package peer

import (
	"net/netip"
	"time"

	"vppn/peer/control"
)

func (a *App) onPing(e PingEvent) {
	peer, ok := a.peersByIP[e.srcVPNIP]
	if !ok {
		// TODO: Log here.
		return
	}

	now := time.Now()

	// If we're the server, respond - this is always necessary as it's used to
	// know if peers are up or down.
	if peer.Role == control.Server {
		a.sendPing(peer, e.ping.PingTS)
	}

	// Compute RTT from server echo.
	if peer.Role == control.Client {
		peer.RTT = now.Sub(time.Unix(0, e.ping.PingTS))
	}

	// If we're public, nothing more to do.
	if a.isPublic {
		return
	}

	// We can only learn our own endpoint from directly-connected peers — Dst
	// is the sender's observation of our WG handshake source.
	if peer.State == StateDirect {
		if dst := e.ping.Dst; dst.IsValid() {
			if dst.Addr().Is4() {
				a.selfV4 = dst
			} else {
				a.selfV6 = dst
			}
		}
		return
	}

	a.addProbe(peer, e.ping.SrcV4, e.ping.SrcV6)
}

func (a *App) addProbe(peer *Peer, v4, v6 netip.AddrPort) {
	endpoint := preferredEndpoint(v4, v6)
	if !endpoint.IsValid() || endpoint == peer.PreferredEndpoint() {
		return
	}
	peer.UpdateEndpoints(v4, v6)
	a.devAddProbe(peer, endpoint)
}