package wireguard

import (
	"context"
	"net"
	"net/netip"
	"time"

	"github.com/sagernet/sing-box/adapter"
	"github.com/sagernet/sing-box/adapter/endpoint"
	"github.com/sagernet/sing-box/common/dialer"
	C "github.com/sagernet/sing-box/constant"
	"github.com/sagernet/sing-box/log"
	"github.com/sagernet/sing-box/option"
	"github.com/sagernet/sing-box/transport/wireguard"
	"github.com/sagernet/sing-dns"
	"github.com/sagernet/sing/common"
	"github.com/sagernet/sing/common/bufio"
	E "github.com/sagernet/sing/common/exceptions"
	"github.com/sagernet/sing/common/logger"
	M "github.com/sagernet/sing/common/metadata"
	N "github.com/sagernet/sing/common/network"
	"github.com/sagernet/sing/service"
)

func RegisterEndpoint(registry *endpoint.Registry) {
	endpoint.Register[option.WireGuardEndpointOptions](registry, C.TypeWireGuard, NewEndpoint)
}

var (
	_ adapter.Endpoint                = (*Endpoint)(nil)
	_ adapter.InterfaceUpdateListener = (*Endpoint)(nil)
)

type Endpoint struct {
	endpoint.Adapter
	ctx            context.Context
	router         adapter.Router
	logger         logger.ContextLogger
	localAddresses []netip.Prefix
	endpoint       *wireguard.Endpoint
}

func NewEndpoint(ctx context.Context, router adapter.Router, logger log.ContextLogger, tag string, options option.WireGuardEndpointOptions) (adapter.Endpoint, error) {
	ep := &Endpoint{
		Adapter:        endpoint.NewAdapterWithDialerOptions(C.TypeWireGuard, tag, []string{N.NetworkTCP, N.NetworkUDP}, options.DialerOptions),
		ctx:            ctx,
		router:         router,
		logger:         logger,
		localAddresses: options.Address,
	}
	if options.Detour == "" {
		options.IsWireGuardListener = true
	} else if options.GSO {
		return nil, E.New("gso is conflict with detour")
	}
	outboundDialer, err := dialer.New(ctx, options.DialerOptions)
	if err != nil {
		return nil, err
	}
	wgEndpoint, err := wireguard.NewEndpoint(wireguard.EndpointOptions{
		Context:    ctx,
		Logger:     logger,
		System:     options.System,
		Handler:    ep,
		UDPTimeout: time.Duration(options.UDPTimeout),
		Dialer:     outboundDialer,
		CreateDialer: func(interfaceName string) N.Dialer {
			return common.Must1(dialer.NewDefault(service.FromContext[adapter.NetworkManager](ctx), option.DialerOptions{
				BindInterface: interfaceName,
			}))
		},
		Name:       options.Name,
		MTU:        options.MTU,
		GSO:        options.GSO,
		Address:    options.Address,
		PrivateKey: options.PrivateKey,
		ListenPort: options.ListenPort,
		ResolvePeer: func(domain string) (netip.Addr, error) {
			endpointAddresses, lookupErr := router.Lookup(ctx, domain, dns.DomainStrategy(options.DomainStrategy))
			if lookupErr != nil {
				return netip.Addr{}, lookupErr
			}
			return endpointAddresses[0], nil
		},
		Peers: common.Map(options.Peers, func(it option.WireGuardPeer) wireguard.PeerOptions {
			return wireguard.PeerOptions{
				Endpoint:                    M.ParseSocksaddrHostPort(it.Address, it.Port),
				PublicKey:                   it.PublicKey,
				PreSharedKey:                it.PreSharedKey,
				AllowedIPs:                  it.AllowedIPs,
				PersistentKeepaliveInterval: it.PersistentKeepaliveInterval,
				Reserved:                    it.Reserved,
			}
		}),
		Workers: options.Workers,
	})
	if err != nil {
		return nil, err
	}
	ep.endpoint = wgEndpoint
	return ep, nil
}

func (w *Endpoint) Start(stage adapter.StartStage) error {
	switch stage {
	case adapter.StartStateStart:
		return w.endpoint.Start(false)
	case adapter.StartStatePostStart:
		return w.endpoint.Start(true)
	}
	return nil
}

func (w *Endpoint) Close() error {
	return w.endpoint.Close()
}

func (w *Endpoint) InterfaceUpdated() {
	w.endpoint.BindUpdate()
	return
}

func (w *Endpoint) PrepareConnection(network string, source M.Socksaddr, destination M.Socksaddr) error {
	return w.router.PreMatch(adapter.InboundContext{
		Inbound:     w.Tag(),
		InboundType: w.Type(),
		Network:     network,
		Source:      source,
		Destination: destination,
	})
}

func (w *Endpoint) NewConnectionEx(ctx context.Context, conn net.Conn, source M.Socksaddr, destination M.Socksaddr, onClose N.CloseHandlerFunc) {
	var metadata adapter.InboundContext
	metadata.Inbound = w.Tag()
	metadata.InboundType = w.Type()
	metadata.Source = source
	for _, localPrefix := range w.localAddresses {
		if localPrefix.Contains(destination.Addr) {
			metadata.OriginDestination = destination
			if destination.Addr.Is4() {
				destination.Addr = netip.AddrFrom4([4]uint8{127, 0, 0, 1})
			} else {
				destination.Addr = netip.IPv6Loopback()
			}
			break
		}
	}
	metadata.Destination = destination
	w.logger.InfoContext(ctx, "inbound connection from ", source)
	w.logger.InfoContext(ctx, "inbound connection to ", metadata.Destination)
	w.router.RouteConnectionEx(ctx, conn, metadata, onClose)
}

func (w *Endpoint) NewPacketConnectionEx(ctx context.Context, conn N.PacketConn, source M.Socksaddr, destination M.Socksaddr, onClose N.CloseHandlerFunc) {
	var metadata adapter.InboundContext
	metadata.Inbound = w.Tag()
	metadata.InboundType = w.Type()
	metadata.Source = source
	metadata.Destination = destination
	for _, localPrefix := range w.localAddresses {
		if localPrefix.Contains(destination.Addr) {
			metadata.OriginDestination = destination
			if destination.Addr.Is4() {
				metadata.Destination.Addr = netip.AddrFrom4([4]uint8{127, 0, 0, 1})
			} else {
				metadata.Destination.Addr = netip.IPv6Loopback()
			}
			conn = bufio.NewNATPacketConn(bufio.NewNetPacketConn(conn), metadata.OriginDestination, metadata.Destination)
		}
	}
	w.logger.InfoContext(ctx, "inbound packet connection from ", source)
	w.logger.InfoContext(ctx, "inbound packet connection to ", destination)
	w.router.RoutePacketConnectionEx(ctx, conn, metadata, onClose)
}

func (w *Endpoint) DialContext(ctx context.Context, network string, destination M.Socksaddr) (net.Conn, error) {
	switch network {
	case N.NetworkTCP:
		w.logger.InfoContext(ctx, "outbound connection to ", destination)
	case N.NetworkUDP:
		w.logger.InfoContext(ctx, "outbound packet connection to ", destination)
	}
	if destination.IsFqdn() {
		destinationAddresses, err := w.router.LookupDefault(ctx, destination.Fqdn)
		if err != nil {
			return nil, err
		}
		return N.DialSerial(ctx, w.endpoint, network, destination, destinationAddresses)
	} else if !destination.Addr.IsValid() {
		return nil, E.New("invalid destination: ", destination)
	}
	return w.endpoint.DialContext(ctx, network, destination)
}

func (w *Endpoint) ListenPacket(ctx context.Context, destination M.Socksaddr) (net.PacketConn, error) {
	w.logger.InfoContext(ctx, "outbound packet connection to ", destination)
	if destination.IsFqdn() {
		destinationAddresses, err := w.router.LookupDefault(ctx, destination.Fqdn)
		if err != nil {
			return nil, err
		}
		packetConn, _, err := N.ListenSerial(ctx, w.endpoint, destination, destinationAddresses)
		if err != nil {
			return nil, err
		}
		return packetConn, err
	}
	return w.endpoint.ListenPacket(ctx, destination)
}