package main

import (
	"bufio"
	"context"
	"log"
	"os"
	"os/exec"
	"os/signal"
	"strings"
	"sync"
	"syscall"
	"time"
)

func main() {
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()

	cmd := exec.CommandContext(ctx, "dbus-monitor", "--session", "type='signal',interface='org.gnome.ScreenSaver'")
	cmdReader, err := cmd.StdoutPipe()
	if err != nil {
		log.Fatalln("cmd.StdoutPipe:", err)
	}
	defer func() {
		_ = cmdReader.Close()
	}()
	cmd.Stderr = os.Stderr

	var wg sync.WaitGroup

	wg.Add(1)
	go func() {
		defer wg.Done()

		_ = cmd.Run()
	}()

	screenSaverCh := make(chan bool, 1)
	defer close(screenSaverCh)
	wg.Add(1)
	go func() {
		defer wg.Done()

		scanner := bufio.NewScanner(cmdReader)
		for scanner.Scan() {
			select {
			case <-ctx.Done():
				return
			default:
				if !strings.Contains(scanner.Text(), "member=ActiveChanged") {
					continue
				}
				if !scanner.Scan() {
					continue
				}
				screenSaverCh <- strings.Contains(scanner.Text(), "boolean true")
			}
		}
	}()

	wg.Add(1)
	go func() {
		defer wg.Done()

		isScreenSaverActive := false
		ticker := time.NewTicker(30 * time.Minute)
		defer ticker.Stop()
		for {
			select {
			case <-ctx.Done():
				return
			case b := <-screenSaverCh:
				isScreenSaverActive = b
			case <-ticker.C:
				if isScreenSaverActive {
					continue
				}
				_ = sendNotification(ctx)
			}
		}
	}()

	wg.Wait()

	log.Println("DONE")
}

func sendNotification(ctx context.Context) error {
	return exec.CommandContext(ctx, "notify-send", "title", "description").Run()
}