package growth

import "slices"

type PeerState string

const (
	PeerReady      PeerState = "READY"
	PeerSuppressed PeerState = "SUPPRESSED"
)

type PeerMerchantValue struct {
	PaidSessions int64 `json:"paidSessions"`
	SessionCount int64 `json:"sessionCount"`
}

type PeerInput struct {
	TerminalScoped       bool                `json:"terminalScoped"`
	MerchantPaidSessions int64               `json:"merchantPaidSessions"`
	Peers                []PeerMerchantValue `json:"peers"`
}

type PeerResult struct {
	State                PeerState         `json:"state"`
	Reason               SuppressionReason `json:"reason,omitempty"`
	EligiblePeerCount    int               `json:"eligiblePeerCount"`
	CombinedPeerSessions int64             `json:"combinedPeerSessions"`
	MedianPaidSessions   int64             `json:"medianPaidSessions"`
	PercentileBPS        int64             `json:"percentileBps"`
}

func EvaluatePeer(input PeerInput) PeerResult {
	result := PeerResult{State: PeerSuppressed, EligiblePeerCount: len(input.Peers)}
	if input.TerminalScoped {
		result.Reason = SuppressionTerminalScope
		return result
	}
	values := make([]int64, 0, len(input.Peers))
	for _, peer := range input.Peers {
		result.CombinedPeerSessions += peer.SessionCount
		values = append(values, peer.PaidSessions)
	}
	if len(values) < 10 || result.CombinedPeerSessions < 1_000 {
		result.Reason = SuppressionInsufficientCohort
		return result
	}
	slices.Sort(values)
	result.State = PeerReady
	result.MedianPaidSessions = median(values)
	var atOrBelow int64
	for _, value := range values {
		if input.MerchantPaidSessions >= value {
			atOrBelow++
		}
	}
	result.PercentileBPS = atOrBelow * 10_000 / int64(len(values))
	return result
}