            double d1,
            double d2):
            m_interpolator(&inter),
            m_gradient_function(&gradient_function),
            m_color_function(&color_function),
            m_d1(iround(d1 * gradient_subpixel_scale)),
            m_d2(iround(d2 * gradient_subpixel_scale))
        {
        }

        //--------------------------------------------------------------------
        interpolator_type& interpolator()
        {
            return *m_interpolator;
        }
        const GradientF& gradient_function() const
        {
            return *m_gradient_function;
        }
        const ColorF& color_function() const
        {
            return *m_color_function;
        }
        double d1() const
        {
            return double(m_d1) / gradient_subpixel_scale;
        }
        double d2() const
        {
            return double(m_d2) / gradient_subpixel_scale;
        }

        //--------------------------------------------------------------------
        void interpolator(interpolator_type& i)
        {
            m_interpolator = &i;
        }
        void gradient_function(GradientF& gf)
        {
            m_gradient_function = &gf;
        }
        void color_function(ColorF& cf)
        {
            m_color_function = &cf;
        }
        void d1(double v)
        {
            m_d1 = iround(v * gradient_subpixel_scale);
        }
        void d2(double v)
        {
            m_d2 = iround(v * gradient_subpixel_scale);
        }

        //--------------------------------------------------------------------
        void prepare() {}

        //--------------------------------------------------------------------
        void generate(color_type* span, int x, int y, unsigned len)
        {
            int dd = m_d2 - m_d1;
            if (dd < 1)
                dd = 1;
            m_interpolator->begin(x + 0.5, y + 0.5, len);
            do
            {
                m_interpolator->coordinates(&x, &y);
                int d = m_gradient_function->calculate(
                    x >> downscale_shift, y >> downscale_shift, m_d2);
                d = ((d - m_d1) * (int)m_color_function->size()) / dd;
                if (d < 0)
                    d = 0;
                if (d >= (int)m_color_function->size())
                    d = m_color_function->size() - 1;
                *span++ = (*m_color_function)[d];
                ++(*m_interpolator);
            } while (--len);
        }

    private:
        interpolator_type* m_interpolator;
        GradientF* m_gradient_function;
        ColorF* m_color_function;
        int m_d1;
        int m_d2;
    };

    //=====================================================gradient_linear_color
    template <class ColorT>
    struct gradient_linear_color
    {
        typedef ColorT color_type;

        gradient_linear_color() {}
        gradient_linear_color(
            const color_type& c1, const color_type& c2, unsigned size = 256):
            m_c1(c1),
            m_c2(c2),
            m_size(size)
            // VFALCO 4/28/09
            ,
            m_mult(1 / (double(size) - 1))
        // VFALCO
        {
        }

        unsigned size() const
        {
            return m_size;
        }
        color_type operator[](unsigned v) const
        {
            // VFALCO 4/28/09
            // return m_c1.gradient(m_c2, double(v) / double(m_size - 1));
            return m_c1.gradient(m_c2, double(v) * m_mult);
            // VFALCO
        }

        void colors(
            const color_type& c1, const color_type& c2, unsigned size = 256)
        {
            m_c1 = c1;
            m_c2 = c2;
            m_size = size;
            // VFALCO 4/28/09
            m_mult = 1 / (double(size) - 1);
            // VFALCO
        }

        color_type m_c1;
        color_type m_c2;
        unsigned m_size;
        // VFALCO 4/28/09
        double m_mult;
        // VFALCO
    };

    //==========================================================gradient_circle
    class gradient_circle
    {
        // Actually the same as radial. Just for compatibility
    public:
        static AGG_INLINE int calculate(int x, int y, int)
        {
            return int(fast_sqrt(x * x + y * y));
        }
    };

    //==========================================================gradient_radial
    class gradient_radial
    {
    public:
        static AGG_INLINE int calculate(int x, int y, int)
        {
            return int(fast_sqrt(x * x + y * y));
        }
    };

    //========================================================gradient_radial_d
    class gradient_radial_d
    {
    public:
        static AGG_INLINE int calculate(int x, int y, int)
        {
            return uround(
                std::sqrt(double(x) * double(x) + double(y) * double(y)));
        }
    };

    //====================================================gradient_radial_focus
    class gradient_radial_focus
    {
    public:
        //---------------------------------------------------------------------
        gradient_radial_focus():
            m_r(100 * gradient_subpixel_scale),
            m_fx(0),
            m_fy(0)
        {
            update_values();
        }

        //---------------------------------------------------------------------
        gradient_radial_focus(double r, double fx, double fy):
            m_r(iround(r * gradient_subpixel_scale)),
            m_fx(iround(fx * gradient_subpixel_scale)),
            m_fy(iround(fy * gradient_subpixel_scale))
        {
            update_values();
        }

        //---------------------------------------------------------------------
        void init(double r, double fx, double fy)
        {
            m_r = iround(r * gradient_subpixel_scale);
            m_fx = iround(fx * gradient_subpixel_scale);
            m_fy = iround(fy * gradient_subpixel_scale);
            update_values();
        }

        //---------------------------------------------------------------------
        double radius() const
        {
            return double(m_r) / gradient_subpixel_scale;
        }
        double focus_x() const
        {
            return double(m_fx) / gradient_subpixel_scale;
        }
        double focus_y() const
        {
            return double(m_fy) / gradient_subpixel_scale;
        }

        //---------------------------------------------------------------------
        int calculate(int x, int y, int) const
        {
            double dx = x - m_fx;
            double dy = y - m_fy;
            double d2 = dx * m_fy - dy * m_fx;
            double d3 = m_r2 * (dx * dx + dy * dy) - d2 * d2;
            return iround(
                (dx * m_fx + dy * m_fy + std::sqrt(std::fabs(d3))) * m_mul);
        }

    private:
        //---------------------------------------------------------------------
        void update_values()
        {
            // Calculate the invariant values. In case the focal center
            // lies exactly on the gradient circle the divisor degenerates
            // into zero. In this case we just move the focal center by
            // one subpixel unit possibly in the direction to the origin (0,0)
            // and calculate the values again.
            //-------------------------
            m_r2 = double(m_r) * double(m_r);
            m_fx2 = double(m_fx) * double(m_fx);
            m_fy2 = double(m_fy) * double(m_fy);
            double d = (m_r2 - (m_fx2 + m_fy2));
            if (d == 0)
            {
                if (m_fx)
                {
                    if (m_fx < 0)
                        ++m_fx;
                    else
                        --m_fx;
                }
                if (m_fy)
                {
                    if (m_fy < 0)
                        ++m_fy;
                    else
                        --m_fy;
                }
                m_fx2 = double(m_fx) * double(m_fx);
                m_fy2 = double(m_fy) * double(m_fy);
                d = (m_r2 - (m_fx2 + m_fy2));
            }
            m_mul = m_r / d;
        }

        int m_r;
        int m_fx;
        int m_fy;
        double m_r2;
        double m_fx2;
        double m_fy2;
        double m_mul;
    };

    //==============================================================gradient_x
    class gradient_x
    {
    public:
        static int calculate(int x, int, int)
        {
            return x;
        }
    };

    //==============================================================gradient_y
    class gradient_y
    {
    public:
        static int calculate(int, int y, int)
        {
            return y;
        }
    };

    //========================================================gradient_diamond
    class gradient_diamond
    {
    public:
        static AGG_INLINE int calculate(int x, int y, int)
        {
            int ax = std::abs(x);
            int ay = std::abs(y);
            return ax > ay ? ax : ay;
        }
    };

    //=============================================================gradient_xy
    class gradient_xy
    {
    public:
        static AGG_INLINE int calculate(int x, int y, int d)
        {
            return std::abs(x) * std::abs(y) / d;
        }
    };

    //========================================================gradient_sqrt_xy
    class gradient_sqrt_xy
    {
    public:
        static AGG_INLINE int calculate(int x, int y, int)
        {
            return fast_sqrt(std::abs(x) * std::abs(y));
        }
    };

    //==========================================================gradient_conic
    class gradient_conic
    {
    public:
        static AGG_INLINE int calculate(int x, int y, int d)
        {
            return uround(
                std::fabs(std::atan2(double(y), double(x))) * double(d) / pi);
        }
    };

    //=================================================gradient_repeat_adaptor
    template <class GradientF>
    class gradient_repeat_adaptor
    {
    public:
        gradient_repeat_adaptor(const GradientF& gradient):
            m_gradient(&gradient)
        {
        }

        AGG_INLINE int calculate(int x, int y, int d) const
        {
            int ret = m_gradient->calculate(x, y, d) % d;
            if (ret < 0)
                ret += d;
            return ret;
        }

    private:
        const GradientF* m_gradient;
    };

    //================================================gradient_reflect_adaptor
    template <class GradientF>
    class gradient_reflect_adaptor
    {
    public:
        gradient_reflect_adaptor(const GradientF& gradient):
            m_gradient(&gradient)
        {
        }

        AGG_INLINE int calculate(int x, int y, int d) const
        {
            int d2 = d << 1;
            int ret = m_gradient->calculate(x, y, d) % d2;
            if (ret < 0)
                ret += d2;
            if (ret >= d)
                ret = d2 - ret;
            return ret;
        }

    private:
        const GradientF* m_gradient;
    };

}

#endif
