#include "interface/backend.h"

#include <cairo-xcb.h>
#include <cairo.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <xcb/randr.h>
#include <xcb/xcb.h>
#include <xcb/xcb_aux.h>
#include <xcb/xcb_icccm.h>
#include <xcb/xcb_keysyms.h>
#include <xcb/xfixes.h>
#include <xcb/xinerama.h>
#include <xcb/xproto.h>

#include "backend/output_utils.h"
#include "backend/x11/cursor.h"
#include "backend/x11/tray.h"
#include "backend/x11/window.h"
#include "base/app.h"
#include "base/array.h"
#include "base/log.h"
#include "base/macros.h"
#include "base/memory.h"
#include "common/window.h"
#include "internal.h"

typedef struct atom_item_t {
  const char *name;
  size_t len;
  xcb_atom_t *atom;
} atom_item_t;

static void atoms_init(backend_t *backend) {
  xcb_connection_t *conn = backend->conn;
  atoms_t *atoms = &backend->atoms;

#define ATOM_ITEM(name) {#name, sizeof(#name) - 1, &atoms->name},
  atom_item_t atom_list[] = {ATOM_LIST(ATOM_ITEM)};
#undef ATOM_ITEM

  xcb_intern_atom_cookie_t cookies[countof(atom_list)];
  for (size_t i = 0; i < countof(atom_list); ++i) {
    const atom_item_t *atom = &atom_list[i];
    cookies[i] = xcb_intern_atom_unchecked(conn, false, atom->len, atom->name);
  }

  xcb_intern_atom_reply_t *reply = nullptr;
  for (size_t i = 0; i < countof(atom_list); ++i) {
    reply = xcb_intern_atom_reply(conn, cookies[i], nullptr);
    if (!reply) continue;

    atom_item_t *atom = &atom_list[i];
    *atom->atom = reply->atom;
    p_delete(&reply);
  }

#define EWMH_ITEM(name) atoms->name,
  xcb_atom_t ewmh_supported_atoms[] = {EWMH_ATOMS(EWMH_ITEM)};
#undef EWMH_ITEM
  auto root = backend->screen->root;
  xcb_change_property(
    conn,
    XCB_PROP_MODE_REPLACE,
    root,
    atoms->_NET_SUPPORTED,
    XCB_ATOM_ATOM,
    32,
    countof(ewmh_supported_atoms),
    ewmh_supported_atoms
  );
}

static void create_wm_check_window(backend_t *backend) {
  xcb_connection_t *conn = backend->conn;
  xcb_window_t root = backend->screen->root;
  uint8_t depth = backend->screen->root_depth;
  xcb_visualid_t v = backend->screen->root_visual;
  uint16_t _c = XCB_WINDOW_CLASS_COPY_FROM_PARENT;
  uint32_t m = XCB_NONE;
  void *p = nullptr;

  xcb_window_t win = xcb_generate_id(conn);
  xcb_create_window(conn, depth, win, root, -1, -1, 1, 1, 0, _c, v, m, p);
  window_set_class_instance(conn, win);

  window_set_name_static(conn, win, APP_NAME);
  uint8_t mode = XCB_PROP_MODE_REPLACE;
  xcb_atom_t prop = backend->atoms._NET_WM_NAME;
  xcb_atom_t type = backend->atoms.UTF8_STRING;
  auto data_len = sizeof(APP_NAME) - 1;
  xcb_change_property(conn, mode, win, prop, type, 8, data_len, APP_NAME);

  prop = backend->atoms._NET_SUPPORTING_WM_CHECK;
  type = XCB_ATOM_WINDOW;
  xcb_change_property(conn, mode, win, prop, type, 32, 1, &win);
  xcb_change_property(conn, mode, root, prop, type, 32, 1, &win);

  prop = backend->atoms._NET_WM_PID;
  type = XCB_ATOM_CARDINAL;
  pid_t pid = getpid();
  xcb_change_property(conn, mode, win, prop, type, 32, 1, &pid);
}

static void create_no_focus_window(backend_t *backend) {
  xcb_connection_t *conn = backend->conn;
  xcb_window_t root = backend->screen->root;
  uint8_t d = backend->screen->root_depth;
  xcb_visualid_t v = backend->screen->root_visual;
  uint16_t _c = XCB_WINDOW_CLASS_COPY_FROM_PARENT;

  xcb_window_t win = xcb_generate_id(conn);
  uint32_t m = XCB_CW_BACK_PIXEL | XCB_CW_BORDER_PIXEL |
               XCB_CW_OVERRIDE_REDIRECT | XCB_CW_COLORMAP;
  const xcb_create_window_value_list_t p = {
    .override_redirect = true,
    .background_pixel = backend->screen->black_pixel,
    .border_pixel = backend->screen->black_pixel,
    .colormap = backend->screen->default_colormap,
  };
  xcb_create_window_aux(conn, d, win, root, -1, -1, 1, 1, 0, _c, v, m, &p);
  window_set_class_instance(conn, win);
  window_set_name_static(conn, win, APP_NAME " no input window");
  xcb_map_window(conn, win);

  backend->window_no_focus = win;
}

backend_t *backend_create(const char *display_name) {
  int screen_num = 0;
  xcb_connection_t *conn = xcb_connect(display_name, &screen_num);
  int xcb_conn_error = xcb_connection_has_error(conn);
  if (xcb_conn_error) {
    fatal("cannot open display %s, error %d", display_name, xcb_conn_error);
  }

  xcb_screen_t *screen = xcb_aux_get_screen(conn, screen_num);
  if (!screen) fatal("cannot get screen info");
  xcb_window_t root = screen->root;

  uint32_t mask = XCB_CW_EVENT_MASK;
  const xcb_params_cw_t params = {
    .event_mask = XCB_EVENT_MASK_SUBSTRUCTURE_REDIRECT,
  };
  xcb_void_cookie_t cookie =
    xcb_aux_change_window_attributes_checked(conn, root, mask, &params);
  if (xcb_request_check(conn, cookie)) {
    fatal(
      "another window manager is already running (cannot select "
      "SubstructureRedirect)"
    );
  }

  backend_t *backend = p_new(backend_t, 1);
  backend->conn = conn;
  backend->screen = screen;
  backend->screenp = screen_num;

  xcb_prefetch_extension_data(conn, &xcb_xfixes_id);
  const xcb_query_extension_reply_t *query =
    xcb_get_extension_data(conn, &xcb_xfixes_id);
  if (query && query->present) {
    xcb_xfixes_query_version_cookie_t cookie = xcb_xfixes_query_version(
      conn,
      XCB_XFIXES_MAJOR_VERSION,
      XCB_XFIXES_MINOR_VERSION
    );
    xcb_xfixes_query_version_reply_t *reply =
      xcb_xfixes_query_version_reply(conn, cookie, nullptr);

    if (reply) {
      backend->have_xfixes = true;
      p_delete(&reply);
    }
  } else {
    backend->have_xfixes = false;
  }

  backend->key_symbols = xcb_key_symbols_alloc(conn);

  cursor_init(backend);
  atoms_init(backend);
  create_wm_check_window(backend);
  create_no_focus_window(backend);

  window_change_cursor(backend, root, ZDWM_CURSOR_NORMAL);

  return backend;
}

void backend_destroy(backend_t *backend) {
  if (!backend) return;

  tray_cleanup(backend);

  p_delete(&backend->config_list.cfgs);
  p_clear(&backend->config_list, 1);

  window_list_cleanup(&backend->unmap);
  window_list_cleanup(&backend->map);
  window_list_cleanup(&backend->kill);

  xcb_key_symbols_free(backend->key_symbols);
  backend->key_symbols = nullptr;

  cursor_cleanup(backend);

  xcb_disconnect(backend->conn);
  backend->conn = nullptr;
  free(backend);
}

int backend_get_fd(backend_t *backend) {
  if (!backend || !backend->conn) return -1;

  return xcb_get_file_descriptor(backend->conn);
}

static bool detect_monitor_by_randr(
  const backend_t *backend,
  output_info_t **outputs,
  size_t *count
) {
  xcb_prefetch_extension_data(backend->conn, &xcb_randr_id);
  const xcb_query_extension_reply_t *query =
    xcb_get_extension_data(backend->conn, &xcb_randr_id);
  if (!query || !query->present) return false;

  xcb_randr_query_version_cookie_t cookie = xcb_randr_query_version(
    backend->conn,
    XCB_RANDR_MAJOR_VERSION,
    XCB_RANDR_MINOR_VERSION
  );
  xcb_randr_query_version_reply_t *reply =
    xcb_randr_query_version_reply(backend->conn, cookie, nullptr);
  if (!reply) return false;

  /* xcb_randr_get_monitors 接口是 1.5 引入的 */
  uint32_t major_version = reply->major_version;
  uint32_t minor_version = reply->minor_version;
  if (major_version < 1 || (major_version == 1 && minor_version < 5)) {
    p_delete(&reply);
    return false;
  }
  p_delete(&reply);

  xcb_randr_get_monitors_cookie_t monitors_cookie =
    xcb_randr_get_monitors(backend->conn, backend->screen->root, 1);
  xcb_randr_get_monitors_reply_t *monitors_reply =
    xcb_randr_get_monitors_reply(backend->conn, monitors_cookie, nullptr);
  if (!monitors_reply) {
    warn("RandR get monitor failed");
    return false;
  }

  int len = xcb_randr_get_monitors_monitors_length(monitors_reply);
  if (len <= 0) {
    p_delete(&monitors_reply);
    return false;
  }

  output_info_t *output_list = p_new(output_info_t, len);
  xcb_randr_monitor_info_iterator_t iter =
    xcb_randr_get_monitors_monitors_iterator(monitors_reply);
  for (int i = 0; iter.rem; xcb_randr_monitor_info_next(&iter), i++) {
    output_info_t *output = &output_list[i];
    output->geometry.x = iter.data->x;
    output->geometry.y = iter.data->y;
    output->geometry.width = iter.data->width;
    output->geometry.height = iter.data->height;

    xcb_get_atom_name_cookie_t name_cookie =
      xcb_get_atom_name_unchecked(backend->conn, iter.data->name);
    xcb_get_atom_name_reply_t *name_reply =
      xcb_get_atom_name_reply(backend->conn, name_cookie, nullptr);

    if (name_reply) {
      char *name = xcb_get_atom_name_name(name_reply);
      int length = xcb_get_atom_name_name_length(name_reply);
      output->name = p_strndup(name, length);
      p_delete(&name_reply);
    }
  }

  p_delete(&monitors_reply);

  if (count) *count = (size_t)len;
  if (outputs) {
    *outputs = output_list;
  } else {
    for (size_t i = 0; i < (size_t)len; i++) p_delete(&output_list[i].name);
    p_delete(&output_list);
  }

  return true;
}

static bool detect_monitor_by_xinerama(
  const backend_t *backend,
  output_info_t **outputs,
  size_t *count
) {
  xcb_prefetch_extension_data(backend->conn, &xcb_xinerama_id);
  const xcb_query_extension_reply_t *query =
    xcb_get_extension_data(backend->conn, &xcb_xinerama_id);
  if (!query || !query->present) return false;

  xcb_xinerama_query_version_cookie_t cookie = xcb_xinerama_query_version(
    backend->conn,
    XCB_XINERAMA_MAJOR_VERSION,
    XCB_XINERAMA_MINOR_VERSION
  );
  xcb_xinerama_query_version_reply_t *version_reply =
    xcb_xinerama_query_version_reply(backend->conn, cookie, nullptr);
  if (!version_reply) return false;
  p_delete(&version_reply);

  xcb_xinerama_is_active_cookie_t active_cookie =
    xcb_xinerama_is_active(backend->conn);
  xcb_xinerama_is_active_reply_t *active_reply =
    xcb_xinerama_is_active_reply(backend->conn, active_cookie, nullptr);
  bool active = active_reply && active_reply->state;
  if (active_reply) p_delete(&active_reply);
  if (!active) return false;

  xcb_xinerama_query_screens_cookie_t screens_cookie =
    xcb_xinerama_query_screens(backend->conn);
  xcb_xinerama_query_screens_reply_t *screens_reply =
    xcb_xinerama_query_screens_reply(backend->conn, screens_cookie, nullptr);

  if (!screens_reply) return false;

  int len = xcb_xinerama_query_screens_screen_info_length(screens_reply);
  if (len <= 0) {
    p_delete(&screens_reply);
    return false;
  }

  xcb_xinerama_screen_info_t *screen_info =
    xcb_xinerama_query_screens_screen_info(screens_reply);
  if (!screen_info) {
    p_delete(&screens_reply);
    return false;
  }

  output_info_t *output_list = p_new(output_info_t, len);
  for (int i = 0; i < len; i++) {
    output_info_t *output = &output_list[i];
    output->geometry.x = screen_info[i].x_org;
    output->geometry.y = screen_info[i].y_org;
    output->geometry.width = screen_info[i].width;
    output->geometry.height = screen_info[i].height;
  }
  p_delete(&screens_reply);

  if (count) *count = (size_t)len;
  if (outputs) {
    *outputs = output_list;
  } else {
    for (size_t i = 0; i < (size_t)len; i++) p_delete(&output_list[i].name);
    p_delete(&output_list);
  }

  return true;
}

backend_detect_t *backend_detect(backend_t *backend) {
  output_info_t *outputs = nullptr;
  size_t count = 0;

  if (detect_monitor_by_randr(backend, &outputs, &count)) {
    backend_detect_t *detect = output_remove_duplication(outputs, count);
    p_delete(&outputs);
    return detect;
  }

  if (detect_monitor_by_xinerama(backend, &outputs, &count)) {
    backend_detect_t *detect = output_remove_duplication(outputs, count);
    p_delete(&outputs);
    return detect;
  }

  output_info_t *output = p_new(output_info_t, 1);
  output->geometry.x = 0;
  output->geometry.y = 0;
  output->geometry.width = backend->screen->width_in_pixels;
  output->geometry.height = backend->screen->height_in_pixels;

  backend_detect_t *detect = p_new(backend_detect_t, 1);
  detect->outputs = output;
  detect->output_count = 1;
  return detect;
}

void backend_detect_destroy(backend_detect_t *detect) {
  if (!detect) return;

  for (size_t i = 0; i < detect->output_count; i++) {
    p_delete(&detect->outputs[i].name);
  }

  p_delete(&detect->outputs);
  free(detect);
}

static void backend_focus_window(backend_t *backend, xcb_window_t window) {
  xcb_connection_t *conn = backend->conn;
  xcb_window_t root = backend->screen->root;
  const atoms_t *atoms = &backend->atoms;
  xcb_atom_t property = atoms->_NET_ACTIVE_WINDOW;
  xcb_timestamp_t time = XCB_TIME_CURRENT_TIME;
  if (window == XCB_WINDOW_NONE || window == root) {
    window = backend->window_no_focus;
    xcb_set_input_focus(conn, XCB_INPUT_FOCUS_PARENT, window, time);
    xcb_delete_property(conn, root, property);
  } else {
    uint8_t mode = XCB_PROP_MODE_REPLACE;
    xcb_atom_t type = XCB_ATOM_WINDOW;
    xcb_set_input_focus(conn, XCB_INPUT_FOCUS_PARENT, window, time);
    xcb_change_property(conn, mode, root, property, type, 32, 1, &window);
    window_takefocus(backend, window);
  }
}

static inline void backend_change_window_list(
  backend_t *backend,
  bool stack_list,
  const effect_window_list_t *list
) {
  xcb_change_property(
    backend->conn,
    XCB_PROP_MODE_REPLACE,
    backend->screen->root,
    stack_list ? backend->atoms._NET_CLIENT_LIST_STACKING
               : backend->atoms._NET_CLIENT_LIST,
    XCB_ATOM_WINDOW,
    32,
    list->count,
    list->windows
  );
}

static void
backend_restack_windows(backend_t *backend, const effect_window_list_t *list) {
  if (list->count == 0) return;

  xcb_connection_t *conn = backend->conn;
  xcb_window_t sibling_window = backend->window_no_focus;
  for (size_t i = 0; i < list->count; ++i) {
    uint16_t mask = XCB_CONFIG_WINDOW_SIBLING | XCB_CONFIG_WINDOW_STACK_MODE;
    xcb_configure_window_value_list_t params = {
      .sibling = sibling_window,
      .stack_mode = XCB_STACK_MODE_ABOVE
    };
    sibling_window = list->windows[i];
    xcb_configure_window_aux(conn, sibling_window, mask, &params);
  }
}

static void window_configure_list_reset(window_configure_list_t *configs) {
  p_clear(configs->cfgs, configs->count);
  configs->count = 0;
}

static void backend_apply_window_configure_list(backend_t *backend) {
  xcb_connection_t *conn = backend->conn;
  window_configure_list_t *configs = &backend->config_list;
  for (size_t i = 0; i < configs->count; ++i) {
    window_configure_t *cfg = &configs->cfgs[i];
    if (!cfg->mask) continue;

    xcb_configure_window_aux(conn, cfg->window, cfg->mask, &cfg->value);
  }
}

static window_configure_t *
find_or_push_configure(window_configure_list_t *configs, xcb_window_t window) {
  window_configure_t *cfg = nullptr;
  for (size_t i = 0; i < configs->count; ++i) {
    cfg = &configs->cfgs[i];
    if (cfg->window == window) return cfg;
  }

  cfg = array_push(configs->cfgs, configs->count, configs->capacity);
  p_clear(cfg, 1);
  cfg->window = window;
  cfg->mask = 0;
  return cfg;
}

static void merge_window_configure_params(
  backend_t *backend,
  const configure_data_t *data
) {
  auto cfg = find_or_push_configure(&backend->config_list, data->window);

#define FIELD_MERGE(MASK, VALUE_FIELD, DATA_FIELD) \
  if (data->changed_fields & (MASK)) {             \
    cfg->mask |= (MASK);                           \
    cfg->value.VALUE_FIELD = data->DATA_FIELD;     \
  }

  FIELD_MERGE(ZDWM_CONFIGURE_FIELD_X, x, x);
  FIELD_MERGE(ZDWM_CONFIGURE_FIELD_Y, y, y);
  FIELD_MERGE(ZDWM_CONFIGURE_FIELD_WIDTH, width, width);
  FIELD_MERGE(ZDWM_CONFIGURE_FIELD_HEIGHT, height, height);
  FIELD_MERGE(ZDWM_CONFIGURE_FIELD_BORDER_WIDTH, border_width, border_width);
  FIELD_MERGE(ZDWM_CONFIGURE_FIELD_SIBLING, sibling, sibling);
  FIELD_MERGE(ZDWM_CONFIGURE_FIELD_STACK_MODE, stack_mode, stack_mode);

#undef FIELD_MERGE
}

static void
backend_bind_key(backend_t *backend, const effect_bind_key_t *bind_key) {
  auto root = backend->screen->root;
  window_grab_keys(backend, root, bind_key->keys, bind_key->count);
}

static void backend_grab_button(
  backend_t *backend,
  const effect_grab_button_t *grab_button
) {
  auto conn = backend->conn;
  auto window = grab_button->window;
  xcb_ungrab_button(conn, XCB_BUTTON_INDEX_ANY, window, XCB_MOD_MASK_ANY);

  auto buttons = grab_button->buttons;
  for (size_t i = 0; i < grab_button->count; ++i) {
    auto button = buttons[i].button;
    auto modifiers = buttons[i].modifiers;
    window_grab_button(backend, window, button, modifiers);
  }
}

static void backend_grab_pointer(backend_t *backend, cursor_t cursor) {
  auto conn = backend->conn;
  auto root = backend->screen->root;
  auto mask = XCB_EVENT_MASK_BUTTON_PRESS | XCB_EVENT_MASK_BUTTON_RELEASE |
              XCB_EVENT_MASK_POINTER_MOTION;
  auto mode = XCB_GRAB_MODE_ASYNC;
  auto xcursor = cursor_get_xcb_cursor(backend, cursor);
  auto time = XCB_TIME_CURRENT_TIME;
  xcb_grab_pointer(conn, false, root, mask, mode, mode, root, xcursor, time);
}

static void backend_merge_effects(
  backend_t *backend,
  const effect_t *effects,
  size_t effect_count
) {
  for (size_t i = 0; i < effect_count; ++i) {
    const effect_t *e = &effects[i];
    switch (e->type) {
    case ZDWM_EFFECT_MAP_WINDOW:
      window_list_push(&backend->map, e->as.map.window);
      window_list_push(&backend->configure, e->as.map.window);
      break;
    case ZDWM_EFFECT_UNMAP_WINDOW:
      window_list_push(&backend->unmap, e->as.unmap.window);
      break;
    case ZDWM_EFFECT_FOCUS_WINDOW:
      backend->focus_window = e->as.focus.window;
      backend->update_focus = true;
      break;
    case ZDWM_EFFECT_KILL_WINDOW:
      window_list_push(&backend->kill, e->as.kill.window);
      break;
    case ZDWM_EFFECT_WITHDRAW_WINDOW:
      window_set_icccm_wm_state(
        backend->conn,
        e->as.withdraw.window,
        XCB_ICCCM_WM_STATE_WITHDRAWN
      );
      break;
    case ZDWM_EFFECT_START_MOVE_WINDOW:
      backend_grab_pointer(backend, ZDWM_CURSOR_MOVE);
      break;
    case ZDWM_EFFECT_START_RESIZE_WINDOW:
      backend_grab_pointer(backend, ZDWM_CURSOR_RESIZE);
      break;
    case ZDWM_EFFECT_MINIMIZE_WINDOW: {
      auto window = e->as.minimize.window;
      xcb_icccm_wm_state_t state = XCB_ICCCM_WM_STATE_NORMAL;
      if (e->as.minimize.value) state = XCB_ICCCM_WM_STATE_ICONIC;
      window_set_icccm_wm_state(backend->conn, window, state);
    } break;
    case ZDWM_EFFECT_MAXIMIZE_WINDOW: {
      auto window = e->as.maximize.window;
      if (e->as.maximize.value) {
        xcb_atom_t max_atoms[] = {
          backend->atoms._NET_WM_STATE_MAXIMIZED_HORZ,
          backend->atoms._NET_WM_STATE_MAXIMIZED_VERT
        };
        window_set_net_wm_state(backend, window, countof(max_atoms), max_atoms);
      } else {
        window_set_net_wm_state(backend, window, 0, nullptr);
      }
    } break;
    case ZDWM_EFFECT_FULLSCREEN_WINDOW: {
      auto window = e->as.fullscreen.window;
      if (e->as.fullscreen.value) {
        auto fullscreen_atom = backend->atoms._NET_WM_STATE_FULLSCREEN;
        window_set_net_wm_state(backend, window, 1, &fullscreen_atom);
      } else {
        window_set_net_wm_state(backend, window, 0, nullptr);
      }
    } break;
    case ZDWM_EFFECT_CONFIGURE_WINDOW:
      merge_window_configure_params(backend, &e->as.configure);
      break;
    case ZDWM_EFFECT_CONFIGURE_NOTIFY:
      window_list_push(&backend->configure, e->as.configure_notify.window);
      break;
    case ZDWM_EFFECT_CHANGE_BORDER_COLOR: {
      xcb_change_window_attributes_value_list_t value = {
        .border_pixel = e->as.change_border_color.color->argb
      };
      xcb_change_window_attributes_aux(
        backend->conn,
        e->as.change_border_color.window,
        XCB_CW_BORDER_PIXEL,
        &value
      );
    } break;
    case ZDWM_EFFECT_CHANGE_WINDOW_LIST:
      backend_change_window_list(backend, false, &e->as.change_window_list);
      break;
    case ZDWM_EFFECT_RESTACK_WINDOWS:
      backend_restack_windows(backend, &e->as.restack_windows);
      backend_change_window_list(backend, true, &e->as.restack_windows);
      break;
    case ZDWM_EFFECT_BIND_KEY:
      backend_bind_key(backend, &e->as.bind_key);
      break;
    case ZDWM_EFFECT_GRAB_BUTTON:
      backend_grab_button(backend, &e->as.grab_button);
      break;
    case ZDWM_EFFECT_UNGRAB_POINTER:
      xcb_ungrab_pointer(backend->conn, XCB_CURRENT_TIME);
      break;
    }
  }
}

static void batch_send_configure_notify(
  xcb_connection_t *conn,
  xcb_window_t *windows,
  size_t count
) {
  if (count == 0) return;

  auto cookie_list = p_new(xcb_get_geometry_cookie_t, count);

  for (size_t i = 0; i < count; ++i) {
    auto window = windows[i];
    cookie_list[i] = xcb_get_geometry(conn, window);
  }

  uint32_t event_mask = XCB_EVENT_MASK_STRUCTURE_NOTIFY;
  for (size_t i = 0; i < count; ++i) {
    auto window = windows[i];
    auto cookie = cookie_list[i];
    auto reply = xcb_get_geometry_reply(conn, cookie, nullptr);
    if (!reply) continue;

    xcb_configure_notify_event_t ev = {
      .response_type = XCB_CONFIGURE_NOTIFY,
      .event = window,
      .window = window,
      .above_sibling = XCB_WINDOW_NONE,
      .x = reply->x,
      .y = reply->y,
      .width = reply->width,
      .height = reply->height,
      .border_width = reply->border_width,
      .override_redirect = false,
    };
    xcb_send_event(conn, false, window, event_mask, (char *)&ev);
    p_delete(&reply);
  }

  p_delete(&cookie_list);
}

static void backend_batch_apply_effects(backend_t *backend) {
  xcb_connection_t *conn = backend->conn;
  if (backend->unmap.count) {
    xcb_grab_server(conn);
    window_clean_event_mask(conn, backend->screen->root);

    window_list_t *unmap = &backend->unmap;
    for (size_t i = 0; i < unmap->count; ++i) {
      xcb_window_t window = unmap->windows[i];
      window_clean_event_mask(conn, window);
      xcb_unmap_window(conn, window);
    }

    root_set_event_mask(backend);
    xcb_ungrab_server(conn);
  }

  for (size_t i = 0; i < backend->map.count; ++i) {
    xcb_window_t window = backend->map.windows[i];
    window_set_event_mask(conn, window);
    xcb_map_window(conn, window);
  }

  for (size_t i = 0; i < backend->kill.count; ++i) {
    window_kill(backend, backend->kill.windows[i]);
  }

  backend_apply_window_configure_list(backend);

  {
    auto windows = backend->configure.windows;
    auto count = backend->configure.count;
    batch_send_configure_notify(conn, windows, count);
  }

  if (backend->update_focus) {
    backend_focus_window(backend, backend->focus_window);
  }
}

bool backend_apply_effect(
  backend_t *backend,
  const effect_t *effects,
  size_t effect_count
) {
  backend->update_focus = false;
  window_configure_list_reset(&backend->config_list);
  window_list_reset(&backend->unmap);
  window_list_reset(&backend->map);
  window_list_reset(&backend->kill);
  window_list_reset(&backend->configure);

  backend_merge_effects(backend, effects, effect_count);
  backend_batch_apply_effects(backend);

  xcb_flush(backend->conn);
  return true;
}

backend_scan_result_t *backend_scan_windows(backend_t *backend) {
  auto conn = backend->conn;
  auto root = backend->screen->root;
  auto cookie = xcb_query_tree_unchecked(conn, root);
  auto reply = xcb_query_tree_reply(conn, cookie, nullptr);
  if (!reply) return nullptr;

  auto length = xcb_query_tree_children_length(reply);
  if (!length) {
    p_delete(&reply);
    return nullptr;
  }

  auto list = xcb_query_tree_children(reply);

  auto result = p_new(backend_scan_result_t, 1);
  auto sub_result = p_new(backend_scan_result_t, 1);

  for (typeof(length) i = 0; i < length; ++i) {
    auto window = list[i];
    auto wa = window_get_attributes(backend, window);
    if (!wa) continue;

    auto override_redirect = wa->override_redirect;
    auto map_state = wa->map_state;
    p_delete(&wa);
    if (override_redirect) continue;

    auto hints = (xcb_icccm_wm_hints_t){0};
    auto hints_getted = window_get_wm_hints(backend, window, &hints);
    if (!(map_state == XCB_MAP_STATE_VIEWABLE ||
          (hints_getted && hints.initial_state == XCB_ICCCM_WM_STATE_ICONIC))) {
      continue;
    }

    auto transient_for = window_get_transient_for(backend, window);
    auto r = transient_for == XCB_WINDOW_NONE ? result : sub_result;
    auto slot = array_push(r->windows, r->count, r->capacity);
    if (
      !populate_window_event(backend, list[i], slot) || slot->override_redirect
    ) {
      window_layer_props_cleanup(&slot->props);
      window_metadata_cleanup(&slot->metadata);
      r->count--;
    }
  }

  p_delete(&reply);

  for (size_t i = 0; i < sub_result->count; ++i) {
    auto slot = array_push(result->windows, result->count, result->capacity);
    *slot = sub_result->windows[i];
  }

  p_clear(sub_result->windows, sub_result->count);
  backend_scan_result_destroy(sub_result);

  if (result->count == 0) {
    backend_scan_result_destroy(result);
    result = nullptr;
    return nullptr;
  }

  return result;
}

void backend_scan_result_destroy(backend_scan_result_t *result) {
  if (!result) return;

  for (size_t i = 0; i < result->count; i++) {
    window_map_request_event_t *ev = &result->windows[i];
    window_layer_props_cleanup(&ev->props);
    window_metadata_cleanup(&ev->metadata);
  }

  p_delete(&result->windows);
  p_delete(&result);
}

backend_bar_window_t backend_create_bar_window(
  backend_t *backend,
  rect_t geometry,
  uint32_t bg_pixel,
  bool enable_tray
) {
  auto conn = backend->conn;
  auto root = backend->screen->root;
  auto visual = window_get_visual(backend, true);

  static xcb_colormap_t colormap = XCB_NONE;
  if (colormap == XCB_NONE) {
    colormap = xcb_generate_id(conn);
    uint8_t alloc = XCB_COLORMAP_ALLOC_NONE;
    xcb_create_colormap(conn, alloc, colormap, root, visual->visual->visual_id);
  }

  window_clean_event_mask(conn, root);
  xcb_grab_server(conn);

  auto window_id = xcb_generate_id(conn);
  uint16_t _class = XCB_WINDOW_CLASS_INPUT_OUTPUT;
  uint32_t value_mask = XCB_CW_OVERRIDE_REDIRECT | XCB_CW_BACK_PIXEL |
                        XCB_CW_BORDER_PIXEL | XCB_CW_EVENT_MASK |
                        XCB_CW_COLORMAP;

  const xcb_create_window_value_list_t value_list = {
    .override_redirect = true,
    .background_pixel = bg_pixel,
    .border_pixel = 0,
    .event_mask = XCB_EVENT_MASK_BUTTON_PRESS | XCB_EVENT_MASK_EXPOSURE,
    .colormap = colormap,
  };
  auto cookie = xcb_create_window_aux_checked(
    conn,
    visual->depth,
    window_id,
    root,
    geometry.x,
    geometry.y,
    geometry.width,
    geometry.height,
    0,
    _class,
    visual->visual->visual_id,
    value_mask,
    &value_list
  );
  if (xcb_request_check(conn, cookie)) fatal("cannot create bar window");

  cookie = xcb_map_window_checked(conn, window_id);
  if (xcb_request_check(conn, cookie)) fatal("cannot map bar window");

  window_set_class_instance(conn, window_id);
  window_set_name_static(conn, window_id, APP_NAME "_bar");

  xcb_ungrab_server(conn);
  root_set_event_mask(backend);
  xcb_aux_sync(conn);

  auto width = geometry.width;
  auto height = geometry.height;
  auto vid = visual->visual;
  auto surface = cairo_xcb_surface_create(conn, window_id, vid, width, height);
  auto cr = cairo_create(surface);

  cairo_surface_destroy(surface);
  p_delete(&visual);

  auto statue = cairo_status(cr);
  if (statue != CAIRO_STATUS_SUCCESS) {
    fatal("cannot create cairo context: %s", cairo_status_to_string(statue));
  }

  if (enable_tray) {
    tray_host_window_t host_window = {
      .window = window_id,
      .width = width,
      .height = height,
      .bg_pixel = bg_pixel,
    };
    tray_init(backend, host_window);
  }

  return (backend_bar_window_t){
    .window_id = window_id,
    .cr = cr,
    .tray = {
      .api = tray_api,
      .handle = backend,
    },
  };
}

void backend_flush(backend_t *backend) { xcb_flush(backend->conn); }