package xrandr

import (
	"fmt"
	"time"

	"github.com/jezek/xgb"
	"github.com/jezek/xgb/randr"
	"github.com/jezek/xgb/xproto"
)

const xSettleTime = 3

type event struct {
	xgb.Event
	xgb.Error
}

func waitForEventSettle(timeout time.Duration, xgbConn *xgb.Conn, rootWindow *xproto.Window) error {
	enable := randr.NotifyMaskScreenChange | randr.NotifyMaskCrtcChange | randr.NotifyMaskOutputChange | randr.NotifyMaskOutputProperty
	if err := randr.SelectInputChecked(xgbConn, *rootWindow, uint16(enable)).Check(); err != nil {
		return fmt.Errorf("failed to check xrandr events: %w", err)
	}

	now := time.Now()
	timeoutTime := now.Add(timeout)

	for {
		eventChannel := make(chan event)
		go func() {
			e, err := xgbConn.WaitForEvent()
			eventChannel <- event{Event: e, Error: err}
		}()

		select {
		case e := <-eventChannel:
			if e.Event == nil && e.Error == nil {
				return fmt.Errorf("X connection closed unexpectedly while waiting for events")
			}
		case <-time.After(xSettleTime * time.Second):
			return nil
		}

		if time.Now().After(timeoutTime) {
			return fmt.Errorf("X events have not settled and timeout was reached")
		}
	}
}