package peer

import (
	"log"
	"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.
	//
	// We make sure we don't set a private address as our public address since we
	// may be connected via LAN to some peers.
	if peer.State == StateDirect {
		if dst := e.ping.Dst; addrIsRoutable(e.ping.Dst) {
			if dst.Addr().Is4() {
				if dst != a.selfV4 {
					log.Printf("Local IPv4 updated: %s -> %s", a.selfV4, dst)
					a.selfV4 = dst
				}
			} else {
				if dst != a.selfV6 {
					log.Printf("Local IPv6 updated: %s -> %s", a.selfV6, dst)
					a.selfV6 = dst
				}
			}
		}
		return
	}

	peer.UpdateEndpoints(e.ping.SrcV4, e.ping.SrcV6)
}

func addrIsRoutable(addrPort netip.AddrPort) bool {
	if addrPort.Port() == 0 {
		return false
	}
	addr := addrPort.Addr()
	return addr.IsGlobalUnicast() && !addr.IsPrivate()
}