#include "color.h"
#include "engine.h"
#include "geometry.h"
#include "util.h"
#include <cstdio>


// MACROS
#define DrawPixel(buffer, width, color, x, y)\
{\
    buffer[width * y + x] = color;\
}


// STRUCTURES
struct BoundingBox
{
    BoundingBox(Point &v0, Point &v1, Point &v2)
    {
        yMin = MIN(v0.y, MIN(v1.y, v2.y));
        yMax = MAX(v0.y, MAX(v1.y, v2.y));

        xMin = MIN(v0.x, MIN(v1.x, v2.x));
        xMax = MAX(v0.x, MAX(v1.x, v2.x));
    }

    float yMin, yMax;
    float xMin, xMax;
};


static void ComputeBarycenter(float *w, Point &v0, Point &v1, Point &v2, Point &p)
{
    float area = (v2.x - v0.x) * (v1.y - v0.y) - (v2.y - v0.y) * (v1.x - v0.x);

    float result[3];
    result[0] = (p.x - v1.x) * (v2.y - v1.y) - (p.y - v1.y) * (v2.x - v1.x);
    result[1] = (p.x - v2.x) * (v0.y - v2.y) - (p.y - v2.y) * (v0.x - v2.x);
    result[2] = (p.x - v0.x) * (v1.y - v0.y) - (p.y - v0.y) * (v1.x - v0.x);

    result[0] /= area;
    result[1] /= area;
    result[2] /= area;

    w[0] = result[0];
    w[1] = result[1];
    w[2] = result[2];
}


// PUBLIC FUNCTIONS
void FillTriangle(
        Engine_Buffer &buffer, ColorU32 &color,
        Point &v0, Point &v1, Point &v2)
{
    BoundingBox box(v0, v1, v2);
    int yMin = (int)ceilf(box.yMin);
    int yMax = (int)ceilf(box.yMax) - 1;
    int xMin = (int)ceilf(box.xMin);
    int xMax = (int)ceilf(box.xMax) - 1;

    for (int y = yMin; y <= yMax; ++y)
    {
        for (int x = xMin; x <= xMax; ++x)
        {
            Point p(x, y, 1.0f);

            float barycenter[3];

            ComputeBarycenter(barycenter, v0, v1, v2, p);

            if (barycenter[0] >= 0 && barycenter[1] >= 0 && barycenter[2] >= 0)
            {
                float zInv =
                    (barycenter[0] * (1.0f/v0.z))
                    + (barycenter[1] * (1.0f/v1.z))
                    + (barycenter[2] * (1.0f/v2.z));

                int pixel = (y * buffer.width + x);

                if (zInv > buffer.zbuffer[pixel])
                {
                    DrawPixel(buffer.buffer, buffer.width, color.u32, x, y);

                    buffer.zbuffer[pixel] = zInv;
                }
            }
        }
    }
}