package routing

// Decision is the route picked for a single skill call.
type Decision int

const (
	DecideLocal Decision = iota
	DecideClaude
)

func (d Decision) String() string {
	if d == DecideLocal {
		return "local"
	}
	return "claude"
}

// Policy holds the floor/ceil thresholds for routing decisions.
//
// Rules (in order):
//
//  1. passRate == nil           → DecideLocal (default-to-local for cost-routable skills)
//  2. *passRate >= Floor        → DecideLocal (trust local)
//  3. *passRate <  Ceil         → DecideClaude (don't trust local)
//  4. otherwise (sample band)   → requestHash low bit picks: 0=local, 1=claude
type Policy struct {
	Floor float64
	Ceil  float64
}

// Decide returns the routing decision for a single call.
// requestHash is consulted only when passRate is in the sample band [Ceil, Floor).
func (p Policy) Decide(passRate *float64, requestHash uint64) Decision {
	if passRate == nil {
		return DecideLocal
	}
	if *passRate >= p.Floor {
		return DecideLocal
	}
	if *passRate < p.Ceil {
		return DecideClaude
	}
	if requestHash&1 == 0 {
		return DecideLocal
	}
	return DecideClaude
}