package net

import (
	"context"
	"fmt"
	"net"
	"runtime"
	"syscall"

	"github.com/vishvananda/netns"
)

type SetBuffer interface {
	SetReadBuffer(bytes int) error
	SetWriteBuffer(bytes int) error
}

type SyscallConn interface {
	SyscallConn() (syscall.RawConn, error)
}

type RemoteAddr interface {
	RemoteAddr() net.Addr
}

// tcpraw.TCPConn
type SetDSCP interface {
	SetDSCP(int) error
}

func IsIPv4(address string) bool {
	return address != "" && address[0] != ':' && address[0] != '['
}

type ListenConfig struct {
	Netns string
	net.ListenConfig
}

func (lc *ListenConfig) Listen(ctx context.Context, network, address string) (net.Listener, error) {
	if lc.Netns != "" {
		runtime.LockOSThread()
		defer runtime.UnlockOSThread()

		originNs, err := netns.Get()
		if err != nil {
			return nil, fmt.Errorf("netns.Get(): %v", err)
		}
		defer netns.Set(originNs)

		ns, err := netns.GetFromName(lc.Netns)
		if err != nil {
			return nil, fmt.Errorf("netns.GetFromName(%s): %v", lc.Netns, err)
		}
		defer ns.Close()

		if err := netns.Set(ns); err != nil {
			return nil, fmt.Errorf("netns.Set(%s): %v", lc.Netns, err)
		}
	}

	return lc.ListenConfig.Listen(ctx, network, address)
}

func (lc *ListenConfig) ListenPacket(ctx context.Context, network, address string) (net.PacketConn, error) {
	if lc.Netns != "" {
		runtime.LockOSThread()
		defer runtime.UnlockOSThread()

		originNs, err := netns.Get()
		if err != nil {
			return nil, fmt.Errorf("netns.Get(): %v", err)
		}
		defer netns.Set(originNs)

		ns, err := netns.GetFromName(lc.Netns)
		if err != nil {
			return nil, fmt.Errorf("netns.GetFromName(%s): %v", lc.Netns, err)
		}
		defer ns.Close()

		if err := netns.Set(ns); err != nil {
			return nil, fmt.Errorf("netns.Set(%s): %v", lc.Netns, err)
		}
	}
	return lc.ListenConfig.ListenPacket(ctx, network, address)
}