package updates

import (
	"fmt"
	"time"
)

// canStart is the whole "may this phase begin" decision. The maintenance
// window deadline only gates the start of a phase: a package manager that is
// already running is never interrupted by it, because killing apt, dnf or
// Windows Update partway through a transaction is worse than letting it
// finish late. A zero deadline is a manual run, which always may start.
func canStart(now, deadline time.Time) bool {
	return deadline.IsZero() || now.Before(deadline)
}

// startGate returns the error reported when a phase is refused.
func startGate(deadline time.Time, phase string) error {
	if canStart(time.Now(), deadline) {
		return nil
	}
	return fmt.Errorf("the maintenance window ended before %s could start", phase)
}