package main

import (
	"fmt"
	"log"
	"os"
	"os/exec"

	"github.com/BurntSushi/xgb"
	"github.com/BurntSushi/xgb/xproto"
)

const (
	width  = 1920
	height = 1080
)

func main() {
	conn, err := xgb.NewConn()
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	screen := xproto.Setup(conn).DefaultScreen(conn)
	window, err := xproto.NewWindowId(conn)
	if err != nil {
		log.Fatal(err)
	}

	values := uint32(xproto.CwBackPixel | xproto.CwEventMask)
	xproto.CreateWindow(conn, screen.RootDepth, window, screen.Root, 0, 0, width, height, 0,
		xproto.WindowClassInputOutput, screen.RootVisual, values,
		[]uint32{screen.BlackPixel, xproto.EventMaskExposure})
	xproto.MapWindow(conn, window)
	conn.Sync()

	// XFCE owns the actual fullscreen policy; use its existing wmctrl helper.
	_ = exec.Command("wmctrl", "-i", "-r", fmt.Sprintf("0x%08x", window), "-b", "add,fullscreen").Run()

	gc, err := xproto.NewGcontextId(conn)
	if err != nil {
		log.Fatal(err)
	}
	xproto.CreateGC(conn, gc, xproto.Drawable(window), xproto.GcForeground|xproto.GcBackground,
		[]uint32{screen.WhitePixel, screen.BlackPixel})
	font := xproto.Font(window)
	xproto.OpenFont(conn, font, uint16(len("fixed")), "fixed")
	xproto.ChangeGC(conn, gc, xproto.GcFont, []uint32{uint32(font)})

	draw := func() {
		xproto.ClearArea(conn, false, window, 0, 0, width, height)
		message := "Brak polaczenia WFB"
		xproto.ImageText8(conn, byte(len(message)), xproto.Drawable(window), gc, 32, 56, message)
		conn.Sync()
	}
	draw()

	for {
		event, err := conn.WaitForEvent()
		if err != nil {
			if os.IsTimeout(err) {
				continue
			}
			return
		}
		if _, ok := event.(xproto.ExposeEvent); ok {
			draw()
		}
	}
}