#include <stdio.h>
#include <stdlib.h>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <glm/glm.hpp>

using namespace glm;

const unsigned int WIN_WIDTH = 1024;
const unsigned int WIN_HEIGHT = 768;
const char TITLE[] = "Tutorial 02";

GLFWwindow *init() {
    if (!glfwInit()) {
        fprintf(stderr, "Failed to iniatialize GLFW\n");
        return NULL;
    }

    glfwWindowHint(GLFW_SAMPLES, 4);               // 4x antialiasing
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); // openGL version 3.3
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
    // dla kompatybilności z MacOS. Normalnie niepotrzebne
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    // nie chcemy starego openGL.

    GLFWwindow *window;
    window = glfwCreateWindow(WIN_WIDTH, WIN_HEIGHT, TITLE, NULL, NULL);

    if (window == NULL) {
        fprintf(stderr, "Failed to open GLFW window\n");
        glfwTerminate();
        return NULL;
    }

    // upewniamy się , czy klawisz "escape" jest łapany odpowiednio
    glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);

    glfwMakeContextCurrent(window);
    glewExperimental = GL_TRUE;
    GLenum err = glewInit();
    if (GLEW_OK != err) {
        fprintf(stderr, "Error: %s\n", glewGetErrorString(err));
        glfwTerminate();
        exit(1);
    }

    return window;
}

GLuint initVAO() {
    glewExperimental = GL_TRUE;
    GLuint VertexArrayID;
    glGenVertexArrays(1, &VertexArrayID);
    glBindVertexArray(VertexArrayID);
    return VertexArrayID;
}

static const GLfloat g_vertex_buffer_data[] = {
    -1.0f, -1.0f, 0.0f,
    1.0f, -1.0f, 0.0f,
    0.f, 1.0f, 0.0f,
};

int main() {
    GLFWwindow *window = init();
    if (!window) {
        return -1;
    }

    initVAO();

    GLuint vertex_buffer;
    glGenBuffers(1, &vertex_buffer);
    glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data),
            g_vertex_buffer_data, GL_STATIC_DRAW);

    do {
        initVAO();
        glEnableVertexAttribArray(0);

        glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
        glVertexAttribPointer(
                0, // attribute 0. Brak uzasadnienia
                3, // rozmiar
                GL_FLOAT, // type
                GL_FALSE, // znormalizowane
                0,        // stride
                (void*)0  // array buffer offset
        );

        glDrawArrays(GL_TRIANGLES, 0, 3);
        glDisableVertexAttribArray(0);

        glfwSwapBuffers(window);
        glfwPollEvents();

    } while (glfwGetKey(window, GLFW_KEY_ESCAPE) != GLFW_PRESS &&
            glfwWindowShouldClose(window) == 0);

    return 0;
}