#include <stdio.h>
//GLEW
#define GLEW_STATIC
#include <GL\glew.h>
//GLFW
#include <glfw3.h>

void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode);

// WINDOW DIMENSIONS
const GLuint WIDTH = 1280, HEIGHT = 720;

// SHADERS
const GLchar* vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 position;\n"
"void main()\n"
"{\n"
"gl_Position = vec4(position.x, position.y, position.z 1.0);\n"
"}\0";
const GLchar* fragmentShaderSource = "#version 330 core\n"
"out vec4 color;\n"
"void main()\n"
"{\n"
"color = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
"}\0";

int main(void)
{
	// INIT CODE
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
	glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);

	GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "LearningOpenGL", nullptr, nullptr);
	if (window == nullptr) {
		printf("Failed to create GLFW window\n");
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);

	glfwSetKeyCallback(window, key_callback);

	glewExperimental = GL_TRUE;
	if (glewInit() != GLEW_OK) {
		printf("Failed to init GLEW\n");
		return -1;
	}

	int width, height;
    glfwGetFramebufferSize(window, &width, &height);  
    glViewport(0, 0, width, height);

	// SETUP RENDER SETTINGS
	GLfloat vertices[] = {
		-0.5f, -0.5f, 0.0f,
		 0.5f, -0.5f, 0.0f,
		 0.0f,  0.5f, 0.0f
	};

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

	// SHADERS!!!!

	// VERTEX SHADER
	GLuint vertexShader;
	vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);
	GLint success;
	GLchar infoLog[512];
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
	if (!success) {
		glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
		printf("ERROR SHADER VERTEX COMPILATION_FAILED\n%s", infoLog);
	}

	// FRAGMENT SHADER
	GLuint fragmentShader;
	fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
	glCompileShader(fragmentShader);
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success) {
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		printf("ERROR SHADER FRAGMENT COMPILATION_FAILED\n%s", infoLog);
	}

	// SHADER LINKING IN SHADER PROGRAM
	GLuint shaderProgram;
	shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);
	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
		printf("ERROR SHADER PROGRAM LINKING_FAILED\n%s", infoLog);
	}

	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);

	glUseProgram(shaderProgram);


	// MAIN GAME LOOP
	while (!glfwWindowShouldClose(window)) {
		glfwPollEvents();

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




		glfwSwapBuffers(window);
	}

	glfwTerminate();
	return 0;
}

// KAY CALLBACK FUNCTIONS
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode)
{
	if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS) {
		glfwSetWindowShouldClose(window, GL_TRUE);
	}
}