#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"
#include <glad\glad.h>
#include <GLFW\glfw3.h>
#include <iostream>

const unsigned int WINDOW_WIDTH = 800;
const unsigned int WINDOW_HEIGHT = 600;


//位置 顏色 文理座標
const char* vertexSource = "#version 330 core\n"
"layout(location = 0) in vec3 aPos;\n"
"layout(location = 1) in vec3 aColor;\n"
"layout(location = 2) in vec2 aTexCoord;\n"
"out vec3 ourColor;\n"
"out vec2 TexCoord;\n"
"void main(){\n"
"gl_Position = vec4(aPos, 1.0);\n"
"ourColor = aColor;\n"
"TexCoord = vec2(aTexCoord.x, aTexCoord.y);\n"
"}\n\0"
;


//GLSL內建自帶的取樣器
const char* fragmentSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"in vec3 ourColor;\n"
"in vec2 TexCoord;\n"
"uniform sampler2D texture1;\n"
"void main(){\n"
"FragColor = texture(texture1, TexCoord);\n"
"}\n\0"
;


void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);


int main()
{

	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#ifdef __APPLE__
		glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // uncomment this statement to fix compilation on OS X
#endif
   
	GLFWwindow* window = glfwCreateWindow(WINDOW_WIDTH, WINDOW_HEIGHT, "Zhongqi", NULL, NULL);
	if (window == NULL)
	{
		std::cout << "Create Window Failed\n" << std::endl;
		glfwTerminate();
		return -1;
	}

	glfwMakeContextCurrent(window);
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
	
	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
			return -1;
	}

	//建立頂點著色器
	int vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexSource, NULL);
	glCompileShader(vertexShader);
	int success;
	char infoLog[512];
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
		std::cout << "Compile Vertex Error :" << infoLog << std::endl;
	}


	//建立片段著色器
	int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentSource, NULL);
	glCompileShader(fragmentShader);
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		std::cout << "Compile Fragment Eror :" << infoLog << std::endl;
	}

	//建立著色器程式
	unsigned int shaderPrograme = glCreateProgram();
	glAttachShader(shaderPrograme, vertexShader);
	glAttachShader(shaderPrograme, fragmentShader);
	glLinkProgram(shaderPrograme);
	glGetProgramiv(shaderPrograme, GL_LINK_STATUS, &success);
	if (!success)
	{
		glGetProgramInfoLog(shaderPrograme, 512, NULL, infoLog);
		std::cout << "Link Programe Error\n" << std::endl;
	}

	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);
	
	//建立頂點資料
	float firstTrangles[] = {
	 //座標              顏色               紋理座標	
	 //top left
     -0.5f,0.5f,0.0f,	1.0f,0.0f,0.0f,		0.0f,1.0f,
	 //top right
     0.5f,0.5f,0.0f,    0.0f,1.0f,0.0f,		1.0f,1.0f,
     //bottom left
     -0.5f,-0.5f,0.0f,  0.0f,0.0f,1.0f,     0.0f,0.0f,
     //bottom right
    0.5f,-0.5f,0.0f,    1.0f,1.0f,0.0f,     1.0f,0.0f 

	};

    //建立索引資料
	unsigned int indexes[] = {
		0,1,3,
		0,2,3
	};

	//建立VAO VBO EBO
	unsigned int VAO, VBO, EBO;
	glGenVertexArrays(1, &VAO);
	glGenBuffers(1, &VBO);
	glGenBuffers(1, &EBO);

	glBindVertexArray(VAO);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	glBufferData(GL_ARRAY_BUFFER, sizeof(firstTrangles), firstTrangles, GL_STATIC_DRAW);

	//設定EBO
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indexes), indexes, GL_STATIC_DRAW);

	//屬性指標
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(0));
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
	glEnableVertexAttribArray(1);
	glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
	glEnableVertexAttribArray(2);

	//製作紋理
	unsigned int firstTexTure;
	glGenTextures(1, &firstTexTure);
	glBindTexture(GL_TEXTURE_2D, firstTexTure);
	/*紋理環繞方式設定為GL_MIRRORED_REPEAT*/
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_MIRRORED_REPEAT);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_MIRRORED_REPEAT);
	/*紋理過濾設定 放大的時候臨近過濾 縮小的時候線性過濾*/
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

	//載入影象檔案 製作紋理
	int texture_width, texture_height, mChannels;
	unsigned char* data = stbi_load("container.jpg", &texture_width, &texture_height, &mChannels, 0);
	//用影象資料生成紋理
	if (data)
	{
		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, texture_width, texture_height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
		glGenerateMipmap(GL_TEXTURE_2D);
		
	}
	else
	{
		std::cout << "Failed Load Image\n" << std::endl;
	}
	//釋放圖形記憶體
	stbi_image_free(data);

	//渲染
	while (!glfwWindowShouldClose(window))
	{
		processInput(window);
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		glBindTexture(GL_TEXTURE_2D, firstTexTure);
		glUseProgram(shaderPrograme);
		glBindVertexArray(VAO);
		//呼叫glDrawElements之前繫結紋理，它會自動把紋理賦值給片段著色器的取樣器：
		
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

		glfwSwapBuffers(window);
		glfwPollEvents();
	}

	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	glDeleteBuffers(1, &EBO);

	// glfw: terminate, clearing all previously allocated GLFW resources.
	// ------------------------------------------------------------------
	glfwTerminate();

	
	return 0;
}

void processInput(GLFWwindow *window)
{
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
		glfwSetWindowShouldClose(window, true);
}

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
	glViewport(0, 0, width, height);
} 
 

效果圖