#define __NR_PIXBLOCK_SCALER_CPP__

#include <glib.h>
#include <cmath>
using std::floor;

#include "libnr/nr-pixblock.h"

namespace NR {

struct RGBA {
    int r, g, b, a;
};

inline int sampley(unsigned const char a, unsigned const char b, unsigned const char c, unsigned const char d, const double len) {
    double lenf = len - floor(len);
    int sum = 0;
    sum += (int)((((-1.0 / 3.0) * lenf + 4.0 / 5.0) * lenf - 7.0 / 15.0)
                 * lenf * 256 * a);
    sum += (int)((((lenf - 9.0 / 5.0) * lenf - 1.0 / 5.0) * lenf + 1.0)
                 * 256 * b);
    sum += (int)(((((1 - lenf) - 9.0 / 5.0) * (1 - lenf) - 1.0 / 5.0)
                  * (1 - lenf) + 1.0) * 256 * c);
    sum += (int)((((-1.0 / 3.0) * (1 - lenf) + 4.0 / 5.0) * (1 - lenf)
                  - 7.0 / 15.0) * (1 - lenf) * 256 * d);
    return sum;
}

inline unsigned char samplex(const int a, const int b, const int c, const int d, const double len) {
    double lenf = len - floor(len);
    int sum = 0;
    sum += (int)(a * (((-1.0 / 3.0) * lenf + 4.0 / 5.0) * lenf - 7.0 / 15.0) * lenf);
    sum += (int)(b * (((lenf - 9.0 / 5.0) * lenf - 1.0 / 5.0) * lenf + 1.0));
    sum += (int)(c * ((((1 - lenf) - 9.0 / 5.0) * (1 - lenf) - 1.0 / 5.0) * (1 - lenf) + 1.0));
    sum += (int)(d * (((-1.0 / 3.0) * (1 - lenf) + 4.0 / 5.0) * (1 - lenf) - 7.0 / 15.0) * (1 - lenf));
    if (sum < 0) sum = 0;
    if (sum > 255*256) sum = 255 * 256;
    return (unsigned char)(sum / 256);
}

/**
 * Sanity check function for indexing pixblocks.
 * Catches reading and writing outside the pixblock area.
 * When enabled, decreases filter rendering speed massively.
 */
inline void _check_index(NRPixBlock const * const pb, int const location, int const line)
{
    if(true) {
        int max_loc = pb->rs * (pb->area.y1 - pb->area.y0);
        if (location < 0 || (location + 4) >= max_loc)
            g_warning("Location %d out of bounds (0 ... %d) at line %d", location, max_loc, line);
    }
}

void scale_bicubic(NRPixBlock *to, NRPixBlock *from)
{
    int from_width = from->area.x1 - from->area.x0;
    int from_height = from->area.y1 - from->area.y0;
    int to_width = to->area.x1 - to->area.x0;
    int to_height = to->area.y1 - to->area.y0;

    double from_stepx = (double)from_width / (double)to_width;
    double from_stepy = (double)from_height / (double)to_height;

    for (int to_y = 0 ; to_y < to_height ; to_y++) {
        double from_y = to_y * from_stepy + from_stepy / 2;
        int from_line[4];
        for (int i = 0 ; i < 4 ; i++) {
            if ((int)floor(from_y) + i - 1 >= 0) {
                if ((int)floor(from_y) + i - 1 < from_height) {
                    from_line[i] = ((int)floor(from_y) + i - 1) * from->rs;
                } else {
                    from_line[i] = (from_height - 1) * from->rs;
                }
            } else {
                from_line[i] = 0;
            }
        }
        for (int to_x = 0 ; to_x < to_width ; to_x++) {
            double from_x = to_x * from_stepx + from_stepx / 2;
            RGBA line[4];
            for (int i = 0 ; i < 4 ; i++) {
                int k = (int)floor(from_x) + i - 1;
                if (k < 0) k = 0;
                if (k >= from_width) k = from_width - 1;
                k *= 4;
                _check_index(from, from_line[0] + k, __LINE__);
                _check_index(from, from_line[1] + k, __LINE__);
                _check_index(from, from_line[2] + k, __LINE__);
                _check_index(from, from_line[3] + k, __LINE__);
                line[i].r = sampley(NR_PIXBLOCK_PX(from)[from_line[0] + k],
                                    NR_PIXBLOCK_PX(from)[from_line[1] + k],
                                    NR_PIXBLOCK_PX(from)[from_line[2] + k],
                                    NR_PIXBLOCK_PX(from)[from_line[3] + k],
                                    from_y);
                line[i].g = sampley(NR_PIXBLOCK_PX(from)[from_line[0] + k + 1],
                                    NR_PIXBLOCK_PX(from)[from_line[1] + k + 1],
                                    NR_PIXBLOCK_PX(from)[from_line[2] + k + 1],
                                    NR_PIXBLOCK_PX(from)[from_line[3] + k + 1],
                                    from_y);
                line[i].b = sampley(NR_PIXBLOCK_PX(from)[from_line[0] + k + 2],
                                    NR_PIXBLOCK_PX(from)[from_line[1] + k + 2],
                                    NR_PIXBLOCK_PX(from)[from_line[2] + k + 2],
                                    NR_PIXBLOCK_PX(from)[from_line[3] + k + 2],
                                    from_y);
                line[i].a = sampley(NR_PIXBLOCK_PX(from)[from_line[0] + k + 3],
                                    NR_PIXBLOCK_PX(from)[from_line[1] + k + 3],
                                    NR_PIXBLOCK_PX(from)[from_line[2] + k + 3],
                                    NR_PIXBLOCK_PX(from)[from_line[3] + k + 3],
                                    from_y);
            }
            RGBA result;
            result.r = samplex(line[0].r, line[1].r, line[2].r, line[3].r,
                               from_x);
            result.g = samplex(line[0].g, line[1].g, line[2].g, line[3].g,
                               from_x);
            result.b = samplex(line[0].b, line[1].b, line[2].b, line[3].b,
                               from_x);
            result.a = samplex(line[0].a, line[1].a, line[2].a, line[3].a,
                               from_x);

            _check_index(to, to_y * to->rs + to_x * 4, __LINE__);
            NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4] = result.r;
            NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 1] = result.g;
            NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 2] = result.b;
            NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 3] = result.a;
        }
    }
}

} /* namespace NR */
/*
  Local Variables:
  mode:c++
  c-file-style:"stroustrup"
  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
  indent-tabs-mode:nil
  fill-column:99
  End:
*/
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