package peer

import (
	"log"
	"net/netip"

	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"

	"vppn/peer/control"
)

func (a *App) onAddPeer(p HubPeer) {
	a.onRemovePeer(p.PubKey)

	peer := &Peer{
		wgPeer:    wgtypes.Peer{PublicKey: p.PubKey},
		VPNIP:     p.VPNIP,
		IsRelay:   p.IsRelay,
		IsPublic:  p.IsPublic,
		Endpoint4: p.EndpointV4,
		Endpoint6: p.EndpointV6,
		Role:      roleFor(a.isPublic, a.vpnIP, p),
	}

	endpoint := peer.PreferredEndpoint()
	if peer.IsPublic && !endpoint.IsValid() {
		// The peer is misconfigured.
		// TODO: Log here.
		return
	}

	a.peersByKey[p.PubKey] = peer
	a.peersByIP[peer.VPNIP] = peer

	if !peer.IsPublic {
		a.devAddPeer(peer)
		return
	}

	a.devAddDirect(peer, endpoint)
}

func (a *App) onRemovePeer(key wgtypes.Key) {
	peer, exists := a.peersByKey[key]
	if !exists {
		return
	}
	a.devRemove(peer)
	delete(a.peersByKey, key)
	delete(a.peersByIP, peer.VPNIP)

	if peer == a.relay {
		a.relay = nil
		a.switchActiveRelay()
	}
}

// switchActiveRelay promotes the lowest-latency relay peer to active.
func (a *App) switchActiveRelay() {
	if a.relay != nil {
		a.devAddDirect(a.relay, a.relay.WGEndpoint())
		a.relay = nil
	}

	var best *Peer
	for _, p := range a.peersByKey {
		if !p.CanRelay() {
			continue
		}

		if best == nil || betterRelay(p, best) {
			best = p
		}
	}
	if best == nil {
		log.Printf("no relay available")
		return
	}

	a.devSetRelay(best, best.WGEndpoint())
	a.relay = best
}

// TODO: Why not < ??
// betterRelay reports whether a is a better relay candidate than b.
// Prefers lower RTT; treats zero RTT (no measurement yet) as worst case.
func betterRelay(a, b *Peer) bool {
	if a.RTT == 0 {
		return false
	}
	if b.RTT == 0 {
		return true
	}
	return a.RTT < b.RTT
}

func preferredEndpoint(v4, v6 netip.AddrPort) netip.AddrPort {
	if v4.IsValid() {
		return v4
	}
	return v6
}

func roleFor(selfIsPublic bool, selfIP netip.Addr, p HubPeer) control.Role {
	if !selfIsPublic && p.IsPublic {
		return control.Client
	}
	if selfIsPublic && !p.IsPublic {
		return control.Server
	}
	return control.RoleFor(selfIP, p.VPNIP)
}