package proxy

type State string

const (
	StateFetched   State = "FETCHED"
	StateChecking  State = "CHECKING"
	StateAvailable State = "AVAILABLE"
	StateSuspect   State = "SUSPECT"
	StateDraining  State = "DRAINING"
	StateUnhealthy State = "UNHEALTHY"
	StateExtracted State = "EXTRACTED"
	StateExpired   State = "EXPIRED"
	StateRemoved   State = "REMOVED"
)

var transitions = map[State]map[State]struct{}{
	StateFetched:   set(StateChecking, StateExpired, StateRemoved),
	StateChecking:  set(StateAvailable, StateUnhealthy, StateExpired, StateRemoved),
	StateAvailable: set(StateSuspect, StateDraining, StateExtracted, StateExpired),
	StateSuspect:   set(StateAvailable, StateUnhealthy, StateDraining, StateExpired),
	StateDraining:  set(StateExpired, StateUnhealthy, StateRemoved),
	StateUnhealthy: set(StateChecking, StateRemoved, StateExpired),
	StateExtracted: set(StateExpired, StateRemoved),
	StateExpired:   set(StateRemoved),
	StateRemoved:   {},
}

func CanTransition(current, next State) bool {
	_, ok := transitions[current][next]
	return ok
}

func set(states ...State) map[State]struct{} {
	result := make(map[State]struct{}, len(states))
	for _, state := range states {
		result[state] = struct{}{}
	}
	return result
}