package updater

import (
	"github.com/tevino/abool"
)

type notifier struct {
	upgradeAvailable *abool.AtomicBool
	notifyChannel    chan struct{}
}

func newNotifier() *notifier {
	return &notifier{
		upgradeAvailable: abool.NewBool(false),
		notifyChannel:    make(chan struct{}),
	}
}

func (n *notifier) markAsUpgradeable() {
	if n.upgradeAvailable.SetToIf(false, true) {
		close(n.notifyChannel)
	}
}

// UpgradeAvailable returns whether an upgrade is available for this file.
func (file *File) UpgradeAvailable() bool {
	return file.notifier.upgradeAvailable.IsSet()
}

// WaitForAvailableUpgrade blocks (selectable) until an upgrade for this file is available.
func (file *File) WaitForAvailableUpgrade() <-chan struct{} {
	return file.notifier.notifyChannel
}