include pch include iostream include glad glad include GLFW glfw3 void

#include "pch.h"
#include <iostream>
#include <glad/glad.h>
#include <GLFW/glfw3.h>

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

const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

const char *vertexShaderSource = "#version 330 core\n"
	"layout (location = 0) in vec3 aPos;\n"
	"void main()\n"
	"{\n"
	"	gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
	"}\0";

const char *fragmentShaderSource = "#version 330 core\n"
	"out vec4 FragColor;\n"
	"void main()\n"
	"{\n"
	"	FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
	"}\0";

int main(int argc, char** argv)
{
	// glfw: initialize and configure
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	// glfw window creation
	GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
	if (window == NULL) {
		std::cout << "Failed to create GLFW window" << std::endl;
		glfwTerminate();
		return EXIT_FAILURE;
	}
	glfwMakeContextCurrent(window);
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

	// glad: load all OpenGL function pointers
	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		std::cout << "Failed to initialize GLAD" << std::endl;
		return EXIT_FAILURE;
	}

	// compiling vertex shader
	unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);
	// check if shader compiled well
	int  success;
	char infoLog[512];
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
	}

	// compile fragment shader
	unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
	glCompileShader(fragmentShader);
	// check if shader compiled well
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
	}

	// link shaders
	unsigned int shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);
	// check if program linked well
	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
	}
	// delete shaders
	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);


	// activate program object
	//glUseProgram(shaderProgram);

	float vertices[] = {
		 0.5f,  0.5f, 0.0f,
		 0.5f, -0.5f, 0.0f,
		-0.5f, -0.5f, 0.0f,
		-0.5f,  0.5f, 0.0f
	};

	unsigned int indices[] = {
		0, 1, 3,	// first triangle
		1, 2, 3		// second triangle
	};
	
	// loading data into graphics card memory
	unsigned int VBO, VAO, EBO;
	glGenVertexArrays(1, &VAO);
	glGenBuffers(1, &VBO);
	glGenBuffers(1, &EBO);
	glBindVertexArray(VAO);

	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(0);
	glBindBuffer(GL_ARRAY_BUFFER, 0);
	glBindVertexArray(0);

	// render loop
	while (!glfwWindowShouldClose(window)) {
		// input
		processInput(window);

		// render
		glClearColor(0.2, 0.3, 0.3, 1.0);
		glClear(GL_COLOR_BUFFER_BIT);

		glUseProgram(shaderProgram);
		glBindVertexArray(VAO);
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

		// check and call all events and swap the buffers
		glfwSwapBuffers(window);
		glfwPollEvents();
	}

	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	//glDeleteBuffers(1, &EBO);
	glfwTerminate();
	return EXIT_SUCCESS;
}

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

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