#define _CRT_SECURE_NO_WARNINGS
#include <windows.h>
#include "glew.h"
#include <gl/GL.h>
#include <stdio.h>
#pragma comment(lib,"opengl32.lib")
#pragma comment(lib, "glew32.lib")

struct Vertex {
	float pos[3];
	float color[4];
};

/**
* @hwnd 发起消息的窗口
* @msg 消息类型
*/
LRESULT CALLBACK GLWindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
	switch (msg) {
	case WM_CLOSE:
		PostQuitMessage(0);
		return 0;
	}

	return DefWindowProc(hwnd, msg, wParam, lParam);//其他消息调用window默认处理函数
}

char* LoadFileContent(const char *path) {
	char* fileContent = nullptr;
	int filesize = 0;
	FILE*pFile = fopen(path, "rb");
	if (pFile) {
		fseek(pFile, 0, SEEK_END);
		int nLen = ftell(pFile);
		if (nLen > 0) {
			rewind(pFile);
			fileContent = new char[nLen + 1];
			fread(fileContent, sizeof(char), nLen, pFile);
			fileContent[nLen] = '\0';
			filesize = nLen;
		}
		fclose(pFile);
	}
	return fileContent;
}

/**
* 创建一个GPU程序
*/
GLuint CreateGPUProgram(const char* vsShaderPath, const char* fsShaderPath) {
	//创建program
	GLuint program = glCreateProgram();

	//创建shader
	GLuint vsShader = glCreateShader(GL_VERTEX_SHADER);
	GLuint fsShader = glCreateShader(GL_FRAGMENT_SHADER);
	//读取shader代码
	const char* vsCode = LoadFileContent(vsShaderPath);
	const char* fsCode = LoadFileContent(fsShaderPath);
	//把shader代码 从内存传到显存
	glShaderSource(vsShader, 1, &vsCode, nullptr);
	glShaderSource(fsShader, 1, &fsCode, nullptr);
	//编译shader
	glCompileShader(vsShader);
	glCompileShader(fsShader);
	
	//绑定shader
	glAttachShader(program, vsShader);
	glAttachShader(program, fsShader);

	//连接
	glLinkProgram(program);

	//解绑shader
	glDetachShader(program, vsShader);
	glDetachShader(program, fsShader);

	//删除shader
	glDeleteShader(vsShader);
	glDeleteShader(fsShader);

	return program;
}
/**
* @hinstance 本应用程序启动实例
* @hPrevInstance 上一次应用程式的实例
* @IpCmdLine 命令行的参数
* @ShowCmd 怎么显示窗口
*/
INT WINAPI WinMain(HINSTANCE hinstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
	/*注册窗口*/
	WNDCLASSEX wndclass;
	wndclass.cbClsExtra = 0; //窗口类型的额外空间，这里不需要
	wndclass.cbSize = sizeof(WNDCLASSEX); //窗口实际占用的内存
	wndclass.cbWndExtra = 0; //窗口的额外空间，这里不需要
	wndclass.hbrBackground = NULL; //窗口背景
	wndclass.hCursor = LoadCursor(NULL, IDC_ARROW); //定义鼠标类型
	wndclass.hIcon = NULL; //应用程序exe文件显示图标
	wndclass.hIconSm = NULL; //应用程序运行时左上角图标
	wndclass.hInstance = hinstance; //本应用程序实例
	wndclass.lpfnWndProc = GLWindowProc; //如果用户操作了窗口，本函数会被调用
	wndclass.lpszClassName = L"GLWindow";//窗口名称
	wndclass.lpszMenuName = NULL;//菜单名称
	wndclass.style = CS_VREDRAW | CS_HREDRAW;//窗口更新时的重绘方式，这里使用垂直重绘和水平重绘
	ATOM atom = RegisterClassEx(&wndclass);
	if (!atom) {
		MessageBox(NULL, L"Register failed", L"Error", MB_OK);
		return  0;
	}

	/*创建窗口*/
	//调整窗口大小
	RECT rect;
	rect.left = 0;
	rect.right = 800;
	rect.top = 0;
	rect.bottom = 600;
	AdjustWindowRect(&rect, WS_EX_OVERLAPPEDWINDOW, NULL);
	int windowWidth = rect.right - rect.left;
	int windowHeight = rect.bottom - rect.top;

	//窗口名称一定要和刚才注册窗口的保持一致
	HWND hwnd = CreateWindowEx(NULL, L"GLWindow", L"OpenGL Window", WS_OVERLAPPEDWINDOW, 100, 100, windowWidth, windowHeight, NULL, NULL, hinstance, NULL);

	//设置渲染环境
	HDC dc = GetDC(hwnd);//获取设备上下文
	PIXELFORMATDESCRIPTOR pfd;
	memset(&pfd, 0, sizeof(PIXELFORMATDESCRIPTOR));
	pfd.nVersion = 1;
	pfd.nSize = sizeof(PIXELFORMATDESCRIPTOR);
	pfd.cColorBits = 32; //颜色缓冲区每个像素为32比特4通道RGBA
	pfd.cDepthBits = 24; //深度缓冲区每个像素大小，24比特表示一个浮点数
	pfd.cStencilBits = 8; //蒙板缓冲区每像素为8比特
	pfd.iPixelType = PFD_TYPE_RGBA; //设置像素类型为RGBA
	pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER; //表示像素最后输出到窗口
																			  //设置像素格式
	int pixelFormat = ChoosePixelFormat(dc, &pfd);
	SetPixelFormat(dc, pixelFormat, &pfd);

	//创建OpenGL渲染环境
	HGLRC rc = wglCreateContext(dc);
	wglMakeCurrent(dc, rc);//设置OpenGL渲染环境生效

	/*glew初始化*/
	glewInit();

	/*创建program*/
	GLuint program = CreateGPUProgram("test.vs", "test.fs");

	/*创建vbo*/
	Vertex vertex[3];

	vertex[0].pos[0] = 0;
	vertex[0].pos[1] = 0;
	vertex[0].pos[2] = -100.0f;
	vertex[0].color[0] = 1.0f;
	vertex[0].color[1] = 1.0f;
	vertex[0].color[2] = 1.0f;
	vertex[0].color[3] = 1.0f;

	vertex[1].pos[0] = 10;
	vertex[1].pos[1] = 0;
	vertex[1].pos[2] = -100.0f;
	vertex[1].color[0] = 1.0f;
	vertex[1].color[1] = 1.0f;
	vertex[1].color[2] = 1.0f;
	vertex[1].color[3] = 1.0f;

	vertex[2].pos[0] = 0;
	vertex[2].pos[1] = 10;
	vertex[2].pos[2] = -100.0f;
	vertex[2].color[0] = 1.0f;
	vertex[2].color[1] = 1.0f;
	vertex[2].color[2] = 1.0f;
	vertex[2].color[3] = 1.0f;
	GLuint vbo;
	glGenBuffers(1, &vbo);
	glBindBuffer(GL_ARRAY_BUFFER, vbo);
	glBufferData(GL_ARRAY_BUFFER, sizeof(float)*7*3, vertex, GL_STATIC_DRAW);
	glBindBuffer(GL_ARRAY_BUFFER, 0);

	glClearColor(1.0f, 1.0f, 0.0f, 1.0f);

	/*显示窗口*/
	ShowWindow(hwnd, SW_SHOW);
	UpdateWindow(hwnd);

	/*监听并处理用户请求*/
	MSG msg;
	while (true) {
		if (PeekMessage(&msg, NULL, NULL, NULL, PM_REMOVE)) {
			if (msg.message == WM_QUIT) {
				break;
			}
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}

		glClear(GL_COLOR_BUFFER_BIT);

		SwapBuffers(dc);
	}

	return 0;
}