package libbox

import (
	"crypto/rand"
	"encoding/hex"
	"errors"
	"net"
	"net/netip"
	"runtime"
	"strconv"
	"sync"
	"syscall"

	"github.com/sagernet/sing-box/adapter"
	C "github.com/sagernet/sing-box/constant"
	"github.com/sagernet/sing-box/experimental/libbox/internal/procfs"
	"github.com/sagernet/sing-box/option"
	tun "github.com/sagernet/sing-tun"
	"github.com/sagernet/sing/common"
	"github.com/sagernet/sing/common/control"
	E "github.com/sagernet/sing/common/exceptions"
	"github.com/sagernet/sing/common/logger"
)

var _ adapter.PlatformInterface = (*platformInterfaceWrapper)(nil)

type platformInterfaceWrapper struct {
	iif                    PlatformInterface
	useProcFS              bool
	networkManager         adapter.NetworkManager
	myTunName              string
	myTunAddress           []netip.Addr
	defaultInterfaceAccess sync.Mutex
	defaultInterface       *control.Interface
	isExpensive            bool
	isConstrained          bool
}

func (w *platformInterfaceWrapper) Initialize(networkManager adapter.NetworkManager) error {
	w.networkManager = networkManager
	return nil
}

func (w *platformInterfaceWrapper) UsePlatformAutoDetectInterfaceControl() bool {
	return w.iif.UsePlatformAutoDetectInterfaceControl()
}

func (w *platformInterfaceWrapper) AutoDetectInterfaceControl(fd int) error {
	return w.iif.AutoDetectInterfaceControl(int32(fd))
}

func (w *platformInterfaceWrapper) UsePlatformInterface() bool {
	return true
}

func (w *platformInterfaceWrapper) OpenInterface(options *tun.Options, platformOptions option.TunPlatformOptions) (tun.Tun, error) {
	if len(options.IncludeUID) > 0 || len(options.ExcludeUID) > 0 {
		return nil, E.New("platform: unsupported uid options")
	}
	if len(options.IncludeAndroidUser) > 0 {
		return nil, E.New("platform: unsupported android_user option")
	}
	routeRanges, err := options.BuildAutoRouteRanges(true)
	if err != nil {
		return nil, err
	}
	tunFd, err := w.iif.OpenTun(&tunOptions{options, routeRanges, platformOptions})
	if err != nil {
		return nil, err
	}
	options.Name, err = getTunnelName(tunFd)
	if err != nil {
		return nil, E.Cause(err, "query tun name")
	}
	options.InterfaceMonitor.RegisterMyInterface(options.Name)
	dupFd, err := dup(int(tunFd))
	if err != nil {
		return nil, E.Cause(err, "dup tun file descriptor")
	}
	options.FileDescriptor = dupFd
	w.myTunName = options.Name
	w.myTunAddress = myTunAddress(options)
	w.iif.RegisterMyInterface(options.Name)
	return tun.New(*options)
}

func (w *platformInterfaceWrapper) ProcessPlatformOptions(options option.TunPlatformOptions) error {
	return nil
}

func myTunAddress(options *tun.Options) []netip.Addr {
	addresses := make([]netip.Addr, 0, len(options.Inet4Address)+len(options.Inet6Address))
	for _, prefix := range options.Inet4Address {
		addresses = append(addresses, prefix.Addr())
	}
	for _, prefix := range options.Inet6Address {
		addresses = append(addresses, prefix.Addr())
	}
	return addresses
}

func (w *platformInterfaceWrapper) MyInterfaceAddress() []netip.Addr {
	return w.myTunAddress
}

func (w *platformInterfaceWrapper) UsePlatformDefaultInterfaceMonitor() bool {
	return true
}

func (w *platformInterfaceWrapper) CreateDefaultInterfaceMonitor(logger logger.Logger) tun.DefaultInterfaceMonitor {
	return &platformDefaultInterfaceMonitor{
		platformInterfaceWrapper: w,
		logger:                   logger,
	}
}

func (w *platformInterfaceWrapper) UsePlatformNetworkInterfaces() bool {
	return true
}

func (w *platformInterfaceWrapper) NetworkInterfaces() ([]adapter.NetworkInterface, error) {
	interfaceIterator, err := w.iif.GetInterfaces()
	if err != nil {
		return nil, err
	}
	var interfaces []adapter.NetworkInterface
	for _, netInterface := range iteratorToArray[*NetworkInterface](interfaceIterator) {
		w.defaultInterfaceAccess.Lock()
		// (GOOS=windows) SA4006: this value of `isDefault` is never used
		// Why not used?
		//nolint:staticcheck
		isDefault := netInterface.Name != w.myTunName && w.defaultInterface != nil && int(netInterface.Index) == w.defaultInterface.Index
		w.defaultInterfaceAccess.Unlock()
		interfaces = append(interfaces, adapter.NetworkInterface{
			Interface: control.Interface{
				Index:     int(netInterface.Index),
				MTU:       int(netInterface.MTU),
				Name:      netInterface.Name,
				Addresses: common.Map(iteratorToArray[string](netInterface.Addresses), netip.MustParsePrefix),
				Flags:     linkFlags(uint32(netInterface.Flags)),
			},
			Type:        C.InterfaceType(netInterface.Type),
			DNSServers:  iteratorToArray[string](netInterface.DNSServer),
			Expensive:   netInterface.Metered || isDefault && w.isExpensive,
			Constrained: isDefault && w.isConstrained,
		})
	}
	interfaces = common.UniqBy(interfaces, func(it adapter.NetworkInterface) string {
		return it.Name
	})
	return interfaces, nil
}

func (w *platformInterfaceWrapper) UnderNetworkExtension() bool {
	return w.iif.UnderNetworkExtension()
}

func (w *platformInterfaceWrapper) NetworkExtensionIncludeAllNetworks() bool {
	return w.iif.IncludeAllNetworks()
}

func (w *platformInterfaceWrapper) ClearDNSCache() {
	w.iif.ClearDNSCache()
}

func (w *platformInterfaceWrapper) RequestPermissionForWIFIState() error {
	return nil
}

func (w *platformInterfaceWrapper) UsePlatformWIFIMonitor() bool {
	return true
}

func (w *platformInterfaceWrapper) ReadWIFIState() adapter.WIFIState {
	wifiState := w.iif.ReadWIFIState()
	if wifiState == nil {
		return adapter.WIFIState{}
	}
	return (adapter.WIFIState)(*wifiState)
}

func (w *platformInterfaceWrapper) UsePlatformConnectionOwnerFinder() bool {
	return true
}

func (w *platformInterfaceWrapper) FindConnectionOwner(request *adapter.FindConnectionOwnerRequest) (*adapter.ConnectionOwner, error) {
	if w.useProcFS {
		var source netip.AddrPort
		var destination netip.AddrPort
		sourceAddr, _ := netip.ParseAddr(request.SourceAddress)
		source = netip.AddrPortFrom(sourceAddr, uint16(request.SourcePort))
		destAddr, _ := netip.ParseAddr(request.DestinationAddress)
		destination = netip.AddrPortFrom(destAddr, uint16(request.DestinationPort))

		var network string
		switch request.IpProtocol {
		case int32(syscall.IPPROTO_TCP):
			network = "tcp"
		case int32(syscall.IPPROTO_UDP):
			network = "udp"
		default:
			return nil, E.New("unknown protocol: ", request.IpProtocol)
		}

		uid := procfs.ResolveSocketByProcSearch(network, source, destination)
		if uid == -1 {
			return nil, E.New("procfs: not found")
		}
		return &adapter.ConnectionOwner{
			UserId: uid,
		}, nil
	}

	result, err := w.iif.FindConnectionOwner(request.IpProtocol, request.SourceAddress, request.SourcePort, request.DestinationAddress, request.DestinationPort)
	if err != nil {
		return nil, err
	}
	return &adapter.ConnectionOwner{
		UserId:              result.UserId,
		UserName:            result.UserName,
		ProcessPath:         result.ProcessPath,
		AndroidPackageNames: result.androidPackageNames,
	}, nil
}

func (w *platformInterfaceWrapper) DisableColors() bool {
	return runtime.GOOS != "android"
}

func (w *platformInterfaceWrapper) UsePlatformNotification() bool {
	return true
}

func (w *platformInterfaceWrapper) SendNotification(notification *adapter.Notification) error {
	return w.iif.SendNotification((*Notification)(notification))
}

func (w *platformInterfaceWrapper) UsePlatformNeighborResolver() bool {
	return true
}

func (w *platformInterfaceWrapper) StartNeighborMonitor(listener adapter.NeighborUpdateListener) error {
	return w.iif.StartNeighborMonitor(&neighborUpdateListenerWrapper{listener: listener})
}

func (w *platformInterfaceWrapper) CloseNeighborMonitor(listener adapter.NeighborUpdateListener) error {
	return w.iif.CloseNeighborMonitor(nil)
}

func (w *platformInterfaceWrapper) UsePlatformShell() bool {
	return w.iif.UsePlatformShell()
}

func (w *platformInterfaceWrapper) CheckPlatformShell() error {
	return w.iif.CheckPlatformShell()
}

func (w *platformInterfaceWrapper) OpenShellSession(user *adapter.PlatformUser, command string, environ []string, term string, rows int32, cols int32) (adapter.ShellSession, error) {
	libboxUser := &PlatformUser{
		Username: user.Username,
		Uid:      int32(user.Uid),
		Gid:      int32(user.Gid),
		HomeDir:  user.HomeDir,
		Shell:    user.Shell,
	}
	if len(user.Groups) > 0 {
		libboxUser.SetGroups(newIterator(common.Map(user.Groups, func(g int) int32 { return int32(g) })))
	}
	session, err := w.iif.OpenShellSession(libboxUser, command, newIterator(environ), term, rows, cols)
	if err != nil {
		return nil, err
	}
	return session, nil
}

func (w *platformInterfaceWrapper) LookupSFTPServer() (string, error) {
	return w.iif.LookupSFTPServer()
}

func (w *platformInterfaceWrapper) ReadSystemSSHHostKey() ([]byte, error) {
	result, err := w.iif.ReadSystemSSHHostKey()
	if err != nil {
		return nil, err
	}
	return []byte(result), nil
}

func (w *platformInterfaceWrapper) TailscaleHostname() string {
	return w.iif.TailscaleHostname()
}

func (w *platformInterfaceWrapper) UsePlatformBridge() bool {
	return w.iif.UsePlatformBridge()
}

func (w *platformInterfaceWrapper) CreateBridge(options adapter.BridgeOptions) (adapter.BridgeSession, error) {
	bridgeOptions := &BridgeOptions{
		BridgeName: options.BridgeName,
		MTU:        int32(options.MTU),
		Interface:  options.Interface,
		RuleIndex:  int32(options.RuleIndex),
		RouteTable: int32(options.RouteTable),
	}
	if options.Inet4Port.IsValid() {
		bridgeOptions.Inet4Port = options.Inet4Port.String()
	}
	if options.Inet6Port.IsValid() {
		bridgeOptions.Inet6Port = options.Inet6Port.String()
	}
	session, err := w.iif.CreateBridge(bridgeOptions)
	if err != nil {
		return nil, err
	}
	return &bridgeSessionWrapper{session}, nil
}

type bridgeSessionWrapper struct {
	session BridgeSession
}

func (w *bridgeSessionWrapper) FileDescriptor() int {
	return int(w.session.FileDescriptor())
}

func (w *bridgeSessionWrapper) Name() string {
	return w.session.Name()
}

func (w *bridgeSessionWrapper) Inet6Active() bool {
	return w.session.Inet6Active()
}

func (w *bridgeSessionWrapper) SetEgress(interfaceName string) error {
	return w.session.SetEgress(interfaceName)
}

func (w *bridgeSessionWrapper) Close() error {
	return w.session.Close()
}

func (w *platformInterfaceWrapper) LookupUser(username string) (*adapter.PlatformUser, error) {
	platformUser, err := w.iif.LookupUser(username)
	if err != nil {
		return nil, err
	}
	return &adapter.PlatformUser{
		Username: platformUser.Username,
		Uid:      int(platformUser.Uid),
		Gid:      int(platformUser.Gid),
		HomeDir:  platformUser.HomeDir,
		Shell:    platformUser.Shell,
		Groups:   common.Map(iteratorToArray[int32](platformUser.Groups()), func(g int32) int { return int(g) }),
	}, nil
}

type neighborUpdateListenerWrapper struct {
	listener adapter.NeighborUpdateListener
}

func (w *neighborUpdateListenerWrapper) UpdateNeighborTable(entries NeighborEntryIterator) {
	var result []adapter.NeighborEntry
	for entries.HasNext() {
		entry := entries.Next()
		if entry == nil {
			continue
		}
		address, err := netip.ParseAddr(entry.Address)
		if err != nil {
			continue
		}
		macAddress, err := net.ParseMAC(entry.MacAddress)
		if err != nil {
			continue
		}
		result = append(result, adapter.NeighborEntry{
			Address:    address,
			MACAddress: macAddress,
			Hostname:   entry.Hostname,
		})
	}
	w.listener.UpdateNeighborTable(result)
}

func AvailablePort(startPort int32) (int32, error) {
	for port := int(startPort); ; port++ {
		if port > 65535 {
			return 0, E.New("no available port found")
		}
		listener, err := net.Listen("tcp", net.JoinHostPort("127.0.0.1", strconv.Itoa(int(port))))
		if err != nil {
			if errors.Is(err, syscall.EADDRINUSE) {
				continue
			}
			return 0, E.Cause(err, "find available port")
		}
		err = listener.Close()
		if err != nil {
			return 0, E.Cause(err, "close listener")
		}
		return int32(port), nil
	}
}

func RandomHex(length int32) *StringBox {
	bytes := make([]byte, length)
	common.Must1(rand.Read(bytes))
	return wrapString(hex.EncodeToString(bytes))
}