#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;
};


// PUBLIC FUNCTIONS
void RenderMesh(Engine_Buffer &buffer, MeshRenderData &mesh)
{
    for(size_t f = 0; f < mesh.culledFaces.size(); ++f)
    {
        unsigned int vIndex0 = mesh.culledFaces[f].vertIndex[0];
        unsigned int vIndex1 = mesh.culledFaces[f].vertIndex[1];
        unsigned int vIndex2 = mesh.culledFaces[f].vertIndex[2];

        Vertex v0 = mesh.vertsTransformed[vIndex0];
        Vertex v1 = mesh.vertsTransformed[vIndex1];
        Vertex v2 = mesh.vertsTransformed[vIndex2];

        // Bounding box used to for iterating over possible pixels of this triangle
        BoundingBox box(v0.point, v1.point, v2.point);
        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;

        // Constants for this triangle used for barycentric calculations
        Vector v01 = v1.point - v0.point;
        Vector v02 = v2.point - v0.point;
        float dot0101 = Vector::Dot(v01, v01);
        float dot0102 = Vector::Dot(v01, v02);
        float dot0202 = Vector::Dot(v02, v02);

        // Iterate bounding box and determine if each point is in the triangle
        for (int y = yMin; y <= yMax; ++y)
        {
            for (int x = xMin; x <= xMax; ++x)
            {
                Point p(x, y, 1.0f);

                Vector v0P = p - v0.point;
                float dot0P01 = Vector::Dot(v0P, v01);
                float dot0P02 = Vector::Dot(v0P, v02);
                float denomInv = 1.0f / ((dot0101 * dot0202) - (dot0102 * dot0102));

                float barycenter[3];
                barycenter[1] = (dot0202 * dot0P01 - dot0102 * dot0P02) * denomInv;
                barycenter[2] = (dot0101 * dot0P02 - dot0102 * dot0P01) * denomInv;
                barycenter[0] = 1.0f - barycenter[1] - barycenter[2];

                // Point is inside the triangle
                if ( (barycenter[0] >= 0.0f)
                        && (barycenter[1] >= 0.0f)
                        && (barycenter[2] >= 0.0f))
                {
                    ColorF32 totalColor;

                    if (mesh.smooth)
                    {
                        totalColor =
                            (barycenter[0] * v0.color)
                            + (barycenter[1] * v1.color)
                            + (barycenter[2] * v2.color);
                    }
                    else
                    {
                        totalColor = mesh.culledFaces[f].color;
                    }

                    ColorU32 color = ColorF32::ConvertToU32(totalColor);


                    float z =
                        (barycenter[0] * v0.point.z)
                        + (barycenter[1] * v1.point.z)
                        + (barycenter[2] * v2.point.z);

                    float zInv = 1.0f / 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;
                    }
                }
            }
        }
    }
}