#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);

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

    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);
    sf::Vertex v_tri[4];
    auto cubeMesh = testObj.GetObjectMesh();

    // Do the vertices projection and perspective divide
    M3D_F3 projVertices[cubeMesh.vertices.size()];
    M3D_V3TransformPersDiv(projVertices, sizeof(M3D_F3), (M3D_F3*)cubeMesh.vertices.data(), sizeof(Vertex), cubeMesh.vertices.size(), MVPMat);

    auto indicePtr = (uint32_t*)cubeMesh.parts[0].indices.data();
    for (uint32_t i = 0; i < cubeMesh.parts[0].indices.size(); i += 3) {
        // Misscontructed indices tree failsafe
        if (i+2 > cubeMesh.parts[0].indices.size())
            break;

        // Simple clipping
        //TODO: implement complete Cohen-Sutherland algo or similar
        if ((projVertices[indicePtr[i]]).z > 0 &&
            (projVertices[indicePtr[i+1]]).z > 0 &&
            (projVertices[indicePtr[i+2]]).z > 0) {

                M3D_VECTOR V1 = M3D_V4LoadF3(&projVertices[indicePtr[i]]);
                M3D_VECTOR V2 = M3D_V4LoadF3(&projVertices[indicePtr[i+1]]);
                M3D_VECTOR V3 = M3D_V4LoadF3(&projVertices[indicePtr[i+2]]);

                V1 = M3D_V3Transform(V1, viewportMat);
                V2 = M3D_V3Transform(V2, viewportMat);
                V3 = M3D_V3Transform(V3, viewportMat);
                //v_tri[v_cnt].position.z = ((far+near)/2)+((far-near)/2)*_2dCoord.z;   //TODO: transform matrix is incomplete

                v_tri[0].position = sf::Vector2f(M3D_V4GetX(V1), M3D_V4GetY(V1));
                v_tri[0].color = cubeMesh.vertices[indicePtr[i]].color;
                v_tri[3] = v_tri[0];
                v_tri[1].position = sf::Vector2f(M3D_V4GetX(V2), M3D_V4GetY(V2));
                v_tri[1].color = cubeMesh.vertices[indicePtr[i+1]].color;
                v_tri[2].position = sf::Vector2f(M3D_V4GetX(V3), M3D_V4GetY(V3));
                v_tri[2].color = cubeMesh.vertices[indicePtr[i+2]].color;
                context.draw(v_tri, 4, sf::LineStrip, sRS);
                //context.draw(v_tri, 3, sf::Triangles, sRS);
        } //TODO: else cut triangle to the window (need vector crossing math...)
    }
}