package fall

type policy struct {
	suspectWindowSeconds float64
	requireRapidDrop     bool
	rapidDropAt          map[string]float64
}

func newPolicy(suspectWindowSeconds float64, requireRapidDrop bool) *policy {
	return &policy{
		suspectWindowSeconds: suspectWindowSeconds,
		requireRapidDrop:     requireRapidDrop,
		rapidDropAt:          make(map[string]float64),
	}
}

func (policy *policy) evaluate(trackID string, poseEvidence PoseEvidence, now float64, state State) Evidence {
	if !poseEvidence.Accepted {
		delete(policy.rapidDropAt, trackID)
		return Evidence{}
	}
	if poseEvidence.RapidVerticalChange {
		policy.rapidDropAt[trackID] = now
	}
	candidate := false
	if state == Suspect {
		candidate = poseEvidence.HorizontalPose
	} else if poseEvidence.HorizontalPose {
		if !policy.requireRapidDrop {
			candidate = true
		} else if droppedAt, found := policy.rapidDropAt[trackID]; found {
			candidate = now-droppedAt <= policy.suspectWindowSeconds
		}
	}
	recovery := (state == Confirmed || state == Recovering) && !poseEvidence.HorizontalPose && !poseEvidence.RapidVerticalChange
	return Evidence{Accepted: true, IsFallCandidate: candidate, IsRecoveryCandidate: recovery}
}