package device

import (
	"fmt"
	"os"

	log "github.com/sirupsen/logrus"
	"golang.org/x/sys/unix"
	"golang.zx2c4.com/wireguard/device"
	"golang.zx2c4.com/wireguard/tun"
	"golang.zx2c4.com/wireguard/tun/netstack"

	"github.com/netbirdio/netbird/client/iface/bind"
	"github.com/netbirdio/netbird/client/iface/configurer"
	"github.com/netbirdio/netbird/client/iface/udpmux"
	"github.com/netbirdio/netbird/client/iface/wgaddr"
)

type TunDevice struct {
	name    string
	address wgaddr.Address
	port    int
	key     string
	mtu     uint16
	iceBind *bind.ICEBind
	tunFd   int

	device         *device.Device
	filteredDevice *FilteredDevice
	udpMux         *udpmux.UniversalUDPMuxDefault
	configurer     WGConfigurer
}

func NewTunDevice(name string, address wgaddr.Address, port int, key string, mtu uint16, iceBind *bind.ICEBind, tunFd int) *TunDevice {
	return &TunDevice{
		name:    name,
		address: address,
		port:    port,
		key:     key,
		mtu:     mtu,
		iceBind: iceBind,
		tunFd:   tunFd,
	}
}

// ErrInvalidTunnelFD is returned when the tunnel file descriptor is invalid (0).
// This typically means the Swift code couldn't find the utun control socket.
var ErrInvalidTunnelFD = fmt.Errorf("invalid tunnel file descriptor: fd is 0 (Swift failed to locate utun socket)")

func (t *TunDevice) Create() (WGConfigurer, error) {
	log.Infof("create tun interface")

	var tunDevice tun.Device
	var err error

	// Validate the tunnel file descriptor.
	// On iOS/tvOS, the FD must be provided by the NEPacketTunnelProvider.
	// A value of 0 means the Swift code couldn't find the utun control socket
	// (the low-level APIs like ctl_info, sockaddr_ctl may not be exposed in
	// tvOS SDK headers). This is a hard error - there's no viable fallback
	// since tun.CreateTUN() cannot work within the iOS/tvOS sandbox.
	if t.tunFd == 0 {
		log.Errorf("Tunnel file descriptor is 0 - Swift code failed to locate the utun control socket. " +
			"On tvOS, ensure the NEPacketTunnelProvider is properly configured and the tunnel is started.")
		return nil, ErrInvalidTunnelFD
	}

	// Normal iOS/tvOS path: use the provided file descriptor from NEPacketTunnelProvider
	var dupTunFd int
	dupTunFd, err = unix.Dup(t.tunFd)
	if err != nil {
		log.Errorf("Unable to dup tun fd: %v", err)
		return nil, err
	}

	err = unix.SetNonblock(dupTunFd, true)
	if err != nil {
		log.Errorf("Unable to set tun fd as non blocking: %v", err)
		_ = unix.Close(dupTunFd)
		return nil, err
	}
	tunDevice, err = tun.CreateTUNFromFile(os.NewFile(uintptr(dupTunFd), "/dev/tun"), 0)
	if err != nil {
		log.Errorf("Unable to create new tun device from fd: %v", err)
		_ = unix.Close(dupTunFd)
		return nil, err
	}

	t.filteredDevice = newDeviceFilter(tunDevice)
	log.Debug("Attaching to interface")
	t.device = device.NewDevice(t.filteredDevice, t.iceBind, device.NewLogger(wgLogLevel(), "[netbird] "))
	// without this property mobile devices can discover remote endpoints if the configured one was wrong.
	// this helps with support for the older NetBird clients that had a hardcoded direct mode
	// t.device.DisableSomeRoamingForBrokenMobileSemantics()

	t.configurer = configurer.NewUSPConfigurer(t.device, t.name, t.iceBind.ActivityRecorder())
	err = t.configurer.ConfigureInterface(t.key, t.port)
	if err != nil {
		t.device.Close()
		t.configurer.Close()
		return nil, err
	}
	return t.configurer, nil
}

func (t *TunDevice) Up() (*udpmux.UniversalUDPMuxDefault, error) {
	err := t.device.Up()
	if err != nil {
		return nil, err
	}

	udpMux, err := t.iceBind.GetICEMux()
	if err != nil {
		return nil, err
	}
	t.udpMux = udpMux
	log.Debugf("device is ready to use: %s", t.name)
	return udpMux, nil
}

func (t *TunDevice) Device() *device.Device {
	return t.device
}

func (t *TunDevice) DeviceName() string {
	return t.name
}

func (t *TunDevice) Close() error {
	if t.configurer != nil {
		t.configurer.Close()
	}

	if t.device != nil {
		t.device.Close()
		t.device = nil
	}

	if t.udpMux != nil {
		return t.udpMux.Close()

	}
	return nil
}

func (t *TunDevice) WgAddress() wgaddr.Address {
	return t.address
}

func (t *TunDevice) MTU() uint16 {
	return t.mtu
}

func (t *TunDevice) UpdateAddr(_ wgaddr.Address) error {
	// todo implement
	return nil
}

func (t *TunDevice) FilteredDevice() *FilteredDevice {
	return t.filteredDevice
}

func (t *TunDevice) GetNet() *netstack.Net {
	return nil
}

// GetICEBind returns the ICEBind instance
func (t *TunDevice) GetICEBind() EndpointManager {
	return t.iceBind
}