#include "Gpu.h"
GPU::GPU() {}

GPU::~GPU() {
	if (mFrameBuffer) {
		delete mFrameBuffer;
	}
}

void GPU::initGL(const uint32_t& width, const uint32_t& height, void* buffer) {
	m_screenWidth = width;
	m_screenHeight = height;
	mFrameBuffer = new FrameBuffer(width, height, buffer);
}

void GPU::clear() {
	std::fill_n(mFrameBuffer->mColorBuffer, mFrameBuffer->mPixelSize, RGBA(0, 0, 0, 0));
	std::fill_n(mFrameBuffer->mDepthBuffer, mFrameBuffer->mPixelSize, FLT_MAX);
}

void GPU::drawPoint(const int& x, const int& y, const RGBA& color, const float& depth) {
	//从窗口左下角开始算起
	if (x < 0 || x >= m_screenWidth || y < 0 || y >= m_screenHeight) { return; }
	uint32_t pixelPos = y * mFrameBuffer->mWidth + x;

	/*depth-test*/
	if (depth > mFrameBuffer->mDepthBuffer[pixelPos]) { return; }
	mFrameBuffer->mColorBuffer[pixelPos] = color;
	mFrameBuffer->mDepthBuffer[pixelPos] = depth;
}

void GPU::drawVerticalLine(const int& x, const int& y_min, const int y_max, const RGBA& color, const float& depth)
{
	for (int i = std::max(y_min,0); i <= std::min(y_max,SCREEN_HEIGHT); i++)
	{
		drawPoint(x, i, color, depth);
	}
}

void GPU::drawRect(const int& x_min, const int x_max, const int y_min, const int y_max, const RGBA& color, const float& depth)
{
	for (int i = x_min; i <= x_max; i++)
	{
		drawVerticalLine(i, y_min, y_max, color, depth);
	}
}

void GPU::drawLine(const int& x_from, const int& y_from, const int& x_to, const int& y_to, const RGBA& color, const float& depth)
{
	int disX = abs((int)(x_to - x_from));
	int disY = abs((int)(y_to - y_from)); 
	int xNow = x_from;
	int yNow = y_from;

  
	int stepX = 0;
	int stepY = 0;
      
	stepX = (x_to > x_from) ? 1 : ((x_to < x_from) ? -1 : 0);
	stepY = (y_to > y_from) ? 1 : ((y_to < y_from) ? -1 : 0);

	bool useXStep = true;
	if (disX < disY)
	{
		useXStep = false;
		SWAP_INT(disX, disY);
	}
	int sumStep = disX;
	int p = 2 * disY - disX;
	for (int i = 0; i < sumStep; i++)
	{
		float _scale = 0;
		if (useXStep)
		{
			if (x_to != x_from)
			{
				_scale = (float)(xNow - x_from) / (float)(x_to - x_from);
			}
		}
		else
		{
			if (y_to != y_from)
			{
				_scale = (float)(yNow - y_from) / (float)(y_to - y_from);
			}
		}
		drawPoint(xNow, yNow, color);
		if (p >= 0)
		{
			if (useXStep)
			{
				yNow += stepY;
			}
			else
			{
				xNow += stepX;
			}
			p -= 2 * disX;
		}      
		if (useXStep)
		{
			xNow += stepX;
		}
		else
		{
			yNow += stepY;
		}
		p += 2 * disY;
	}
}