#if 0
mkdir -p build
clang -o build/demo -g wayland_libdecor_egl.c -I/usr/include/libdecor-0 -ldecor-0 -lwayland-client -lwayland-egl -lEGL
exit 0
#endif

/*
** Reading From:
** (1) Wayland Docs         https://wayland.freedesktop.org/docs/html/
** (egl) EGL spec           https://registry.khronos.org/EGL/sdk/docs/man/
** (libdecor.h)             /usr/include/libdecor-0/libdecor.h
** 
** (nodocs-wl_egl) I cannot find any documentation for wl_egl_ except for
** headers and example code.
*/

/* [1] IMPORTANT NOTE @see([1] in wayland_xdg_egl.c) */

#include <wayland-client.h>
#include <libdecor.h>
#include <wayland-egl.h>
/*~ NOTE: wayland-egl.h *before* EGL/ */
#include <EGL/egl.h>
#include <EGL/eglext.h>
#include <GL/glcorearb.h>

#include <stdio.h>
#include <string.h>

// X(N:name,R:return,P:params)
#define GL_FUNCS_XLIST(X)\
X(glDrawBuffer, void, (GLenum buf)) \
X(glViewport, void, (GLint x, GLint y, GLsizei w, GLsizei h)) \
X(glClear, void, (GLbitfield mask)) \
X(glClearColor, void, (GLfloat r, GLfloat g, GLfloat b, GLfloat a))

#define X(N,R,P) R (*N)P = 0;
GL_FUNCS_XLIST(X)
#undef X

typedef struct Ctx{
  /* globals */
  struct wl_display    *wl_display;
  struct wl_registry   *wl_registry;
  struct wl_compositor *wl_compositor;
  struct xdg_wm_base   *xdg_wm_base;
  struct libdecor      *libdecor;
  
  /* window */
  struct wl_surface     *wl_surface;
  struct libdecor_frame *libdecor_frame;
  struct wl_egl_window  *wl_egl_window;
  int configured;
  int w;
  int h;
  int close_signal;
  //struct xdg_surface   *xdg_surface;
  //struct xdg_toplevel  *xdg_toplevel;
  //struct wl_region     *wl_region;
  EGLDisplay egl_display;
  EGLContext egl_context;
  EGLSurface egl_surface;
} Ctx;

static Ctx ctx = {0};


/* (1) Appendix A: wl_registry::global
** " The event notifies the client that a global object with the given 
**   name is now available "
*/
static void
wlevent__wl_registry_global(void *data, struct wl_registry *registry,
                            uint32_t name, const char *interface,
                            uint32_t version){
  /* (1) Appendix A: wl_registry::bind
  ** " Binds a new, client-created object to the server "
  */
  
  if (strcmp(interface, "wl_compositor") == 0){
    ctx.wl_compositor = (struct wl_compositor*)
      wl_registry_bind(registry, name, &wl_compositor_interface, 1);
  }
}

/* (1) Appendix A: wl_registry::global_remove */
static void
wlevent__wl_registry_global_remove(void *data, struct wl_registry *registry,
                                   uint32_t name){}

const struct wl_registry_listener wl_registry_listener = {
  wlevent__wl_registry_global,
  wlevent__wl_registry_global_remove,
};


/* (libdecor.h) libdecor_interface::error " An error event " */
static void
libdecorevent__error(struct libdecor *libdecor, enum libdecor_error error,
                     const char *msg){}

struct libdecor_interface libdecor_interface = {
  libdecorevent__error
};


/* (libdecor.h) libdecor_frame_interface::configure
** " A new configuration was received. An application should respond to
**   this by creating a suitable libdecor_state, and apply it using
**   libdecor_frame_commit. "
*/
static void
libdecorevent__frame_configure(struct libdecor_frame *frame,
                               struct libdecor_configuration *config,
                               void *udata){
  int w = ctx.w;
  int h = ctx.h;
  /* (libdecor.h)
  ** " Get the expected size of the content for this configuration. "
  */
  if (libdecor_configuration_get_content_size(config, frame, &w, &h)){
    
    /* (libdecor.h) " Create a new content surface state. " */
    struct libdecor_state *state = libdecor_state_new(w, h);
    
    /* (libdecor.h) libdecor_frame_commit
    ** " Commit a new window state. This can be called on application
    **   driven resizes when the window is floating, or in response to
    **   received configurations, i.e. from e.g. interactive resizes
    **   or state changes. "
    */
    libdecor_frame_commit(frame, state, config);
    
    /* (libdecor.h) " Free a content surface state. " */
    libdecor_state_free(state);
  }
  ctx.configured = 1;
  ctx.w = w;
  ctx.h = h;
}

/* (libdecor.h) libdecor_frame_interface::close
** " The window was requested to be closed by the compositor. "
*/
static void
libdecorevent__frame_close(struct libdecor_frame *frame, void *udata){
  ctx.close_signal = 1;
}

/* (libdecor.h) libdecor_frame_interface::commit
** " The window decoration asked to have the main surface to be
**   committed. This is required when the decoration is implemented
**   using synchronous subsurfaces. "
*/
static void
libdecorevent__frame_commit(struct libdecor_frame *frame, void *udata){
  wl_surface_commit(ctx.wl_surface);
}

/* (libdecor.h) libdecor_frame_interface::dismiss_popup
** " Any mapped popup that has a grab on the given seat should be dismissed. "
*/
static void
libdecorevent__frame_dismiss_popup(){
  
}

/* (libdecor.h) libdecor_frame_interface::dismiss_popup
** " Any mapped popup that has a grab on the given seat should
**   be dismissed. "
*/
struct libdecor_frame_interface libdecor_frame_interface = {
  libdecorevent__frame_configure,
  libdecorevent__frame_close,
  libdecorevent__frame_commit,
  libdecorevent__frame_dismiss_popup,
};


int main(){
  /*~ NOTE:
  **~ initialize Wayland, Libdecor, & EGL
  */
  
  /* (1) Appendix B: wl_display_connect
  ** " Connect to a Wayland display. "
  */
  ctx.wl_display = wl_display_connect(0);
  if (ctx.wl_display == 0){
    printf("wl_display_connect failed\n");
  }
  
  /* (1) Appendix A: wl_display::get_registry
  ** " creates a registry object that allows the client to list 
  **   and bind the global objects available from the compositor "
  */
  if (ctx.wl_display != 0){
    ctx.wl_registry = wl_display_get_registry(ctx.wl_display);
    if (ctx.wl_registry == 0){
      printf("wl_display_get_registry failed\n");
    }
  }
  
  if (ctx.wl_registry != 0){
    /* [1] */
    wl_registry_add_listener(ctx.wl_registry, &wl_registry_listener, 0);
    
    /* (1) Appendix B: wl_display::dispatch
    ** " Dispatch events on the default event queue. If the default
    **   event queue is empty, this function blocks until there are
    **   events to be read from the display fd. "
    */
    wl_display_dispatch(ctx.wl_display);
    
    /* (1) Appendix B: wl_display_roundtrip
    ** " Block until all pending request are processed by the server "
    */
    wl_display_roundtrip(ctx.wl_display);
    
    if (ctx.wl_compositor == 0){
      printf("failed to get wl_compositor\n");
    }
  }
  
  /* (libdecor.h) " Create a new libdecor context for the given wl_display " */
  if (ctx.wl_display != 0 && ctx.wl_compositor != 0){
    ctx.libdecor = libdecor_new(ctx.wl_display, &libdecor_interface);
  }
  
  int opengl_load_success = 0;
  if (ctx.libdecor != 0){
    /* (egl) eglGetDisplay
    ** " obtains the EGL display connection for the native display "
    */
    ctx.egl_display = eglGetDisplay(ctx.wl_display);
    if (ctx.egl_display == 0){
      printf("eglGetDisplay failed\n");
    }
    
    /* (egl) eglInitialize
    ** " initializes* the EGL display connection obtained with eglGetDisplay "
    */
    int egl_init_success = 0;
    EGLint major = 0, minor = 0;
    if (ctx.egl_display != 0){
      egl_init_success = eglInitialize(ctx.egl_display, &major, &minor);
      if (!egl_init_success){
        printf("eglInitialize failed\n");
      }
    }
    
    // print version
    if (egl_init_success){
      printf("EGL version %d.%d\n", major, minor);
      if (major < 1 || (major == 1 && minor < 5)){
        printf("version 1.5 or higher\n");
        egl_init_success = 0;
      }
    }
    
    /* (egl) eglBindAPI 
    ** " defines the current rendering API for EGL in the thread it is
    **   called from "
    */
    EGLBoolean bind_api_success = 0;
    if (egl_init_success){
      bind_api_success = eglBindAPI(EGL_OPENGL_API);
    }
    
    /* (egl) eglCreateContext
    ** " creates an EGL rendering context for the current rendering API
    **   (as set with eglBindAPI) and returns a handle to the context "
    */
    if (bind_api_success){
      EGLint attr[] = {
        EGL_CONTEXT_MAJOR_VERSION, 3,
        EGL_CONTEXT_MINOR_VERSION, 3,
        EGL_CONTEXT_OPENGL_PROFILE_MASK, EGL_CONTEXT_OPENGL_CORE_PROFILE_BIT,
        EGL_NONE,
      };
      ctx.egl_context = eglCreateContext(ctx.egl_display, EGL_NO_CONFIG_KHR, EGL_NO_CONTEXT, attr);
      if (ctx.egl_context == EGL_NO_CONTEXT){
        printf("eglCreateContext failed\n");
      }
    }
    
    /* (egl) eglMakeCurrent
    ** " binds context to the current rendering thread "
    */
    EGLBoolean make_current_success = 0;
    if (ctx.egl_context != 0){
      make_current_success = eglMakeCurrent(ctx.egl_display, EGL_NO_SURFACE, EGL_NO_SURFACE, ctx.egl_context);
      if (!make_current_success){
        printf("eglMakeCurrent failed\n");
      }
    }
    
    /* (egl) eglGetProcAddress
    ** " returns the address of the client API or EGL function "
    */
    if (make_current_success){
      opengl_load_success = 1;
#define X(N,R,P) N = (R(*)P)(eglGetProcAddress(#N)); if (N == 0) opengl_load_success = 0;
      GL_FUNCS_XLIST(X)
#undef X
      if (!opengl_load_success){
        printf("GL procedure loading failed\n");
      }
    }
  }
  
  /*~ NOTE:
  **~ Create a window
  */
  
  if (opengl_load_success){
    ctx.w = 640;
    ctx.h = 480;
    
    /* (1) Appendix A: wl_compositor::create_surface
    ** " create new surface "
    */
    ctx.wl_surface = wl_compositor_create_surface(ctx.wl_compositor);
    if (ctx.wl_surface == 0){
      printf("wl_compositor_create_surface failed\n");
    }
  }
  
  if (ctx.wl_surface != 0){
    /* (libdecor.h) " Decorate the given content wl_surface. " */
    ctx.libdecor_frame = libdecor_decorate(ctx.libdecor, ctx.wl_surface,
                                           &libdecor_frame_interface, 0);
  }
  
  if (ctx.libdecor_frame != 0){
    /* (libdecor.h) " Set the title of the window. " */
    libdecor_frame_set_title(ctx.libdecor_frame, "Example Window");
    
    /* (libdecor.h) " This translates roughly to xdg_toplevel_set_min_size() "
    **~ NOTE: I recommend setting this to something greater than 0 on each
    **  axis, to prevent some artifacts when resize goes 0 or negative.
    */
    libdecor_frame_set_min_content_size(ctx.libdecor_frame, 80, 60);
    
    /* (libdecor.h) " Map the window. " */
    libdecor_frame_map(ctx.libdecor_frame);
    
    /* (nodocs-wl_egl) */
    ctx.wl_egl_window = wl_egl_window_create(ctx.wl_surface, ctx.w, ctx.h);
    if (ctx.wl_egl_window == EGL_NO_SURFACE){
      printf("wl_egl_window_create failed\n");
    }
  }
  
  if (ctx.wl_egl_window != EGL_NO_SURFACE){
    /* (nodocs-wl_egl) eglChooseConfig
    ** " returns in configs a list of all EGL frame buffer configurations
    **   that match the attributes specified in attrib_list "
    */
    EGLConfig configs[64];
    EGLint config_cap = sizeof(configs)/sizeof(*configs);
    EGLint config_count = 0;
    {
      EGLint attributes[] = {
        EGL_SURFACE_TYPE,      EGL_WINDOW_BIT,
        EGL_CONFORMANT,        EGL_OPENGL_BIT,
        EGL_RENDERABLE_TYPE,   EGL_OPENGL_BIT,
        EGL_COLOR_BUFFER_TYPE, EGL_RGB_BUFFER,
        EGL_RED_SIZE,      8,
        EGL_GREEN_SIZE,    8,
        EGL_BLUE_SIZE,     8,
        EGL_DEPTH_SIZE,   24,
        EGL_STENCIL_SIZE,  8,
        EGL_NONE,
      };
      if (!eglChooseConfig(ctx.egl_display, attributes, configs, config_cap, &config_count)){
        printf("eglChooseConfig failed\n");
        config_count = 0;
      }
    }
    
    /* (egl) eglCreateWindowSurface
    ** " creates an on-screen EGL window surface and returns a handle to it "
    */
    {
      EGLint attributes[] = {
        EGL_RENDER_BUFFER, EGL_BACK_BUFFER,
        EGL_NONE,
      };
      for (EGLint i = 0; i < config_count; i += 1){
        ctx.egl_surface = eglCreateWindowSurface(ctx.egl_display, configs[i], ctx.wl_egl_window, attributes);
        if (ctx.egl_surface != EGL_NO_SURFACE){
          break;
        }
      }
      if (ctx.egl_surface == EGL_NO_SURFACE){
        printf("eglCreateWindowSurface failed\n");
      }
    }
  }
  
  /* (egl) eglMakeCurrent */
  EGLBoolean make_current_success2 = 0;
  if (ctx.egl_surface != EGL_NO_SURFACE){
    make_current_success2 = eglMakeCurrent(ctx.egl_display, ctx.egl_surface, ctx.egl_surface, ctx.egl_context);
  }
  
  /* (egl) eglSwapInterval 
  ** " specifies the minimum number of video frame periods per buffer swap
  **   for the window associated with the current context "
  */
  EGLBoolean swap_interval_success = 0;
  if (make_current_success2){
    swap_interval_success = eglSwapInterval(ctx.egl_display, 1);
    if (!swap_interval_success){
      printf("eglSwapInterval failed\n");
    }
  }
  
  /*~ NOTE: Main loop */
  int exit_loop = 0;
  if (!swap_interval_success){
    exit_loop = 1;
  }
  for (;!exit_loop;){
    /* (libdecor.h)
    ** " Dispatch events. This function should be called when data is available on
    **   the file descriptor returned by libdecor_get_fd(). If timeout is zero, this
    **   function will never block. "
    */
    libdecor_dispatch(ctx.libdecor, 0);
    
    if (ctx.close_signal){
      exit_loop = 1;
    }
    
    /* (nodocs-wl_egl) */
    wl_egl_window_resize(ctx.wl_egl_window, ctx.w, ctx.h, 0, 0);
    
    /*~ NOTE: render */
    {
      glDrawBuffer(GL_BACK);
      glViewport(0, 0, 640, 480);
      glClearColor(0.40f, 0.90f, 0.15f, 1.f);
      glClear(GL_COLOR_BUFFER_BIT);
    }
    
    /* (egl) eglSwapBuffers
    ** " back-buffered window surface, then the color buffer is copied 
    **   (posted) to the native window associated with that surface "
    */
    EGLBoolean swap_success = eglSwapBuffers(ctx.egl_display, ctx.egl_surface);
    if (!swap_success){
      printf("eglSwapBuffers failed\n");
    }
  }
  
  /* (1) #Client-classwl__display_1a9150a7e3213a58b469a6966e60a9f108
  ** " Close the connection to display "
  */
  if (ctx.wl_display != 0){
    wl_display_disconnect(ctx.wl_display);
  }
  
  return(0);
}