#include <iostream>
#include <glad/glad.h> 
#include <GLFW/glfw3.h>
#include <shaders/shader.hpp>

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);
	//glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);

	GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
	if (window == NULL)
	{
		std::cout << "Failed to create GLFW window" << std::endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);

	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		std::cout << "Failed to initialize GLAD" << std::endl;
		return -1;
	}

	glViewport(0, 0, 800, 600);

	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

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

	unsigned int indices[] = {  // note that we start from 0!
	    0, 1, 2
	};

	unsigned int VBO;
	glGenBuffers(1, &VBO);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

	unsigned int VAO;
	glGenVertexArrays(1, &VAO);
	glBindVertexArray(VAO);

	unsigned int EBO;
	glGenBuffers(1, &EBO);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
	glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

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

	Shader ourShader("shaders/shader.vs", "shaders/shader.fs");

	while(!glfwWindowShouldClose(window))
	{
		processInput(window);

		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		ourShader.use();
		glBindVertexArray(VAO);
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
		glBindVertexArray(0);

		glfwSwapBuffers(window);
		glfwPollEvents();    
	}

	glfwTerminate();

	return 0;
}

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);
	}
}