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

#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);

int main(void) {
  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_window_t wid = xcb_generate_id(connection);

  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: {}
  }

  int win_w = 150, win_h = 150;
  uint32_t mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK,
           values[2] = {
             screen->white_pixel,
             XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_STRUCTURE_NOTIFY | XCB_EVENT_MASK_FOCUS_CHANGE
           };
  xcb_create_window(connection,
      XCB_COPY_FROM_PARENT,
      wid, screen->root,
      0, 0, win_w, win_h, 0,
      XCB_WINDOW_CLASS_INPUT_OUTPUT,
      screen->root_visual, mask, 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 ((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, win_w, win_h);
              cr = cairo_create(surface);
              win_w = evt->width;
              win_h = evt->height;
            }
          }
          break;
        case XCB_FOCUS_IN:
          printf("focus in\n");
          break;
        case XCB_FOCUS_OUT:
          printf("focus out\n");
          break;
        case XCB_EXPOSE:
          printf("expose\n");
          break;
        case XCB_DESTROY_NOTIFY:
          cairo_destroy(cr);
          running = false;
          break;
        default:
          printf("event: %d\n", event->response_type);
          break;
      }
      free(event);
    }

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

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

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, sin(t) * 0.5 + 0.5, cos(t) * 0.5 + 0.5, 0);
  cairo_rectangle(cr, win_w * 0.5, win_h * 0.5, sin(t) * 0.5 * win_w, cos(t) * 0.5 * win_h);
  cairo_fill(cr);
  xcb_flush(connection);
  t += 1.0 / 60.0;
}