#include "3DRenderer.hpp"


// Rendering order:
//   model matrix (Object SRT) -> view matrix (camera matrix inverted) -> proj matrix -> clipping -> perspective divide -> viewport transformation -> Rasterizer (draw pixels inside projected triangles on 2D screen)
//   object coordinate -> world coordinate -> camera coordinate -> clip/screen coordinate
//
// Rasterizer inputs elements:
//   - texture-buffer (2D array of pixels color value)
//   - z-buffer (2D array of float representing the nearest pixel's depth, all pixels beyond are ignored)
//   - projected vertices-buffer on screen (using vertices-buffer and projection function)
//
// Refs:
//   * https://en.wikipedia.org/wiki/3D_projection
//   * https://www.scratchapixel.com/lessons/3d-basic-rendering/rasterization-practical-implementation/overview-rasterization-algorithm.html

Graphic3DRenderer::Graphic3DRenderer() {
    if (mMainCamera == nullptr) {
        mMainCamera = std::make_unique<Camera>();
        mMainCamera->SetPosition(0.0f, 3.0f, -20.0f);
        mMainCamera->SetFrustrum(90.0f, 1280.f/324.f, 1.0f, 100.f);
        mMainCamera->UpdateCamView();
    }
}

Graphic3DRenderer::~Graphic3DRenderer() {}

void Graphic3DRenderer::Draw(sf::RenderTexture& context) {
    sf::BlendMode sBM = sf::BlendNone;
    sf::RenderStates sRS(sBM);
    sf::Color yep[] = {sf::Color::White, sf::Color::Blue, sf::Color::Green, sf::Color::Red, sf::Color::Magenta, sf::Color::Cyan, sf::Color::Yellow};

    static float thetaAngle = 0.31f;
    thetaAngle = thetaAngle >= 6.283185f ? -6.283185f : thetaAngle + 0.004f;
    bool clipped = false;

    M3D_MATRIX viewMat = mMainCamera->GetView();
    M3D_MATRIX projMat = mMainCamera->GetProj();
    M3D_MATRIX modelMat = M3D_MIdentity() * M3D_TransformMatrixScaling(10.0f, 10.0f, 10.0f) * M3D_TransformMatrixRotationX(thetaAngle) * M3D_TransformMatrixRotationZ(0.5f*thetaAngle) * M3D_TransformMatrixTranslate(0.0f, 0.0f, 5.0f);
    M3D_MATRIX viewProjMat = (viewMat) * (projMat);
    M3D_MATRIX MVPMat = modelMat * viewProjMat;
    M3D_MATRIX viewportMat = M3D_TransformMatrixViewport(1280.0f, 324.f, 0.0f, 0.0f);
    uint8_t v_cnt = 0, yep_cnt = 0;
    sf::Vertex v_tri[4];
    M3D_F3 _2dCoord;
    
    for (const auto _v : testObj.mMesh) {
        M3D_VECTOR _vV = M3D_V4LoadF3(&_v.pos);
        M3D_VECTOR projV = M3D_V3Transform(_vV, MVPMat);
        //projV = M3D_V3Transform(projV, viewProjMat);
        
        // Clipping (simple)
        if (M3D_V4GetZ(projV) <= 0)
            clipped = true;

        // Perspective divide
        M3D_VECTOR _w = M3D_V4SplatW(projV);
        projV = M3D_V4Divide(projV, _w);

        // Viewport transform
        projV = M3D_V3Transform(projV, (viewportMat));
        M3D_V4StoreF3(&_2dCoord, projV);
        v_tri[v_cnt].position.x = _2dCoord.x;
        v_tri[v_cnt].position.y = _2dCoord.y;
        //v_tri[v_cnt].position.z = ((far+near)/2)+((far-near)/2)*_2dCoord.z;   //TODO: transform matrix is incomplete
        v_tri[v_cnt].color = yep[yep_cnt % 5];

        if (v_cnt++ >= 2) {
            if (!clipped) {
                v_tri[3] = v_tri[0];
                context.draw(v_tri, 4, sf::LineStrip, sRS);
                //context.draw(v_tri, 3, sf::Triangles, sRS);
            }
            v_cnt = 0;
            yep_cnt++;
            clipped = false;
        }
    }
}