package model

import (
	"net/netip"
	"time"
)

// Lease states.
const (
	// LeaseActive: the client holds the address until End.
	LeaseActive = "active"
	// LeaseReleased: the client gave the address back. The row stays so
	// the client gets the same address next time, if it is still free.
	LeaseReleased = "released"
	// LeaseExpired: the lease ran out (the state is computed: an active
	// lease past its End).
	LeaseExpired = "expired"
	// LeaseDeclined: a client said the address is in use by someone else
	// (DHCPDECLINE), or it answered a ping. It isn't handed out until End.
	LeaseDeclined = "declined"
)

// Lease is an address handed out, or held back.
type Lease struct {
	IP       netip.Addr `json:"ip"`
	SubnetID int64      `json:"subnet_id"`
	MAC      string     `json:"mac"`
	ClientID string     `json:"client_id,omitempty"`
	// Hostname is the name the client sent (option 12 or 81).
	Hostname string    `json:"hostname"`
	State    string    `json:"state"`
	Start    time.Time `json:"start"`
	End      time.Time `json:"end"`
	// Interface is where the client was last seen.
	Interface string    `json:"interface"`
	Updated   time.Time `json:"updated"`
	// LastSeen is when the client last answered a ping (nil: never).
	// Clients that block pings stay online while their lease lasts.
	LastSeen *time.Time `json:"last_seen,omitempty"`
}

// StateAt is the lease's state at a time (an active lease past its end
// has expired).
func (l *Lease) StateAt(now time.Time) string {
	if l.State == LeaseActive && !now.Before(l.End) {
		return LeaseExpired
	}
	return l.State
}

// ActiveAt reports whether the lease holds its address at a time.
func (l *Lease) ActiveAt(now time.Time) bool {
	return l.State == LeaseActive && now.Before(l.End)
}

// HeldAt reports whether the address can't be handed out to another
// client at a time: an active or declined lease that hasn't ended.
func (l *Lease) HeldAt(now time.Time) bool {
	return (l.State == LeaseActive || l.State == LeaseDeclined) && now.Before(l.End)
}

// Owns reports whether the lease belongs to a client: by client
// identifier when both have one, else by MAC address.
func (l *Lease) Owns(mac, clientID string) bool {
	if l.ClientID != "" && clientID != "" {
		return l.ClientID == clientID
	}
	return l.MAC != "" && l.MAC == mac
}