text: #include <glad/glad.h>
  #include <GLFW/glfw3.h>
  
  #include <glm/glm.hpp>
  #include <glm/gtc/matrix_transform.hpp>
  #include <glm/gtc/type_ptr.hpp>
  
  #include "filesystem.h"
  #include "shader_m.h"
  #include "camera.h"
  #include "model.h"
  
  #include <iostream>
  
  void framebuffer_size_callback(GLFWwindow* window, int width, int height);
  void mouse_callback(GLFWwindow* window, double xpos, double ypos);
  void scroll_callback(GLFWwindow* window, double xoffset, double yoffset);
  void processInput(GLFWwindow *window);
  
  // settings
  const unsigned int SCR_WIDTH = 800;
  const unsigned int SCR_HEIGHT = 600;
  
  // camera
  Camera camera(glm::vec3(0.0f, 0.0f, 3.0f));
  float lastX = SCR_WIDTH / 2.0f;
  float lastY = SCR_HEIGHT / 2.0f;
  bool firstMouse = true;
  
  // timing
  float deltaTime = 0.0f;
  float lastFrame = 0.0f;
  
  int main()
  {
      // 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);
      glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // uncomment this statement to fix compilation on OS X
  
      // glfw window creation
      // --------------------
      GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "Modeller", NULL, NULL);
      if (window == NULL)
      {
          std::cout << "Failed to create GLFW window" << std::endl;
          glfwTerminate();
          return -1;
      }
      glfwMakeContextCurrent(window);
      glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
      glfwSetCursorPosCallback(window, mouse_callback);
      glfwSetScrollCallback(window, scroll_callback);
  
      // tell GLFW to capture our mouse
      glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
  
      // glad: load all OpenGL function pointers
      // ---------------------------------------
      if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
      {
          std::cout << "Failed to initialize GLAD" << std::endl;
          return -1;
      }
  
      // configure global opengl state
      // -----------------------------
      glEnable(GL_DEPTH_TEST);
  
      // build and compile shaders
      // -------------------------
      Shader ourShader("shader.vs", "shader.fs");
  
      // load models
      // -----------
      Model ourModel(FileSystem::getPath("resources/objects/planet/planet.obj"));
  
      
      // draw in wireframe
      //glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
  
      // render loop
      // -----------
      while (!glfwWindowShouldClose(window))
      {
          // per-frame time logic
          // --------------------
          float currentFrame = glfwGetTime();
          deltaTime = currentFrame - lastFrame;
          lastFrame = currentFrame;
  
          // input
          // -----
          processInput(window);
  
          // render
          // ------
          glClearColor(0.05f, 0.05f, 0.05f, 1.0f);
          glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  
          // don't forget to enable shader before setting uniforms
          ourShader.use();
  
          // view/projection transformations
          glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);
          glm::mat4 view = camera.GetViewMatrix();
          ourShader.setMat4("projection", projection);
          ourShader.setMat4("view", view);
  
          // render the loaded model
          glm::mat4 model;
          model = glm::translate(model, glm::vec3(0.0f, -1.75f, 0.0f)); // translate it down so it's at the center of the scene
          model = glm::scale(model, glm::vec3(0.2f, 0.2f, 0.2f));	// it's a bit too big for our scene, so scale it down
          ourShader.setMat4("model", model);
          ourModel.Draw(ourShader);
  
  
          // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
          // -------------------------------------------------------------------------------
          glfwSwapBuffers(window);
          glfwPollEvents();
      }
  
      // glfw: terminate, clearing all previously allocated GLFW resources.
      // ------------------------------------------------------------------
      glfwTerminate();
      return 0;
  }
  
  // process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
  // ---------------------------------------------------------------------------------------------------------
  void processInput(GLFWwindow *window)
  {
      if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
          glfwSetWindowShouldClose(window, true);
  
      if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
          camera.ProcessKeyboard(FORWARD, deltaTime);
      if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
          camera.ProcessKeyboard(BACKWARD, deltaTime);
      if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS)
          camera.ProcessKeyboard(LEFT, deltaTime);
      if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS)
          camera.ProcessKeyboard(RIGHT, deltaTime);
  }
  
  // glfw: whenever the window size changed (by OS or user resize) this callback function executes
  // ---------------------------------------------------------------------------------------------
  void framebuffer_size_callback(GLFWwindow* window, int width, int height)
  {
      // make sure the viewport matches the new window dimensions; note that width and 
      // height will be significantly larger than specified on retina displays.
      glViewport(0, 0, width, height);
  }
  
  // glfw: whenever the mouse moves, this callback is called
  // -------------------------------------------------------
  void mouse_callback(GLFWwindow* window, double xpos, double ypos)
  {
      if (firstMouse)
      {
          lastX = xpos;
          lastY = ypos;
          firstMouse = false;
      }
  
      float xoffset = xpos - lastX;
      float yoffset = lastY - ypos; // reversed since y-coordinates go from bottom to top
  
      lastX = xpos;
      lastY = ypos;
  
      camera.ProcessMouseMovement(xoffset, yoffset);
  }
  
  // glfw: whenever the mouse scroll wheel scrolls, this callback is called
  // ----------------------------------------------------------------------
  void scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
  {
      camera.ProcessMouseScroll(yoffset);
  }
  