package pool

// CapacityReadResult is the fixed outcome of one authoritative inventory read.
type CapacityReadResult string

const (
	CapacityReadSuccess CapacityReadResult = "success"
	CapacityReadError   CapacityReadResult = "error"
)

// CapacityObservation contains one Controller-side inventory sample. Its
// UpstreamID and SourceID are for process-local aggregation only and must not
// be exposed as Prometheus labels.
type CapacityObservation struct {
	UpstreamID      string
	SourceID        string
	Result          CapacityReadResult
	Managed         int
	AvailableSlots  int64
	EffectiveSlots  int64
	PendingExpected int
}

// CapacityObserver receives cold-path Provider inventory samples. It must
// return promptly and must not issue another inventory read or persistent I/O.
type CapacityObserver interface {
	ObserveCapacity(CapacityObservation)
	RemoveCapacityUpstream(upstreamID, sourceID string)
}