// x-run: ~/scripts/runc.sh % -lX11 -lcairo -lxcb -lm

#include <string.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <xcb/xcb.h>
#include <xcb/xproto.h>
#include <cairo/cairo.h>
#include <cairo/cairo-xcb.h>
#include <unistd.h>
#include <math.h>

#define EVENT(T, A, B) T *A = (T *)B

void render(xcb_connection_t *connection, int wid, cairo_t *cr, int win_w, int win_h);
void set_window_title(xcb_connection_t *connection, xcb_window_t wid, const char *title);

bool get_window_geometry(xcb_connection_t *connection, xcb_window_t wid, xcb_rectangle_t *rect);
bool get_window_name(xcb_connection_t *connection, xcb_window_t wid, char *name);
bool get_window_attributes(xcb_connection_t *connection, xcb_window_t wid, xcb_get_window_attributes_reply_t *reply);

xcb_window_t find_subwindow(xcb_connection_t *connection, xcb_window_t win, int w, int h);

int main(void) {
  char buffer[8192];
  xcb_connection_t *connection = xcb_connect(getenv("DISPLAY"), NULL);
  if (!connection) {
    fprintf(stderr, "xcb_connect() failed\n");
    return EXIT_FAILURE;
  }

  xcb_screen_t *screen = xcb_setup_roots_iterator(xcb_get_setup(connection)).data;

  xcb_visualtype_t *visual = NULL;
  {
    for (
        xcb_depth_iterator_t iter_depth = xcb_screen_allowed_depths_iterator(screen);
        iter_depth.rem;
        xcb_depth_next(&iter_depth)) {
      int visual_length = xcb_depth_visuals_length(iter_depth.data);
      visual = xcb_depth_visuals(iter_depth.data);
      for (int i = 0; i < visual_length; i++) {
        if (visual->visual_id == screen->root_visual) {
          goto found_visual;
        }
      }
    }
found_visual: {}
  }

  xcb_window_t root = find_subwindow(connection, screen->root, -1, -1);
  xcb_window_t parent = find_subwindow(connection, root, screen->width_in_pixels, screen->height_in_pixels);

  printf("parent: 0x%08x\n", parent);

  xcb_window_t wid = xcb_generate_id(connection);

  int win_w = screen->width_in_pixels, win_h = screen->height_in_pixels;
  uint32_t mask = XCB_CW_BACK_PIXEL | XCB_CW_BACKING_STORE | XCB_CW_OVERRIDE_REDIRECT | XCB_CW_EVENT_MASK,
           values[] = {
             screen->white_pixel,
             XCB_BACKING_STORE_ALWAYS,
             1,
             XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_STRUCTURE_NOTIFY | XCB_EVENT_MASK_FOCUS_CHANGE
           };
  xcb_create_window(
      connection,
      XCB_COPY_FROM_PARENT, /* depth */
      wid, parent,
      0, 0, win_w, win_h, 0,
      XCB_WINDOW_CLASS_INPUT_OUTPUT,
      screen->root_visual, mask, values);

  {
    const static uint32_t values[] = { XCB_STACK_MODE_BELOW };
    xcb_configure_window(connection, wid, XCB_CONFIG_WINDOW_STACK_MODE, values);
  }
  xcb_map_window(connection, wid);
  xcb_flush(connection);

  cairo_surface_t *surface = cairo_xcb_surface_create(connection, wid, visual, win_w, win_h);
  cairo_t *cr = cairo_create(surface);

  xcb_generic_event_t *event;
  bool running = true;

  while (running) {
    while (running && (event = xcb_poll_for_event(connection))) {
      switch (event->response_type & ~0x80) {
        case XCB_CONFIGURE_NOTIFY:
          {
            EVENT(xcb_configure_notify_event_t, evt, event);
            if (win_w != evt->width || win_h != evt->height) {
              printf("resize %dx%d -> %dx%d\n", win_w, win_h, evt->width, evt->height);
              cairo_destroy(cr);
              surface = cairo_xcb_surface_create(connection, wid, visual, evt->width, evt->height);
              cr = cairo_create(surface);
              win_w = evt->width;
              win_h = evt->height;
            }
          }
          break;
        case XCB_REPARENT_NOTIFY:
          printf("reparent\n");
          break;
        case XCB_MAP_NOTIFY:
          printf("map\n");
          break;
        case XCB_FOCUS_IN:
          break;
        case XCB_FOCUS_OUT:
          break;
        case XCB_EXPOSE:
          {
            EVENT(xcb_expose_event_t, evt, event);
            printf("expose %dx%d+%d+%d\n", evt->width, evt->height, evt->x, evt->y);
          }
          break;
        case XCB_DESTROY_NOTIFY:
          cairo_destroy(cr);
          running = false;
          break;
        default:
          printf("event: %d\n", event->response_type & ~0x80);
          break;
      }
      free(event);
    }

    snprintf(buffer, 8191, "size: %dx%d", win_w, win_h);
    set_window_title(connection, wid, buffer);

    if (running) {
      render(connection, wid, cr, win_w, win_h);
      usleep(1000000 / 60);
    }
  }

  xcb_destroy_window(connection, wid);
  xcb_disconnect(connection);
  return EXIT_SUCCESS;
}

void render(xcb_connection_t *connection, int wid, cairo_t *cr, int win_w, int win_h) {
  static float t = 0.0;
  xcb_clear_area(connection, 0, wid, 0, 0, 0, 0);
  cairo_set_source_rgb(cr, 0.0, 0.5 - sin(t) * 0.5, 0.5 - cos(t) * 0.5);
  cairo_paint(cr);

  cairo_set_source_rgb(cr, sin(t) * 0.5 + 0.5, cos(t) * 0.5 + 0.5, 0);
  cairo_set_line_width(cr, 5);
  cairo_set_line_join(cr, CAIRO_LINE_JOIN_BEVEL);
  cairo_move_to(cr, win_w * 0.5, win_h * 0.5);
  cairo_line_to(cr, (sin(t) * 0.5 + 0.5) * win_w, (cos(t) * 0.5 + 0.5) * win_h);
  cairo_stroke(cr);

  xcb_flush(connection);
  t += 1.0 / 60.0;
}

void set_window_title(xcb_connection_t *connection, xcb_window_t wid, const char *title) {
  xcb_change_property(connection,
      XCB_PROP_MODE_REPLACE,
      wid,
      XCB_ATOM_WM_NAME,
      XCB_ATOM_STRING,
      8,
      strlen(title), title);
  xcb_flush(connection);
}

bool get_window_geometry(xcb_connection_t *connection, xcb_window_t wid, xcb_rectangle_t *rect) {
  xcb_get_geometry_cookie_t cookie = xcb_get_geometry(connection, wid);
  xcb_get_geometry_reply_t *reply = xcb_get_geometry_reply(connection, cookie, 0);
  if (!reply) return false;

  rect->x = reply->x;
  rect->y = reply->y;
  rect->width = reply->width;
  rect->height = reply->height;

  free(reply);
  return true;
}

bool get_window_name(xcb_connection_t *connection, xcb_window_t wid, char *name) {
  xcb_get_property_cookie_t cookie = xcb_get_property(connection, 0, wid, XCB_ATOM_WM_NAME, XCB_ATOM_STRING, 0, 0);
  xcb_get_property_reply_t *reply = xcb_get_property_reply(connection, cookie, 0);
  if (!reply) {
    name[0] = 1;
    return false;
  }

  int len = xcb_get_property_value_length(reply);
  if (len == 0) {
    name[0] = 2;
    free(reply);
    return false;
  }

  strcpy(name, xcb_get_property_value(reply));

  free(reply);
  return true;
}

bool get_window_attributes(xcb_connection_t *connection, xcb_window_t wid, xcb_get_window_attributes_reply_t *out) {
  xcb_get_window_attributes_cookie_t cookie = xcb_get_window_attributes(connection, wid);
  xcb_get_window_attributes_reply_t *reply = xcb_get_window_attributes_reply(connection, cookie, 0);
  if (!reply) return false;
  memcpy(out, reply, sizeof(xcb_get_window_attributes_reply_t));
  free(reply);
  return true;
}

xcb_window_t find_subwindow(xcb_connection_t *connection, xcb_window_t win, int w, int h) {
  xcb_query_tree_reply_t *qt_reply;
  xcb_query_tree_cookie_t qt_cookie = xcb_query_tree(connection, win);

  if ((qt_reply = xcb_query_tree_reply(connection, qt_cookie, 0))) {
    xcb_window_t *children = xcb_query_tree_children(qt_reply);
    xcb_rectangle_t rect;
    xcb_get_window_attributes_reply_t attrs;
    for (int i = 0; i < xcb_query_tree_children_length(qt_reply); i++) {
      if (!get_window_geometry(connection, children[i], &rect)) continue;
      if (!get_window_attributes(connection, children[i], &attrs)) continue;

      if (attrs.map_state != 0 && rect.width == w && rect.height == h) {
        free(qt_reply);
        return children[i];
      }
    }
    free(qt_reply);
  }
  return win;
}