include/appglfw.hxx

#pragma once

#ifdef USE_IMGUI
#include <imgui.h>
#include <backends/imgui_impl_glfw.h>
#include <backends/imgui_impl_opengl3.h>
#endif // USE_IMGUI

#define GL_GLEXT_PROTOTYPES
#include <GL/gl3w.h>
#include <GLFW/glfw3.h>
#include <cmath>
#include <cstdio>
#include <cfloat>
#include <cstring>

// Shader interface helper variables.
template<auto index, typename type_t = @enum_type(index)>
[[using spirv: in((int)index)]]
type_t shader_in;

template<auto index, typename type_t = @enum_type(index)>
[[using spirv: out((int)index)]]
type_t shader_out;

template<auto index, typename type_t = @enum_type(index)>
[[using spirv: uniform((int)index)]]
type_t shader_sampler;

template<auto index, typename type_t = @enum_type(index)>
[[using spirv: uniform((int)index)]]
type_t shader_ubo;

template<auto index, typename type_t = @enum_type(index)>
[[using spirv: buffer((int)index)]]
type_t shader_buffer;

template<auto index, typename type_t = @enum_type(index)>
[[using spirv: buffer((int)index), readonly]]
type_t shader_readonly;

template<auto index, typename type_t = @enum_type(index)>
[[using spirv: buffer((int)index), writeonly]]
type_t shader_writeonly;

template<typename type_t>
const char* enum_to_string(type_t e) {
  static_assert(std::is_enum_v<type_t>);
  switch(e) {
    @meta for enum(type_t e2 : type_t) {
      case e2:
        return @enum_name(e2);
    }
    default:
      return nullptr;
  }
}

inline void print_matrix(const mat4& m) {
  for(int row = 0; row < 4; ++row)
    printf("%f %f %f %f\n", m[0][row], m[1][row], m[2][row], m[3][row]);
}

constexpr vec4 qmul(vec4 q, vec4 p) {
  return vec4(
    q.w * p.xyz + p.w * q.xyz + cross(q.xyz, p.xyz),
    p.w * q.w - dot(p.xyz, q.xyz)
  );
}

constexpr vec4 qinv(vec4 q) {
  // Change the sign of the imaginary components.
  q.xyz = -q.xyz;
  return q;
}

// https://users.aalto.fi/~ssarkka/pub/quat.pdf
constexpr vec4 qlog(vec4 q) {
  vec3 v = normalize(q.xzy);
  return vec4(v * acosf(q.w), 0);
}

constexpr vec4 slerp(vec4 q0, vec4 q1, float t) {
  float d = dot(q0, q1);
  float theta_0 = acosf(d);
  float theta = theta_0 * t;

  vec4 q2 = normalize(q1 - q1 * d);
  return q0 * cosf(theta) + q2 * sinf(theta);
}

inline mat4 make_perspective(float fov, float ar, float near, float far) {
  float f = 1 / tan(fov / 2);

  if(FLT_MAX == far) {
    return mat4(
      f / ar, 0, 0,                      0,
      0,      f, 0,                      0,
      0,      0, -1,                    -1,    
      0,      0, -2 * near,              0
    ); 

  } else {
    float range = near - far;
    return mat4(
      f / ar, 0, 0,                      0,
      0,      f, 0,                      0,
      0,      0, (far + near) / range,  -1,    
      0,      0, 2 * far * near / range, 0
    ); 
  }
}

inline mat4 make_lookat(vec3 eye, vec3 at, vec3 up) {
  vec3 zaxis = normalize(eye - at);
  vec3 xaxis = normalize(cross(up, zaxis));
  vec3 yaxis = cross(zaxis, xaxis);
  return mat4(
    xaxis.x,          yaxis.x,          zaxis.x,          0,
    xaxis.y,          yaxis.y,          zaxis.y,          0,
    xaxis.z,          yaxis.z,          zaxis.z,          0,
    -dot(xaxis, eye), -dot(yaxis, eye), -dot(zaxis, eye), 1
  );
}

inline mat4 make_scale(vec3 scale) {
  return mat4(
    scale.x, 0, 0, 0,
    0, scale.y, 0, 0,
    0, 0, scale.z, 0,
    0, 0, 0,       1
  );
}

inline mat4 make_translate(vec3 translate) {
  return mat4(
    1, 0, 0, 0,
    0, 1, 0, 0,
    0, 0, 1, 0,
    translate, 1
  );
}

inline mat4 make_rotateX(float angle) {
  float s = sin(angle);
  float c = cos(angle);
  return mat4(
    1,  0,  0,  0,
    0,  c, -s,  0,
    0,  s,  c,  0,
    0,  0,  0,  1
  );
}

inline mat4 make_rotateY(float angle) {
  float s = sin(angle);
  float c = cos(angle);
  return mat4(
    c,  0, -s,  0,
    0,  1,  0,  0,
    s,  0,  c,  0,
    0,  0,  0,  1
  );
}

inline mat4 make_rotateZ(float angle) {
  float s = sin(angle);
  float c = cos(angle);
  return mat4(
    c, -s,  0,  0,
    s,  c,  0,  0,
    0,  0,  1,  0,
    0,  0,  0,  1
  );
}

inline mat4 make_rotate(vec3 angles) {
  mat4 x = make_rotateX(angles.x);
  mat4 y = make_rotateY(angles.y);
  mat4 z = make_rotateZ(angles.z);
  return z * y * x;
}

////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////

template<typename type_t>
void specialize_shader(GLuint shader, const char* name, const type_t& obj) {
  const int count = @member_count(type_t);
  GLuint indices[count];
  GLuint values[count] { };
  @meta for(int i = 0; i < count; ++i) {
    indices[i] = i;
    memcpy(values + i, &@member_value(obj, i), sizeof(@member_type(type_t, i)));
  }

  glSpecializeShader(shader, name, count, indices, values);
}

////////////////////////////////////////////////////////////////////////////////

struct camera_t {
  vec3 origin = vec3();
  float pitch = 0;
  float yaw = 0; 
  float distance = 10.f;

  // Perspective terms.
  float fov = radians(60.f);
  float near = .05;
  float far = FLT_MAX;

  void adjust(float pitch2, float yaw2, float d2);

  vec3 get_eye() const noexcept;
  mat4 get_view() const noexcept;
  mat4 get_perspective(int width, int height) const noexcept;

  vec3 x_axis() const noexcept {
    return normalize(cross(vec3(0, 1, 0), z_axis()));
  }
  vec3 y_axis() const noexcept {
    return cross(z_axis(), x_axis());
  }
  vec3 z_axis() const noexcept {
    return normalize(get_eye() - origin);
  }

  mat4 get_xform(int width, int height) const noexcept;

  void set_from_frame(vec3 eye, vec3 xaxis, vec3 yaxis, float distance);
};

inline void camera_t::adjust(float pitch2, float yaw2, float d2) {
  pitch = clamp(pitch + pitch2, -radians(80.f), radians(80.f));
  yaw = fmod(yaw + yaw2, 2 * M_PI);
  distance = exp(log(distance) + d2);
}

inline vec3 camera_t::get_eye() const noexcept {
  return vec3(
    sin(yaw) * cos(pitch) * distance,
               sin(pitch) * distance,
    cos(yaw) * cos(pitch) * distance
  ) + origin;
}

inline mat4 camera_t::get_view() const noexcept {
  return make_lookat(get_eye(), origin, vec3(0, 1, 0));
}

inline mat4 camera_t::get_perspective(int width, int height) const noexcept {
  float ar = (float)width / height;
  return make_perspective(fov, ar, near, far);
}

inline mat4 camera_t::get_xform(int width, int height) const noexcept {
  return get_perspective(width, height) * get_view();
}

inline void camera_t::set_from_frame(vec3 eye, vec3 xaxis, vec3 yaxis, 
  float distance) {

  this->distance = distance;
  vec3 zaxis = cross(xaxis, yaxis);
  origin = eye - distance * zaxis;

  eye -= origin;
  yaw = atan2(eye.x, eye.z);
  pitch = atan2(eye.y, length(eye.xz));
}

////////////////////////////////////////////////////////////////////////////////

class app_t {
public:
  app_t(const char* name, int width = 1280, int height = 720);
  void loop();
  virtual void display() { }

  virtual void pos_callback(int xpos, int ypos) { }
  virtual void size_callback(int width, int height) { }
  virtual void close_callback() { }
  virtual void refresh_callback() { }
  virtual void focus_callback(int focused) { }
  virtual void framebuffer_callback(int width, int height);

  virtual void cursor_callback(double xpos, double ypos);
  virtual void button_callback(int button, int action, int mods);

  virtual void key_callback(int key, int scancode, int action, int mods) { }

  virtual void debug_callback(GLenum source, GLenum type, GLuint id, 
    GLenum severity, GLsizei length, const GLchar* message);

protected:
  GLFWwindow* window = nullptr;
  camera_t camera { };
  int captured = false;
  double last_x, last_y;

private:
  static void _pos_callback(GLFWwindow* window, int xpos, int ypos);
  static void _size_callback(GLFWwindow* window, int width, int height);
  static void _close_callback(GLFWwindow* window);
  static void _refresh_callback(GLFWwindow* window);
  static void _focus_callback(GLFWwindow* window, int focused);
  static void _framebuffer_callback(GLFWwindow* window, int width, int height);

  static void _cursor_callback(GLFWwindow* window, double xpos, double ypos);
  static void _button_callback(GLFWwindow* window, int button, int action,
    int mods);

  static void _key_callback(GLFWwindow* window, int key, int scancode, 
    int action, int mods);

  static void _debug_callback(GLenum source, GLenum type, GLuint id, 
    GLenum severity, GLsizei length, const GLchar* message, 
    const void* user_param);

  void register_callbacks();
};

app_t::app_t(const char* name, int width, int height) {
  glfwWindowHint(GLFW_DOUBLEBUFFER, 1);
  glfwWindowHint(GLFW_DEPTH_BITS, 24);
  glfwWindowHint(GLFW_STENCIL_BITS, 8);
  glfwWindowHint(GLFW_SAMPLES, 4); // HQ 4x multisample.
  glfwWindowHint(GLFW_DECORATED, GLFW_TRUE);

  // glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 6);

  window = glfwCreateWindow(width, height, name, nullptr, nullptr);
  glfwMakeContextCurrent(window);
  glfwSwapInterval(1);

  register_callbacks();

  glEnable(GL_DEBUG_OUTPUT);
  glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS);
  glDebugMessageCallback(_debug_callback, this);

  glfwGetWindowSize(window, &width, &height);
  glViewport(0, 0, width, height);

#ifdef USE_IMGUI
  // Create an ImGui context.
  ImGui::CreateContext();

  // Setup Platform/Renderer bindings
  ImGui_ImplGlfw_InitForOpenGL(window, true);
  ImGui_ImplOpenGL3_Init("#version 460");
#endif // USE_IMGUI
}

void app_t::register_callbacks() {
  glfwSetWindowUserPointer(window, this);
  glfwSetWindowPosCallback(window, _pos_callback);
  glfwSetWindowSizeCallback(window, _size_callback);
  glfwSetWindowCloseCallback(window, _close_callback);
  glfwSetWindowRefreshCallback(window, _refresh_callback);
  glfwSetWindowFocusCallback(window, _focus_callback);
  glfwSetFramebufferSizeCallback(window, _framebuffer_callback);

  glfwSetCursorPosCallback(window, _cursor_callback);
  glfwSetMouseButtonCallback(window, _button_callback);

  glfwSetKeyCallback(window, _key_callback);
}

void app_t::loop() {
  while(!glfwWindowShouldClose(window)) {
    glfwPollEvents();

#ifdef USE_IMGUI
    // Start the Dear ImGui frame
    ImGui_ImplOpenGL3_NewFrame();
    ImGui_ImplGlfw_NewFrame();
    ImGui::NewFrame();
#endif

    // Call the subscriber class.
    display();

#ifdef USE_IMGUI
    // Render the ImGui frame over the application.
    ImGui::Render();
    ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
#endif

    glfwSwapBuffers(window);
  }
}

void app_t::framebuffer_callback(int width, int height) {
  glViewport(0, 0, width, height);
}

void app_t::cursor_callback(double xpos, double ypos) {
  if(captured) {
    double dx = xpos - last_x;
    double dy = ypos - last_y;

    if(GLFW_PRESS == glfwGetKey(window, GLFW_KEY_LEFT_SHIFT)) {
      // Translate.
      vec3 xaxis = camera.x_axis();
      vec3 yaxis = camera.y_axis();

      vec3 eye = camera.get_eye();
      eye += xaxis * dx / 100 - yaxis * dy / 100;

      camera.set_from_frame(eye, xaxis, yaxis, camera.distance);

    } else if(GLFW_PRESS == glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_RIGHT)) {
      camera.adjust(0, 0, dy / 100.f);

    } else {
      camera.adjust(-dy / 100.f, dx / 100.f, 0);
    }

    last_x = xpos;
    last_y = ypos;
  }
}

void app_t::button_callback(int button, int action, int mods) {
  bool is_release = 
    GLFW_RELEASE == glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_LEFT) && 
    GLFW_RELEASE == glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_RIGHT);

  if(!is_release && !captured) {
    glfwGetCursorPos(window, &last_x, &last_y);
    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
    captured = true;
    
  } else if(is_release && captured) {
    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_NORMAL);
    captured = false;
  }
}

void app_t::debug_callback(GLenum source, GLenum type, GLuint id, 
  GLenum severity, GLsizei length, const GLchar* message) { 

  if(GL_DEBUG_SEVERITY_HIGH == severity) {
    printf("OpenGL: %s\n", message);
    exit(1);
  }
}

void app_t::_pos_callback(GLFWwindow* window, int xpos, int ypos) {
  app_t* app = static_cast<app_t*>(glfwGetWindowUserPointer(window));
  app->pos_callback(xpos, ypos);
}
void app_t::_size_callback(GLFWwindow* window, int width, int height) {
  app_t* app = static_cast<app_t*>(glfwGetWindowUserPointer(window));
  app->size_callback(width, height);
}
void app_t::_close_callback(GLFWwindow* window) {
  app_t* app = static_cast<app_t*>(glfwGetWindowUserPointer(window));
  app->close_callback();
}
void app_t::_refresh_callback(GLFWwindow* window) {
  app_t* app = static_cast<app_t*>(glfwGetWindowUserPointer(window));
  app->refresh_callback();
}
void app_t::_focus_callback(GLFWwindow* window, int focused) {
  app_t* app = static_cast<app_t*>(glfwGetWindowUserPointer(window));
  app->focus_callback(focused);
}
void app_t::_framebuffer_callback(GLFWwindow* window, int width, int height) {
  app_t* app = static_cast<app_t*>(glfwGetWindowUserPointer(window));
  app->framebuffer_callback(width, height);
}

void app_t::_cursor_callback(GLFWwindow* window, double xpos, double ypos) {
#ifdef USE_IMGUI
  // Let ImGui have the mouse if the cursor is above its windows.
  ImGuiIO& io = ImGui::GetIO();
  if(io.WantCaptureMouse)
    return;
#endif

  app_t* app = static_cast<app_t*>(glfwGetWindowUserPointer(window));
  app->cursor_callback(xpos, ypos);
}
void app_t::_button_callback(GLFWwindow* window, int button, int action,
  int mods) { 

#ifdef USE_IMGUI
  // Let ImGui have the mouse if the cursor is above its windows.
  ImGuiIO& io = ImGui::GetIO();
  if(io.WantCaptureMouse)
    return;
#endif

  app_t* app = static_cast<app_t*>(glfwGetWindowUserPointer(window));
  app->button_callback(button, action, mods);
}

void app_t::_key_callback(GLFWwindow* window, int key, int scancode, 
  int action, int mods) { 

#ifdef USE_IMGUI
  // Let ImGui have the mouse if the cursor is above its windows.
  ImGuiIO& io = ImGui::GetIO();
  if(io.WantCaptureKeyboard)
    return;
#endif

  app_t* app = static_cast<app_t*>(glfwGetWindowUserPointer(window));
  app->key_callback(key, scancode, action, mods);
}

void app_t::_debug_callback(GLenum source, GLenum type, GLuint id, 
  GLenum severity, GLsizei length, const GLchar* message, 
  const void* user_param) {

  app_t* app = (app_t*)user_param;
  app->debug_callback(source, type, id, severity, length, message);
}

////////////////////////////////////////////////////////////////////////////////