#include <X11/Xlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <X11/keysym.h>
#include <stdbool.h>

int WIDTH = 1920;
int HEIGHT = 1080;

void hex_color(XColor *color, Display *display, Colormap cm, const char *hexcode) {
    XParseColor(display, cm, hexcode, color);
    XAllocColor(display, cm, color);
}

void fill_color(Display *display, Window window, GC gc, Colormap cm, const char *hexcode) {
    XColor color;
    hex_color(&color, display, cm, hexcode);
    XSetForeground(display, gc, color.pixel);
    XFillRectangle(display, window, gc, 0, 0, WIDTH, HEIGHT);
}

void black(Display *display, Window window, GC gc, Colormap cm) {
    fill_color(display, window, gc, cm, "#000000");
}

void white(Display *display, Window window, GC gc, Colormap cm) {
    fill_color(display, window, gc, cm, "#FFFFFF");
}

int main(void) {
    Display *display;
    Window window;
    int screen;
    XEvent event;
    
    display = XOpenDisplay(NULL);
    if (display == NULL) {
        fprintf(stderr, "Cannot open display\n");
        exit(1);
    }
    
    screen = DefaultScreen(display);
    window = XCreateSimpleWindow(display, RootWindow(display, screen), 100, 100,
                                WIDTH, HEIGHT, 1, BlackPixel(display, screen),
                                WhitePixel(display, screen));
    
    XSelectInput(display, window, ExposureMask | KeyPressMask);
    XMapWindow(display, window);
    
    GC gc = XCreateGC(display, window, 0, NULL);
    Colormap cm = DefaultColormap(display, screen);
    
    XColor black;
    hex_color(&black, display, cm, "#000000");

    XColor white;
    hex_color(&white, display, cm, "#FFFFFF");

    while (1) {
        XNextEvent(display, &event);
        if (event.type == Expose) {
            // loop forever (until q)
            static int is_black = false;
            while (1) {
                // set color to black
                XSetForeground(display, gc, black.pixel);
                for (int i = 0; i < 50; ++i) {
                    int x = (WIDTH / 2) + (i % 10) * 5;
                    int y = (HEIGHT / 2) + (i / 10) * 5;
                    XDrawRectangle(display, window, gc, x, y, 1, 1);
                }
                XFlush(display);
                sleep(2);

                while (XPending(display)) {
                    XNextEvent(display, &event);
                    if (event.type == KeyPress) {
                        KeySym key = XLookupKeysym(&event.xkey, 0);
                        if (key == XK_q || key == XK_Q) {
                            printf("Stopping...\n");
                            exit(0);
                        }
                    }
                }
            }
        }
    }
    
    XFreeGC(display, gc);
    XDestroyWindow(display, window);
    XCloseDisplay(display);
    return 0;
}