package domain

import "time"

// Signal is an attention record — something the lab noticed that needs
// attention and possibly action. Dual entity: has an entities row + a
// signals table row for indexed querying.
type Signal struct {
	EntityID        UUID
	Kind            string
	Severity        string
	TargetEntityID  UUID
	CheckID         UUID
	Evidence        string
	LikelyCause     string
	State           string
	OccurrenceCount int
	FirstSeenAt     time.Time
	LastSeenAt      time.Time
	FlapCount       int
	HoldDownUntil   *time.Time
	MuteUntil       *time.Time
	CreatedAt       time.Time
	UpdatedAt       time.Time
}

// Signal lifecycle states (see lifecycle_defs in seeds/ontology.yaml).
const (
	SignalRaised       = "raised"
	SignalAcknowledged = "acknowledged"
	SignalActing       = "acting"
	SignalMuted        = "muted"
	SignalResolved     = "resolved"
	SignalFailed       = "failed"
)

// Signal severities.
const (
	SeverityInfo     = "info"
	SeverityWarning  = "warning"
	SeverityCritical = "critical"
)

// ValidSignalTransitions defines legal state transitions.
var ValidSignalTransitions = map[string][]string{
	SignalRaised:       {SignalAcknowledged, SignalMuted, SignalResolved},
	SignalAcknowledged: {SignalActing, SignalResolved, SignalMuted},
	SignalActing:       {SignalResolved, SignalRaised, SignalFailed},
	SignalFailed:       {SignalAcknowledged},
	SignalMuted:        {SignalRaised},
}

// CanTransition returns true if from→to is a legal signal state transition.
func (s *Signal) CanTransition(to string) bool {
	allowed, ok := ValidSignalTransitions[s.State]
	if !ok {
		return false
	}
	for _, a := range allowed {
		if a == to {
			return true
		}
	}
	return false
}